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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1110. hydrus
Quoting sarahjola:

yeah that thing is spinning pretty good. i was wondering about that. your not only funny, but your like a weather nostradamus. lol!
weatherdamus in da house,yeeaaahhh!
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Quoting hydrus:
you would melt, Iceman

nah, he would float. lol! just kidding iceman
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1108. hydrus
Quoting sarahjola:

oh, didn't know that. didn't erika blow up during the day and die at night? or was it the other way around?
Sometimes there are other factors involved that will cause convective bursts whether it is day or night.
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Quoting hydrus:
there is shear in the BOC but it should calm down in 36 hours or so. The upper low that is moving across the Caribbean Sea might get interesting when it enters the western side due to warm sea surface temperatures and lessening shear.

yeah that thing is spinning pretty good. i was wondering about that. your not only funny, but your like a weather nostradamus. lol!
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1104. hydrus
Quoting iceman55:
KoritheMan easy .I don't need no pool
you would melt, Iceman
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Quoting pipelines:

nope, daytime heating also only occurs over land, it has the opposite effect over water.

oh, didn't know that. didn't erika blow up during the day and die at night? or was it the other way around?
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1101. hydrus
Quoting sarahjola:
i think i see a little spin in the blob in the boc. i know the storms have calmed down for the night, but i'll bet it blows up with daytime heating. does anyone think that this may turn into something? does it have a chance. i'm not wishcasting, just asking.
there is shear in the BOC but it should calm down in 36 hours or so. The upper low that is moving across the Caribbean Sea might get interesting when it enters the western side due to warm sea surface temperatures and lessening shear.
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Sorry for the bold! was not intentional!
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Quoting sarahjola:
i think i see a little spin in the blob in the boc. i know the storms have calmed down for the night, but i'll bet it blows up with daytime heating. does anyone think that this may turn into something? does it have a chance. i'm not wishcasting, just asking.

nope, daytime heating also only occurs over land, it has the opposite effect over water.
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Quoting hydrus:

Thanks for the reply! Started to think I was on everyones ignore list! Wish there was something to track but am glad for the inactivaty and peace of mind for a while!
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Quoting hydrus:
Hello Sarajola, it is very quiet here tonight.

yeah it is. i see you are keeping it interesting with your humor. you and iceman55 are too funny.
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i think i see a little spin in the blob in the boc. i know the storms have calmed down for the night, but i'll bet it blows up with daytime heating. does anyone think that this may turn into something? does it have a chance. i'm not wishcasting, just asking.
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1093. hydrus
Quoting texascoastres:
Good evening, everyone. Anything going on in the tropics? Haven't been on in a few days. Working weird hours!
quiet out there. lots of spins though...
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1092. hydrus
Quoting sarahjola:

lol!
Hello Sarajola, it is very quiet here tonight.
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Good evening, everyone. Anything going on in the tropics? Haven't been on in a few days. Working weird hours!
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1090. Grothar
Nite all! Stay well. And be nice to each other.
Wake me if anything develops overnight!! I want to see interesting maps in the morning.
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Quoting hydrus:
I hate cat food......there is no cat in it ...they lied..

lol!
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Quoting KoritheMan:


FMA is awesome. Have you watched Brotherhood yet?



I watched the first season. I'm waiting for couple of chapter more, is tedious to wait a week or more to see one, but more when i get interesting.

came out #23 of brotherhood, i wait the #30 for viewed all in a day.




one piece
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Quoting iceman55:
KoritheMan .use to


If you lack a swimming pool, how can you possibly enjoy heat?
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1086. hydrus
Quoting iceman55:
hydrus lol
Iceman55.lol
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1084. hydrus
Quoting iceman55:
lolol cat food haha
then why are you not Heatman?
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Quoting iceman55:
and i love heat


I'm guessing you have a swimming pool?
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1080. hydrus
Quoting iceman55:
i hate cold
I hate cat food......there is no cat in it ...they lied..
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and i love snow lol
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Quoting canehater1:
I wanted to take a minute to thank everyone on here for providing interesting dialogue to sift
thru this year..Dr. Master's posts are a nice compliment to the NHC forecasts..StormW provides good updates when needed, and there are alot of knowledgeable folks on here that
stimulate good discussions..I use this blog as a supplement to official information in my job as a Supply Vessel captain in the Gulf of Mexico, and will continue to do so...


