Tropical Cyclone Report: Hurricane Kirk (AL112012)
Note: The Tropical Cyclone Report (TCR) below contains comprehensive, yet easily understandable, information on each tropical cyclone, including synoptic history, casualities and damages, provided by a multitude of different, official resources, and the post-season analysis best track (six-hourly position fixes and intensities). A tropical cyclone is defined as a warm-core, non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters with organized deep convection and a closed surface wind circulation about a well-defined center. These include depressions—cyclones that did not attain 34-knot sustained winds—storms, and hurricanes. It should be noted that, while I strive to produce the most accurate information for the particular cyclone listed below, these reports...including the storms' position and intensity...are not official and are no way associated with the National Hurricane Center or any other branch of the National Oceanic and Atmospheric Administration. Please visit the Atlantic TCR page and the East Pacific TCR page for official reports on any desired cyclone within a particular season.
Tropical Cyclone Report
Hurricane Kirk (AL112012)
Duration: 28 August – 2 September
By: TropicalAnalystwx13
Produced on: 28 November 2012
Kirk was a Category 2 (on the Saffir-Simpson Hurricane Wind Scale) over the eastern Atlantic that did not affect land as a tropical cyclone.
a. Synoptic history
A tropical wave, viewed with disorganized shower and thunderstorm activity and a defined area of cyclonic turning, exited the west coast of Africa and into the eastern Atlantic during the afternoon hours of 22 August. Initially, the wave slowly organized under a low wind shear, minimal dry air, and warm sea surface temperature environment, but a subsequent increase in vertical wind shear, due to a large upper-level low located roughly midway between the northern Leeward Islands and the Cape Verde Islands, led to the heavily sheared appearance on geostationary imagery by late on 23 August. As the wave rounded the southern periphery of an unusually strong ridge of high pressure in the northeastern Atlantic it continued to show a high level of low-level vorticity. A weakness in the ridge by 26 August allowed the wave to move more north-northwesterly into cooler waters and within a region of continued high wind shear. At the time, the prospects of tropical or subtropical development were lower than previously given, but a gradual decrease in wind shear on 28 August led to the formation of Tropical Depression Eleven at 1800z while centered about 1425 miles southwest of the Azores Islands. The best track positions and intensities are listed in Table 1 at the bottom of this entry (to be added).
Moderate southwesterly wind shear continued to impart on the depression shortly after formation due to the large upper-level low to its west over the Central Atlantic. The initial forecast was that this wind shear would prevent the depression from becoming anything more than a tropical storm, with absorption into a mid-latitude trough expected by five days out. However, a drop in wind shear, forecast only by the SHIPS and LGEM models, allowed for gradual intensification to occur. A tremendous burst of convection, with cloud tops cooler than -80 °C, occurred around 2100z, and satellite intensity estimates at 0000z the following day gave credence to the formation of Tropical Storm Kirk at that time. Wind shear initially kept the low-level center displaced slightly from the mid-level center, but by the pre-dawn hours of 30 August, a series of microwave passes indicated the development of an eyewall. At 1200z Kirk became a Category 1 hurricane on the Saffir-Simpson Hurricane Wind Scale, and by 1800z a well-defined eye was evident on geostationary imagery.
As cloud tops cooled in the eyewall and the inner-core temperature warmed, satellite intensity estimates increased enough to declare Kirk a Category 2 hurricane at 0000z on 31 August. By this time wind shear had finally decreased to conducive levels, as evidenced by upper-level low in the western quadrant of the system. Kirk reached its peak intensity of 95 knots, just below major hurricane intensity, at 0600z on 31 August before the storm began to enter cooler waters and a more stable air mass. The coldest cloud tops became displaced to the east of the low-level center and the inner-core structure dissipated; Kirk weakened back to a high-end Category 1 hurricane at 1200z before becoming a tropical storm once more at 1200z on 1 September. A small ball of convection fired the following morning as the tropical storm accelerated to the east-northeast across the open east-central Atlantic, but cooler sea surface temperatures and the influence of a frontal zone to the west of the cyclone cooled the core, transitioning Kirk into a post-tropical cyclone at 1800z on 2 September. The front imparting on the western side of the cyclone merged fully with the system over the course of the next few hours as Kirk continued over open seas, no threat to land.
