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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Does anyone track southern hemispheric cyclones. the season's coming up.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
QS this morning showing weak surface low near 13N 34W moving slowly west
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1308. Dakster


HURRICANE WARNINGS posted for Miami, FL.

The 'canes are playing Georgia Tech...



BTW - I see all our yellow circles disappeared... No chance for anything to develope at the moment?
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I'm just amazed how the ex-fred has even had any convection left after visiting almost the whole eastern atl..lol..granted it's not much (so far) but it could be funny if it does come back after all the experts had it dead. the carrib mess is just that alot of mess, but it does have a chance...not that i'm no way near any expert, just a novice who loves this time of year...
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Quoting Nolehead:
morning everyone, yep T-spin seen this alos....looks like Fred isn't dead just yet....that UL in carrib is very interesting...


Don't know if anything will happen with either as chances are slim for both. But, its certainly worth watching off and on today! I believe the ULL in the Caribbean as it near the GOM could very well be close to becoming a surface low ......these things take alot of time to come down.
Member Since: September 2, 2007 Posts: 178 Comments: 20439
morning everyone, yep T-spin seen this alos....looks like Fred isn't dead just yet....that UL in carrib is very interesting...
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xFred is pulling away from the ULL....is Fred now ready for his comeback...a growing puff just occured!

Member Since: September 2, 2007 Posts: 178 Comments: 20439
Thunderstorms are building over the COC of the ULL in the Caribbean. Need to see if this continues. If so, we might have a player.

Member Since: September 2, 2007 Posts: 178 Comments: 20439
1301. Keys99
From the Key West Morning Discussion

What type of weather feature is this?

WEAK LOW LEVEL UNDULATION ASSOCIATED WITH THE
NORTHERN EXTENT OF A GOOD YEAR TIRE TUTT CELL WILL MIGRATE THROUGH
OUR REGION FRIDAY AFTERNOON AND EVENING..
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Joe B at Accuweather has some intersesting comments regarding Fred-Ex this morning.


THURSDAY AM
HANGING ON BY A THREAD FRED SHEDS HIS UPPER LOW.

I dont know if any of you caught what Fred did yesterday, but the upper low with Fred was the result of Fred getting so strong early in his lifetime. A powerful hurricane will "build" its low pressure all the way to where the outflow level is because it pushes the outflow level up higher than when it is embryonic. This simply means the column of warm air at the center of the storm is deeper and stronger. In any case Fred weakened from below to above. The upper low is not a cold low as we saw in the Caribbean yesterday, but a leftover warm feature.

Well Fred has nothing left except its low level system now and so the "help" he was getting is gone. It will be tougher to develop thunderstorms now but only if he revs them up and sustains them does he have a chance.

I have been digging into Bob Harts phase diagram of tropical cyclones and like what he is doing. I may use his objective analysis to decide what was and what wasnt when seasons end. He had the Jersey Devil that hit friday as a Subtropical storm, which I have no problem with as it would have been classified. I have a simpler way of doing things. closed rotary circulation, gales in at least one quad, over water over 25c name it. keep the name on till its gone. We can sub label them if you like. Remember folks, once north of 25 north its tough to get the perfect symmetry that we see in the tropics. But it doesnt mean in the face of history, they are not worthy of names.

The models are having fun over the central plains. I am a UKMET fan right now ( or put it this way, it looks more like what I believe will happen) but no model is showing Fred making its comeback.

Perhaps my 9 storms this year will wind up overdone, though again what developed and hit jersey will count.

I get a kick out of the reliance on the Sept 10th date as this magic mid point. I think we can all agree, this year and last year, we got shut down pretty strongly at the "height" of the season and I think such things are predictable.. cause we did it last year and we are doing again now ( remember we had as many in the 10 day period in August as the following 20-30 days at the so called "height" of the season). All this being said, the strong uptick of the SOI that has occurred means there should be a couple more and perhaps in areas that have not seen a thing yet ( most of the gulf and the Caribbean)

thanks for reading ciao for now *****
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tornadodude, yea I get it. Fair enough.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting cchsweatherman:


I'll take a "well below all season forecasts"-type season any year. I'm hoping that this continued benign hurricane season will continue the rest of the season since everyone in the Atlantic basin really needs a respite from the consecutive active and destructive seasons we have had.


