Summary of the 2010 Atlantic and East Pacific hurricane seasons

By: KoritheMan , 12:55 AM GMT on December 02, 2010

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Since the season has drawn to a close, I will be writing a detailed seasonal summary on both the 2010 Atlantic and Pacific hurricane seasons. I'll begin with the Atlantic.

2010 Atlantic hurricane season

The 2010 Atlantic hurricane season is the third most active season on record (such records go back to 1851, though there is much ambiguity and uncertainty in these records prior to the satellite era, which began in the early 1960s). The season produced 19 named storms, 12 hurricanes, and 5 major hurricanes. These numbers are well-above the long-term average of 10/6/2, respectively. The 12 hurricanes observed this year ties a record that was last set in 1969. 2005, however, still holds the record for the most number of hurricanes in a given season -- at 15. The number of hurricanes and major hurricanes, respectively, are over 50% of the long-term mean.

In terms of Accumulated Cyclone Energy (ACE) index, the 2010 season is the 12th most active, and the observed ACE total of 160 (rounded) is well-above the long-term average.

Interestingly, despite the large amount of named storms, the United States mainland experienced no hurricane landfall this year, although Hurricane Earl passed about 100 miles east of North Carolina's Outer Banks throughout the morning hours on September 3 as a Category 2 hurricane. However, there were no reports of sustained hurricane force winds on the United States, mainland, or otherwise, in association with Earl (though gusts to that strength did occur across the Outer Banks and extreme coastal North Carolina).

Hurricane Paula also briefly posed a threat to south Florida and the Florida Keys.

Additionally, Hurricane Alex, a powerful and rare June hurricane, exacerbated containment/capping efforts for the Deepwater Horizon oil spill, despite the center of the large hurricane being located several hundred miles southwest of the spill location.

Tropical Storm Bonnie, after making landfall in south Florida as a minimal tropical storm, also threatened the oil spill, causing an evacuation of any local and federal crews in the area until after the storm had safely passed. Bonnie's impact on land, however, both in Florida and in Louisiana, was minimal.

Tropical Storm Hermine, although having made landfall in northeast Mexico, moved inland across southern and central Texas, producing hurricane force wind gusts (as high as 70 kt in some locations) across deep south Texas, as well as some minor flooding across portions of central and north-central Texas, including the Dallas/Fort Worth metro area.

Bonnie was the only direct United States tropical storm landfall this year, although Tropical Depression Two and Tropical Depression Five both made landfall in the country, though the latter had dissipated as a tropical cyclone prior to moving ashore coastal Mississippi on August 12. The depression's then made an anticyclonic loop over Mississippi, Alabama, Georgia, and the Florida Panhandle, ultimately reemerging into the northern Gulf of Mexico on August 16. The system then made a second and final northern Gulf Coast landfall on August 17, once again in Mississippi, but was not able to regenerate.

Records show that only on four other occasions has the United States avoided a hurricane landfall when eight or more hurricanes have been present in a season: 1951, 1990, 2000, and 2001. A likely contributing factor to this was this year's La Nina event. Although La Nina does indeed (generally) increase tropical cyclone activity over the basin, it is also notorious for generating substantial 500 mb ridging along and just north of the Greater Antilles. This ridge typically has a westward extension all the way into the western Gulf of Mexico, which tends to force many storms that manage to penetrate the Caribbean Sea equatorial, into Central America or the Yucatan Peninsula -- such storms in the latter case then have a rather strong tendency to continue onward to another landfall in Mexico. This appears to have been the case in 2010, with all but one of the Caribbean storms (Paula) impacting either Central America or Mexico.

La Nina also tends to cause an anomalous eastward mean position of the Bermuda-Azores high pressure ridge, due to anomalous 500 mb troughing along the United States east coast. Such troughing to the north of the Greater Antilles/Caribbean deep-layer ridge tends to recurve most storms away from the mainland United States that manage to penetrate west of 65°W. Such a setup also tends to place Bermuda under the gun though, as also occurred this year (five tropical cyclone impacts were noted on that island in 2010).

Lastly, both Puerto Rico, a commonwealth of the United States, along with the Bahamas, a British commonwealth, were threatened by a hurricane strike: the former with Hurricane Earl (which passed to the north of the island), and the latter with Hurricane Tomas, which passed over the Turks and Caicos Islands as a Category 1 hurricane.

Central America and Mexico appear to have bore the brunt of this season. Hurricane Alex struck near Ambergris Cay, Belize as a 55 kt tropical storm on June 27 then traversed the Yucatan Peninsula, where it spread tropical storm force winds and heavy rainfall. Alex emerged into the Bay of Campeche on June 28, and then ultimately made landfall near Soto la Marina in the Mexican state of Tamaulipas early on July 1 as a 105 mph Category 2 hurricane with an unusually low central pressure of 947 mb.

Alex produced severe flooding across portions of northern Mexico, particularly in mountainous areas. Total damage is estimated to be at nearly $2 billion (2010 USD).

Next on the list for Mexican hits was Tropical Storm Hermine, which, as previously alluded to, made landfall in northeast Mexico just south of Matamoros as a 60 kt tropical storm early on September 8.

Mexico also had the misfortune of experiencing the most damaging storm of the season: Hurricane Karl. Karl made landfall along the Yucatan Peninsula as a small 55 kt tropical storm on the morning of September 15 about 30 miles east-northeast of Chetumal, Mexico. Karl then emerged into the Bay of Campeche on September 16. Subsequently, Karl steadily intensified, ultimately becoming a Category 3 hurricane with sustained winds of 120 mph while offshore Veracruz. Unexpectedly, and for reasons not readily apparent at this point, Karl weakened slightly before making landfall just north of Veracruz, though the hurricane was still at Category 3 intensity at the time of landfall on September 17.

Karl quickly dissipated as it moves southwestward across the mountainous terrain of southeastern Mexico. Karl caused a total of 22 fatalities, mostly from flooding in Veracruz.

Karl was also the first major hurricane landfall anywhere along the Gulf Coast since Hurricane Wilma in 2005.

Tropical Storm Matthew made landfall over northeastern Nicaragua on the evening of September 24. Matthew then traversed Honduras and emerged into the Gulf of Honduras about noon on the 25th, before making a final landfall over central Belize. Heavy rains and associated flooding was reported across portions of Central America, and Matthew is blamed on over 125 deaths, most of them direct results of the storm.

Hurricane Richard also made landfall across central Belize on the evening of October 24 as an intensifying Category 1 hurricane. Widespread power outages were reported. Richard emerged into the Bay of Campeche as a severely weakened tropical depression early on October 26, and quickly dissipated.

In addition to these areas, Bermuda was also impacted, directly or indirectly, by several tropical cyclones throughout the season. These storms were: Colin, Danielle, Fiona, Igor, and Shary.

Atlantic Canada also saw its share of tropical activity, as Hurricane Earl sped through the area in early September as a strong tropical storm, making landfall along the southwest coast of Nova Scotia. Earl caused only minimal damage across Atlantic Canada.

Hurricane Igor also caused severe damage to portions of Atlantic Canada as a rapidly transitioning (to extratropical) hurricane, with damage totaling over $160,000,000 (2010 USD).

There were also an unusual amount of storms concentrated in the deep tropics in 2010, with a total of seven named storms observed in this region (Colin, Danielle, Earl, Fiona, Gaston, Igor, Julia, and Lisa.

In addition, there was a vigorous tropical wave which was tracked across much of the Atlantic during the second week of June and into the third. This wave nearly spawned a tropical depression several hundred miles east of the Leeward Islands on June 13 until it succumbed to strong upper-tropospheric vertical wind shear. It is interesting to note that such vigorous weather systems in the deep tropics during June, along with tropical cyclones, are usually harbingers of an active season, as obviously occurred this year. Prior to this, such an event last occurred in 2008 with the formation of Hurricane Bertha in early July.

The exact mechanisms behind this phenomenon are unclear, but there is a distinct and overt correlation between anomalously eastward-forming tropical cyclones (or even strong tropical disturbances) and an active season as a whole. It could perhaps be an indication that conditions are unusually favorable in the deep tropics during such years, since a lot of Cape Verde/deep tropics activity tends to follow such events during such years.

There were also an unusually large amount of healthy tropical waves this season, especially during the early part of the season (May-July), and also an unusual amount of tropical cyclones that had their origin within an African easterly wave (tropical wave). Strong subsidence associated with persistent and frequent outbreaks of the Saharan Air Layer (SAL) prevented many of these waves from undergoing tropical cyclogenesis until the third week of August, however. The SAL occurs annually, and is characterized by a westward-moving dust storm that originates in the Sahara Desert of Africa. As the strong easterly winds in this region blow the dust westward, it inevitably makes it into the Atlantic basin. Sometimes, this dust can extend as far west as the eastern Caribbean Sea.

It is theorized that the aerosols contained within the dry, dust-laden airmass of the SAL inhibits convective development, a key element required for tropical cyclogenesis.

It has been observed that a wetter-than-average rainy season during the previous year will usually mitigate SAL outbreaks during the successive year, thereby causing the central and eastern Atlantic to become more ripe for tropical cyclogenesis.

As mentioned earlier, this year was characterized by an unusually large amount of tropical cyclones developing from tropical waves. Indeed, only Hermine, Nicole, and Shary (3 of 19 named storms) appear to have originated from something other than a tropical wave. Short-lived Tropical Depression Two, which struck extreme south Texas in early July, also had its origin from a tropical wave. Short-lived Tropical Depression Five did not, however, instead originating within a decaying frontal zone over the Bahamas during the second week of August.

Other interesting records to note about the season include the abrupt and unexpected intensification of Hurricane Julia to a Category 4 during the month of September. This makes Julia the strongest major hurricane so far east in the historical record, surpassing the old record previously held by Hurricane Eight of 1926.

In addition, two simultaneous Category 4 hurricanes were active on September 15 -- Igor and Julia. The last time such an event occurred in the basin was during 1926, when the Great Miami Hurricane and Hurricane Four were both Category 4 storms for a six-hour period at 06 UTC September 16.

2010 also boasts the third highest number of Category 4 hurricanes in a single season, with four -- indeed, only two other seasons, 2005 and 1999, had more. Out of the five observed major hurricanes this year, only Karl failed to achieve Category 4 status. Additionally, 2010 saw the earliest formation of the fourth Category 4 or stronger hurricane in a season (on September 15), eclipsing the previous record set by Hurricane Gert, once again in 1999. Gert became a Category 4 just three hours later.

There was also another new record set in 2010 with the formation of four Category 4 or stronger hurricanes in a mere 20-day period, shattering the previous record, 24 days, once again boasted by 1999.

Also, 11 named storms formed between the period of August 22 and September 29. This beats the previous record of the formation 9 named storms during this period, which occurred in 1933, 1949, 1984, and 2002.

Monthly summaries

June

One tropical cyclone, Alex, was observed during the month. Alex became the second strongest June hurricane (in terms of central pressure) on record, behind Hurricane Audrey in 1957. Alex was also the strongest June hurricane since Hurricane Alma of 1966, and the first June hurricane since Hurricane Allison in 1995.

It is not an usual occurrence to have a named storm before the start of July: historical records show that a June storm occurs about once every other year on average. However, a June hurricane occurs on a much less consistent basis, and Alex's Category 2 strength and 947 mb pressure for the month is quite unusual.

July

Two tropical cyclones were observed during the month of July: short-lived Tropical Depression Two and short-lived Tropical Storm Bonnie. Additionally, Hurricane Alex dissipated over central Mexico early on July 2. On average, one tropical cyclone per year is observed during the month of July.

August

After a relatively quiet start to the Atlantic season, the month of August showed a marked increase in tropical cyclone activity, with five tropical cyclones, including four named storms and two hurricanes, forming during the month. Both hurricanes were major hurricanes. Short-lived Tropical Depression Five formed over the eastern Gulf of Mexico from a decaying frontal trough, and quickly dissipated as it moved northwestward toward the central Gulf Coast. Following the depression was Tropical Storm Colin, followed by hurricanes Danielle and Earl, both of which were long-lived Cape Verde hurricanes, and both of which also became major hurricanes. Additionally, Tropical Storm Fiona formed during the last of the month.

These totals are are a bit above the long-term average in terms of number of named storms, but the number of hurricanes and especially major hurricanes were well-above the long-term average for the month. Both Danielle and Earl attained Category 4 status.

September

Above average activity continued into September, where eight named storms were observed. Only two other times in recorded history has such an event occurred: once in 2007 and also during 2002. Additionally, Hurricane Earl persisted through the first few days of the month, as did Tropical Storm Fiona. Of these eight observed named storms during the month, four became hurricanes, and three of those became major hurricanes (Igor, Julia, and Karl).

October

Five tropical cyclones were observed during the month of October (Otto, Paula, Richard, Shary, and Tomas), all of which became hurricanes. Records show that the five observed hurricanes during the month is second only to 1870, where six were observed. However, much of these hurricanes, with the exception of Tomas, were relatively short-lived, and as such, did not contribute much to the overall ACE total.

November

No tropical cyclones were observed to form during the month of November, although Hurricane Tomas, which formed in late October, persisted into the first week of the month, and also reattained hurricane status during the month. A November hurricane is a pretty respectable feat, regardless of its origin.

It is most notable that Tomas' reintensification to a hurricane during the month of November marks the fourth consecutive season in which a hurricane has appeared in November. Historical records show that this is a unique occurrence the basin, and shatters the previous record for three consecutive seasons with November hurricanes, last set in 1984-1986.

Individual storm summaries

Hurricane Alex: June 25 - July 2

Alex was a strong Category 2 hurricane that made its first landfall along the coast of Belize as a strong tropical storm on June 27. It made its second and final landfall along the coast of extreme northeast Mexico as a 90 kt Category 2 hurricane early on July 1.

