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 hydrus:
Ya know what Floodman, when that upper low (or whatever it is) gets in to the Western Caribbean Sea, that water is so warm, it could hit the surface and we could have a rapid forming storm..JMO...If the shear stays low.


I would have to agree; the other thing is that when a system decides to drop to the surface it does it fairly quickly
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ok no tropical wave, either way AOI 3 and 4 has the best shot
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Post 196 - Yep it is interesting all right. What is doubly confusing is the the Japan Meteorological Center (JMA) also uses 10 minute sustained winds and classifies Choi Wan with 100 knot winds at its center, this actually makes it weaker than Hamish - confusing or what....
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Quoting melwerle:
Morning Everyone...checking in and it seems as though things have been pretty quiet so far.

Relatively warm out here today - thought perhaps we were having a Santa Ana yesterday since the winds were blowing pretty steady. No fires down this way though.


Howdy, mel!
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Quoting Patrap:
whats with the blob off of cuba
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Quoting BurnedAfterPosting:


AOIs 3 and 4 are not the ones closer to home, they are the other 2 lol

AOI 3 is the wave in the Eastern Caribbean interacting with the ULL

AOI 4 is the wave by the CV Islands



there's no wave in the Eastern Caribbean


Quoting BurnedAfterPosting:


Its a ULL interacting with a tropical wave


nope no surface feature analyzed. Its all elevated convection not surface based convection. Though the trades were noted slowing down in the region so some speed convergence maybe going on.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
189 - Beautiful images. It's an awesome storm, luckily with no land interaction except the odd island or two. Here's a link from the Tokyo Typhoon Center:

Link
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Quoting 69Viking:


They are the ones closer to home so they sure are! My guess is the AOI in the BOC will just continue the onslaught of rain for NW Florida and other portions of the SE U.S. It's amazing how some areas are flooding but then not to far down the road (a state or two over) they are begging for rain to end severe drought. Weather sure is a complicated monster when it wants to be!


AOIs 3 and 4 are not the ones closer to home, they are the other 2 lol

AOI 3 is the wave in the Eastern Caribbean interacting with the ULL

AOI 4 is the wave by the CV Islands
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Morning all..Sept is the Active Time.

Lots of potential,no threats yet though.

Swirls from Africa to the ArkLaTex..
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Quoting funeeeg:
Post 162 - Link The Australian scale is different in that it classifies based on 10 minute average sustained winds. It was a Cat 5 on the Australian scale and Cat 4 on the Saffir Simpson scale which uses 1 minute maximum sustained winds. Hamish had 150mph on the SS scale or Cat 4 and 130mph on the Australian scale or Cat 5.


You are correct, they use the Austrialian Tropical Cyclone intensity Scale, which we discussed the other night. Very interesting. Did not know that until the other night. Always wondered why the reports differed so widely.
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Quoting BurnedAfterPosting:


AOIs' 3 and 4 are the ones to watch


Yep i agree......but, don't rule or boy Freddie Krugger out.....
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Quoting 69Viking:


They are the ones closer to home so they sure are! My guess is the AOI in the BOC will just continue the onslaught of rain for NW Florida and other portions of the SE U.S. It's amazing how some areas are flooding but then not to far down the road (a state or two over) they are begging for rain to end severe drought. Weather sure is a complicated monster when it wants to be!

Very true. thankfully, the mess in TX last week helped put a serious dent in the drought in south TX.
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Quoting Patrap:


Morning Pat!
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186. Patrap 12:38 PM

Ok Pat, that is cool. What am I looking at? I haven't a clue as to what that is telling me. Help.
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Post 162 - Link The Australian scale is different in that it classifies based on 10 minute average sustained winds. It was a Cat 5 on the Australian scale and Cat 4 on the Saffir Simpson scale which uses 1 minute maximum sustained winds. Hamish had 150mph on the SS scale or Cat 4 and 130mph on the Australian scale or Cat 5.
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Today's Tropical Update

Yesterday's post - Structure of a tropical cyclone: Microwave Imagery of Choi-Wan

2009/259 - 09/16 at 01 :25 UTC
Super Typhoon Choi-wan (15W) west of the Mariana Islands, Pacific Ocean
Satellite: Terra



Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting BurnedAfterPosting:


AOIs' 3 and 4 are the ones to watch


They are the ones closer to home so they sure are! My guess is the AOI in the BOC will just continue the onslaught of rain for NW Florida and other portions of the SE U.S. It's amazing how some areas are flooding but then not to far down the road (a state or two over) they are begging for rain to end severe drought. Weather sure is a complicated monster when it wants to be!
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Quoting RJinBoyntonBeachFL:
I predict Fred will strike S/N Carolina as a minimal Cat 1 storm 9 days out. No scientific back up, just my gut.


