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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1059. hydrus
Quoting iceman55:
nono cold air
I wonder if this front is as potent as predicted, will there be severe weather associated with it.
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1058. JLPR
Quoting antonio28:


Isabela and you?


Carolina
pretty far away xD
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1056. hydrus
Quoting Grothar:


Is one allowed to write to the administration in defense of someone, or would that result in a ban as well.
yeah, TornadoDude is alright.
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MONDAY THROUGH NEXT WEDNESDAY...THE GFS CONTINUES TO TREND FASTER
WITH MOVING THE INITIAL STRONG SHORTWAVE TROUGH QUICKLY
SOUTH/SOUTHEAST FROM THE NORTHERN PLAINS TO THE LOWER MISSISSIPPI/
TENNESSEE VALLEY REGIONS ON TUESDAY WHILE THE ECMWF IS SITUATED
FARTHER NORTHWEST IN THE CENTRAL PLAINS. THIS WILL AFFECT THE
TIMING OF A FAIRLY STRONG COLD FRONT THAT SHOULD MOVE THROUGH THE
LOCAL AREA AROUND TUESDAY. THE GFS APPEARS TO BE A BIT FAST SO
HAVE TRENDED CLOSER TO THE ECMWF. A CHANCE OF SHOWERS AND
THUNDERSTORMS WILL REMAIN IN THE FORECAST UNTIL FRONTAL PASSAGE.
WILL HAVE TO RESOLVE THE MODEL TIMING ISSUES...BUT IN GENERAL WILL
SEE DRIER AND COOLER AIR TUESDAY NIGHT AND WEDNESDAY.

From N.O> fcast discussion......can't wait!
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1054. Grothar
Quoting KEEPEROFTHEGATE:

yep that it will
when admin finds out


Is one allowed to write to the administration in defense of someone, or would that result in a ban as well.
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Quoting lordhuracan01:
Evening everyone


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


where are you lol?
its 81F xD


Isabela and you?
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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).
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1047. JLPR
Quoting Weather456:
The Bahamas probably outranks all

81 cyclones TS or greater since 1851


my area San Juan stands at 50
im happy to be below various islands xD

yet PR is divided in 4 categories, so I have no idea how many in total for the whole island
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Quoting thelmores:
At this time last night, I had a hard time finding Fred's circ...... and confirmed this morning, no longer at the surface.

I am convinced now, that Fred is no longer a player...... it will never survive the dry air which surrounds it...... and in its path.



Fred exhibited the strongest "naked" circulation I have ever seen..... which is why I did not write it off..... until now.

I give Fred less than a 10% chance of regenerating.....

Not a down-caster, just a realist..... the artist formerly known as Fred is in the record books......

just my $.02........




You could be right, but the south and east side of Freddy are not nearly as dry as they were. Watch how the green is vanishing on all sides of him. I'm not convinced that Freddy is dead.

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The Bahamas probably outranks all

81 cyclones TS or greater since 1851
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1042. hydrus
Quoting stormpetrol:
Link
Check this out!
Hey, I remember that one now!..On December 24 1989, we had snow in S.W.FL. granted it did not stick to the ground, but it was snow flurries and lots of them. Jim Reif was the Met back then on channel 11 and pointed out the low that spanked the Caymans. It is neat when something comes along and sparks you memory!
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Quoting kmanislander:


Hi Alaina

I was off travelling for a week but there really wasn't anything happening other than Fred threatening to make a comeback LOL

I have my fingers crossed that we can make it through the season without major incident


Yea its definately been an interesting season! I personally think we will be ok but mother nature is unpredictable as we all know, more waiting and watching.
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Saint Kitts since 1851 - 65 cyclones bringing TS or greater winds

The Caymans since 1851 - 61 cyclones bringing TS or greater

Its very tight but thats why Saint Kitts is 2nd in the Caribbean.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Well, time to finish off the last few episodes of the Sopranos LOL.

Bye for now
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Quoting alaina1085:
Evening everyone!

Kman good to see ya back blogging.


Hi Alaina

I was off travelling for a week but there really wasn't anything happening other than Fred threatening to make a comeback LOL

I have my fingers crossed that we can make it through the season without major incident
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Quoting kmanislander:


With shear the way it's been so far I think we could see the season shut down by early October. Already the Atl is starting to look like the first week of October. The CV season may be over.


Amen to that. The storms are fun to watch, track & forcast but I really would rather not have any.
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Evening everyone!

Kman good to see ya back blogging.
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At this time last night, I had a hard time finding Fred's circ...... and confirmed this morning, no longer at the surface.

I am convinced now, that Fred is no longer a player...... it will never survive the dry air which surrounds it...... and in its path.



Fred exhibited the strongest "naked" circulation I have ever seen..... which is why I did not write it off..... until now.