Alex was the first June hurricane since Hurricane Allison in 1995, and also the second strongest June hurricane on record, in terms of central pressure. It was also the strongest observed June hurricane since Hurricane Alma in 1966.


The origins of Alex can probably be traced back to a tropical wave which crossed the coast of west Africa on June 14. The wave progressed steadily westward across the Atlantic Ocean, and showed no signs of organization in the associated shower activity during this time. However, when the wave reached the eastern Caribbean Sea on the morning of June 21, shower activity increased significantly, and also began to show some signs of organization. An area of low pressure formed along the wave axis that same day while the system was located a couple hundred miles south of Puerto Rico.

The wave continued westward across the central Caribbean Sea over the following couple of days, and remained disorganized. Analysis of satellite imagery during this time suggests a bit of westerly shear, likely associated with the Tropical Upper Tropospheric Trough (TUTT), whose axis was located north of the Greater Antilles during this time.

Nevertheless, the wave continued westward where it soon found a more favorable upper wind environment across the western Caribbean Sea. A large increase in deep convection occurred in association with the wave at 2100 UTC June 24 while located about 150 miles southwest of Jamaica. Convection continued to increase as the wave continued west-northwestward. By 2100 UTC June 25, the wave had gained enough organization to be considered a tropical depression while centered about 345 miles southeast of Cozumel, Mexico.

The newly-developed tropical depression continued moving generally west-northwest under the influence of a deep-layer ridge over the Gulf of Mexico. The depression became a tropical storm at 0900 UTC June 26 while located about 220 miles east of Belize City, Belize. Alex steadily intensified while continuing west-northwest toward Belize. The cyclone made landfall just north of Belize City around 0000 UTC June 27. At the time of landfall, Alex's intensity was 55 kt, and doppler radar imagery from Belize indicated that Alex was close to become a hurricane prior to landfall.

Alex turned to the northwest as it moved across the western portion of the Yucatan Peninsula. The cyclone weakened to a tropical depression overland. By about 2100 UTC, Alex emerged into the Bay of Campeche about 55 miles south-southwest of Campeche, Mexico as a tropical depression. Alex quickly regained tropical storm status. Subsequently, the storm slowed considerably and turned northward as a mid- to upper-level trough passed by to the north of the system. However, Alex soon turned back to the northwest with an increase in forward speed as the trough lifted out and the ridge rebuilt in its wake.

Initially, cold water upwelling near the western and northern coasts of the Yucatan Peninsula, caused by the cyclone's slow forward speed, along with some slight upper-tropospheric vertical shear, and dry air entrainment, prevented Alex from significantly strengthening as it moved across the Bay of Campeche and southwest Gulf of Mexico. The storm's unusually large size also might have played a part. Nevertheless, Alex became a hurricane at 0300 UTC June 29 while located about 255 miles southeast of Brownsville, Texas.

The hurricane continued to slowly intensify as it moved generally northwestward. Alex turned westward at 2100 UTC June 30 while approaching the coast of northeastern Mexico. Shortly thereafter, Alex became a Category 2 hurricane, still continuing westward. Alex made landfall in the Mexican state of Tamaulipas near Soto la Marina as an intensifying Category 2 hurricane with an unusually low central pressure of 947 mb (indeed, such a pressure is more characteristic of a high-end Category 3 or low-end Category 4) at 0200 UTC July 1. At the time of landfall, Alex's sustained winds are estimated to be at 90 kt (105 mph).

After moving inland, Alex turned southwest and weakened, becoming a tropical storm at 1200 UTC July 1. Alex continued to weaken while gradually back to the west. The cyclone dissipated at 0300 UTC July 2 while centered about 35 miles north-northeast of Zacatecas, Mexico.



Figure 1. Track of Hurricane Alex.

Tropical Depression Two: July 8 - July 9

Tropical Depression Two was a short-lived tropical cyclone that made landfall along the extreme south Texas coast during the second week of July.

The origins of this depression appear to have come from a tropical wave that crossed the coast of Africa on June 24. The wave moved westward across the Atlantic Ocean with little discernment on satellite imagery until it reached the western Caribbean Sea on July 3, where an increase in shower activity occurred. The wave subsequently showed some signs of organization prior to moving inland along the Yucatan Peninsula on July 6. Once over the southwest Gulf of Mexico, surface observations on July 7 indicate that a low pressure area formed along the wave axis.

Subsequent surface data, as well as that from a NOAA reconnaissance research mission, indicate that the wave developed into a tropical depression at 0000 UTC July 8 while centered about 250 miles southeast of Brownsville, Texas. The newly-developed tropical depression moved northwestward under the influence of a mid-level ridge over the southern United States over the next 12 hours, before abruptly turning westward while located east of Brownsville. This sudden westward movement was accompanied by a decrease in the overall forward speed of the tropical cyclone.

At 1400 UTC that same day, the depression made landfall along the extreme southern end of South Padre Island just northeast of Port Isabel. The depression then continued moving across extreme south Texas and into northeastern Mexico by 0000 UTC July 9. The cyclone then degenerated into a remnant low pressure area shortly thereafter.

It also gradually turned to the northwest once again over the following 24 hours, dissipating entirely over northern Mexico by early on July 10.



Figure 2. Track of Tropical Depression Two.

Tropical Storm Bonnie: July 22 - July 24

Bonnie was a short-lived minimal tropical storm that made landfall along the southern Florida coast then moved across the central Gulf of Mexico, dissipating before reaching the southeastern Louisiana coast.

Bonnie formed from a tropical wave that moved off the coast of Africa on July 11. The wave was accompanied by some mid-level rotation as it emerged from the coast, along with some deep convection, which was displaced to the east of the wave axis. As it moved across the Atlantic Ocean over the next several days, the wave remained largely devoid of any appreciable deep convection. However, when the system neared 50W near 1200 UTC July 17, a marked increase in convection occurred. Such convection, however, appeared to have been confined to well ahead of the wave axis, hence the system was still disorganized at this time.

The wave continued moving west to west-northwest and spawned a low pressure area along its southern portion at about 0600 UTC July 18 while the system was located about 600 miles east of the Windward Islands. Disorganized and pulsating deep convection would come and go with the wave over the next couple of days as it moved west-northwest through the northern Leeward Islands, but upper-tropospheric vertical wind shear associated with a well-defined upper cold low centered several hundred miles north of Hispaniola prevented significant development during this time.

Nevertheless, the wave produced locally heavy rainfall and strong gusty winds as it moved through the northern Leeward Islands, Puerto Rico, and Hispaniola from the 19th through early on the 22nd. Analysis of water vapor imagery indicates that this low gradually retreated westward toward the eastern Gulf of Mexico beginning on the 20th. As a result, vertical shear gradually decreased, apparently enough to allow a tropical depression to form from the wave at 1500 UTC July 22 while located about 265 miles southeast of Nassau in the Bahamas.

The depression quickly became a tropical storm at around 2200 UTC that same day while centered about 200 miles southeast of Nassau. Bonnie moved steadily west-northwest to northwest at about 15 kt after forming, steered between the mid-tropospheric flow between a well-defined upper low (the same one that was centered north of Hispaniola several days earlier) over the eastern Gulf of Mexico and the Atlantic subtropical ridge to the north.

As the Gulf of Mexico upper low retreated westward, the subtropical ridge was able to strengthen further, which caused Bonnie to increase its forward speed a bit, and also prompted a more steady and unvarying west-northwest movement. This, along with dry air entrainment and upper-level southwesterly vertical wind shear, both factors induced by the aforementioned upper low, caused Bonnie's surface circulation to become less well-defined prior to moving ashore southern Florida in Miami-Dade county near Cutler Ridge at 1500 UTC July 23 as a 35 kt tropical storm.

Bonnie quickly weakened to a tropical depression as it moved swiftly west-northwest across southern Florida, with nearly all of the associated deep convection decreasing within a mere six-hour period. Bonnie emerged into the extreme eastern Gulf of Mexico near 0000 UTC July 24 as a tropical depression. During this time, Bonnie was a swirl of low-clouds with no associated deep convection.

As Bonnie moved quickly west-northwest across the eastern and central Gulf of Mexico, strong southeasterly shear and dry air associated with an upper low to the west and a mid-tropospheric ridge to the north prevented the cyclone from significantly reintensifying. A highly confluent upper-level wind flow may have also played a part, as such situations have in the past been shown to be unfavorable for tropical cyclogenesis and intensification.

Bonnie produced intermittent bursts of deep convection near the low-level center until about 1100 UTC that same day, but such bursts were transient and quickly sheared from the low-level center due to strong upper-level winds. Bonnie degenerated into an elongated surface trough at around 2100 UTC July 24 prior to moving inland across extreme southeast Louisiana that evening.



Figure 3. Track of Tropical Storm Bonnie.

Tropical Storm Colin: August 2 - August 8

Colin was a 50-kt tropical storm that remained over the open waters of the Atlantic Ocean to the west of Bermuda.

Colin developed from an interaction between a surface trough and a tropical wave over the eastern Atlantic Ocean. The trough, which was centered several hundred nautical miles southwest of the Cape Verde Islands, was generated by a slow, westward-moving tropical wave that emerged from the coast of Africa on July 28. As the nearly stationary trough detached from it, the aforementioned tropical wave continued moving westward across the Atlantic Ocean. A couple of days later, another, secondary tropical wave entered the Atlantic Ocean from Africa. This wave was larger and moving faster than the trough. On July 31, these two meteorological features began to interact and generated a broad area of low pressure about 750 miles west-southwest of the Cape Verde Islands early on August 1. Shower activity associated with the low increased later that day, but the system lacked a well-defined surface circulation. On August 2, data from ASCAT indicated that the system had a definite closed circulation at the surface, which indicated that a tropical depression had formed from this area at 1200 UTC.

The depression moved steadily to the west-northwest at about 15 to 20 kt along the south side of the Atlantic subtropical ridge. Convection gradually became better organized, and the cyclone strengthened to a tropical storm at 0600 UTC August 3 while located about 840 miles east of the Lesser Antilles. By 1200 UTC that same day, Colin significantly accelerated, its forward speed increasing to 25 to 30 kt. Consequently, Colin failed to maintain a closed surface circulation and degenerated into a broad area of low pressure by 1800 UTC that day. Colin's remnants would continue to move unusually quickly toward the west-northwest over the following 24 hours before a deceleration in the forward speed was noted. Colin also continued to produce sustained winds of tropical storm force despite having dissipated as a tropical cyclone.

A reconnaissance aircraft investigating Colin while it was located northeast of the Leeward Islands on August 4 found flight-level winds of 47 kt within the system, but no closed surface circulation. When Colin approached a weakness in the subtropical ridge over the western Atlantic Ocean on August 5, it decelerated further. This decrease in forward speed allowed a closed low-level center to redevelop at 1200 UTC that day, based on both conventional and microwave satellite images. During this time, Colin had organized deep convection and was also producing sustained tropical storm force winds. Consequently, the cyclone is estimated to have once again become a tropical storm at that time while located about 280 miles north-northeast of San Juan, Puerto Rico.

Convection formed a little closer to the center late that evening, despite an unfavorable upper-level environment characterized by strong vertical shear. At 2100 UTC August 5, reconnaissance data indicate that Colin attained its peak intensity of 50 kt. Shortly thereafter, strong westerly shear weakened the thunderstorm activity and pushed it to the east of the low-level center, and by 0600 UTC August 6, Colin had weakened, its winds dropping down to 40 kt. That same day, the cyclone turned northward and some additional deceleration occurred during this time.

By the next day, Colin had begun moving toward the northeast, embedded within deep southwesterly flow associated with an unseasonably deep-layered trough moving off the east coast of the United States. During this day, Colin weakened further, as convection remained displaced to the east of the low-level center. By 0000 UTC August 8, Colin weakened to a tropical depression while centered about 170 miles south-southwest of Bermuda. Over the following several hours, Colin's low-level center became diffuse and ill-defined. As a result, Colin dissipated while located about 100 miles southwest of Bermuda. Nevertheless, the low produced wind gusts of tropical storm force along with some rain as it passed to the west of the island later that day.

Early the next day, the remnant trough had dissipated about 150 miles northwest of Bermuda.



Figure 4. Track of Tropical Storm Colin.

Tropical Depression Five: August 10 - August 11

Tropical Depression Five was a short-lived tropical depression that dissipated before reaching the coast of Mississippi. It made a clockwise loop across portions of the deep south before moving back into the northern Gulf of Mexico, where it made another landfall along the coast of Mississippi on August 17.

A decaying upper-level trough, the same one that recurved Tropical Storm Colin, was located across the western Atlantic Ocean and the Bahamas on August 8. The trough moved westward across the Florida peninsula and into the eastern Gulf of Mexico on the 8th and 9th while underneath the influence of a building ridge. Late on August 9, a surface low had formed from this trough while centered offshore the southwest coast of Florida. Initially, the low consisted of a broad surface circulation with disorganized shower activity while moving slowly to the southwest. On August 10 turned to the west and then west-northwest while becoming better organized. By 1800 UTC that same day, the system had become well-enough organized to be considered a tropical depression while centered about 105 miles west of Naples, Florida.

The tropical cyclone moved slowly west-northwest, and shortly after 0000 UTC August 11, convection associated with the system had diminished, likely due to strong vertical wind shear and a dry mid-tropospheric environment associated with a nearby upper-level cold low. The system degenerated into a broad area of low pressure by 0600 UTC that same day as the surface circulation became ill-defined. At this time, the system was located about 125 miles west of Naples. Later that day, the system accelerated to the northwest, and, as the low approached the southeastern Louisiana coastline on August 12, the low-level center became a little better defined.

