First Category 5 storm of the year is Choi-Wan

By: Dr. Jeff Masters , 1:38 PM GMT on September 16, 2009

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The remains of Hurricane Fred continue to generate sporadic bursts of heavy thunderstorm activity over the middle Atlantic Ocean. These thunderstorms were generating winds up to 30 mph, according to this morning's QuikSCAT pass. However, QuikSCAT also showed that the remains no longer have a surface circulation. Water vapor satellite loops show that ex-Fred has moved beneath an upper-level low pressure system. This low features dry air on all sides, and this dry air will interfere with any redevelopment of Fred. While wind shear is now moderate, 10 - 15 knots, and is expected to remain in the moderate range for the next five days, the presence of so much dry air will require at least three days for the remains of Fred to overcome and regenerate a surface circulation. Only the HWRF model redevelops Fred, predicting it will develop on Sunday as it approaches the Bahama Islands. NHC is giving ex-Fred a low (less than 30% chance) of developing into a tropical depression by Friday. Fred's remains will be near the Bahamas on Sunday, and near Florida on Monday night. It is possible that a strong trough of low pressure expected to develop over the eastern U.S. early next week will turn Fred's remains northwards into South Carolina/North Carolina on Monday/Tuesday.

This morning's QuikSCAT pass shows a surface circulation near 13N 32, with a small region of heavy thunderstorms to the north. This region is about 450 miles west of the Cape Verdes Islands, and is headed west at about 10 mph. Satellite imagery shows a decrease in the amount of heavy thunderstorm activity this morning, and high wind shear of 20 knots is interfering with development. A band of high wind shear lies just to the north of the disturbance, and will continue to interfere with the system's development over the next three days. NHC is giving the system a low (less than 30% chance) of developing into a tropical depression by Friday.

The GFS model is predicting development of a new tropical wave coming off the coast of Africa early next week.


Figure 1. The remains of Hurricane Fred (left) keep on chugging across the Atlantic. A tropical wave is 450 miles west of the Cape Verdes Islands (right). The thunderstorms of the Inter-Tropical Convergence Zone (ITCZ) are far to the south, off the coast of Africa.

Super Typhoon Choi-Wan hits Category 5 strength
This year's first Category 5 tropical cyclone is Super Typhoon Choi-Wan, which intensified into a Category 5 storm with 160 mph sustained winds yesterday afternoon. Choi-Wan is over the open ocean south of Japan, and is not expected to impact any land areas. It is unusual to have to the globe's first Category 5 storm form this late in the year. Indeed, global tropical cyclone activity as measured by the ACE index, which measures destructive potential, has been near historic lows over the past two years. Only one Category 5 storm was recorded in 2008--Super Typhoon Jangmi, which attained winds of 165 mph at 06 GMT on September 27, as it approached the north coast of Taiwan. The last time so few Category 5 storms were recorded globally was in 1974, when there were none.

We got a rare treat yesterday when the Cloudsat satellite caught a perfect cross section through Choi-Wan when it was a Category 4 super-typhoon with 150 mph winds (Figure 2). The CloudSat satellite, launched in 2006, carries the first satellite-based millimeter wavelength cloud radar. It is the world's most sensitive cloud-profiling radar, more than 1000 times more sensitive than current weather radars. It collects data about the vertical structure of clouds, including the quantities of liquid water and ice, and how clouds affect the amount of sunlight and terrestrial radiation that passes through the atmosphere. The satellite has a narrow field of view, so can image only a small portion of the planet each day. About once per year, CloudSat happens to slice through the eye of an Atlantic hurricane. This happened last month, when Cloudsat caught a remarkable view of Hurricane Bill.


