99L a threat to develop; damage from Typhoon Megi still largely unknown

By: Dr. Jeff Masters , 1:38 PM GMT on October 19, 2010

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Heavy thunderstorm activity has increased and grown more organized this morning over the southwestern Caribbean between Honduras and the Cayman Islands, in association with a tropical disturbance (Invest 99L). The storm is bringing heavy rain to the Cayman Islands; two inches has fallen so far this morning at Savannah on Grand Cayman Island. Recent satellite imagery shows that 99L has some rotation, and the winds on the northeast coast of Honduras at Puerto Lempira have shifted to the west-northwest, implying that 99L may be developing a surface circulation. Wind shear is a moderate 10 - 20 knots, which is low enough to allow some slow development. Water vapor satellite loops reveal that the atmosphere in the Western Caribbean is moist enough to support development, and the waters beneath are plenty warm, at 29°C. The latest SHIPS model forecast predicts that wind shear over the Western Caribbean will mostly remain in the moderate range, 10 - 20 knots, for the remainder of the week. The current north-northwest motion of 99L should continue until Wednesday, when a strong ridge of high pressure is forecast to build in, forcing 99L to the south or west. However, steering currents will be weak Wednesday through Friday, making it difficult to predict where 99L may wander to. The only models that develop 99L are the GFDL and HWRF. The GFDL model predicts that 99L will spend enough time over water to develop into a hurricane, and brings the storm to the coast of Mexico's Yucatan Peninsula on Sunday morning. The HWRF model has 99L making landfall over Honduras late this week, before the storm has a chance to develop into a hurricane. NHC is giving 99L a 40% chance of developing into a tropical depression by Thursday. I believe the odds are higher, near 60%. The Hurricane Hunters are on call to investigate 99L this afternoon.


Figure 1. Morning satellite image of Invest 99L.

Damage from Super Typhoon Megi still largely unknown
The power is still out and communications are down over the majority of the northern portion of the Philippines' Luzon Island blasted by Typhoon Megi yesterday, so the extent of the destruction wrought by the great storm is still largely unknown. Preliminary news reports indicate that at least 10 people died, and the northern Philippine province of Isabela suffered severe damage. Megi hit Luzon on Monday morning at 3:30 UTC as a Category 5 super typhoon with sustained winds of 165 mph and a central pressure of 914 mb. Baguio near the west coast of northern Luzon received 7.72" of rain from the storm, and many mountainous regions likely received over a foot of rain.


Figure 2. Rainfall rates in excess of 1 inch per hour (orange colors) were observed by the polar-orbiting F-18 satellite in association with Megi at 00:40 UTC October 19, 2010. Image credit: Navy Research Lab, Monterey.

Passage over Luzon Island destroyed Megi's eyewall and inner core region, and the storm compensated by expanding and intensifying the portions of its circulation that were over water. Now that its center is back over water in the South China Sea, Megi has re-developed its inner core and has built a formidable new eyewall. At the same time, Megi has been able to maintain its larger size, and is now a much larger typhoon than when it hit the Philippines. This is similar to what happened to Hurricane Ike in 2008 when it passed over Cuba, and helped give Ike a very destructive storm surge when it came ashore over Texas. Wind shear is a low 5 - 10 knots over Megi, and the waters of the South China sea have a very high total heat content to great depth, so Megi should be able to intensify into a very dangerous Category 4 storm by Thursday. The larger size of Megi means that it will be able to deliver a significant storm surge in excess of ten feet to the coast of China of Friday or Saturday, when the storm is expected to make landfall near Hong Kong. As the storm approaches the coast on Friday, wind shear is expected to rise to the moderate or high range, and the total heat content of the ocean will drop significantly, so some weakening is to be expected. Still, Megi will probably hit China as a major Category 3 typhoon,bringing a significant storm surge, high winds, and widespread torrential rains that will likely make this a multi-billion dollar disaster for China.

"Daily Downpour" airing this afternoon
Our live Internet radio show, "Daily Downpour", will be airing today at 4pm EDT. The call in number is 415-983-2634, or you can post a question to broadcast@wunderground.com. You can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml, and I'll be discussing the latest info on Invest 99L with hosts Shaun Tanner and Tim Roche.