Although the remnants of the depression produced sustained winds of 20 to 25 kt during this time, convection associated with the system failed to significantly organize. Late that day, the low moved slowly northward across the Chandeleur Islands offshore the southeast Louisiana coast then turned northeastward and made landfall along the coast of Mississippi at 0600 UTC August 13. Subsequently, the system executed a clockwise loop over portions of Mississippi, Alabama, Georgia, and the Florida panhandle and re-emerged back into the northern Gulf of Mexico on August 16.

The next day, the low turned northwestward and made another landfall along coastal Mississippi. The low continued moving to the northwest before dissipating over southwest Mississippi by 0600 UTC August 18.



Figure 5. Track of Tropical Depression Five.

Hurricane Danielle: August 21 - August 31

Danielle was a powerful Category 4 hurricane that remained well out at sea during mid-to-late August.

Danielle's origins can be linked to a tropical wave that exited the coast of Africa on August 18. Initially, any deep convection associated with the wave was confined primarily to the Intertropical Convergence Zone (ITCZ) to the south. However, by about 0900 UTC the next day, convection became more of a direct feature of the tropical wave, rather than the ITCZ. This increase in convection occurred while the wave was centered a couple hundred miles southeast of the Cape Verde Islands. By around 0600 UTC August 20, the wave spawned an area of low pressure while centered several hundred miles southwest of the Cape Verde Islands.

Nevertheless, the wave remained fairly disorganized over the next couple of days, as it was embedded within an active ITCZ over the eastern Atlantic. Indeed, on August 21, satellite images showed a remarkable decrease in convective coverage and vigor, possibly due to competing influences from the ITCZ, along with some mid-level dry air from the north being advected into the developing circulation of the tropical wave. However, by about 2100 UTC that same day, convection once again began to increase, at which point the system is estimated to have become a tropical depression while located several hundred miles southwest of the Cape Verde Islands. Initially, the depression consisted of distinct curved bands, especially to the west, but limited convection near the center.

However, early the next day, convection began to develop closer to the center, though it remained limited in areal coverage and intensity until about 2100 UTC that day, when a marked increase in both the coverage and extent of the convection was noted near the low-level center. At this time, the cyclone is estimated to have become a tropical storm. Danielle initially moved northwest, but soon moved west-northwest underneath the influence of the subtropical ridge to the north. Under a favorable environment characterized by light vertical wind shear and a moist atmosphere, Danielle steadily intensified, becoming a hurricane at 2100 UTC August 23 while centered about 1320 miles east of the Lesser Antilles. Danielle continued to strengthen, and became a Category 2 hurricane with sustained winds of 85 kt at 0900 UTC August 24 while centered about 1100 miles east of the Lesser Antilles. Interestingly, satellite imagery during this time indicates that the hurricane was actually more organized several hours before attaining Category 2 status.

Almost immediately after reaching Category 2 status, Danielle unexpectedly weakened, the storm's winds dropping from 85 kt to 70 kt. The cause of the weakening appears to be strong westerly vertical wind shear associated with a weak mid- to upper-level low that was centered several hundred miles northwest of the hurricane. This same shear also acted to ingest very dry mid-tropospheric air from the west into the core, further contributing to the observed drastic weakening during this time. Danielle continued to weaken and briefly fell below hurricane strength by 2100 UTC that same day. Danielle regained hurricane status just six hours later.

Danielle turned to the northwest near 2100 UTC August 25 as it reached a break in the Atlantic subtropical ridge. As the aforementioned upper-level cold low retreated southwestward, vertical shear gradually subsided whilst simultaneously becoming more southerly to southeasterly. This particular upper flow pattern generally favors intensification. Consequently, Danielle was able to regain Category 2 status late that evening. Danielle continued moving northwestward while gradually intensifying. The system became a major hurricane at 0600 UTC August 27 while centered about 585 miles southeast of Bermuda. During this time, satellite images indicated a well-organized hurricane, with a well-defined eye surrounded by a ring of deep convection, especially to the south. Additionally, the hurricane had a remarkable poleward outflow channel during this time, likely due to interaction with an amplifying mid- to upper-level trough located across the US east coast and western Atlantic Ocean.

The hurricane became a Category 4 just three hours later. At this time, maximum 1-minute sustained surface winds were estimated to be in excess of 115 kt. Danielle turned north-northwestward at 0300 UTC August 27 while continuing to approach Bermuda. Just three hours later, Danielle weakened to a Category 3. The weakening appears to be the result of an eyewall replacement cycle, common of intense hurricanes. Danielle weakened further to a Category 2 hurricane and turned northward at 1200 UTC that same day and then north-northeastward just three hours later.

Danielle continued to gradually weaken due to increasing southwesterly vertical wind shear associated with the aforementioned upper trough, along with passage over cooler sea surface temperatures (SSTs). The hurricane turned to the northeast at 0900 UTC August 29 and began to accelerate. In addition, the storm fell below Category 2 strength during this time, with winds dropping to 80 kt. Danielle continued moving generally northeastward with increasing acceleration. However, by late on August 29, the hurricane slowed down significantly. Danielle would continue moving generally northeastward for the remainder of its lifetime, ultimately becoming extratropical at 0300 UTC August 30 while centered about 475 miles southeast of Cape Race, Newfoundland.

The extratropical remnants could be tracked for another day or so on satellite imagery before they became absorbed into a larger and stronger extratropical low moving across the north Atlantic Ocean.



Figure 6. Track of Hurricane Danielle.

Hurricane Earl: August 25 - September 7

Earl was another powerful Category 4 hurricane. It impacted the northern Leeward Islands and Puerto Rico as an intensifying Category 2 hurricane. Earl then came perilously close to the Outer Banks of North Carolina on September 3 before making a final landfall along the coast of Nova Scotia. Earl became extratropical shortly thereafter as it interacted with a frontal zone.

Earl developed from a vigorous tropical wave that moved off the coast of Africa on August 22. As it moved off the coast, the wave was accompanied by a large area of very deep convection, though said convection soon dwindled significantly as the wave adapted to its new oceanic environment over the far eastern Atlantic Ocean. An increase in convection was noted in association with the wave around 1200 UTC August 23 while the system was centered about 150 miles west of the western coast of Africa. Shortly thereafter, the system spawned an area of low pressure and continued moving westward across the deep tropical Atlantic.

Convection associated with the wave diminished once again on August 24, but the system's low-level circulation became better defined during this time. The wave continued to display signs of organization on satellite imagery as it moved generally westward across the Atlantic Ocean. By 1500 UTC August 25, the wave had gained enough organization to be considered a tropical depression while centered about 430 miles west of the southernmost Cape Verde Islands. The depression quickly strengthened to become a tropical storm just six hours later.

Earl moved generally westward across the Atlantic Ocean over the next several days, well-embedded within the low- to mid-tropospheric easterly trade wind flow characteristic of the Northern Hemisphere tropical regions. During this time, only a slow strengthening of the tropical cyclone was noted. Earl was also moving at an unusually fast forward speed of about 20 kt during this time, with some additional acceleration noted on the 28th as it approached the northern Leeward Islands. This fast forward speed could be cited as a potential factor in why the cyclone failed to significantly strengthen for the first 72 hours or so of its existence despite a seemingly favorable atmospheric and oceanic environment. Nevertheless, Earl became a hurricane near 1230 UTC August 29 while centered about 365 miles east of the northernmost Leeward Islands.

The hurricane experienced a significant deceleration in the forward speed throughout the 29th as it continued moving generally westward toward the northern Leeward Islands. This pronounced slowing can probably be attributed to a slight weakness in the subtropical ridge along 60W caused by the same mid- to upper-level trough that captured Hurricane Danielle. Earl turned west-northwestward at 1800 UTC August 29. The hurricane became an 85 kt Category 2 hurricane late that same day while it was centered about 50 miles east-northeast of Barbuda. Earl continued to gradually intensify as it moved west-northwest through the northern Leeward Islands. It became a Category 3 hurricane at 1500 UTC August 30 while centered about 165 miles east of San Juan, Puerto Rico. At this time, maximum sustained winds were estimated to be near 105 kt.

Earl became a Category 4 hurricane (115 kt) near 2100 UTC August 30 as it began to pull away from the Virgin Islands, still moving west-northwest. Earl passed about 105 miles north of San Juan during the early morning hours of August 31 and produced tropical storm force winds across a large section of Puerto Rico, though hurricane force winds remained well offshore. Earl continued moving west-northwest until a turn to the northwest occurred near 2100 UTC August 31 as the system encountered a break in the subtropical ridge induced by Hurricane Danielle as well as a weak mid- to upper-level low located to the west of Earl, over the Bahamas. During the time of the northwest turn, Earl was located about 150 miles east-northeast of Grand Turk Island in the Bahamas.

Over the next several hours, Earl weakened, its winds dropping slightly from 115 kt to 110 kt. Analysis of water vapor imagery during this time suggests that the hurricane ingested a rather large amount of dry air into its core from the west. Earl regained Category 4 status just a little later, near 2100 UTC September 1. Six hours later, Earl intensified a little more, its winds increasing to 120 kt. During this time, Earl also possessed a remarkably low central pressure for a low-end Category 4 hurricane; reconnaissance observations during this time revealed a pressure of 932 mb. At 0600 UTC September 2, Earl turned to the north-northwest. At 0900 UTC that same day, Earl reached its peak intensity of 125 kt while centered roughly 410 miles south of Cape Hatteras, North Carolina.

Earl turned northward at 1500 UTC that same day as it steadily approached the North Carolina coast. The hurricane also steadily weakened subsequent to reaching its peak intensity. Satellite imagery indicates that the eye became much less distinct near 1800 UTC September 2. The weakening appears to have been caused by strong southwesterly upper-level winds associated with an unusually sharp and amplified deep-layer trough moving across the eastern United States. This shear also acted to push dry air into the southwest periphery of Earl, though this dry air does not appear to have made it into the core. Lastly, Earl appears to have ingested a bit of dry continental air over the United States mainland into its circulation from the north, as satellite imagery throughout the 2nd revealed a rather sizable dry slot along the northern half of the circulation. This dry air did indeed penetrate the core.

Indeed, by 2100 UTC September 2, Earl had weakened significantly, its winds dropping to 100 kt. Earl continued to slowly weaken, dropping below major hurricane status at 0000 UTC September 3. At 0300 UTC that same day, Earl passed just east of the Outer Banks of North Carolina as it turned north-northeastward. By 0900 UTC, the hurricane passed about 85 miles east of Cape Hatteras, North Carolina. Earl weakened to a Category 1 (75 kt) near 1500 UTC and accelerated as it headed toward the general direction of southeastern New England. Earl turned northeastward near 2100 UTC. The storm weakened to a 60 kt tropical storm near 0300 UTC September 4 while centered about 90 miles east-southeast of Nantucket, Massachusetts. It should be noted that, even though Earl was steadily weakening as it approached coastal North Carolina and New England, it remained an unusually large tropical cyclone, with sustained tropical storm force winds extending outward more than 200 miles from the center during this time.

Earl continued to accelerate toward the northeast under the influence of the aforementioned trough. Earl made landfall along the Nova Scotia coast east of Cape Sable near 1400 UTC September 4 as a 60 kt tropical storm. Earl turned toward the north-northeast near 2100 UTC while moving across the Gulf of St. Lawrence and the forward speed increased to near 40 kt by 0000 UTC September 5. Earl became extratropical while centered over Atlantic Canada about 180 miles southwest of Mary's Harbour, Labrador. During this time, Earl was well-involved with a large frontal zone to the west.



Figure 7. Track of Hurricane Earl.

Tropical Storm Fiona: August 30 - September 3

Fiona was a tropical storm that remained out to sea, but passed close to the island of Barbuda in the northern Leeward Islands. The system also approached Bermuda, but dissipated before reaching it.

Fiona originated from a large tropical wave that moved off the coast of Africa on August 25 and 26. The wave displayed a large mass of deep convection as it emerged from the coast. Surface observations from western Africa indicate that the wave possessed a well-defined low- to mid-level cyclonic circulation before even moving off the coast. Indeed, by August 27, as the wave was moving across the extreme eastern portion of the Atlantic Ocean, a low pressure area developed along the wave axis. The wave continued westward over the next several days, and most of the associated convection had dissipated over a 24-hour period beginning on August 29. Nevertheless, the tropical wave acquired a well-defined low-level circulation the next day, and deep convection also increased. It is thus estimated that a tropical depression formed from this wave at at 1200 UTC August 30 while located about 900 miles east of the Lesser Antilles.

By 1800 UTC, the depression strengthened into a tropical storm after data from a reconnaissance aircraft and satellite data revealed that the system was producing sustained tropical storm force winds. Fiona moved quickly west-northwest at a very fast forward speed of 20 to 25 kt over the following 24 hours and began to steadily intensify after 1200 UTC August 31 whilst approaching the northern Leeward Islands. On September 1, Fiona rounded the western periphery of the Atlantic subtropical ridge, and, as a consequence, turned to the northwest, with the center passing about 55 miles northeast of Barbuda near 1200 UTC. In spite of being located in an environment of strong and increasing northeasterly vertical wind shear, likely associated with outflow from powerful Hurricane Earl, Fiona managed to reach a peak intensity of 55 kt by 1800 UTC that same day while simultaneously moving away from the Leeward Islands.

The tropical cyclone quickly weakened, however, as relentless northeasterly wind shear continued to impinge upon the circulation center. Fiona continued moving to the northwest over the ensuring 24 hours but a turn to the north-northwest and then north occurred thereafter, on September 2 and 3. This movement was caused by a mid-level ridge to the east, along with the powerful cyclonic circulation associated with large and powerful Hurricane Earl to the west, which was nearing the Carolinas during this time. Outflow from Earl continued to impart vertical shear over Fiona, with the shear increasing to over 30 kt early on September 3, during which time Fiona's low-level center became exposed from the deep convection. Just after 1800 UTC that day, all deep convection associated with Fiona dissipated.