Well RJ, there are some hints in the pattern and modeling that seem to support your gut feeling for some form of threat to these areas in the next week. Lets see what happens!
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Thank you. It does bother me when I see people that feel like they have to apologize for being themselves. Far too many personal attacks on this blog. Far too much testosterone also.

Quoting Grothar:


Do you blame these people for putting in disclaimers every time they make a statement? Especially newcomers, who are actually frightened to ask a question for fear of being trampled upon. That was very kind of you to answer her that way. Too bad more do not follow your manners.
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all the areas of interest or what i will called areas of disturbed weather which i have analysed this morning, the one that has caught my attention is the one at 7N 26W moving west at 15 mph. although it is at a low latitude and some may what to think that it is too low for development i believe that this area has the potential for cyclogenesis. there is some cyclonic turnig and although shear is a bit on the high side which is expected to be conducive the next 48 hrs . the track of this disturbance i expect to continue west because of the A/B high which has rebuilt to it;s north. this reminiscent of the same area where Ivan evolved at the same time 5 years ago. this area will have to be watched very closely for signs of development
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Quoting TampaSpin:

Today AOI and Tropical Update


AOIs' 3 and 4 are the ones to watch
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Quoting SQUAWK:
Sheri that was not meant to be a put down. I just wanted you to know that we did not think you were dumb and so you did not need to preface the question with a disclaimer. Not at all meant in a derogatory way.



Do you blame these people for putting in disclaimers every time they make a statement? Especially newcomers, who are actually frightened to ask a question for fear of being trampled upon. That was very kind of you to answer her that way. Too bad more do not follow your manners.
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Today is 10 yr anniversary of Floyd.
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Quoting AussieStorm:
Good Evening all.
Just wondering about Dr. Jeff Masters' Wunder Blog Title.....First Category 5 storm of the year is Choi-Wan. What about Severe Tropical Cyclone Hamish, Intensity: 215 km/h (130 mph) (10-min), 925 hPa (mbar)




Wasn't Hamish the 1st Cat 5 of the year????

Note: In June 2009, Severe Tropical Cyclone Hamish was retired by the Bureau of Meteorology

Hamish was a Cat 4.
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Quoting Grothar:


It should have read the most annoying and persistant. However, using a superlative in that context, would simply be acceptable by most teachers, since it was not meant to be a technical phrase contained in a dissertation. It is a double superlative using "most" preceding the "est" form of the adjective, which is never acceptable.

Grammar aside, I still like reed's blogs. If we were to correct each other's English, we would never get to discuss the weather.

Too bad most people do not understand when sentences are preceded with words like "might" and "could". It would prevent a lot of unnecessary arguments. They are modals auxiliary words intended to express possibility, not fact.


Wow!
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Quoting Floodman:


We'll have to watch in the 700mb range
Ya know what Floodman, when that upper low (or whatever it is) gets in to the Western Caribbean Sea, that water is so warm, it could hit the surface and we could have a rapid forming storm..JMO...If the shear stays low.
Member Since: September 27, 2007 Posts: 1 Comments: 22728
Has kmanislander been on here lately?
Have not seen him in a while.
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Quoting Grothar:


I see another who has a grasp on the language. So eloquently put and to the point. You don't mince words, do you Flood? I think that is why I enjoy reading your blogs. What is your feeling on EX-FRED-open wave feature, swirl. Just want to cover everything lest I be chastised for using the incorrect nomenclature.


He is just that, the EX-Fred. Without a closed LLC he'll have a very difficult time trying to re-form. I agree with most on here that he will not have the energy or the environment to re-form without a little outside help.