b. Meteorological statistics
Observations used to determine the peak intensity of Hurricane Kirk include satellite intensity estimates from the University of Wisconsin's-Cooperative Institute for Meteorological Satellite Studies Advanced Dvorak Technique (UW-CIMSS), the Tropical Analysis and Forecasting Branch (TAFB), and the Satellite Analysis Branch (SAB). Data from the Advanced Microwave Sounding Unit (AMSU) and Advanced Scatterometer (ASCAT) passes were also useful in constructing the best track of Kirk.
The 95 knot peak intensity of Hurricane Florence on 31 August at 0600z is based on a satellite intensity estimate of T5.0/90-kts from SAB and TAFB, as well as T5.5/102 knots from UW-CIMSS, during the pre-dawn hours of that day. While it is possible Kirk may have briefly been a major hurricane there is not enough evidence for an upgrade.
There were no ship reports of winds of tropical storm force associated with Kirk.
c. Casualty and Damage statistics
There were no reports of damage or casualties associated with Kirk.
d. Forecasting and Warning Critique
The development of Hurricane Kirk was forecast well in advance due to extraordinary model support up to a week out. The precursor to the hurricane was first mentioned in the Tropical Weather Outlook late on 22 August, assessed with a low chance of tropical development, and was subsequently raised to a medium chance of tropical development by late on 24 August. These probabilities were once again raised to the high category by the early morning hours of 27 August as the disturbance developed a large area of symmetric, deep shower and thunderstorm activity. The outlook at 1200z on 28 August, six hours before genesis, stated that, “any further increase in organization could result in the formation of a tropical depression.”
Figure 1. Satellite imagery of Hurricane Kirk at peak intensity.
Tropical Cyclone Report: Tropical Storm Florence (AL062012)
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Note: The Tropical Cyclone Report (TCR) below contains comprehensive, yet easily understandable, information on each tropical cyclone, including synoptic history, casualities and damages, provided by a multitude of different, official resources, and the post-season analysis best track (six-hourly position fixes and intensities). A tropical cyclone is defined as a warm-core, non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters with organized deep convection and a closed surface wind circulation about a well-defined center. These include depressions—cyclones that did not attain 34-knot sustained winds—storms, and hurricanes. It should be noted that, while I strive to produce the most accurate information for the particular cyclone listed below, these reports...including the storms' position and intensity...are not official and are no way associated with the National Hurricane Center or any other branch of the National Oceanic and Atmospheric Administration. Please visit the Atlantic TCR page and the East Pacific TCR page for official reports on any desired cyclone within a particular season.
Tropical Cyclone Report
Tropical Storm Florence (AL062012)
Duration: 3 August – 6 August
By: TropicalAnalystwx13
Produced on: 27 November 2012
Florence was a short-lived tropical cyclone over the eastern Atlantic Ocean that dissipated with no effects to land in early August 2012.
a. Synoptic history
The formation of Tropical Storm Florence is attributed to a low-latitude tropical wave that emerged off the west coast of Africa southeast of the Cape Verde Islands early on 2 August. At the time, the wave was observed with disorganized shower and thunderstorm activity but a well-defined area of cyclonic turning. As the disturbance tracked towards the west-northwest it encountered a region of moderate wind shear and dry air, but warm sea surface temperatures. Despite less than ideal atmospheric conditions, convection became increasingly defined as a closed, well-defined area of low pressure developed at the surface, and it is estimated that the system became a tropical depression at 0600z on 4 August. The best track positions and intensities are listed in Table 1 at the bottom of this entry (to be added).