Fiona became post-tropical at 0000 UTC September 4 while located about 95 miles south of Bermuda. During this time, the former tropical cyclone is estimated to have had sustained surface winds of 35 kt. Six hours later, winds dropped below gale force, and the remnants of Fiona moved northeastward before losing their identity about 175 miles northeast of Bermuda.



Figure 8. Track of Tropical Storm Fiona.

Tropical Storm Gaston: September 1 - September 2

Gaston was a weak and short-lived tropical storm that dissipated in a single day, due to a very dry thermodynamic environment over the eastern tropical Atlantic.

The vigorous tropical wave that spawned Gaston moved off the coast of Africa on August 28. The wave possessed some deep convection as it emerged from the coast. A convective burst generated a mid-level circulation near the wave axis on August 30, and the convection organized around that center later that day. On August 31, the wave generated a large surface low. By that evening, the wave had developed curved convective banding signatures. Satellite and scatterometer data early on September 1 indicate that the aforementioned banding features associated with the wave increased. Additionally, the overall circulation with the wave became better defined, and it is estimated that a tropical depression formed from this wave near 0600 UTC while centered about 800 miles west-southwest of the Cape Verde Islands. The depression became a tropical storm just six hours later, when a burst of deep convection was noted over the center.

Deep convection began to wane late on September 1 as Gaston moved slowly westward. On September 2, the cyclone weakened to a tropical depression, and by 1800 UTC that same day, Gaston had degenerated into a remnant area of low pressure while located midway between Africa and the Lesser Antilles. Gaston's remnants continued moving westward across the tropical Atlantic, and deep convection once again increased near the center late on September 3. The next day, Gaston nearly became a tropical depression again. During this time, Gaston possessed a well-defined low-level center along with a shallow curved convective band wrapping cyclonically around the center. Nevertheless, deep convection failed to maintain its organization, and Gaston did not redevelop into a tropical cyclone.

The remnants continued generally westward across the Atlantic Ocean, and an increase in convection was noted as the system approached the Leeward Islands on September 6, though the system as a whole continued to become less defined during this time. A mid-level ridge built to the north of the low and forced it westward into the Caribbean Sea with some acceleration. Deep convection increased during the daylight hours on September 7, but data from a NOAA G-IV research mission into the system revealed the overall circulation had continued to become less organized since the previous flight, with very little signature noted above 850 mb. Early on September 8, convection had dissipated and the system degenerated into an open trough axis later that day while located southeast of the Dominican Republic.



Figure 9. Track of Tropical Storm Gaston.

Tropical Storm Hermine: September 6 - September 8

Hermine was a strong tropical storm that made landfall along the coast of extreme northeast Mexico in early September. Hermine then moved into southern Texas, where it produced hurricane force wind gusts. The cyclone then continued northwest and dumped heavy rains across portions of central Texas.

Hermine had its origins from the remnants of Eastern Pacific Tropical Depression Eleven-E. While the depression was moving across southeast Mexico and weakening on September 4, satellite imagery indicated that the system was producing deep convection over water across the southern Bay of Campeche in the southwest Gulf of Mexico beginning around 0300 UTC. Convection waned significantly near 1800 UTC that same day, and also decreased in areal coverage, as well. This would prove to be a most beneficial development, however, as with less convection, the system's overall size was smaller. Hence, it was able to ultimately tighten up a well-defined center without much effort.

Despite the waning of the convection, the system displayed a rather concentrated of showers and thunderstorms across the southern Bay of Campeche while centered a couple hundred miles west of the western portion of the Yucatan Peninsula near 1800 UTC. By 2315 UTC September 4, a broad surface low had formed within this area. The system might have been further enhanced by divergent flow aloft associated with a mid- to upper-level trough and associated cold front over Louisiana and the northern Gulf of Mexico. Deep convection subsequently decreased near the center, but a vigorous and large burst of convection, located within a band stretching from south to north, developed to the east of the low, over the Yucatan Peninsula and southeast Mexico.

Near 1200 UTC September 5, the system once again showed an increase in convection near the center, this time while centered about 150 miles miles east of Veracruz. Additionally, banding features became evident during this time as well, as the overall circulation became better defined. Subsequent to this, deep convection once again waned, but the system retained a well-organized structure, with upper-level outflow evident to the north, along with a vigorous low- to mid-tropospheric circulation. The system moved slowly northwestward under the influence of a low- to mid-level ridge located to the east across the central and eastern Gulf of Mexico. Deep convection increased once again near the center around 0000 UTC September 6. During this time, the system was located a few hundred miles southeast of Brownsville, Texas. Convection continued to increase and organize, and it is estimated that a tropical depression formed from this area near 0300 UTC that same day.

After genesis, the cyclone continued moved northward while quickly strengthening. The system attained tropical storm status by 0900 UTC while centered about 235 miles southeast of La Pesca, Mexico. Hermine turned north-northwest by 1500 UTC while continuing to steadily intensify. Hermine reached its peak intensity of 60 kt near 0200 UTC September 7 while located about 80 miles south-southeast of Brownsville, Texas. During this time, doppler radar data from Brownsville indicated that Hermine possessed an eye-like feature, indicating that the cyclone was intensifying up until landfall. Hermine continued north-northwestward and made landfall in extreme northeast Mexico about 40 miles south of Brownsville near 0130 UTC September 7 as a 60 kt tropical storm. However, the sustained wind to gust ratio associated with Hermine was rather large. Consequently, the system produced hurricane force wind gusts across portions of south Texas several hours after it had moved inland.

After moving inland, Hermine moved north-northwest into south Texas within just several hours. The cyclone continued moving steadily north-northwest across south, south-central, and then finally central Texas. Hermine turned to the north near 1500 UTC September 7 while located about 60 miles northwest of Corpus Christi. During this time, the cyclone was still a tropical storm possessing maximum sustained surface winds of 35 kt. Hermine turned once again to the north-northwest near 2100 UTC, still a tropical storm. Hermine finally weakened to a tropical depression near 0000 UTC September 8 while located just 5 miles southwest of Brady, Texas. The remnants of the cyclone turned northward and northeastward ahead of a mid- to upper-level trough moving across the central United States.



Figure 10. Track of Tropical Storm Hermine.

Hurricane Igor: September 8 - September 21

Igor was a powerful Category 4 hurricane that nearly became a Category 5 over the open Atlantic east of the Leeward Islands. Igor then curved near Bermuda, bringing hurricane force wind gusts to the island. It then impacted Newfoundland before becoming extratropical.

Igor also broke the record for the largest Atlantic basin tropical cyclone by gale diameter, which was previously held by Hurricane Olga in 2001. Igor had a gale force wind diameter in excess of 920 miles, while Olga had a diameter of 863 miles.


Igor developed from a vigorous tropical wave that was first observed over western Niger on September 4. Surface observations suggest that the system was already accompanied by a low pressure system during this time. The wave entered the eastern Atlantic Ocean from western Africa early on September 6. The system generated organized deep convection while continuing westward, along with a well-defined low- to mid-level circulation. The wave also battled easterly vertical wind shear associated with the Atlantic subtropical ridge to the north, which kept most of the associated convection confined to the western portion of the circulation. Convection waned substantially beginning at around 1500 UTC September 7. Convection refired near 0000 UTC September 8. The wave continued to organize, and was immediately designated a 35 kt tropical storm near 1500 UTC that day while centered about 95 miles southeast of the southernmost Cape Verde Islands. However, analysis of satellite imagery earlier in the day suggests that the system was probably a tropical depression several hours earlier, near 1200 UTC.

Initially, Igor continued to battle about 20-30 kt of easterly shear, which kept the convection displaced to the west of the low-level center. Despite this, the cyclone managed to intensify slightly, reaching 40 kt near 2100 UTC while located about 75 miles south-southwest of Praia, Cape Verde. Shortly thereafter, however, Igor succumbed to the easterly shear and weakened, with deep convection almost entirely disappearing by 0900 UTC September 9. Around this time, Igor was nearly stationary, then began to move erratically from north to north-northwest with a gradual increase in forward speed. The cyclone dropped below tropical storm intensity near 2100 UTC that day while located about 155 miles west-northwest of the southernmost Cape Verde Islands. Shortly thereafter, Igor turned to the west-northwest, then west. A significant increase in convection was noted beginning at around 2100 UTC September 9. Over the following 12 hours, the shear slowly diminished, as noted by an expansion of the upper-level outflow to the east.

This allowed Igor's center to gradually move underneath the deep convection, and the system was operationally upgraded to a tropical storm once again near 1500 UTC September 10. However, analysis of satellite imagery indicates that the cyclone likely regained strength several hours earlier. Igor continued moving westward across the tropical Atlantic while steadily intensifying. By 0900 UTC September 11, Igor's winds increased to just under hurricane strength while it was centered about 915 miles west of the Cape Verde Islands. Igor appeared to be a little better organized several hours earlier, however, and the convection was deteriorating during this time, with a noticeable absence along the northern periphery of the circulation center. In addition, between 0400 and 0600 UTC September 11, Igor displayed an eye-like feature on satellite imagery within the midst of the central dense overcast (CDO). This eye featured had disappeared by 0900 UTC, however, when Igor's winds increased to 60 kt.

Deep convection continued to decrease with Igor throughout the next several hours, though the cyclone did not weaken during this time. The catalyst for Igor's decrease in organization can probably be attributed to mid-level dry air entrainment into the northern periphery of the circulation. Deep convection increased near the center by 1500 UTC that same day. Igor became a hurricane by 0300 UTC September 12 while centered about 1230 miles east of the Leeward Islands. A well-defined eye became apparent on conventional satellite imagery near 0900 UTC that same day. Subsequent to this, the hurricane underwent a period of rapid intensification, its winds increasing from 70 kt to 130 kt in about a 24 hour period beginning from about 0900 UTC September 12 to 0900 UTC September 13.

Igor continued westward and weakened slightly to 120 kt near 0300 UTC September 14, though the hurricane was still a large and formidable Category 4 on the Saffir-Simpson Hurricane Wind Scale during this time. The likely cause of Igor's observed weakening is an eyewall replacement cycle; both satellite and microwave imagery during this time suggested that a concentric, secondary eyewall was developing outside the inner eyewall. Igor turned to the west-northwest at 0900 UTC that same day, during which time the hurricane's winds decreased further, to 115 kt. Igor once again began a strengthening trend beginning near 2100 UTC and ending near 0300 UTC September 15. During this time, Igor's winds increased to near 135 kt, just shy of Category 5 status. At that time, the hurricane was centered about 605 miles east of the northern Leeward Islands, still moving west-northwestward. Shortly thereafter, the cloud pattern deteriorated markedly, with convection decreasing substantially in the western eyewall. Indeed, the southwest portion of the hurricane's eyewall was partially open during this time, as indicated by various microwave images.

Atmospheric conditions remained favorable during this time, though water vapor images suggest that Igor might have entrained a bit of dry air into its circulation from the west. It also appears that hard-to-predict structural changes, which are common of intense hurricanes, caused the observed weakening of Igor during this time. Igor would fluctuate in intensity over the next day or so. The storm turned northwest near 1500 UTC September 16 and dropped to Category 3 intensity (110 kt) near 2100 UTC. During this time, Igor's radius of sustained hurricane force winds increased dramatically. Throughout much of the day on the September 17, Igor appears to have ingested some dry air due to an upper-level low to the east. Consequently, the cloud pattern continued to deteriorate as the storm approached Bermuda, with the eye becoming less distinct. Igor's CDO became a little more symmetric near 1800 UTC, but reconnaissance observations during this time suggest that the hurricane continued to gradually weaken.

Igor dropped to Category 2 (90 kt) status near 2100 UTC that same day while about 625 miles south-southeast of Bermuda. However, Igor remained an exceptionally large hurricane during this time, with sustained tropical storm force winds extending outward up to nearly 350 miles from the center. Igor restrengthened somewhat (to 95 kt) near 0300 UTC September 18 as it continued to march toward Bermuda. Igor would maintain this intensity until around 1800 UTC, when additional reconnaissance observations indicated that the hurricane once again weakened (to 90 kt). Igor turned north-northwest near 0300 UTC September 19, and northward by 1200 UTC. During this time, Igor's winds were at 80 kt. Igor continued to gradually weaken as it approached Bermuda. Igor turned north-northeastward near 0000 UTC September 20, during which time it was located about 60 miles west-southwest of Bermuda, relentlessly lashing that island with hurricane force wind gusts.

Igor made its closest approach to Bermuda several hours later, passing less than 50 miles west of the island. The hurricane accelerated and moved generally north-northeastward until around 1800 UTC that same day, when it turned northeastward under the influence of a mid- to upper-level trough and associated cold front to the west. Additional accelerated occurred as the hurricane approached Newfoundland. Indeed, by 1500 UTC September 21, while located about 35 miles south-southeast of Cape Race, Igor was moving at a very fast forward speed of about 40 kt, well-embedded within the high latitude westerlies. Igor became extratropical near 2100 UTC while centered about 125 miles north-northeast of St. Johns, Newfoundland. Igor's remnants could be traceable across the Labrador Sea over the next day or so, but they eventually became absorbed into a larger extratropical cyclone.



Figure 11. Track of Hurricane Igor.

Hurricane Julia: September 12 - September 20

Julia was a powerful Category 4 hurricane that impacted the southernmost Cape Verde Islands with rain and gusty winds as a minimal tropical storm, but remained out at sea otherwise.

