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 OracleDeAtlantis:


I'm not looking for best case scenarios here, I'm looking for worst case scenarios, and hearing the Weather Channel say don't worry be happy, while I can see outflow developing rapidly, is contradicting my intuition. Also, this thing is moving through some of deepest warm water in the world.


LMAO...I hear them saying that in the Tropics Update:

Here's a little song I wrote
About the MJO down-stroke
Don't Worry
Be Happy!

The wind may be blowing hard outside
Your house is filling with the rising tide
Don't Worry
Be Happy!
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THIS IS FRED:







THIS IS YOUR BRAIN ON FRED:




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Hey guys, I posted a new blog, I would appreciate your feedback, thanks!
-Matt
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Quoting TriniGirl26:


i asked a question something like that yesterday and didn't get a response sooo i can't help u but i am wondering as well.


I'm not looking for best case scenarios here, I'm looking for worst case scenarios, and hearing the Weather Channel say don't worry be happy, while I can see outflow developing rapidly, is contradicting my intuition. Also, this hybrid "thing" is moving towards some of deepest warm water in the world.

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Quoting iceman55:
BayouBorn1965 how


Oh no, maybe my strange sense of humor got the best of me. You posted a map that looked like a hand pointing with the wrong finger.
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Quoting victoriahurricane:
Still mostly a lurker here, but didn't Claudette form from a ULL? Or was it already at mid-levels?


If memory serves, Claudette was strong at the mid levels (500-700mb)
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Still mostly a lurker here, but didn't Claudette form from a ULL? Or was it already at mid-levels?
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Quoting ParanoidAndroid:


hydrus, same question to you. is this what's going on in the SE Caribbean or too early to tell?
Nothing will happen unless it makes its way to the Western Caribbean Sea and starts organizing deep convection around the center of circulation. For this to happen there cannot any vertical shearing. which it will begin to feel in the Central Caribbean Sea. After that its wait and see.
Member Since: September 27, 2007 Posts: 1 Comments: 21491
Quoting iceman55:





I get it. . . . you're funny.
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Wow. I quit lurking and asked a question and it was answered by 18768 of you. Thanks everyone. Very informative for me. I wish I had found this blog a while ago.
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Quoting ElConando:
A transition from a ULL to tropical system does take a while. Conditions for the most part are prime for it, however as 456 says it is rare.


Cyclone Catarina was developed from an ULL


link
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A transition from a ULL to tropical system does take a while. Conditions for the most part are prime for it, however as 456 says it is rare.
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Quoting iceman55:
KimberlyB what imagges?


#326 - sorry, was trying to make a funny and failed. lol
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Quoting seminolesfan:
Never been a fan of the polls in here, but I'll try to make one up.

A)WINDSMURF=WEATERSTUDENT

B)WINDSMURF=/=WEATERSTUDENT


all of the above? xD
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Quoting ParanoidAndroid:


Thanks floodman. So is that going on now with the ULL south of PR? Or is it too early to tell? Looks like it has some tropical characteristics to my untrained eye.


As Weather456 pointed out, a ULL transition to an LLC is an uncommon occurence...when I look at the vorticity I see nothing below 500mb...doesn't look like it from here, but what do I know...LOL
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Quoting hydrus:
It is a complex subject, several things can effect haw fast a ULL can reach the surface and become tropical cyclone. It was years ago, but I saw an upper low move over Hispaniola and upon entering the ocean almost immediately became tropical. on the satellite loop it seemed like the interaction with land helped it to reach the surface.


hydrus, same question to you. is this what's going on in the SE Caribbean or too early to tell?
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Quoting WINDSMURF:

he lives in miami/hialeah
Never been a fan of the polls in here, but I'll try to make one up.

A)WINDSMURF=WEATHERSTUDENT

B)WINDSMURF=/=WEATHERSTUDENT
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Quoting iceman55:





Is it just me that thinks that image is flipping us off? Yes? Oh. Sorry.
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Quoting PortABeachBum:


If you haven't read it, Erik Larson's book "Isaac's Storm" reveals the problems (and politics) of predictions in those days.


ah, interesting, I will definitely have to read that, thanks
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Quoting tornadodude:


...We also discussed the Galveston Hurricane of 1900, and how the Cubans said it was going into the Gulf, but the US forecasters called for it to go to the East Coast, ...


If you haven't read it, Erik Larson's book "Isaac's Storm" reveals the problems (and politics) of predictions in those days.
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Quoting Weather456:
We are beating a dead horse. I have been reading some of these posts and some people just do this every single day. We want Fred to develop so much we ignoring facts here.

The negative factors outweigh the positive factors with Fred and the upper low in the Eastern Caribbean.

ULL transition to a tropical cyclone is an uncommon phenomenon and is not as easy as one think. Give the tropics time.


Yes--Patience is best especially with the environmental factors involved this year. The trackable energy that was "Fred" may be a player and potential threat in some fashion in a few days.
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Quoting Weather456:
ULL transition to a tropical cyclone is an uncommon phenomenon and is not as easy as one think. Give the tropics time.


ok thanks 456...i was just wondering...we finally get the rain and it looks like it don't want to stop :)...ok leaving work now and off to classes...laterz
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Quoting presslord:
Dr. Masters got on board with the S/N Carolina issue ...I'm so proud of him...


Press, you know I like you but, you are just plain wrong on the Carolinas thing.
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Quoting presslord:
Flood...so far things are good...hope you're well...


Well, we all limp a little after a while, huh? I'm good, all things being equal...
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Quoting Hurricane009:
Where does he live???

he lives in miami/hialeah
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Quoting WINDSMURF:
weatherstudent must be extremely upset that no storm has come his way this year


yeah, maybe, but can we please refrain from talking about him? he tends to annoy most of us and has ended up on most our ignore lists, thanks
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Quoting Floodman:


It may typically take somewhere in that time frame; transition of the ULL to the surface, enough energy and moisture to create the requisite convection I guess...


Thanks floodman. So is that going on now with the ULL south of PR? Or is it too early to tell? Looks like it has some tropical characteristics to my untrained eye.
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Quoting ParanoidAndroid:
What's the process for a ULL to become a tropical cyclone? What is required and why does it typically take about three days? Obviously, I'm not a meteorologist. Just a long-time weather nerd. Anyone care to educate me a bit?
It is a complex subject, several things can effect how fast a ULL can reach the surface and become tropical cyclone. It was years ago, but I saw an upper low move over Hispaniola and upon entering the ocean almost immediately became tropical. on the satellite loop it seemed like the interaction with land helped it to reach the surface.
Member Since: September 27, 2007 Posts: 1 Comments: 21491
puerto rico ...sorry about the sp
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Flood...so far things are good...hope you're well...
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weatherstudent must be extremely upset that no storm has come his way this year
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notice the swirl sw of puerto rice on wv loop...very interesting...any thoughts??
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Howdy, press...how's things?
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Dr. Masters got on board with the S/N Carolina issue ...I'm so proud of him...
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Quoting ParanoidAndroid:


lol. I dunno. I read that above somewhere in a comment. Perhaps I should have quoted it.


It may typically take somewhere in that time frame; transition of the ULL to the surface, enough energy and moisture to create the requisite convection I guess...
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CAROLINAS!!!!!!!!!!
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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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