Not only that, but 2009 really kept alot in check after the seasons of 2005 and 2004 which really damage alot of judgements about the season. That's why 2009 was the least active yr since the blogs started.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Weather456:
With below normal shear and increase ibn MJO pulse in October, we may see another name storm or two but it might still be well below all seasonal forecasts, since its downhill from here.


I'll take a "well below all season forecasts"-type season any year. I'm hoping that this continued benign hurricane season will continue the rest of the season since everyone in the Atlantic basin really needs a respite from the consecutive active and destructive seasons we have had.
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Exvcept for the European Forecasts which predicted around 6. it might be more but still close. They predicted 15 in 2008. So there're doing pretty good.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
NRL named a new invest...invest 98E off the coast of Manzanillo. :)
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With below normal shear and increase ibn MJO pulse in October, we may see another name storm or two but it might still be well below all seasonal forecasts, since its downhill from here.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Good morning everyone! Been quite a while since the last time I even visited the blog, but its good to be back.

In analyzing the latest satellite imagery, CIMSS products, and computer models this morning, the Atlantic continues to remain quiet and I anticipate this continuing for at least another week as upper level winds are unfavorable across the basin.

Given the fact that remnant Fred has lost its surface circulation, the current influence from an upper level low, and still rather unfavorable upper level environment, I'm pretty confident in saying that we won't see regeneration with ex-Fred and we could close the books on the system.

Since I have gotten through all my tests and labs this week, I will try and update the CCHS Weather Center site sometime between late this morning to tomorrow afternoon. I really can't give a definite time.
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1292. IKE
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Quoting tropicofcancer:


You have lost all credibility with me here. You are a featured blogger and you are posting petty stuff like this???


You cannot please all of the people all of the time.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1290. IKE
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT THU SEP 17 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS.

$$
FORECASTER BROWN
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Quoting tornadofan:


Would you like some cheese with your whine?


If you could explain to me what that means, that would be very helpful.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Weather456:


I havnt looked at all the details yet but I hope next hurricane season is active and not becuz I love tracking tropical cyclone or I want see destruction. So that those annoying bias downcaster/wishcasters could shut up sometimes with their constant complaining about this season from day 1.


You have lost all credibility with me here. You are a featured blogger and you are posting petty stuff like this???
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Quoting Weather456:


I havnt looked at all the details yet but I hope next hurricane season is active and not becuz I love tracking tropical cyclone or I want see destruction. So that those annoying bias downcaster/wishcasters could shut up sometimes with their constant complaining about this season from day 1.


Would you like some cheese with your whine?
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1286. IKE
Reads like the forecaster on the latest TWD is getting a little frustrated...

"TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU SEP 17 2009

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST
FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1015.

...TROPICAL WAVES...

AN EASTERN ATLANTIC OCEAN TROPICAL WAVE THAT WAS ALONG 23W/24W
AT 17/0000 UTC WAS NOT ALL THAT EASY TO DISCERN IN MY OPINION
AT 16/1800 UTC IN THE THEN-CURRENT VISIBLE SATELLITE IMAGERY.
IT CONTINUES TO BE AS NON-EVIDENT NOW AS IT WAS TWELVE HOURS
AGO. I REALLY DO NOT KNOW WHAT PEOPLE ARE LOOKING AT FOR THIS
ONE.
WARMING CLOUD TOP TEMPERATURES AND DISSIPATING BUT STILL
LINGERING PRECIPITATION ARE FROM 10N TO 18N BETWEEN 25W AND 27W.
THESE CLOUDS AND WHATEVER AMOUNT OF PRECIPITATION DO NOT
VERIFY OR AUTHENTICATE THE EXISTENCE OF THIS WAVE.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 81W/82W TO THE SOUTH 15N
MOVING WEST 10 TO 15 KT. THIS WAVE ALSO IS IMPOSSIBLE TO FIND.
NO SIGNIFICANT DEEP CONVECTIVE PRECIPITATION IS ASSOCIATED WITH
THIS WAVE."