A strong tropical wave was detected over western Africa on September 11, accompanied by low- to mid-level cyclonic turning along with a 1012 mb surface low pressure area. Early on September 12, the wave entered the eastern Atlantic Ocean, where it continued to display signs of organization on satellite imagery. The system spawned a tropical depression near 1500 UTC that day while centered about 250 miles southeast of the southernmost Cape Verde Islands. Initially, the cyclone battled some moderate easterly shear, which kept the bulk of the thunderstorm activity confined to the western portion of the circulation. Additionally, this shear also appears to have entrained some slight dry air into the tropical cyclone, which kept the convection fairly shallow initially. Nevertheless, the depression continued to slowly organize, and became a tropical storm near 0300 UTC September 13 while about 110 miles southeast of the southernmost Cape Verde Islands.

Julia moved steadily west-northwest over the next several days while slowly intensifying. The system became a hurricane near 0900 UTC September 14 while centered roughly 330 miles west of the Cape Verde Islands. Julia underwent a period of rapid intensification subsequent to this, attaining Category 3 (110 kt) status by 0530 UTC September 15. During this time, Julia was located about 490 miles west of the Cape Verde Islands, still moving to the west-northwest. Julia strengthened further to reach its peak intensity of 115 kt, Category 4, near 0900 UTC. Simultaneously, the hurricane turned northwestward as an upper-level trough located to the northeast of the storm weakened the ridge to the east. By 2100 UTC, Julia weakened slightly to Category 3 (110 kt) intensity due to strong southwesterly to south-southwesterly vertical wind shear induced by the aforementioned upper trough, whose axis was centered several hundred miles east of the Azores and extended southwestward for several hundred miles.

The hurricane experienced a significant increase in the forward speed by 1500 UTC September 16, its forward speed increasing to around 20 kt. All the while, Julia turned back to the west-northwest as it came under the influence of a developing upper low to the south, which had apparently detached from the trough. Julia fell below hurricane status near 0300 UTC September 17 while centered about 1535 miles west-southwest of the Azores. The tropical cyclone also turned back to the northwest during this time. Near 0300 UTC September 19, Julia turned northward. Later that day, the storm turned toward the east-northeast then northeast. The storm would oscillate between these two motions before turning eastward by 1500 UTC September 20.

During this time, Julia became extratropical while located about 1100 miles west of the Azores. The remnants made a prolonged anticyclonic loop, generating intermittent and brief bursts of deep convection over the next several days, which were not well organized due to strong upper-level shear.



Figure 12. Track of Hurricane Julia.

Hurricane Karl: September 14 - September 18

Karl was a Category 3 hurricane that made landfall along the coast of Mexico near Veracruz. Karl was the first major hurricane landfall along the Gulf Coast since Hurricane Wilma in 2005. Karl was also one of the strongest hurricanes ever observed in the Bay of Campeche, and possibly the strongest. Karl produced severe flooding in Veracruz.

Karl's origins can be traced to a weak tropical wave that crossed the coast of Africa on September 1. The wave propagated steadily westward across the tropical Atlantic Ocean for the next several days, with little to no associated convection. A slight increase in overall shower activity was noted several hundred miles east of the northeastern coast of South America near 0600 UTC September 7, but this activity remained highly disorganized. Shower activity would remain minimal in association with the wave until a small burst occurred near 1800 UTC September 8 while the system was centered a couple hundred miles east of the southern Windward Islands. Convection increased over the next day or so but remained disorganized. Near 1800 UTC September 9, the system spawned a low pressure area while centered a couple hundred miles northeast of the coast of Venezuela.

A significant increase in convection was observed early on September 11 but it began to wane again early that afternoon. The system was located in a very dry airmass during this time, which may have been responsible for the observed decrease in convection. Convection would continue to wax and wane over the next several days. Another increase in convection was noted near 0900 UTC September 14 while the system was centered several hundred miles east of the Yucatan Peninsula. Convection continued to increase and organize, with the formation of curved bands along the northern semicircle near 1200 UTC. The system was designated a tropical storm near 2100 UTC, but likely became a tropical depression several hours earlier, near 1500 UTC. Initially, Karl consisted of a small area of thunderstorms with a large and well-defined curved convective band to the north.

By 0300 UTC September 15, Karl had completely shed the aforementioned rainband, which allowed it to tighten its inner core. Consequentially, the cyclone began to intensify, and its winds reached 55 kt near 0900 UTC. Karl would maintain this intensity until landfall occurred along the eastern Yucatan Peninsula just a little bit to the east-northeast of Chetumal at about 1245 UTC. Prior to landfall, doppler radar data from Belize City, Belize, suggested that Karl was developing an eye, though reconnaissance observations did not support hurricane strength. Karl weakened while crossing the Yucatan Peninsula, but remain well-organized, maintaining tropical storm status throughout the crossing. The cyclone emerged into the Bay of Campeche during the early morning hours of September 16. Karl quickly intensified while turning westward, becoming a hurricane near 1500 UTC while centered about 150 miles west of Campeche, Mexico.

The hurricane continued moving westward toward the coast of southwestern Mexico. Karl continued to steadily intensify, becoming a 105 kt Category 3 near 0900 UTC September 17 while located about 70 miles east of Veracruz, Mexico. Unexpectedly, Karl became slightly less organized before making landfall just north of Veracruz near 1630 UTC September 17, with the winds decreasing and the central pressure increasing. At the time of landfall, Karl was assumed to have sustained winds in excess of 100 kt. Karl quickly weakened over the mountains of southwestern Mexico as it turned to the west-southwest, weakening to a tropical storm by 0000 UTC September 18. Karl dissipated shortly thereafter, with deep convection completely vanishing near the diffuse center.



Figure 13. Track of Hurricane Karl.

Hurricane Lisa: September 20 - September 26

Lisa was a hurricane that meandered over the eastern Atlantic under a weak steering regime and ultimately dissipated over the Atlantic without incident.

The tropical wave which spawned Hurricane Lisa moved off the coast of Africa on September 16. A couple days later, the wave generated a low pressure area while centered to the southwest of the Cape Verde Islands. Throughout September 19 and 20, the low-level circulation associated with the wave gradually became better defined, with a gradual increase in convective organization also noted during this time. At 1800 UTC September 20, while centered about 400 miles west of the Cape Verde Islands, the system spawned a tropical depression. The newly-developed tropical cyclone moved unclimatologically northward due to a weakness in the Atlantic subtropical ridge. This weakness was induced by a large mid- to upper-level trough moving across the northeast Atlantic Ocean. Just six hours later, the depression strengthened to become a tropical storm. Lisa reached an intensity of 40 kt at 0600 UTC September 21.

The cyclone turned southeastward and then eastward the next day as it came underneath the influence of weak mid-level westerly flow associated with the aforementioned trough. On September 22, convection dwindled, possibly due to the entrainment of drier air into the circulation. As a result, Lisa weakened to a tropical depression near 1800 UTC that same day. This would prove to be temporary, however, as Lisa regained tropical storm status about 18 hours later. Subsequently, the cyclone turned to the northeast and underwent a period of rapid intensification beginning early on September 24. Lisa turned northward and its winds increased from 35 kt to 65 kt (hurricane status) in about a 21-hour period on September 24. Late that day, a small eye became evident on satellite imagery, and Lisa reached its peak intensity of 75 kt at 0000 UTC September 25 while located about 240 miles northwest of the Cape Verde Islands.

Shortly thereafter, Lisa moved over progressively cooler waters and also into an area of strong westerly vertical wind shear. As a result, the small hurricane quickly weakened, and by 1200 UTC September 26, the system was only a tropical depression. Convection dissipated shortly thereafter, and Lisa degenerated into a broad area of low pressure six hours later. The remnant low moved northwestward for about 36 hours before turning northward and decelerating. By 0600 UTC September 29 while centered about 515 miles south-southwest of the Azores.



Figure 14. Track of Hurricane Lisa.

Tropical Storm Matthew: September 23 - September 26

Matthew was a short-lived tropical storm that impacted portions of Central America as a moderate tropical storm. Matthew produced prodigious rains which killed over 100 across the continent. Its remnants may have contributed to the formation of Tropical Storm Nicole several days later.

Matthew was generated by a tropical wave that moved off the coast of Africa on September 14. The wave moved westward across the Atlantic Ocean, producing disorganized shower activity. On September 18, convection began to increase a little while the system was centered several hundred miles east of the southern Windward Islands. The wave passed through the Windward Islands early on September 19, and entered the eastern Caribbean Sea later that day. The wave continued moving slowly westward across the eastern and central Caribbean Sea, generating a broad surface low pressure center near 0000 UTC September 22 while centered north of the island of Curacao. Convection increased substantially beginning near 0900 UTC September 23. Convection continued to increase, and by 1500 UTC that day, the system became a tropical depression while centered about 485 miles east of Puerto Cabezas, Nicaragua.

The depression quickly became a tropical storm. Matthew moved steadily westward toward Central America and reached its peak intensity of 45 kt near 0900 UTC. At that time, Matthew was located about 240 miles east of Puerto Cabezas. The cyclone continued moving westward with significant acceleration occurring by 1500 UTC. Matthew made landfall along the extreme eastern coast of Honduras late in the afternoon hours of September 24 with 45 kt winds. Within hours, Matthew turned to the west-northwest, and emerged into the Gulf of Honduras near 0900 UTC September 25. The cyclone was severely weakened during this time due to passage over the rugged terrain of Honduras, but was nevertheless still a tropical storm.

Matthew quickly moved inland over Belize, and also quickly weakened to a tropical depression. Matthew dissipated over western Guatemala near 1500 UTC September 26.



Figure 15. Track of Tropical Storm Matthew.

Tropical Storm Nicole: September 28 - September 29

Nicole was a short-lived tropical storm that threatened south Florida but dissipated before reaching it. The remnants of the cyclone, in conjunction with an approaching cold front, produced record-breaking floods across portions of North Carolina.

Nicole's genesis appears to have been initiated by the complex interaction between an area of disturbed weather over the extreme southwest Caribbean Sea, which became evident on September 25 to the north of Panama, and remnant energy from former Tropical Storm Matthew. The area of disturbed weather over the southwestern Caribbean moved slowly northward, while Matthew continued moving west-northwest over the rugged terrain of Central America and southeastern Mexico. Initially, the system appeared to be consolidating to the east of Nicaragua on September 26, but this was short-lived as on September 27, the area moved closer to Matthew's dissipating circulation, the latter of which was pushed eastward back into the western Caribbean Sea by an approaching cold front moving across the Gulf of Mexico. This triggered a widespread and highly disorganized area of showers and thunderstorms. Because of the broad nature of the system at this point, several areas of vorticity rotating about a mean center were evident throughout much of the day on the 27th.

Despite this, convection began to steadily consolidate throughout the day while the system was located a couple hundred miles southeast of the Isle of Youth, and a broad area of low pressure developed within the system early that day. The system was still quite broad at this point, however, with several areas of competing vorticity. It is assumed that the low gained enough organization to be designated a tropical depression near 1500 UTC September 28 while centered about 180 miles south of Havana, Cuba. The tropical cyclone moved northeast to north-northeastward with little change in strength, as the atmospheric environment was not conducive for strengthening, with strong southwesterly to south-southwesterly vertical wind shear impinging upon the system from the previously mentioned cold front. In addition, the strongest winds and heaviest precipitation were confined primarily to the southeast of the center, with very little deep convection and strong wind noted near the broad center.

Early on September 29, satellite imagery and surface observations indicate that the depression reformed its center a little to the east. Such situations are not uncommon in struggling tropical cyclones such as this one. The system moved inland along the south-central coast of Cuba to the east of Havana near 0600 UTC that day. Shortly thereafter, deep convection began to increase substantially to the south of the center over the northwestern Caribbean Sea. The cyclone became a tropical storm near 1500 UTC while still centered over central Cuba. Nicole emerged over the Florida Straits shortly thereafter, where its low-level center became very poorly-defined and diffuse. The cyclone dissipated near 2100 UTC September 29 while still moving across the Florida Straits. The remnants of Nicole eventually became absorbed into a large baroclinic system that developed over the mid-Atlantic. Nicole's remnant tropical moisture interacted with the aforementioned extratropical cyclone to generate record, flooding rainfall across a wide portion of North Carolina.



Figure 16. Track of Tropical Storm Nicole.

Hurricane Otto: October 6 - October 10

Otto was a minimal hurricane that remained harmlessly out to sea.

The precursor to Otto was a tropical wave that crossed the coast of Africa on September 26. Very little convection was noted with the wave over the next several days as it tracked westward. As the system interacted with a mid- to upper-level trough over the central Atlantic Ocean on September 29, however, convection increased somewhat. The wave continued to produce deep convection over the next several days, but lacked a well-defined surface circulation center. As the wave moved across the northern Leeward Islands on October 4, surface observations and scatterometer data indicate that the system was composed of a broad and elongated trough of low pressure. The system gradually became better defined, and satellite and surface observations suggest that the system became a subtropical depression near 0600 UTC October 6 while located about 230 miles north-northwest of San Juan, Puerto Rico. The subtropical designation was chosen because the surface low of the cyclone was underneath an upper-level trough and the storm also had a large radius of maximum wind.

Six hours later, the depression became a subtropical storm. Otto decelerated and turned north-northwest while it steadily intensified. By 0000 UTC October 7, reconnaissance aircraft observations indicate that Otto's winds increased to near 55 kt. Shortly thereafter, banding features became less defined, and, as Otto drifted northward during the overnight and early morning hours of October 7, it weakened. Early that day, however, deep convection formed near the center, and Otto made the transition to a tropical storm near 1200 UTC. Subsequently, the cyclone intensified, becoming a hurricane by 1200 UTC October 8, and reached its peak intensity of 75 kt about 12 hours later. During that time, Otto accelerated northeastward under the influence of a trough to the west. Vertical wind shear increased on October 9, which caused the storm to weaken, falling below hurricane status that evening. By 0600 UTC October 10, Otto became extratropical while centered about 900 miles east-northeast of Bermuda.