Thunderstorm activity and the level of organization continued to increase after formation and Tropical Depression Six is estimated to have intensified into Tropical Storm Florence at 1200z on 4 August. Further intensification occurred over the coming days, and following a series of ASCAT passes and satellite intensity estimates, Florence is thought to have reached its peak intensity of 55 knots at 0000z on 5 August; at this time the cyclone was characterized by an irregular central dense overcast and broken spiral bands south of the center. A subsequent increase in wind shear over the following hours led to deep convection in association with Florence being dramatically decreased in intensity and coverage. The storm weakened to a tropical depression by 0000z on 6 August at which time the center of circulation with completely exposed to view. Twelve hours later, no longer meeting the criteria of a tropical cyclone, Florence was declared a non-convective remnant area of low pressure before completely dissipating over the central Atlantic two days later.
b. Meteorological statistics
Observations used to determine the peak intensity of Tropical Storm Florence include satellite intensity estimates from the University of Wisconsin's-Cooperative Institute for Meteorological Satellite Studies Advanced Dvorak Technique (UW-CIMSS), the Tropical Analysis and Forecasting Branch (TAFB), and the Satellite Analysis Branch (SAB). Data from the Advanced Microwave Sounding Unit (AMSU) and Advanced Scatterometer (ASCAT) passes were also useful in constructing the best track of Florence.
The 55 knot peak intensity of Tropical Storm Florence at 0000z on 5 August is based on a series of satellite intensity estimates of T3.4/53-kt from the University of Wisconsin's Cooperative Institute for Meteorological Satellite Studies Advanced Dvorak Technique (UW-CIMSS ADT).
There were no ship reports of winds of tropical storm force associated with Florence.
c. Casualty and Damage statistics
There were no reports of damage or casualties associated with Florence.
d. Forecasting and Warning Critique
The development of Tropical Storm Florence was well-forecast, primarily due to model support of the storm several days in advance. The tropical wave that developed into Florence was introduced into the personal Tropical Weather Outlook 48 hours before genesis, marked with a Medium chance (30-50%) of tropical cyclone formation. This probability was increased to a High chance (>60%) 24 hours before the development of the storm.
Figure 1. Satellite imagery of Tropical Storm Florence at peak intensity.
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Updated: 10:09 PM GMT on January 08, 2013
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Tropical Cyclone Report: Hurricane Bud (EP022012)
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Note: The Tropical Cyclone Report (TCR) below contains comprehensive, yet easily understandable, information on each tropical cyclone, including synoptic history, casualities and damages, provided by a multitude of different, official resources, and the post-season analysis best track (six-hourly position fixes and intensities). A tropical cyclone is defined as a warm-core, non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters with organized deep convection and a closed surface wind circulation about a well-defined center. These include depressions—cyclones that did not attain 34-knot sustained winds—storms, and hurricanes. It should be noted that, while I strive to produce the most accurate information for the particular cyclone listed below, these reports...including the storms' position and intensity...are not official and are no way associated with the National Hurricane Center or any other branch of the National Oceanic and Atmospheric Administration. Please visit the Atlantic TCR page and the East Pacific TCR page for official reports on any desired cyclone within a particular season.
Tropical Cyclone Report
Hurricane Bud (EP022012)
Duration: 21 May – 26 May 2012
By: TropicalAnalystwx13
Produced on: 26 November 2012
Hurricane Bud was the earliest-forming major hurricane in May in recorded history for the East Pacific basin, and also one of only three May major hurricanes in the basin. The system brought tropical storm conditions to the coastline of Mexico before rapidly dissipating offshore.
a. Synoptic history
The formation of Hurricane Bud can be attributed to a low-latitude tropical wave that emerged off the west coast of Africa and entered the eastern Pacific by mid-May. As indicated by a series of Hovmöller diagrams, the wave departed from the coast of Africa on 5 May and spent over a week crossing the Central Atlantic and Central and eastern Caribbean before entering the West Caribbean on 12 May. As the disturbance entered the eastern Pacific basin and encountered a region of sea surface temperatures greater than 27 °C, convection gradually formed around a developing surface low several hundred miles south of the coastline of Mexico, but was ultimately hindered by intense southeasterly wind shear. A subsequent slight decrease in wind shear on 20 May allowed further consolidation of the shower and thunderstorm activity with the area of low pressure, but the level of organization during did not quite meet the criterion of a tropical cyclone. However, as spiral banding become more prominent during the pre-dawn hours of 21 May, a small yet organized central dense overcast pattern developed atop the disturbance’s low-level circulation, leading to the formation of a tropical depression at 0600z. The best track positions and intensities are listed in Table 1 at the bottom of this entry (to be added).