I give Fred less than a 10% chance of regenerating.....

Not a down-caster, just a realist..... the artist formerly known as Fred is in the record books......

just my $.02........
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Quoting JLPR:


yep its just too quiet
I think we should have Grace before September ends but im not sure what could happen after that xD


With shear the way it's been so far I think we could see the season shut down by early October. Already the Atl is starting to look like the first week of October. The CV season may be over.
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1031. KEEPEROFTHEGATE (Mod)
Quoting kmanislander:


Careful, circumventing a ban can lead to a permanent ban

yep that it will
when admin finds out
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Quoting kmanislander:


I remember that. The bar freezer from Sunset House was on the South Sound road.
The dumpster across from Wholesome Bakery next to the liquor store was in the Tower Building parking lot.
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Quoting stormpetrol:
Link
Check this out!
Excellent article.
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Quoting purduemet:
Hey guys, this is matt, my other name got banned for a day for an off topic image, go figure :P


Careful, circumventing a ban can lead to a permanent ban
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1026. JRRP
lol?
Link
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1023. JLPR
Quoting kmanislander:


Hi there. Quiet times now. Makes one wonder if the season has a surprise or two in store .


yep its just too quiet
I think we should have Grace before September ends but im not sure what could happen after that xD
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Quoting stormwatcherCI:
Ok thanks. Just talking about the bad Nor'wester we had in 1989 that did so much damage on the waterfront. I remember a lot of the buildings the water went right through and so much damage to the road.


I remember that. The bar freezer from Sunset House was on the South Sound road.
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Quoting hydrus:
I would like to know more about that Christmas NorthWester if you have time.
Link
Check this out!
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Quoting JLPR:


Hello :)


Hi there. Quiet times now. Makes one wonder if the season has a surprise or two in store .
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I shouldn't have looked back....

stormpetrel, I think that stormcarib website is the one I was looking for earlier.

I'm noticing that in their ranking of ATL basin places, 4 of the top 5 places for tropical cyclone strikes or brushes are in the NW Bahamas:

1 Abaco (March Harbour), Bahamas
2 Grand Bahama, Bahamas
3 Bimini, Bahamas
4 Saba, NA
5 Nassau, New Providence, Bahamas

They also note that The Bahamas as a region has been hit by major storms as often as the entire Western Caribbean.... and nearly twice as often as the Eastern Caribbean.

Some pretty interesting stats....

Now I REALLY need to get to bed... lol
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Quoting kmanislander:


No, there is nothing to suggest anything going on there other than rain. That area is due to diffluence on the SE side of the ULL that is progressing West of there.

No vorticity at any level.
Ok thanks. Just talking about the bad Nor'wester we had in 1989 that did so much damage on the waterfront. I remember a lot of the buildings the water went right through and so much damage to the road.
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1017. JLPR
Quoting antonio28:


Welcome back Kman! Unussual low 70 sept night here in PR.


where are you lol?
its 81F xD
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1016. JLPR
Quoting kmanislander:
Good evening all

I have not been on for the past 10 days or so due to travel obligations and the absence of activity. Just thought I would stop by to say hello.

Not a lot out there to speak of and little on the horizon. An unbelievably quiet peak season.

Looks like some rain on the way for the NW Caribbean when the ULL gets here.


Hello :)
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Quoting stormwatcherCI:
You don't think there is any chance for something to develop from the blob west of the Antilles ?


No, there is nothing to suggest anything going on there other than rain. That area is due to diffluence on the SE side of the ULL that is progressing West of there.

No vorticity at any level.
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Quoting stormpetrol:

Mitch in 98,Michelle 2001,Wilma 2005, and Dean 2007 affected us worst than some of those listed even though Mitch, Michelle and Wilma was like 140-160 miles at closest approach, Dean was like 80-100 miles. The Nor'wester of Christmas Day 1989 destroyed Northwest point , WestBay and did plenty damage downtown.
I know a lot of people talk about Gilbert but I really don't remember us being terribly affected by him although East End seems to get the worst of most of the hurricanes that come close to us but when Gilbert passed I was still living in GT.
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1012. hydrus
Quoting stormpetrol:

Mitch in 98,Michelle 2001,Wilma 2005, and Dean 2007 affected us worst than some of those listed even though Mitch, Michelle and Wilma was like 140-160 miles at closest approach, Dean was like 80-100 miles. The Nor'wester of Christmas Day 1989 destroyed Northwest point , WestBay and did plenty damage downtown.
I would like to know more about that Christmas NorthWester if you have time.
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Quoting antonio28:


Welcome back Kman! Unussual low 70 sept night here in PR.


Hi there

Sounds really nice. Flew over you last Friday on the way back from Barbados LOL

Nice smooth ride.
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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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