As for the rest of your comment, thank you **bows deeply** I enjoy your entries as well!
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Glad you understand. I really did not mean it in a negative way. I have seen you start many of your questions with that same kind of statement and wanted you to know that no one here thinks you or your questions are dumb.

Quoting catastropheadjuster:


Squawk, I am sorry for my quote, sorry took it the wrong way. I appreciate it, sorry again.

Sheri
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Upward MJO can be a big mess, Downward MJO considerably less..

I just wanted to let Sheri know I really appreciated the question...I swear I was thinking the same thing and also didn't want to appear "dumb"...and I really, really appreciate Flood's poem...such a Renaissance Man!

I just read StormW's blog post for today. The weather patterns really are complicated.

It's kind of driving me nuts... anybody got any opinions, advice, for those of us in disaster assistance? Sure, I'm always supposed to be ready... but need to supplement with different stuff for different seasons, geographical areas. My suitcase is looking really disheveled ... New England for Bill, no, take out the sweaters...the Carolinas...oh WHOOPS, North or South Carolina? Florida (AGAIN?) Texas (OH NO NOT AGAIN!!!)
You guys get the drift. Think I can close the suitcase for the season? I'm thinking not with all the flooding down south right now.

Obviously I'm NO met, but enjoy reading the blog and thanks for informing us laypeople. And for tolerating us very nicely most of the time. I'll be quiet now and hope for some counsel.
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Choi-Wan has great banding, so annular he is not at this time. CDO is very smmetrical and eye is large. I believe his eye has not changed much since yesterday, but I noticed that the cold clouds warmed to -50 to -60C, while now they are at -70C.
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Quoting StormW:


Sheri,
I also have a link under my recommended links section of my blog on the MJO.


StormW- Well good afternoon my friend thanks i will go look at that to. I hope you have a great day.
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Today AOI and Tropical Update
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Quoting AussieStorm:

So our BOM classified Hamish as a Cat 5 yet NHC classified Hamish as a Cat 4. What is there 2 different if not more scales of classification?


Hamish had top winds of 145mph, that isnt a CAT 5 in this part of the world, maybe it is over there.
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Quoting Floodman:


You keep on asking and let them be upset...not really our problem if they have a board up their a$$, is it?

druseljic just posted a great link on the MJO; that should prertty much explain it to you...


I see another who has a grasp on the language. So eloquently put and to the point. You don't mince words, do you Flood? I think that is why I enjoy reading your blogs. What is your feeling on EX-FRED-open wave feature, swirl. Just want to cover everything lest I be chastised for using the incorrect nomenclature.
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Quoting SQUAWK:
Sheri that was not meant to be a put down. I just wanted you to know that we did not think you were dumb and so you did not need to preface the question with a disclaimer. Not at all meant in a derogatory way.



Squawk, I am sorry for my quote, sorry took it the wrong way. I appreciate it, sorry again.

Sheri
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Quoting AussieStorm:
Good Evening all.
Just wondering about Dr. Jeff Masters' Wunder Blog Title.....First Category 5 storm of the year is Choi-Wan. What about Severe Tropical Cyclone Hamish, Intensity: 215 km/h (130 mph) (10-min), 925 hPa (mbar)




Wasn't Hamish the 1st Cat 5 of the year????
Not unless it had sustained winds of 156 mph or higher. He is probably using the Saffir-Simpson scale.
Member Since: September 27, 2007 Posts: 1 Comments: 22728
158 :-)
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Sheri that was not meant to be a put down. I just wanted you to know that we did not think you were dumb and so you did not need to preface the question with a disclaimer. Not at all meant in a derogatory way.

Quoting catastropheadjuster:


Excuse me,I did ask the question.
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Quoting BurnedAfterPosting:


Hamish was a CAT 4 and is now the 3rd strongest cyclone of the year behind Choi-Wan and Jimena

So our BOM classified Hamish as a Cat 5 yet NHC classified Hamish as a Cat 4. Why is there 2 different if not more scales of classification?
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Morning Everyone...checking in and it seems as though things have been pretty quiet so far.

Relatively warm out here today - thought perhaps we were having a Santa Ana yesterday since the winds were blowing pretty steady. No fires down this way though.
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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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