The gradually weakening extratropical remnants of Otto were identifiable for another four days. Initially, the extratropical cyclone moved northeastward but then slowed and turned southeast near the Azores on October 12 and 13. By 0600 UTC October 14, the system lost its frontal characteristics and became a swirl of low clouds. The system slowed further at this point and eventually dissipated about 250 miles west of Morocco near 0000 UTC October 18.



Figure 17. Track of Hurricane Otto.

Hurricane Paula: October 11 - October 15

Paula was a small but powerful Category 2 hurricane that made landfall along the extreme northern portion of western Cuba as a strong tropical storm. Paula dissipated over the Florida Straits thereafter.

A weak area of showers developed to the north of Panama late on October 4. The system produced some deep convection over the next several days as it drifted northwestward, eventually generating an area of low pressure near 1800 UTC October 7 while located across the southwestern Caribbean Sea. A very dry airmass, along with some southeasterly vertical wind shear associated with an upper-level anticyclone centered across the eastern Caribbean Sea, inhibited development of this low over the next several days. The system became a little better organized throughout the day on October 10, but strong vertical shear would ensure that the associated convection did not cover the center. The system continued to display signs of organization as it continued moving slowly northwestward, and it is possible that a westward-moving tropical wave assisted the eventual development of this system. The system approached the coast of Nicaragua on the morning of October 11, and nearly moved ashore. The low remained just offshore, however, which enabled it to become a tropical storm that day near 1500 UTC while centered about 365 miles south-southeast of Cozumel, Mexico. Analysis of satellite imagery from earlier in the day suggests, however, that the system was probably a tropical depression several hours earlier.

Paula skirted the eastern coast of Honduras while intensifying. The cyclone became a hurricane near 0900 UTC October 12. Paula was an unusually small hurricane, and would remain that way throughout its lifetime. Shortly thereafter, Paula turned northward and decelerated as it felt the effects of a strong cold front moving across the central and northern Gulf Coast states and the adjacent Gulf of Mexico. The hurricane attained its peak intensity of 85 kt near 1745 UTC October 12. At that time, the tiny hurricane was located about 140 miles south-southeast of Cozumel. Paula passed just a little to the east of the northeastern tip of the Yucatan Peninsula on the morning of October 13. Shortly thereafter, Paula nearly stalled, and drifted slowly northeast to north-northeast toward the general direction of western Cuba. Paula gradually weakened from this point onward due to strong southwesterly shear associated with the aforementioned cold front, along with dry air entrainment from the Gulf of Mexico. Paula weakened to a tropical storm near 1500 UTC October 14, while simultaneously turning eastward.

The cyclone continued moving eastward with a gradual increase in forward speed, hugging the extreme northern coast of Cuba. The system made landfall along the extreme northern coast of Cuba near Puerto Esperanza late in the afternoon hours of October 14. Paula continued to traverse the coast roughly parallel to the Florida Straits. The cyclone weakened to a tropical depression near 0900 UTC October 15, as the system lost all its deep convection. Paula dissipated shortly thereafter.



Figure 18. Track of Hurricane Paula.

Hurricane Richard: October 21 - October 26

Richard was a Category 1 hurricane that made landfall along the coast of Belize in late October.

Richard's genesis can probably be linked to a tropical wave that moved off the coast of Africa late on October 2. The wave reached the eastern Caribbean Sea on October 10 and was not very distinct on satellite images at that time. The wave reached the southwestern Caribbean Sea on October 11, where it generated a small burst of thunderstorms. Over the next several days, the system moved very slowly and erratically and continued to generate disorganized shower activity over a large portion of the western and southwestern Caribbean Sea. The wave began to become more distinct and organized late on October 15 while centered north of Panama. The system spawned an area of low pressure early on October 18 and turned more to the northwest and then north. Throughout much of the day on October 20, the low drifted eastward whilst steadily organizing. Early on October 21, the system became a tropical depression while centered roughly 125 miles south of Grand Cayman.

The depression quickly turned southeastward while continuing to move only very slowly. Near noon on October 21, the depression became a tropical storm. Richard executed a very gentle counter-clockwise bend over the next several days, and passed very near the northeastern coast of Honduras late on October 23. The next day, Richard became a hurricane as it neared the Bay Islands of Honduras. The hurricane made landfall along the coast of Belize just to the south-southwest of Belize City near 0045 UTC October 25 as an 80 kt hurricane. After landfall, the hurricane's eye became better defined. In the past, frictional convergence between the land and the storm has been shown to temporarily tighten up the core of the storm, which can sometimes lead to some temporary intensification during and just after landfall. This appears to have been the case with Richard.

As such, Richard was slow to weaken, and the system was still a minimal hurricane several hours later while located near the Belize/Guatemala border. Shortly thereafter, Richard weakened to a tropical storm as it continued moving west-northwest and northwestward. The system weakened to a tropical depression near 1500 UTC October 25. Early on October 26, as Richard neared the Bay of Campeche, nearly all deep convection had dissipated, with only a loose and poorly-defined band of shallow precipitation remaining over the Yucatan Peninsula. Richard's center reached the Bay of Campeche near 0900 UTC October 26. The system dissipated shortly thereafter as it continued moving northwestward in the low-level flow. Strong west-southwesterly vertical shear and dry air prohibited the cyclone from regaining strength, despite sufficiently warm sea surface temperatures.



Figure 19. Track of Hurricane Richard.

Hurricane Shary: October 29 - October 30

Shary was a short-lived late October hurricane that threatened Bermuda but ended up passing to the east of the island without incident.

A cold front moved into the western Atlantic Ocean on October 19. On October 24, a concentrated and distinct area of showers began to detach from the front while located several hundred miles east of the Bahamas. The area of disturbed weather moved generally eastward over the next couple of days but remained disorganized due to strong upper-level shear. On October 26, the system interacted with an upper low that was centered a couple hundred miles to the southwest and began to generate a concentrated but disorganized mass of convection, which enabled it to gradually work its way from 200 mb to the surface. The upper low gradually moved westward and deamplified. This development was most favorable for tropical cyclogenesis, as it decreased the vertical shear over the system, and also lessened the dry air surrounding it. As a result, convection began to form closer to the center on October 27, and a poleward outflow channel also became apparent.

As the area moved west-northwestward to northwestward over the next day or two, it gradually became better organized. Organized bands of convection began to become prominent to the north of the low-level center, which was becoming better defined all the while. Persistent but shallow convection remained relatively close to the center throughout the 28th and into the 29th. By 0300 UTC October 29, the system was organized enough to be designated a tropical storm while centered about 350 miles south of Bermuda. At the time of genesis, Shary was still somewhat involved with the aforementioned upper cold low, which at this point was located several hundred miles to the south of the tropical cyclone. Shary was moving northwest at a fast forward clip of about 20 kt upon developing. A steady deceleration was noted as the cyclone came increasingly under the influence of a weak steering regime due to a strong cold front moving across the western Atlantic Ocean.

Shary turned northward late on October 29, then accelerated toward the northeast shortly thereafter as it came under the influence of mid- to upper-level southwesterly flow associated with the western Atlantic trough/cold front. Shary passed to the east of Bermuda early on October 30. Interestingly, despite moving over progressively cooler waters, as well as battling strong southwesterly vertical shear associated with the cold front, microwave satellite images during the early part of October 30 indicated that Shary had developed an eye, although this eye was not evident on conventional satellite imagery. Concurrent with this development, deep convection increased substantially near the center, where it had previously been lacking. Based on this, it is assumed that Shary became a hurricane near 0900 UTC that day while centered about 325 miles east-northeast of Bermuda. Late that day, Shary had become absorbed by the cold front as it quickly overtook the tropical cyclone.



Figure 20. Track of Hurricane Shary.

Hurricane Tomas: October 29 - November 7

Tomas was a Category 2 hurricane that impacted portions of the Windward Islands, especially Barbados and St. Lucia, with the latter reporting sustained winds of 80-85 kt. Tomas was the most damaging hurricane for the island since Hurricane Janet in 1955.

Tomas then weakened but ultimately restrengthened to a minimal hurricane before impacting western Haiti and extreme eastern Cuba as a Category 1. Fortunately, flooding in Haiti was not as severe as originally anticipated. Tomas then impacted the Turks and Caicos Islands before becoming extratropical over the open Atlantic Ocean.


Tomas developed from a vigorous tropical wave which crossed the coast of Africa on October 20. The system displayed unusually deep convection for such a late-season tropical wave. Convection soon waned, however, as the wave marched steadily westward across the eastern tropical Atlantic Ocean. An increase in thunderstorm activity was noted on October 26 while the system was centered several hundred miles east of the southern Windward Islands. The wave began to show signs of organization throughout the day on October 27, especially late in the day, with some banding features noted. Indeed, the wave spawned a surface low near 1800 UTC that same day. Convection increased near the consolidating low-level center near 0900 UTC October 29 while the system was located a few hundred miles southeast of the southern Windward Islands. Banding features also became better defined during this time. The system continued to organize, and became a tropical storm near 2100 UTC that day while centered about 200 miles southeast of Barbados.

Tomas moved steadily west-northwest toward the Windward Islands while intensifying. Such a motion is quite uncommon, climatologically speaking, for a tropical cyclone this far east in the Atlantic during late October. Alas, the subtropical ridge was anomalously strong to the north of Tomas during the first several days of the tropical cyclone's existence. Tomas passed near Barbados early on October 30, and became a hurricane shortly thereafter while centered about 40 miles south-southeast of St. Lucia. Late that day, Tomas moved very near St. Lucia, with its northern eyewall producing sustained winds near 80-85 kt on that island. Tomas intensified to its peak intensity of 85 kt, Category 2 strength, near 0600 UTC October 31 as it began to pull away from the Windward Islands. The hurricane turned westward late that day as the subtropical ridge to the north strengthened. All the while, Tomas was weakening steadily as it came under the influence of strong upper-level westerly vertical wind shear.

The system weakened to a tropical storm near 0300 UTC November 1 while moving across the eastern Caribbean Sea. Tomas moved south of west for a fair bit of the day, but then turned to a more steady westward course. Tomas turned back to the west-northwest near 0900 UTC November 3 as it weakened to a tropical depression. Satellite images during this time indicate that the tropical cyclone was embedded within a large area of disturbed weather across the southwest and south-central Caribbean Sea. Indeed, the system nearly dissipated during this time, with the low-level circulation becoming broad and elongated. Nevertheless, Tomas was ultimately able to overcome the negative influence of the large monsoon gyre in which it was embedded, and the cyclone regained tropical storm status near 2100 UTC that day while centered about 305 miles south-southwest of Port-au-Prince, Haiti. During this time, Tomas was moving slowly northwest to north-northwest as it began to feel the effects of a major cold front moving into the western Atlantic.

The cyclone turned north-northeastward early on November 4. Tomas became a hurricane again near 0900 UTC November 5 as it approached the southwestern peninsula of Haiti, with winds increasing to 70 kt. Tomas passed very near the southwestern peninsula of Haiti near 1200 UTC that day, reaching its peak of 75 kt while doing so. Tomas passed between eastern Cuba and western Haiti, and the hurricane moved through the Windward Passage late that day. Southwesterly shear began to increase on November 6 as Tomas accelerated northeastward under the influence of the aforementioned cold front. As a result, Tomas fell below hurricane intensity near 0900 UTC that day as it passed over the Turks and Caicos Islands. Tomas regained hurricane intensity near 2315 UTC that day while moving northeastward across the Atlantic about 250 miles north-northeast of Grand Turk Island. The system's winds increased to 70 kt by 0000 UTC November 7. The system decelerated significantly as it came underneath the influence of weak steering currents ahead of the cold front.

Tomas became extratropical near 2100 UTC November 7 while located about 500 miles south-southwest of Bermuda. The system became absorbed by the cold front the next day.



Figure 21. Track of Hurricane Tomas.

Seasonal totals

Tropical cyclones: 21
Named storms: 19
Hurricanes: 12
Major hurricanes: 5
Category 5's: N/A
ACE: 160

List of storms

Hurricane Alex
Tropical Depression Two
Tropical Storm Bonnie
Tropical Storm Colin
Tropical Depression Five
Hurricane Danielle
Hurricane Earl
Tropical Storm Fiona
Tropical Storm Gaston
Tropical Storm Hermine
Hurricane Igor
Hurricane Julia
Hurricane Karl
Hurricane Lisa
Tropical Storm Matthew
Tropical Storm Nicole
Hurricane Otto
Hurricane Paula
Hurricane Richard
Hurricane Shary
Hurricane Tomas



Figure 22. Tracks of all observed tropical cyclones during the 2010 Atlantic hurricane season.

2010 Pacific hurricane season

The 2010 Pacific hurricane season was the quietest on record since routine satellite measurements of that basin began in 1971. Only seven named storms were observed, though there were several unnamed tropical depressions that failed to become tropical storms. Additionally, there were only three observed hurricanes, with two of these reaching major hurricane intensity (sustained winds of 111 mph or greater). These numbers are well below the long-term average of 15 named storms, 8 hurricanes, and 3 major hurricanes, respectively. Indeed, likely due in part to a cold PDO (Pacific Decadal Oscillation), the Eastern Pacific basin has been unusually quiet since 1995. Of course, the current state of the PDO doesn't tell the whole story, and it is obvious that this year's strong La Nina event also played a critical role in the large amount of inactivity that this season experienced.