Despite the slight decrease in southeasterly wind shear, conditions remained quite unfavorable for significant development of the tropical depression. A combination of satellite intensity estimates from several agencies revealed the formation of Tropical Storm Bud around 0000z 22 May. By the following day, with an anticyclone flow aloft, steady to quick intensification of the cyclone began. Bud strengthened into a Category 1 hurricane at 2100z on 23 May as it began a turn to the north-northeast in response to a mid-level trough across the United States Midwest, and a Category 2 hurricane by 1500z the following morning. Data from a NOAA Air Force Reserve mission during the afternoon hours of 24 May revealed 100 knot winds at maximum, which would typically indicate a peak at that intensity. However, given that satellite intensity estimates were higher a few hours previous, Bud’s peak intensity of 105 knots is estimated at 2100z that same day; this is supported by geostationary imagery, which showed the storm with the coolest cloud tops at that time.
As Bud approached the southwestern coastline of Mexico, intense vertical wind shear from the mid-level trough to its north caused dramatic weakening. In a 24 hour timespan, Bud weakened from its peak of 105 knots to 60 knots and further to a tropical depression by 0600z on 26 May. As the circulation drew drier air off the mountainous terrain of Mexico it gradually became unraveled, and it is estimated that Bud degenerated into a remnant area of low pressure at 1200z 26 May, having been void of organized, deep convection for 18 hours or longer. The circulation dissipated six hours later.
b. Meteorological statistics
Observations used to determine the peak intensity of Hurricane Bud include data from a NOAA Air Force Reserve aircraft, satellite intensity estimates from the University of Wisconsin's-Cooperative Institute for Meteorological Satellite Studies Advanced Dvorak Technique (UW-CIMSS), Tropical Analysis and Forecasting Branch (TAFB), and the Satellite Analysis Branch (SAB). Data from the Advanced Microwave Sounding Unit (AMSU) was also useful in constructing the best track of Hurricane Bud.
Data from the NOAA Air Force Reserve Hurricane Hunter aircraft during the afternoon hours of 24 May indicated peak winds of 100 knots in the cyclone at the time. Giving merit to the possibility that Bud may have been a little stronger a few hours previous, as indicated by T-numbers of T5.5/102 knots and T6.0/115 knots from SAB and UW-CIMSS, respectively, the peak intensity of the cyclone was set at 105 knots for 2100z on 24 May.
The development of Bud at 0000Z on 22 May marks the earliest formation of the second tropical storm on record for the East Pacific; the previous record was 29 May. Bud’s upgrade to major hurricane intensity at 2100z on 24 May marks the formation of the earliest-known Category 3 hurricane or higher for the eastern Pacific basin during that month. In addition, Hurricane Bud is one of only three rare May major hurricanes in the East Pacific basin, with the other two being Hurricane Adolph of the 2001 Pacific hurricane season and Hurricane Alma of the 2002 Pacific hurricane season.
The airport located in Manzanilo, Mexico briefly recorded tropical storm-force wind gusts on 25 May, gusting to a peak of 55 mph around 1800z. Heavy rainfall and waves washed out roads and brought down trees along the coastline, but no major damage was reported.
c. Casualty and Damage statistics
Only minor tree and road damage was recorded along the coastline of Mexico as the circulation of Bud remained mainly offshore. No fatalities were reported as a result of the storm.
d. Forecast and Warning critique
N/A.
Personal Tropical Weather Outlooks (TWOs) were not produced for any tropical cyclone until 1 August.
Figure 1. Satellite imagery of Hurricane Bud at peak intensity.
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Updated: 10:00 PM GMT on January 08, 2013
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