I agree, that's why I've decided to join in posting for the first time this evening after lurking for a while.
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1073. hydrus
Quoting iceman55:
hydrus yep best time .
It was just a theory but I figured,what the heck. Besides,what do you care if it gets cold....you are the iceman dude!
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1072. hydrus
Quoting canehater1:
I wanted to take a minute to thank everyone on here for providing interesting dialogue to sift
thru this year..Dr. Master's posts are a nice compliment to the NHC forecasts..StormW provides good updates when needed, and there are alot of knowledgeable folks on here that
stimulate good discussions..I use this blog as a supplement to official information in my job as a Supply Vessel captain in the Gulf of Mexico, and will continue to do so...
Well said, I believe those of us who are really interested in weather know how important this blog is to our studies. To me it is a privilege to communicate with the people here.
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Quoting lordhuracan01:


yes
and this is Monkey D. Luffy of one piece and i saw (Gumdam 00,wing, seed..), full metal alchemist, soul eater, ghost in the shell, (dragon ball,z, gt..) and more


FMA is awesome. Have you watched Brotherhood yet?
Member Since: Posts: Comments:
I wanted to take a minute to thank everyone on here for providing interesting dialogue to sift
thru this year..Dr. Master's posts are a nice compliment to the NHC forecasts..StormW provides good updates when needed, and there are alot of knowledgeable folks on here that
stimulate good discussions..I use this blog as a supplement to official information in my job as a Supply Vessel captain in the Gulf of Mexico, and will continue to do so...
Member Since: September 8, 2008 Posts: 1 Comments: 1078
Quoting NCHurricane2009:
The Water Vapor loop in post 1046 looks great, tells a lot of information. You can see there is one upper trough digging southward over the Great Lakes, one off of the U.S. east coast, and a TUTT system orientied southwest to northeast (upper low in eastern Caribbean, upper low entagled with ex-Fred, and upper low in NE Atlantic). So many upper troughs/lows this year hampering tropical cyclones in the Atlantic.

I wonder if El Nino has anything to do with increasing upper troughs in the Atlantic (is that how there's increased shear in the Atlantic in El Nino?) Does anyone know what can cause an unseasonable upper trough pattern during the peak of the season?
yes, It does , el nino is a big factor obviously.
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1067. hydrus
Quoting NCHurricane2009:
The Water Vapor loop in post 1046 looks great, tells a lot of information. You can see there is one upper trough digging southward over the Great Lakes, one off of the U.S. east coast, and a TUTT system orientied southwest to northeast (upper low in eastern Caribbean, upper low entagled with ex-Fred, and upper low in NE Atlantic). So many upper troughs/lows this year hampering tropical cyclones in the Atlantic.

I wonder if El Nino has anything to do with increasing upper troughs in the Atlantic (is that how there's increased shear in the Atlantic in El Nino?) Does anyone know what can cause an unseasonable upper trough pattern during the peak of the season?
It seems to produce plenty of rain in Scotland.
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1066. hydrus
Quoting iceman55:
hydrus see no cold air here in slidell la haha
Oh yeah?-wait till December, January and February come to Slidell. get those fires burnin....
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Quoting NCHurricane2009:
Evening all,

This is my first time posting on this blog, been watching this blog for a long time though. Its interesting to get different view points from here on what's going on in the tropics.

I do keep a journal of Atlantic tropical cyclone activity, recording disturbances that make it into the NHC Tropical Weather Outlook in addition to the tropical cyclones that do occur (helps me personally in seeing patterns of what's going on). On my first blog post (Trends in 2009 Atlantic Hurricane Season) I have a sort of lengthy discussion on how this season has unfolded and why I think this season is currently quiet (just my thoughts).
A very concise and detailed analysis...I think we can call this a "modified " El Nino in that Pacific SST's are only slightly different from normal and in a different Area than normal..
Member Since: September 8, 2008 Posts: 1 Comments: 1078
The Water Vapor loop in post 1046 looks great, tells a lot of information. You can see there is one upper trough digging southward over the Great Lakes, one off of the U.S. east coast, and a TUTT system orientied southwest to northeast (upper low in eastern Caribbean, upper low entagled with ex-Fred, and upper low in NE Atlantic). So many upper troughs/lows this year hampering tropical cyclones in the Atlantic.

I wonder if El Nino has anything to do with increasing upper troughs in the Atlantic (is that how there's increased shear in the Atlantic in El Nino?) Does anyone know what can cause an unseasonable upper trough pattern during the peak of the season?
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Quoting JLPR:


Carolina
pretty far away xD
Aguadilla , here, glad that there are smart young people interested in weather in my homeland.
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Quoting KoritheMan:


From the looks of your avatar, I take it you're an anime fan? That's awesome!


yes
and this is Monkey D. Luffy of one piece and i saw (Gumdam 00,wing, seed..), full metal alchemist, soul eater, ghost in the shell, (dragon ball,z, gt..) and more
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.