And what they say about Freddie....

"THE SURFACE TROUGH
THAT IS THE LAST REMNANT OF FRED IS ALONG 58W/59W FROM 20N TO
28N."
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Quoting Hurricane009:
We are going to have a VERY active season next year.


I havnt looked at all the details yet but I hope next hurricane season is active and not becuz I love tracking tropical cyclone or I want see destruction. So that those annoying bias downcaster/wishcasters could shut up sometimes with their constant complaining about this season from day 1.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1278. IKE
Quoting leftovers:
doubt it trend this yr is for a lot of windshear most likely continue through out the season got my three licks in your turn bloggers


LOL...you'll be labeled a downcaster. Get ready...put your shield up!
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1277. IKE
Quoting leftovers:
no but were a heck of alot closer than we were a month ago


And I don't see anything for the next 10 days based on the ECMWF.
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Sept and no invest anywhere. Doe's this mean the Atlantic season is over?
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Member Since: July 24, 2005 Posts: 407 Comments: 19076
Good Morning all

The tropics appear quiet this morning. Expect a reminder when the TWO is posted.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Just before I go, here's TAFB's take on FredEx's location and state by Sunday....



I find it amazing that anything of Fred made it across the ATL, given the hostile conditions encountered. OTOH, I'm not surprised it's headed straight for the Bahamas.... lol

Have a great day, everyone....
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Quoting btwntx08:

maybe the bahamas also theres is no way it can enter the carribean where he is now lol
That's what pple thought about Ike at first....
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Morning all.

I see very little is expected from Marty....

What's the latest on Choi-wan?

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1264. HadesGodWyvern (Mod)
National Hurricane Center
Tropical Cyclone Warning #5
TROPICAL CYCLONE MARTY (EP162009)
9:00 AM UTC September 17 2009
=================================

At 6:00 AM UTC, Tropical Storm Marty (1003 hPa) located at 19.7N 112.9W or 260 NM southwest of the southern tip of Baja California Peninsula has sustained winds of 40 knots with gusts of 50 knots. The cyclone is reported as moving north-northwest at 4 knots

Gale-Force Winds
================
60 NM from the center

Forecast and Intensity
====================
12 HRS: 20.2N 113.1W - 45 knots (Tropical Storm)
24 HRS: 21.0N 113.5W - 45 knots (Tropical Storm)
48 HRS: 23.0N 115.5W - 30 knots (Tropical Depression)
72 HRS: 24.0N 117.0W - 25 knots (Low Pressure Area)
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Wind shear is not a problem, for there are no streaming patterns in the clouds.

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Notice the elongated patch of vorticity at 500mb. This ExFred interacting with the upper level, which is causing dry air entrainment at the mid-upper levels. Although the interaction is less pronounced than yesterday, it is still giving it a hard time to consolidate.

*If it ever wishes to redevelop, it must abstain from that ULL*

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Albeit hostile for tropical cyclogenesis, ExFred is in better conditions than it was a couple of days ago. It was directly under the upper level low yesterday, which was advecting dry air at the mid to upper level lows, causing convective activity to periodically wane.Excessive exposure to such conditions has caused to lose its circulation, and it will be much harder for it to regenerate. The models are still expecting wind shear to decrease into favorable conditions over the next couple of days, and thus I will not say possible regeneration is NOT out of the question.
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Niether will the mass of to the East I say, assuming the two share the same humidity
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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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