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 iceman55:
TexasHurricane .?


What?
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting KerryInNOLA:
It's called a forecast, an opinion, not etched in stone.


True...
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting mobilegirl81:
What is the situation with the entity in the carribean?
When it moves over the warmer waters of the Western Caribbean, the attention to this area will increase. As of now, no formation.
Member Since: September 27, 2007 Posts: 1 Comments: 20547
"There will be no Gulf hurricanes this year, as alreay forecast at the start of the season."

There may not be any this year, but still seems odd to say there will be none, when we aren't done with the season yet....
Member Since: July 2, 2009 Posts: 0 Comments: 2811
698. Floodman
10:29 PM GMT on September 16, 2009
Quoting TexasHurricane:


What do you mean, moving back? I thought it was going east....


retrograde...had sun earlier here in Central DFW and now it's raining
Member Since: August 2, 2006 Posts: 10 Comments: 9922
697. HadesGodWyvern (Mod)
10:28 PM GMT on September 16, 2009
Jakarta Tropical Cyclone Warning Center

TCWC Jakarta Tropical Cyclone Outlook
======================================
There is a low chance of 91S.INVEST to form into a tropical cyclone.

(grr I can not read Javanese)

Tropical Cyclone Formation Potential
=====================================
Thursday: Low
Friday: Moderate
Saturday: Moderate

Joint Typhoon Warning Center

Tropical Cyclone Disturbance Summary (1130z 16SEPT)
===================================================
An area of convection (91S) located at 3.3S 95.8E or 1415 NM east of Diego Garcia. Recent animated multispectral satellite imagery indicates slow consolidation of a loosely organized area of convection persisting off the western coast of Sumatra. A 0659z AMSU-B Microwave image depicts deep central convection flanking the western periphery of a well-defined, and partially exposed, low level circulation center. A 2338z Quikscat image suggest that winds may be as high as 15-20 knots at the center. Despite an improved convective signature and well defined low level circulation center, vertical wind shear in excess of 40 knots will be a limiting factor in further consolidation and strengthening.

Maximum sustianed winds near the center is 15-20 knots with a minimal central pressure of 1008 MB. The potential for this disturbance to form into a significant tropical cyclone within the next 24 hours is POOR.
Member Since: May 24, 2006 Posts: 50 Comments: 44895
695. mobilegirl81
10:28 PM GMT on September 16, 2009
What is the situation with the entity in the carribean?
Member Since: August 31, 2008 Posts: 0 Comments: 833
693. katlbeach
10:27 PM GMT on September 16, 2009
Quoting Floodman:


A little trip down memory lane: The Swirl from Ipanenma



A little more contemporary
"I kissed a swirl and I liked it" :-]
Member Since: September 22, 2008 Posts: 0 Comments: 42
691. KEEPEROFTHEGATE (Mod)
10:24 PM GMT on September 16, 2009
Quoting TexasHurricane:


What do you mean, moving back? I thought it was going east....
retrograding actually
Member Since: July 15, 2006 Posts: 169 Comments: 53308
690. centex
10:23 PM GMT on September 16, 2009
Quoting TexasHurricane:


What do you mean, moving back? I thought it was going east....
It did go east now coming back SW, we were almost done with it. It will go back E again eventually.
Member Since: August 10, 2007 Posts: 0 Comments: 3232
685. TexasHurricane
10:21 PM GMT on September 16, 2009
Quoting centex:
That pesky low is moving back into Texas.


What do you mean, moving back? I thought it was going east....
Member Since: July 2, 2009 Posts: 0 Comments: 2811
684. hydrus
10:20 PM GMT on September 16, 2009
Quoting caneluver:


Yeah, I was there cleaning up in Punta Gorda (Bal Harbor condos)
LOLOL... I probably saw ya few times.
Member Since: September 27, 2007 Posts: 1 Comments: 20547
683. ElConando
10:20 PM GMT on September 16, 2009
Quoting atmoaggie:

*Wiping away tears as the office-mates look oddly at the laughing atmoaggie*


Happy I made your day :)
Member Since: September 6, 2009 Posts: 2 Comments: 3710
682. tbrett
10:18 PM GMT on September 16, 2009
Quoting Nevis1:
"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.



The damage from HUGO is STILL visible on Nevis today. The entire island of Monteserrat was in the eye.

there is still visible damage from Hugo on Montserrat, though a lot of the damaged villas was covered by the damage done by the volcano.
Member Since: July 20, 2007 Posts: 0 Comments: 107
680. centex
10:18 PM GMT on September 16, 2009
That pesky low is moving back into Texas.
Member Since: August 10, 2007 Posts: 0 Comments: 3232
678. lordhuracan01
10:17 PM GMT on September 16, 2009
Member Since: August 11, 2009 Posts: 0 Comments: 244
676. hydrus
10:14 PM GMT on September 16, 2009
Quoting caneluver:


Yeah, but it sure was a fun one for tracking purposes.
Maybe for you, after Charlie the only tracking I was doing was for ice, gas and supplies....It was not pleasant.
Member Since: September 27, 2007 Posts: 1 Comments: 20547
674. seminolesfan
10:13 PM GMT on September 16, 2009
Quoting caneluver:
I do think the US will be hit by at least one hurricane this year. It might not be a Ivan or Floyd, but a cane non the less will smack the US somewhere.
Nice Guesscast there buddy!
Member Since: June 14, 2006 Posts: 0 Comments: 2108
668. druseljic
10:09 PM GMT on September 16, 2009
Quoting caneluver:
I do think the US will be hit by at least one hurricane this year. It might not be a Ivan or Floyd, but a cane non the less will smack the US somewhere.


Dr Master had a similar point a few blogs ago that the CONUS would see a storm that would require emergency response if I'm not mistaken.
Member Since: August 13, 2007 Posts: 0 Comments: 655
666. lordhuracan01
10:08 PM GMT on September 16, 2009


low shear for the next days
Member Since: August 11, 2009 Posts: 0 Comments: 244
665. Walshy
10:08 PM GMT on September 16, 2009
Member Since: May 17, 2009 Posts: 2 Comments: 904
664. druseljic
10:06 PM GMT on September 16, 2009
Quoting caneluver:


Yeah, but it sure was a fun one for tracking purposes.


And 2005 was simply nerve wracking, lol!
Member Since: August 13, 2007 Posts: 0 Comments: 655
660. Tejano72
10:01 PM GMT on September 16, 2009
Downtown Fort Worth, Texas

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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.