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 P451:
Labeling users as wishcasters or downcasters is pointless. We all have our opinions. We all have our M.O. for all to see. Some of us see a storm and are "positive" about it developing even when the conditions aren't there to support such an opinion. Some of us are "negative" about a storm developing even when the signs are there that it can and will.

Why is it of such importance?

I will never understand.

This is a blog primarily filled full of weather hobbyists, with a few aspiring meteorologists peppered in along with a couple of actual certified individuals in some capacity and experience.

This isn't the NHC, this isn't the NWS, nothing said here should be used as fact when looking out for one's or one's family's own safety.

So I really don't get the bickering over a wishcaster, downcaster, or what have you.

We all enjoy the weather, we all enjoy commenting on it, and we all have our opinions on what we see in regards to images, maps, and models.

I really don't understand the problem AT ALL.





amen
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109. jipmg
Quoting P451:
Labeling users as wishcasters or downcasters is pointless. We all have our opinions. We all have our M.O. for all to see. Some of us see a storm and are "positive" about it developing even when the conditions aren't there to support such an opinion. Some of us are "negative" about a storm developing even when the signs are there that it can and will.

Why is it of such importance?

I will never understand.

This is a blog primarily filled full of weather hobbyists, with a few aspiring meteorologists peppered in along with a couple of actual certified individuals in some capacity and experience.

This isn't the NHC, this isn't the NWS, nothing said here should be used as fact when looking out for one's or one's family's own safety.

So I really don't get the bickering over a wishcaster, downcaster, or what have you.

We all enjoy the weather, we all enjoy commenting on it, and we all have our opinions on what we see in regards to images, maps, and models.

I really don't understand the problem AT ALL.




it gets annoying, people start saying "X storm is going to be a fish, or its going to die off like everyting else" despite models saying otherwise, or latest satellite imagery saying otherwise, just saying it with no proof just personal bias gets annoying, same thing goes for wishcasting.
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This one appears non tropical

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting catastropheadjuster:
I'd like to ask a question and don't mean to sound dumb. But here we go What does the upward MJO mean? I mean what does it do to help develop anything or does it even do that?

Sheri


the upward phase of the MJO helps to generate convection just like the downward phase of the MJO supresses convection
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If I may pull a comparison here...

Choi-Wan

Katrina
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Quoting seminolesfan:
The updates still haven't gone through on it, have they? I'm speaking of the algorithm and programming updates, not input. I think I remember some talk of that being in the pipeline around the early season time frame, but they were delaying making the changes operational to allow more verification time.


Not sure...maybe someone more in tune with the models can tell us.

All i know is, the model has been intensifying everything this year...
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101. jipmg
Quoting stormpetrol:
Wonder if the ULL SW of PR might be making its way to the surface? just wondering?


its trying:

http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8vor3.html
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I'd like to ask a question and don't mean to sound dumb. But here we go What does the upward MJO mean? I mean what does it do to help develop anything or does it even do that?

Sheri
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Quoting Weather456:


has to be non tropical, I dont see how that has no circle of any kind anymore, I dont get it

last I saw it was attached to a warm front
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Wonder if the ULL SW of PR might be making its way to the surface? just wondering?
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THANK YOU STORM YOUR INFO. IS ALWAYS VALUABLE
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Member Since: July 24, 2005 Posts: 407 Comments: 19076
Looking at big ball of convection moving North off
Mexico into BOC...Interesting...
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Hi JRRP...I'm looking at the same thing.
It seems to be starting to develop a life of its own.
CaribbeanLoop
There is 40k of shear to its west.
ShearMap
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In lurk mode for now to watch and wait if anything develops over the next few days; plenty of naked swirls and dry air out there in the Atlantic Basin to keep an eye on.
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Good morning everyone! Sure is a lot of spinning going on in the Atlantic! I guess we're lucky conditions don't favor any rapid development of anything. That ULL South of Puerto Rico is interesting though, been watching it since last night and it seems to be pulling in a lot of moisture. That one could be trouble if it could work itself down to the surface.
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00 Z FredEx Dynamic Models (More sophisticated models)

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Quoting SQUAWK:
Looks like it is starting to form some circulation to me.



a circulation has been there for a good while now. About 3 days now.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting SQUAWK:
Looks like it is starting to form some circulation to me.



like many other systems this year, NHC wont name it, so dont expect it
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Looks like it is starting to form some circulation to me.