Unlike in the Atlantic, where La Nina is notorious for reducing the mean vertical wind shear, keeping the jet stream locked in a more northerly mean position throughout the summer, this phenomenon is known for producing an opposite effect in the East Pacific. La Nina is characterized by anomalous cooling of the sea surface temperatures from the equatorial coast of South America westward to the International Dateline. Due to the unusually cool water temperatures in that part of the basin, the extra heat energy (instability) that is present during neutral ENSO or El Nino years is severely compromised. As a corollary, the primary focus for heat energy (convection) is confined to the Atlantic, including the Caribbean Sea. This greatly reduces the amount of heat energy available in the basin for tropical cyclogenesis.

The mean vertical wind shear also increases dramatically in the basin during La Nina events due to increased upper-level easterly flow.

In terms of Accumulated Cyclone Energy (ACE), this season produced values well below the long-term mean, with an index of only 49.6 observed. The bulk of this ACE was contributed during the month of June, where the highest total ever observed during the month occurred, eclipsing the old record last set in 1984.

The season began early with the formation of Tropical Storm Agatha on May 29. Agatha moved northeastward and crossed the Mexico/Guatemala border late that day. Agatha dissipated on May 30, but its remnants entered the western Caribbean Sea and generated some deep convection on May 31 and June 1.

Tropical Depression Two-E came perilously close to making landfall along the coast of central Mexico during the middle of June, but dissipated before it was able to do so. The remnants of the depression produced heavy rainfall across portions of Mexico over the following couple of days.

Hurricane Celia was a powerful Category 5 hurricane that remained over the open waters of the basin. Not only was Celia notable for this feat, it was even more notable for being the strongest June hurricane in the basin since Hurricane Ava in 1973.

Hurricane Darby was another June major hurricane that dissipated before reaching the southwest coast of Mexico. With the formation of two major hurricanes by June 25, Darby made history, becoming the earliest second major hurricane on record, surpassing the old record last set in 1978, when Hurricane Daniel became a major hurricane on June 30.

Tropical Storm Georgette was a short-lived tropical storm that made landfall along the southeastern tip of the Baja Peninsula, then made a second landfall along the west coast of Mexico as a tropical depression.

Monthly summaries

May

One tropical cyclone, Tropical Storm Agatha, was observed during the month. On average, a tropical storm develops every other May.

June

June was a remarkably active month, with three named storms and two hurricanes observed (Blas, Celia, and Darby). Both hurricanes were major hurricanes. In addition, one short-lived tropical depression formed during the month. On average, about two tropical storms and one hurricane form every June, with a major hurricane occurring about once every other year.

July

After a remarkably active start to the season, no named storms were observed during the month of July. This is a very rare event, having last occurred in 1966. Despite this, however, one tropical depression did form during the month. On average, about four named storms, two hurricanes, and one major hurricane occur during the month.

August

Two named storms, Estelle and Frank, were observed during the month. In addition, one unnamed tropical depression also developed. Frank became a hurricane. These numbers are well below the long-term average of 4 named storms, 2 hurricanes, and 1 major hurricane for the month.

In terms of ACE, August saw an index that was roughly 40% of norm.

September

Three tropical cyclones were observed during the month, but only one of these became a tropical storm (Georgette). On average, three named storms, two hurricanes, and one major hurricane are observed during the month.

In terms of ACE, this is the quietest September on record since the satellite era began in 1971.

October

The month of October saw no tropical cyclones. On average, two named storms and one hurricane form every year, with a major hurricane occurring about once every other year.

November

No tropical cyclones were observed during November. On average, a named storm occurs during the month every few years.

Individual storm summaries

Tropical Storm Agatha: May 29 - May 30

Agatha was a weak tropical storm that impacted portions of southeast Mexico and Central America with torrential rains. These rains generated floods that killed hundreds, primarily in Guatemala.

Agatha had a rather complex origin. The primary weather system responsible was a tropical wave that crossed the coast of Africa on May 8. The wave crossed Central America on May 21. Shower activity increased on May 24 while the system was centered a few hundred miles west of Costa Rica. The next day, the system developed a broad surface low pressure area, and the first Dvorak classifications were initiated. However, the low failed to become much better organized over the next several days as it moved westward to a position a few hundred miles south of the Gulf of Tehuantepec. During this time, two additional tropical waves crossed Central America and were ultimately entrained into the broad area of low pressure. It is unclear what effect these waves had, if any, on the eventual genesis of Agatha.

On May 28, an ASCAT pass indicated that the low-level circulation was becoming better organized. The system became a tropical depression near 0000 UTC May 29 while centered about 155 miles southwest of Tapachula, Mexico. The newly-developed tropical cyclone moved northeastward between a mid- to upper-level trough over the Gulf of Mexico and a mid- to upper-tropospheric ridge over the western Caribbean Sea. Six hours later, the depression became a tropical storm. Agatha reached a peak intensity of 40 kt near 1800 UTC that same day, with landfall occurring near Champerico, Guatemala near 2230 UTC. At the time of landfall, Agatha was still packing winds of 40 kt. The cyclone weakened as it continued moving northeastward into the mountains of the Sierra Madre. Agatha dissipated on May 30 while centered across western Guatemala.

The remnants of the tropical cyclone may have contributed to the formation of a broad surface low over the western Caribbean Sea on May 31.



Figure 23. Track of Tropical Storm Agatha.

Tropical Depression Two-E: June 16 - June 17

Tropical Depression Two-E was a short-lived tropical depression that moved very close to the southern coast of Mexico before dissipating. The remnants produced heavy rains, but no damage or fatalities were reported.

A tropical wave moved off the coast of Africa on June 2. The wave entered the East Pacific on June 13-14. Convective organization began to increase as the system neared the Gulf of Tehuantepec, and it is assumed that the system spawned a tropical depression near 0600 UTC June 16. At the time of genesis, the depression was centered about 95 miles south of Salina Cruz, Mexico. Strong northeasterly shear kept the associated deep convection confined to the west and southwest of the low-level center as the cyclone moved slowly west-northwest. By 1630 UTC June 16, ASCAT data indicated that the depression reached a peak intensity of 30 kt. However, by 0000 UTC June 17, convection became disorganized and conventional and microwave satellite data indicate that the depression lost its well-defined low-level center by 0600 UTC that day, signifying the demise of this short-lived tropical cyclone.



Figure 24. Track of Tropical Depression Two-E.

Tropical Storm Blas: June 17 - June 21

Blas was a tropical storm that remained out in the open waters of the eastern Pacific basin during the middle to latter part of the month of June.

The development of Blas was triggered by a tropical wave that moved off the coast of Africa on May 30. The wave traversed the Atlantic Ocean for the next ten days, producing very little deep convection. An increase in the associated convection was noted on June 9-10 as the system crossed Central America. By June 13, an area of low pressure developed along the wave axis. Two days later, the system closed off its surface circulation. The low meandered from June 15-17, and convection was not persistent enough during this period to designate the system a tropical cyclone. Finally, convection began to become persistent early on June 17, and it is estimated that the system became a tropical depression near 0600 UTC that day while located about 265 miles south-southwest of Manzanillo, Mexico. A ship report near 1500 UTC of 40 kt sustained surface winds in the tropical cyclone indicate that Blas became a tropical storm near 1200 UTC.

Blas accelerated toward the northwest then west-northwest under the influence of a building mid-tropospheric anticyclone to the east. Through 1800 UTC June 18, strong northeasterly vertical wind shear prevented any significant intensification of Blas. Subsequently, the shear abated somewhat, allowing the cyclone to reach its peak intensity of 55 kt by 1200 UTC June 19. Shortly thereafter, Blas began to move into a more stable airmass associated with the 26C SST isotherm. Consequentially, deep convection diminished significantly, and Blas weakened to a tropical depression near 0000 UTC June 21 and became a remnant low near 1800 UTC that day while centered about 620 miles west-southwest of the southern tip of Baja California. The remnants moved generally westward over the next 24 hours, and dissipated after 0000 UTC June 23.



Figure 25. Track of Tropical Storm Blas.

Hurricane Celia: June 18 - June 28

Celia was a strong Category 5 hurricane that reached an estimated peak intensity of 140 kt while moving across the eastern Pacific basin. Celia was the strongest June hurricane since Hurricane Ava in 1973.

Celia developed from a tropical wave that emerged from the coast of Africa on June 5. The wave moved westward across the Atlantic Ocean with little incident, entering the Eastern Pacific basin by June 17. Convection associated with the slow-moving wave increased later that day, and a surface low developed along the wave axis near 0600 UTC June 18 while centered about 230 miles southeast of Puerto Escondido, Mexico. Over the ensuing 12 to 24 hours, a well-defined curve convective band developed to the north of the center, and it is estimated that the system became a tropical depression near 1800 UTC that day, located about 320 miles southeast of Acapulco, Mexico. Though the low-level center became better defined over the next several hours, convection associated with the system practically vanished by 0000 UTC June 19. Deep convection returned over the next several hours, while the cloud pattern became better organized. The depression became a tropical storm near 1145 UTC June 19. At this time, Celia was centered near 290 miles south-southeast of Acapulco.

The cyclone moved slowly west-southwest to westward over the next few days. This movement was the result of the cyclone being dominated by low-level westerly flow and upper-level northeasterly flow. The discrepancy between the low- and upper-level flow created moderate northeasterly vertical wind shear over the tropical cyclone, but Celia was nonetheless able to steadily intensify, attaining hurricane status by 1800 UTC June 20 while located about 310 miles south of Acapulco. Over the next couple days, however, the shear increased further, and prevented Celia from significantly intensifying. As a result, the hurricane's intensity fluctuated between 65 and 85 kt from 1800 UTC June 21 until 1200 UTC June 13. Early on June 23, Celia began moving just north of due west with some acceleration. Northeasterly shear decreased over the system, which allowed the hurricane to intensify fairly quickly; its intensity increased from 75 kt at 0600 UTC to 95 kt by 1800 UTC that day.

Shortly thereafter, however, the convective pattern associated with the hurricane became less organized, and the well-defined eye that had appeared earlier became less apparent as northeasterly shear once again increased. Celia continued for another 6 to 12 hours, but the inner core reorganized thereafter. During this time, vertical wind shear over the hurricane decreased. As a result, Celia underwent a period of rapid intensification as it moved west-northwestward in response to an amplifying mid- to upper-level trough that weakened the subtropical ridge to the north. Within just 18 hours, Celia's intensity went from 90 to 140 kt, with Celia reaching its peak near 0000 UTC June 25 as a Category 5 hurricane. The hurricane weakened rapidly over the next several days as it moved across progressively cooler water and entered a more stable airmass. Early on June 26, the storm fell below major hurricane intensity and by 0000 UTC June 27, Celia weakened to a tropical storm while located about 830 miles west-southwest of the southern tip of the Baja Peninsula.

Abruptly, Celia slowed down on June 27 as the western periphery of the subtropical ridge eroded further as a result of the aforementioned trough, which at this time was amplifying along the west coast of the United States. Celia lost nearly all of its associated convection and decelerated even further while bending to the west-southwest to southwest in the lower-tropospheric steering flow on June 28. Thereafter, Celia turned east-northeast in response to low-level westerly flow. The cyclone completed a counter-clockwise loop and became a remnant area of low pressure near 0000 UTC June 29 while centered about 900 miles west-southwest of the southern tip of the Baja Peninsula. Celia's remnants drifted northward for another day before dissipating.



Figure 26. Track of Hurricane Celia.

Hurricane Darby: June 23 - June 28

Darby was the third tropical storm to form during the month of June, marking the end to an exceptionally active month. Darby was also the earliest formation of a second major hurricane, eclipsing the previous record set by Hurricane Daniel in 1978. Darby remained out at sea, but its remnants eventually approached the coast of southern Mexico as they moved around the southern periphery of large Atlantic Hurricane Alex.

A vigorous tropical wave moved off the coast of Africa on June 8. The wave lost nearly all of its associated convection within 24 hours of moving over water. The wave continued moving westward across the Atlantic Ocean, and failed to generate significant convection until it reached the far East Pacific on June 19. On June 20, a small area of low pressure developed along the wave axis about 150 miles southwest of Costa Rica. During this time, the low decelerated and turned to the west-northwest. Convection gradually increased and became better organized, and the wave became a tropical depression near 0000 UTC June 23 while located about 330 miles south-southeast of Salina Cruz, Mexico. The cyclone quickly strengthened, becoming a tropical storm by 0600 UTC June 23. By 0600 June 24, Darby became a hurricane. The storm would slow even further over the next few days as it continued moving west-northwest, with the forward speed decreasing to less than 5 kt by June 26. Darby remained in an environment of weak vertical shear during this time and underwent two periods of rapid intensification -- the first was experienced from 30 to 60 kt from 0000 UTC June 23 to 0000 UTC June 24. The second was experienced from 1800 UTC June 24 to 1800 UTC June 25, during which time the cyclone's winds increased from 75 to 105 kt. This would turn out to be Darby's peak intensity; it was centered about 215 miles south-southwest of Acapulco, Mexico during this time.

Subsequently, the small hurricane turned westward with deceleration. Early on June 27, a large area of low- to mid-tropospheric westerly flow emanating from large and powerful Hurricane Alex, located to the northeast of Darby over the southwestern Gulf of Mexico, briefly caused Darby to become stationary about 250 miles south-southwest of Zihuatanejo, Mexico. Later that day, Darby turned east-northeastward as it began to become pulled into the large circulation of Alex. Darby began to weaken during this time as strong northeasterly vertical wind shear associated with the upper-level outflow of Alex impinged upon the system. Indeed, Darby weakened quicker than it had strengthened, becoming a tropical storm near 0600 UTC June 27. By 1200 UTC June 28, Darby weakened to a tropical depression while located more than 150 miles south of Acapulco. Six hours later, Darby became a remnant area of low pressure as the aforementioned shearing winds aloft effectively removed the deep convection from the center of the tropical cyclone.