Jeff Masters

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Quoting wunderkidcayman:
hey guys I was just looking at the shortwave loop and I can see that the COC is completely naked 99L location at 18.5N 82.5W moving westbound
???????Where u get west from ?
Member Since: October 9, 2008 Posts: 0 Comments: 8392
1172. IKE
Quoting PensacolaDoug:
Mornin' Ike.


Morning.
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1171. IKE
Tampa,FL forecast...

Friday: Sunny, with a high near 86. Northeast wind between 3 and 5 mph.

Friday Night: Mostly clear, with a low around 64. East northeast wind around 6 mph.

Saturday: Sunny, with a high near 87. East wind around 5 mph.

Saturday Night: Mostly clear, with a low around 67. East wind around 6 mph.

Sunday: Mostly sunny, with a high near 87. East wind around 5 mph becoming calm.

Sunday Night: Partly cloudy, with a low around 69.

Monday: Mostly sunny, with a high near 87.

Monday Night: Partly cloudy, with a low around 71.

Tuesday: Mostly sunny, with a high near 87.
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Mornin' Ike.
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hey guys I was just looking at the shortwave loop and I can see that the COC is completely naked 99L location at 18.5N 82.5W moving westbound
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morning all, like i have been saying the GFDL has this 99L nailed, going out this morning to buy another generator.
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1163. scott39
The convection of 99L is displaced from the COC. This is the only factor keeping it from becoming a TD. This will change.
Member Since: June 13, 2009 Posts: 0 Comments: 6860
Recon on the runway should be on their way shortly.


Experimental FIMZ




Loop
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Quoting FLstormwarning:
I got called a troll yesterday by saying this was going to happen. Well what i can i say I shouldn't listen to people who have no clue on forecasting. People don't seem to get the fact the FL is in a perfect setup to get hit by a cat 1 hurricane and maybe even a strong cat 2 by next Tuesday or Wednesday. I think landfall could be near Sarasota based on steering at that time.

http://www.coaps.fsu.edu/~maue/extreme/hwrf/invest99l.2010102006/invest99l.2010102006_anim.html
I pray this does not occur as it would be very bad for Cayman.
Member Since: October 9, 2008 Posts: 0 Comments: 8392
1159. IKE
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Quoting shikori:
JGHS


As a person who is involved with the Ed system in the Cayman's, it pleases me no end to find students getting involved in learning from blogs like this. Looking forward to reading your comments!!
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99L is not as small of a system as it might appear, in fact the circulation though not strong covers quite a large area, JMO
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Quoting FLstormwarning:
IKE GOM door has opened up early next week. How can you downcast now? Models are clearly painting a ugly scenario for the west coast of FL.
what you posted closest to florida i see is just north of cuba
Member Since: September 11, 2010 Posts: 1 Comments: 4724
1154. WxLogic
If 99L is able to survive the bit of shear is currently and will be on for the next 2 to 3 days then it could have a chance as a High pressure builds across the E CONUS and W ATL region forcing it to stall and acquire a W displacement.

Current NAO still call for a little dip before attempting to establish a bit more TROF(s) across E CONUS:



HWRF is starting to lean some towards GDFL as not slamming it directly into Honduras/Nicaragua region like before. If 99L stalls in the region is currently on at this time it might unfortunately have a chance.
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1153. IKE
Quoting FLstormwarning:
IKE GOM door has opened up early next week. How can you downcast now? Models are clearly painting a ugly scenario for the west coast of FL.


See post 1151. This isn't coming near Florida. Not in the next 5-7 days.
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1151. IKE
Key West...