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Simply Amazing

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting rwdobson:
"Only the HWRF model redevelops Fred"

the same model that brought us Major Hurricane Danny and Major Hurricane Erika strikes again...
The updates still haven't gone through on it, have they? I'm speaking of the algorithm and programming updates, not input. I think I remember some talk of that being in the pipeline around the early season time frame, but they were delaying making the changes operational to allow more verification time.
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00 Z FredEX Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)


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This evening's 8pm HKT (GMT+8) weather chart from the HK Observatory for this end of the Pacific.
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Member Since: July 24, 2005 Posts: 407 Comments: 19076
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
Quoting Floodman:


I'll have to do a little research but I was thinking that the MJO was to be upward by the end of September...

Yep. Upward MJO is over the CPAC right now, and its neutral in the EPAC. The ATL basin should be getting upward MJO over the next week or so.

Not a good setup with the high SSTs we have in the ATL, Caribbean, and GOM right now.
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Quoting BurnedAfterPosting:
456 what do you think of each of those 3 areas?

NHC dropped the circle for the area of the bahamas, while most models develop it as StormW said



Its on my blog.

Elsewhere, a well-define upper low is spinning across the Northeastern Caribbean Sea producing scattered showers across the area from 60-70W south of 20N. Expect overcast skies with periodic showers and thunderstorms across the Lesser Antilles throughout the day. This area will be monitored for any signs of development as it shifts west.

A non-tropical low is developing just north of the Bahamas and even through the cold front south of the system disintegrated into a surface trough, this feature is still expected to develop as a non-tropical system. However, the southern part will be watch, especially if both systems (the other being Fred) meets.

Some of the models are showing development in the Eastern Atlantic, and even though the wave that is expected to develop has a well-define close circulation, it still is having trouble to produce sustainable convection.

There is another wave that is about to emerge over the Eastern Atlantic that could develop, as it remains vigorous
.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting weathermanwannabe:
Thanks Dr. M; No comment on the broad circulation south of PR?


Its a ULL interacting with a tropical wave
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Thanks Dr. M; No comment on the broad circulation south of PR?
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456 what do you think of each of those 3 areas?

NHC dropped the circle for the area of the bahamas, while most models develop it as StormW said
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Quoting Floodman:


Howdy, everyone...

So with the A/B High building back into the CONUS, what is the MJO doing?


Good Morning everyone and Hey Flood. It's been a quite season Thank God. It's been 5 yrs since Ivan and still Folks recuperating from that one you can still go over to Baldwin County,Al, little towns like Stockton,Bay Minette, and other ones and still see the damage from Ivan.

Sheri
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Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting StormW:
Hi gang!

Hot off the press!

TROPICAL WEATHER SYNOPSIS SEPTEMBER 16, 2009 ISSUED 11:00 A.M. EDT
Thanks, Storm
What do you make of the big blowup of c onvection in southern BOC near Mexican coast?
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Three areas of interest

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


From what I've been able to tell... the downward MJO should be moving towards the C/E ATL while the Carib and W ATL should be on a neutral MJO.


I'll have to do a little research but I was thinking that the MJO was to be upward by the end of September...
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Thanks for the write-up on Choi-wan, Dr Masters. The Cloudsat imagery is quite an eye-opener. According to the Saipan Tribune, the residents of the islands of Alamagan and Agrihan are all safe. Alamagan received a direct hit by the cyclone's eye, and winds of 145 mph were reported.
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scenario
Quoting Floodman:


Howdy, everyone...

So with the A/B High building back into the CONUS, what is the MJO doing?


From what I've been able to tell... the downward MJO should be moving towards the C/E ATL while the Carib and W ATL should be on a neutral MJO.
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Fred ex fred showing stronger vortocity
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Thx Doc...

12Z NAM still showing ridging on the E CONUS with a 1024 High and Fred's remnants moving W. For now ECMWF (Mid level energy), NOGAPS, and CMC are still displaying a like scenario.
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64. JRRP
see you later...
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Quoting TampaSpin:
Looks like our Trough protection will be gone for the next 7 days or more...as the Bermuda high builds west into the ConUs.


Howdy, everyone...

So with the A/B High building back into the CONUS, what is the MJO doing?
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Quoting mobilegirl81:
It will be interesing to see if this ridge does what it is forecasted to do and keeps Fred on more westerly track.


Fred might move WSW for a while upcoming!
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Quoting reedzone:


Look at the phrase..

"Fred COULD be the talk of 2009 Hurricane Season. "LOL"

I was just having fun yesterday, this wasn't really a prediction. However, it will probably be the talk of the season as the most longest and annoying storm this year.


Most longest??????
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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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