Darby continued to move slowly east-northeast into the Gulf of Tehuantepec, during which time a brief convective burst occurred to the south of the center early on June 29. The convection failed to persist, however, and Darby dissipated after 1800 UTC that same day while centered offshore the southern coast of Mexico.



Figure 27. Track of Hurricane Darby.

Tropical Depression Six-E: July 14 - July 16

Tropical Depression Six-E was a short-lived tropical depression that did not make landfall.

The depression developed from a tropical wave that emerged from the African coast on June 28. The wave moved across Central America and entered the Eastern Pacific basin on July 9. A couple days later, the wave spawned a broad area of low pressure to the south of the Guatemalan coast. As the system passed south of the Gulf of Tehuantepec on July 12, convection increased. The low moved west-northwest parallel to the southern coast of Mexico, and the low-level circulation became better defined. The system displayed curved convective bands along the western semicircle early on July 14. By 1200 UTC that day, the system became a tropical depression while centered about 285 miles south-southwest of Manzanillo, Mexico. Initially, the cyclone moved west-northwestward under the influence of low- to mid-tropospheric ridging to the north. The next day, however, the system turned to the northwest as the ridge weakened.

Moderate easterly shear prohibited strengthening of the cyclone, and as the system moved across cooler waters on July 16, deep convection disappeared later that day. By 1800 UTC that same day, the depression degenerated into a broad area of low pressure. The remnant low turned west to west-northwest; this general heading would continue until the system dissipated by 1200 UTC July 18, during which time it was located about 600 miles west-southwest of the southern tip of the Baja Peninsula.



Figure 28. Track of Tropical Depression Six-E.

Tropical Storm Estelle: August 6 - August 10

Estelle was a strong tropical storm that was notable for ending a prolonged lack of tropical cyclone activity over the eastern Pacific basin during what is normally a very busy portion of the season. Estelle was the first tropical storm to form in the basin in 44 days.

Estelle was spawned from a tropical wave that left the coast of Africa on July 22. The wave produced little convection until it entered the eastern Caribbean Sea on July 29, where it interacted with an upper-level trough. The wave displayed some signs of organization on satellite imagery as it entered the western Caribbean Sea, but the system moved across Central America on August 2 and was thus not able to organize significantly. The wave produced a large area of convection over southeast Mexico late on August 3, with a thunderstorm complex moving southward from the Isthmus of Tehuantepec into the far eastern Pacific. Subsequent to the dissipation of this thunderstorm complex, a weak area of low pressure developed just south of the Gulf of Tehuantepec the next day. The low moved west-northwest and gradually became better organized. The system became a tropical depression near 0000 UTC August 6 while centered about 120 miles southwest of Acapulco, Mexico. The system strengthened to become a tropical storm about 12 hours later.

The cyclone apparently had a center reformation early on August 7, as indicated by analysis of microwave satellite imagery during this time, but in general, Estelle continued moving west to west-northwest to the south of the subtropical ridge. Early on August 8, Estelle reached its peak intensity of 55 kt, with a mid-level eye feature evident on microwave imagery during this time. Thereafter, the cyclone gradually weakened under the influence of cooler waters, a more stable thermodynamic environment, and increasing southeasterly vertical wind shear. Late on August 8, Estelle turned westward with deceleration. On August 9, a further increase in shear was noted which caused Estelle to weaken to a tropical depression near 1800 UTC that day. The cyclone became a remnant low about 12 hours later while it was located about 370 miles south-southwest of the southern tip of the Baja Peninsula. The remnants drifted to the southeast and were ultimately entrained into the Intertropical Convergence Zone (ITCZ) on August 10.



Figure 29. Track of Tropical Storm Estelle.

Tropical Depression Eight-E: August 20 - August 22

Tropical Depression Eight-E was a short-lived tropical depression that remained away from the coast of Mexico.

This tropical cyclone appears to have been ignited by a tropical wave that emerged from the coast of Africa on August 4. The wave produced a respectable storm cluster as it exited the coast, but this activity dissipated on August 5. Nevertheless, the wave displayed some signs of organization in the observed cloud pattern as it traversed the eastern Atlantic over the next few days, with a distinct low- to mid-level circulation noted. As the wave interacted with an upper-level trough centered to the north of the Greater Antilles on August 11, an increase in convection was noted on satellite imagery. The wave entered the eastern Pacific on August 16, subsequent to traversing Central America. The wave remained fairly indistinct on satellite imagery until late on August 17, when an increase in shower activity was noted to the south of Acapulco, Mexico. The system moved slowly but steadily to the northwest and an area of low pressure developed along the wave axis on August 19 while located several hundred miles south of the southern tip of the Baja Peninsula.

Concurrently, deep convection began to increase substantially. This convection displayed signs of organization, but was displaced to the west of the low-level center due to strong easterly shear. The system gained enough organization to be designated a tropical depression near 1230 UTC August 20, located about 230 miles west of Manzanillo, Mexico. Easterly shear continued to arrest development as the cyclone moved slowly to the northwest. The storm turned west-northwest early on August 21 as it became a shallower cyclone and became steered by the lower-tropospheric flow. The system dissipated near 0300 UTC August 21, with most of the associated convection having dissipated. The remnants continued westward for the next day or so before losing their identity.



Figure 30. Track of Tropical Depression Eight-E.

Hurricane Frank: August 21 - August 28

Frank was a Category 1 hurricane that remained largely out to sea during late August, though the system did come fairly close to Socorro Island.

The tropical wave that generated Frank was difficult to track from Africa. It was first identified as an area of convection and a low-level wind shift near the southern Windward Islands on August 15. The amount of convection associated with the wave fluctuated as it moved across the Caribbean Sea over the next several days, but satellite images during this time suggested that there was a distinct cyclonic circulation at the mid-levels of the atmosphere. As the wave traversed Central America on August 19, deep convection increased, but did not become concentrated until August 21 while over the Gulf of Tehuantepec, during which time the area of low pressure associated with the wave became better defined. Curved bands developed later that day, and deep convection also increased near the center. Consequently, it is estimated that the system became a tropical depression near 1800 UTC that day while centered about 180 miles southeast of Salina Cruz, Mexico.

The depression drifted westward in an environment of weak steering currents. Over the next day, the depression changed little in organization. Nevertheless, the system became a tropical storm near 1200 UTC August 22. Frank moved westward at about 6 kt parallel to the Mexican coastline while intensifying. However, Frank weakened on August 23 as strong northeasterly shear impinged upon the system and weakened the convection. The next day, convection refired and reorganized. Near 1200 UTC August 25, Frank became a hurricane after analysis of microwave imagery revealed an eyewall. Over the next day or so, the eye was intermittently apparent on conventional satellite images, but it remained well-defined on microwave images. At 1800 UTC August 26, Frank attained its peak intensity of 80 kt while located about 300 miles south of the southern tip of Baja California.

Thereafter, Frank began to weaken as it moved toward the northwest and all associated deep convection dissipated when it encountered cooler waters and strong vertical wind shear. At 1800 UTC August 28, the cyclone became a broad area of low pressure while centered about 200 miles southwest of the southern tip of the Baja Peninsula.



Figure 31. Track of Hurricane Frank.

Tropical Depression Ten-E: September 3 - September 4

Tropical Depression Ten-E was another short-lived tropical depression that remained out at sea.

A tropical wave emerged from the coast of Africa on August 14. The wave produced little deep convection as it traveled across the Atlantic Ocean, but shower activity began to increase on August 26 when the wave moved across Central America and entered the eastern Pacific basin. Over the next several days, the associated convection remained disorganized and displaced to the west of the low-level center due to strong upper-level easterly vertical wind shear. Shower activity became better organized on September 1 and 2, but the system lacked a well-defined surface circulation during that time. Near 0000 UTC September 3, however, the system gained enough organization to be considered a tropical depression while centered about 220 miles south-southeast of the southern tip of the Baja Peninsula. Over the next day or so, the cyclone moved northwestward between a ridge over Mexico and an upper-level trough to the west, over the open waters of the basin.

The depression failed to strengthen due to strong easterly shear and quick passage over cooler sea surface temperatures. On September 4, the depression moved over cooler waters and degenerated into a remnant low by 1200 UTC that day while centered about 160 miles west-southwest of the southern tip of the Baja Peninsula. The remnants of the cyclone moved northwestward for the next day or so before dissipating.



Figure 32. Track of Tropical Depression Ten-E.

Tropical Depression Eleven-E: September 3 - September 4

Tropical Depression Eleven-E was a short-lived tropical depression that made landfall along the southeastern Mexican coast as a 30 kt tropical depression. The remnants of the depression contributed to the formation of Atlantic basin Tropical Storm Hermine over the southwest Gulf of Mexico.

The depression produced heavy rains over portions of southeast Mexico, but no damage or casualty reports have been received.


The genesis of the depression can probably be attributed to a tropical wave that emerged from the coast of Africa on August 20. Despite a very favorable atmospheric and thermodynamic environment present across the eastern Atlantic Ocean during this time, significant development of this wave appears to have been inhibited by Hurricane Danielle to the west, and a convectively active tropical wave to the east, the latter of which would ultimately become Hurricane Earl. The wave was very difficult to track on satellite imagery over the next several days, and it appears that the wave was briefly absorbed by Danielle on August 22. The wave managed to break free from Danielle's influence on August 25, however, but it still remained very weak and diffuse at that time. The wave entered the eastern Caribbean Sea on August 26, generating a weak area of showers subsequent to passing through the Windward Islands.

Convection began to increase with the system on August 27 as it moved across the south-central Caribbean Sea. The wave continued westward and generated a large area of cloudiness and thunderstorms across the southwest and western Caribbean Sea on August 28. The system entered the far eastern Pacific on August 29. The wave generated a widespread area of disorganized convection on September 2. This convection stretched from Costa Rica westward for several hundred miles to the south of Acapulco, Mexico. Convection began to become more focused on September 3 about 150 miles southeast of Salina Cruz, Mexico. Near 2300 UTC that day, the system became a tropical depression while centered about 95 miles southeast of Salina Cruz. Initially, the cyclone moved only slowly to the northwest, but as the surrounding steering regime became better defined, the depression experienced some acceleration. The system moved inland near Salina Cruz early on September 4, and dissipated shortly thereafter.

The remnants of the storm contributed to the development of Atlantic Tropical Storm Hermine over the southwest Gulf of Mexico.



Figure 33. Track of Tropical Depression Eleven-E.

Tropical Storm Georgette: September 20 - September 23

Georgette was a weak tropical storm that made two landfalls: one along the southern tip of the Baja Peninsula, and another along the mainland of western Mexico. The second landfall occurred as a tropical depression.

Georgette developed from a tropical wave that crossed the coast of Africa on September 1. Little deep convection was noted with the wave until it approached the Lesser Antilles on September 9. As the wave progressed through the Caribbean Sea, a portion of it spawned Atlantic Hurricane Karl in the western Caribbean on September 14. The remainder of the wave continued westward and crossed Mexico on September 17 and 18 and entered the eastern Pacific on September 19. Convection increased along the wave axis that day and on September 20, with a well-defined surface circulation becoming apparent near 1200 UTC that day. It is estimated that a tropical depression formed during this time while centered about 210 miles south-southeast of Cabo San Lucas, Mexico. Shortly after genesis, convection diminished substantially, likely as a result of strong easterly shear. Despite the reduction in the associated convection, however, an ASCAT pass over the cyclone near 1800 UTC suggest that the winds increased to 35 kt, marking the formation of a tropical storm during this time.

Upon forming, Georgette was centered roughly 180 miles south-southeast of Cabo San Lucas. The cyclone moved northwest to north-northwest under the influence of the western periphery of a mid-level ridge to the east over Mexico. Georgette made landfall along the southern tip of the Baja Peninsula near San Jose del Cabo around 1800 UTC September 21 with an intensity of 35 kt. After landfall, the cyclone continued northward across southeastern Baja California, weakening to a tropical depression by 0000 UTC September 22. Shortly afterward, Georgette moved into the Gulf of California and continued moving northward. Little change in strength was noted until the system made landfall along the western coast of mainland Mexico near San Carlos around 2200 UTC that day. Georgette dissipated over the mountainous terrain of western Mexico by 0600 UTC September 23.



Figure 34. Track of Tropical Storm Georgette.

Seasonal totals

Tropical cyclones: 12
Named storms: 7
Hurricanes: 3
Major hurricanes: 2
Category 5's: 1
ACE: 49.6

List of storms

Tropical Storm Agatha
Tropical Depression Two-E
Tropical Storm Blas
Hurricane Celia
Hurricane Darby
Tropical Depression Six-E
Tropical Storm Estelle
Tropical Depression Eight-E
Hurricane Frank
Tropical Depression Ten-E
Tropical Depression Eleven-E
Tropical Storm Georgette



Figure 35. Track map of all observed tropical cyclones during the 2010 East Pacific hurricane season.

Acknowledgments

National Hurricane Center
NOAA's GIBBS satellite archives
Wikipedia
Weather Underground

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2. traumaboyy
8:16 AM GMT on December 02, 2010
All I got is wow!!

Great job!!
Member Since: August 18, 2008 Posts: 0 Comments: 2266
1. MiamiHurricanes09
2:10 AM GMT on December 02, 2010
Impressive overview. Great read.
Member Since: September 2, 2009 Posts: 130 Comments: 21195

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About KoritheMan

I'm just a 23 year old with an ardent passion for weather. I first became aware of this interest after Tropical Storm Isidore struck my area in 2002.

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