Figure 2. Top: conventional visible satellite image of Super Typhoon Choi-Wan at 3:57 UTC Tuesday, 9/15/09 from Japan's MTSAT. Bottom: cross section through Choi-Wan's eye taken at the same time, from the CloudSat cloud radar instrument. The CloudSat pass occurs along the red line in the top image. The CloudSat pass runs from south (left side of CloudSat image) to north (right side of CloudSat image). At the time of the image, Choi-Wan was strengthening into a Category 4 Super Typhoon (150 mph winds, 928 mb pressure), and reached Category 5 strength fourteen hours after this image was taken. In the CloudSat image, one can see 6+ isolated towers, marking the positions of spiral bands on the south side of the center. The eye is remarkably well-defined, with symmetric "hot towers" extending up to 55,000 feet, sloping outward with height. The thin solid grey line at 5 km marks the 0°C temperature line. Ice particles falling inside the hurricane melt at an altitude just below the 0°C line, creating a "bright band" of orange echoes throughout most of the hurricane. This is one a few inner eye images CloudSat has captured of an Category 4/5 tropical cyclone. Image credit: NASA/Colorado State University/Navy Research Lab, Monterey.

Twenty years ago today
On September 16, 1989, Hurricane Hugo weakened slightly as it underwent an eyewall replacement cycle. The tight inner eyewall that we had flown through the previous day had contracted to the point where it became unstable and collapsed. A new eyewall formed out of an outer spiral band, and Hugo's highest winds dropped to 140 mph--Category 4 strength. As this was occurring, the storm began a more northwesterly path and slowed down, in response to a region of low pressure north of Puerto Rico. By midnight, Hugo was only an hour away from its first encounter with land--the Lesser Antilles island of Guadeloupe.

Back on Barbados, our one undamaged P-3 Orion Hurricane Hunter aircraft flew a mission into Hugo, while the crew of the damaged aircraft remained on the ground. Our plane was grounded until a team of experts from the mainland could fly out and perform a detailed x-ray analysis of the wings to determine if the high g-forces we endured had caused structural damage. This might take a week, so the plan was to fly us back to Miami on a commercial jet. However, Hugo had forced the cancellation of virtually every commercial flight in the eastern Caribbean that day, so we were stuck on the island. Most of us spent a frustrated day touring the island on rented mopeds, getting a look at Hugo from the ground. We got thoroughly drenched by one of Hugo's outermost spiral bands, but the hurricane was too far away to bring any winds more than 20 mph to the island.

That night, our already jangled nerves got a new jolt--a tropical depression had formed due east of Barbados, and was headed right for us. In two days time, it seemed likely that Tropical Storm Iris would be paying us a visit.


Figure 3. AVHRR visible satellite image of Hurricane Hugo taken on September 16, 1989. Image credit: Google Earth rendition of the NOAA HURSAT data base.

Jeff Masters

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Quoting BurnedAfterPosting:
2009 season is over?

LMFAO I have never heard anything so stupid in my entire life, its no wonder the joker is blocked by just about everyone LMAO



I'm not saying hurricane season 2009 is other. I'm just discussing about next year. I'm thinking 2 more storms this season.
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TWC reporting low in TX and LA like a TS. LOL@ the Media and Hurricane Season 2009.
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Quoting btwntx08:
hi all
Quoting StormW:
Good evening!

Good evening you two.
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2009 season is over?

LMFAO I have never heard anything so stupid in my entire life, its no wonder the joker is blocked by just about everyone LMAO


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I'm predicting 2 to 3 more named storms for the rest of the 2009 season
Then 2010?? Probably 12 or more. We'll see I guess
Member Since: July 1, 2008 Posts: 13 Comments: 7437
Quoting hydrus:
Yeah, where is Bill Gates now? huh?

He's probably making new viruses for Windows.
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Quoting iceman55:
Ameister12 nope .cost 120billion.

Double wow!
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Quoting Ameister12:
2009 USD saying Katrina's damage was $90.9 billion. Wow!
Yeah, where is Bill Gates now? huh?
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Quoting HadesGodWyvern:
if they make it through nearly 50 names in one season, that would be terrible.