.LONG TERM (FRIDAY NIGHT THROUGH TUESDAY)...
THE MID LATITUDE LONGWAVE TROUGH WILL CONTINUE PROGRESSING OFFSHORE
FROM THE EASTERN SEABOARD FRIDAY NIGHT AND SATURDAY...ALLOWING A MID
LEVEL RIDGE TO BUILD OVER FLORIDA.
SURFACE HIGH PRESSURE WILL
STRENGTHEN ALONG THE CAROLINA COAST AND OVER THE WESTERN ATLANTIC...
LEADING TO INCREASING EASTERLY FLOW ACROSS THE KEYS. THE AIRMASS
WILL REMAIN FAIRLY DRY WITH PWATS HOVERING AROUND 1.2 INCHES THROUGH
SATURDAY...THEN GRADUALLY INCREASING TO AROUND 1.5 INCHES BY EARLY
NEXT WEEK. A WEATHER PATTERN MORE TYPICAL OF APRIL SEEMS LIKELY FOR
THE KEYS DURING THIS TIME...WITH A DEEP DRY LAYER IN THE MID/UPPER
LEVELS AND A SIGNIFICANT MID LEVEL SUBSIDENCE INVERSION CAPPING OFF
SHALLOW LOW LEVEL MOISTURE WITHIN BRISK EASTERLY FLOW. WOULD EXPECT
JUST ISOLATED MAINLY LATE NIGHT AND EARLY MORNING SHOWER ACTIVITY IN
SUCH A PATTERN...AND WILL MAINTAIN DIME POPS THROUGH THE PERIOD.

EXPECT LITTLE CHANGE TO TEMPS...WITH HIGHS IN THE MID 80S AND LOWS IN
THE MID TO UPPER 70S.

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Quoting ackee:
I am think the NHC will wait until recon go out theirs they will however up the number to 80 or higher


Do you know when recon will go in? Seems to me that ppl will not really take this seriously until TD is declared but then NHC knows best...maybe it will just go away...I pray for that anyway.
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Quoting ackee:
I think NHC waiting for more info when Recon go out there we have better IDEA still think we see a TD#19 later today
I agree.
Member Since: October 9, 2008 Posts: 0 Comments: 8392
Quoting stormwatcherCI:
Are you getting a lot of rain down there ? BTW, good morning.

Just a drizzle now, but i think its going to be one nasty day!
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A tiny bit of convection beginning to fire over the coc now and even less to the west.
Member Since: October 9, 2008 Posts: 0 Comments: 8392
1145. ackee
Quoting stormpetrol:
Good Morning, as far as I'm concerned, the NHC is postponing the inevitable on this one, I've seen sheared systems upgraded before, first it was lack of convection, now shear, IMO watches and warnings need to be issued, but that is my opinion only!
I think NHC waiting for more info when Recon go out there we have better IDEA still think we see a TD#19 later today
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Quoting shikori:
give me a link to what u r showing stormwatcher
I posted the link for the shear tendencies. It shows decreasing shear to the NW of the system.
Member Since: October 9, 2008 Posts: 0 Comments: 8392
Quoting stormpetrol:
Good Morning, as far as I'm concerned, the NHC is postponing the inevitable on this one, I've seen sheared systems upgraded before, first it was lack of convection, now shear, IMO watches and warnings need to be issued, but that is my opinion only!
Are you getting a lot of rain down there ? BTW, good morning.
Member Since: October 9, 2008 Posts: 0 Comments: 8392
1140. scott39
NHC says 99L is drifting Eastward. COC is moving farther E for now.
Member Since: June 13, 2009 Posts: 0 Comments: 6860
Quoting shikori:
I think the sheer might be decreasing a little.
Link
Member Since: October 9, 2008 Posts: 0 Comments: 8392
Good Morning, as far as I'm concerned, the NHC is postponing the inevitable on this one, I've seen sheared systems upgraded before, first it was lack of convection, now shear, IMO watches and warnings need to be issued, but that is my opinion only!
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Quoting clwstmchasr:


From post #1119

2. REMARKS: CURRENT MODEL GUIDANCE IS DEPICTING GRADUAL INTENSIFICATION
OF A LOW SITUATED OVER THE NORTHWESTERN CARIBBEAN. THIS SYSTEM IS MOVING
NORTH AT APPROXIMATELY 9 KNOTS. THIS SYSTEM IS CENTERED OVER WARM
SEA SURFACE TEMPERATURES OF 85 TO 90 DEGREES FAHRENHEIT, WEAK VERTICAL
WIND SHEAR, AND UNDER THE WESTERN PORTION OF AN UPPER LEVEL ANTICYCLONE
WHICH SHOULD HELP TO ENHANCE THE DEVELOPMENT OF THIS TROPICAL FEATURE.
look like conditions are expected to become more favorable shortly
Member Since: September 11, 2010 Posts: 1 Comments: 4724
1135. scott39
Wind shear is a short term problem for 99L.
Member Since: June 13, 2009 Posts: 0 Comments: 6860
1133. scott39
99L will meander possibly until Friday. TD is not likely at 8am.
Member Since: June 13, 2009 Posts: 0 Comments: 6860
ABNT20 KNHC 201136
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT WED OCT 20 2010

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

A LOW PRESSURE SYSTEM CENTERED ABOUT 150 MILES SOUTHWEST OF GRAND
CAYMAN IS DRIFTING EASTWARD. ALTHOUGH STRONG UPPER-LEVEL WINDS ARE
CURRENTLY INHIBITING SIGNIFICANT DEVELOPMENT...THESE WINDS ARE
EXPECTED TO BECOME MORE FAVORABLE FOR A TROPICAL DEPRESSION TO FORM
DURING THE NEXT DAY OR SO.
AN AIR FORCE RESERVE RECONNAISSANCE
AIRCRAFT IS SCHEDULED TO INVESTIGATE THIS SYSTEM LATER THIS
MORNING. INTERESTS IN THE NORTHWESTERN CARIBBEAN SEA SHOULD
CONTINUE TO MONITOR THE PROGRESS OF THIS DISTURBANCE. THERE IS A
HIGH CHANCE...70 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS. REGARDLESS OF DEVELOPMENT...HEAVY
RAINFALL IS POSSIBLE OVER THE CAYMAN ISLANDS AND JAMAICA DURING THE
NEXT COUPLE OF DAYS.

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

$$
FORECASTER CANGIALOSI/STEWART
Member Since: October 9, 2008 Posts: 0 Comments: 8392
Quoting KEEPEROFTHEGATE:
ALERT ATCF MIL 99X XXX 101019180000
2010101918
17.4 276.6
20.7 276.0
100
17.4 276.6
200000
1010200000
1
WTNT21 KNGU 200000
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/1. FORMATION OF A TROPICAL CYCLONE IS POSSIBLE WITHIN 100 NM EITHER
SIDE OF A LINE FROM 17.5N 83.5W TO 20.8N 84.0W OVER THE NEXT 24 HOURS.
AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF A NUMBERED TROPICAL CYCLONE
WARNING AT THIS TIME.
2. REMARKS: CURRENT MODEL GUIDANCE IS DEPICTING GRADUAL INTENSIFICATION
OF A LOW SITUATED OVER THE NORTHWESTERN CARIBBEAN. THIS SYSTEM IS MOVING
NORTH AT APPROXIMATELY 9 KNOTS. THIS SYSTEM IS CENTERED OVER WARM
SEA SURFACE TEMPERATURES OF 85 TO 90 DEGREES FAHRENHEIT, WEAK VERTICAL
WIND SHEAR, AND UNDER THE WESTERN PORTION OF AN UPPER LEVEL ANTICYCLONE
WHICH SHOULD HELP TO ENHANCE THE DEVELOPMENT OF THIS TROPICAL FEATURE.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR ALLOWED TO
EXPIRE BY 210000Z.//



This alert appears to be from yesterday afternoon; are there any newer ones?
Member Since: November 8, 2009 Posts: 4 Comments: 13551
1128. ackee
Quoting CaribbeanStorm:


If this is not at least TD then I have not learned anything after watching this blog for such a long time - LOL.
I am think the NHC will wait until recon go out theirs they will however up the number to 80 or higher
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Good morning,
Dry air digging in deeper from the NW and getting closer from the SE as well. Wind shear 20 to 30 kts to the north and west and most convection to the NE of the low. Do not see RI anytime soon?
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Quoting shikori:


Not to mention JGHS if rains are torrential for an hour water almost overtakes all the corridors.
CHHS too.
Member Since: October 9, 2008 Posts: 0 Comments: 8392
Quoting ackee:
it will be intresting to see what NHC say at 8am


If this is not at least TD then I have not learned anything after watching this blog for such a long time - LOL.
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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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