Of course!
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Quoting help4u:
I see all the hurricane wishcasters here tonight for 2010.With this season over i predict a much more active year next year with 8 named storms and 4 hurricanes all of them fish storms.
Fishstorms? Naaahhh!...I have never seen a storm with gills or fins on it.
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940. HadesGodWyvern (Mod)
if they make it through nearly 50 names in one season, that would be terrible.
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2009 USD saying Katrina's damage was $90.9 billion. Wow!
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Quoting BahaHurican:
Cuba gets 'em from every direction.... N, S, E, W, and all of the lesser compass points.... lol... poor Cuba also seems to be in the recurve zone...
Western Cuba has huge dead forests, from being repeatedly hit by huge hurricanes for millenniums, The whole of Cuba has them, but not the same as the west.
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I see all the hurricane wishcasters here tonight for 2010.With this season over i predict a much more active year next year with 8 named storms and 4 hurricanes all of them fish storms.
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I'm thinking 16 storms. Give or take.
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El Nino was severely under-forecast on my part - that should appear in the 2009 Hurricane Season Forecast Verification next April. Thus it stress the point that ENSO will usually govern over all other conditions.

All other variables verified such as below normal tropical wave frequencies, near normal ssts, nuetral NAO with a positive bias.
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Quoting Hurricane009:
We may have more. What would happen if we went through all the names, and then the next row of names???


Then they're all called Karen
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Quoting Hurricane009:
Usually.

I thought so.
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928. JLPR
Quoting Hurricane009:
We may have more. What would happen if we went through all the names, and then the next row of names???


The end of the World lol
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Quoting BahaHurican:
I used to have a link to a website that was counting # of strikes and brushes for countries / islands / cities in the basin. But now I can't find it...
I know I have seen this mentioned a few places but can't find it right now although I think once a hurricane is in the Caribbean it generally affects almost every island once it makes it's way towards the w or wnw.
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Does neutral usually mean the cyclone activity is above average?
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922. JLPR
Quoting BahaHurican:
I also read somewhere that weak el nino / la nina years can be nearly as active as neutral years. I have a feeling the timing of the el nino makes a difference, too.


Actually 1995 was a La niña year and its ACE stand slightly above 2004
there is also 1950 but I don't know what was in control that year
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Quoting BahaHurican:
Didn't someone spot Karen earlier this season?
I helped spot Karen.
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Quoting stormwatcherCI:
Wikipedia but I have read it other places also. Give me a few minutes and I will tell you where else.
I used to have a link to a website that was counting # of strikes and brushes for countries / islands / cities in the basin. But now I can't find it...
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Quoting JLPR:


well then
we all know what we must fear =P
Neutral years aren't nice =|

and if we go neutral then 2010 might be quite active


From my 2008 Hurricane Season Outlook

Due to the weakening trend of La Nina over the past few months and the model forecasts presented in figures 1 and 2, it’s fair to say that we will experience a neutral to slightly warm episode this hurricane season. This is not so good, as past experience have shown that neutral years are the most active on record. Table 2 shows the top 10 active hurricane season in the past 58 years.

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Quoting Weather456:


not a classic one though
I also read somewhere that weak el nino / la nina years can be nearly as active as neutral years. I have a feeling the timing of the el nino makes a difference, too.
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914. JLPR
Quoting Weather456:


not a classic one though


you got that right xD
not quiet at all
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Quoting Patrap:


Re: 846

I'd like to see a similar map, but instead of showing dots, show line segments representing the size of the storm somehow -- maybe the extent of hurricane force winds?
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Quoting BahaHurican:
IIRC, nuetral years are the ones most likely to produce powerful storms and high ACE.....


you are correct sir
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911. JLPR
Quoting Weather456:


neutral


well then
we all know what we must fear =P
Neutral years aren't nice =|

and if we go neutral then 2010 might be quite active
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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