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 scott39:
Wont it be ripped to shreads by the wind shear in the GOM?

Yes, exactly. Also have to intialize the freaking models. That dude doesnt even notice that the Low is farther west than its actually location on the GFDL. Another reason why it is out to lunch.
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Quoting 7544:

agree with fla has to keep two eyes open looks like at this hour and the plane might find a ts and not a td . and could take a wilma path imo . but is really looking like ts richard at this hour . any one agree ?


Recon was finding TS winds yesterday. If the core has indeed tightened up I would expect to see a jump straight to Richard. Pressure is down to 1007 from yesterdays 1009 so, one would assume winds have gone up. Convection has been sustained, albeit sheared. Shear shouldn't keep them from classifying, Nicole proved that.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
I will be back once data from the HH starts coming in
Member Since: August 19, 2006 Posts: 0 Comments: 15826
Complete Update

A Cat 5... WTF



AOI
AOI AOI AOI

AOI AOI AOI

TS BUSTED FORECAST ALIBI
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*peeks head in doorway, sees arguing, and leaves*

-Credit to IKE-
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Looking forward to Bob and Levi's forecast video posts.
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1217. 7544

agree with fla has to keep two eyes open looks like at this hour and the plane might find a ts and not a td . and could take a wilma path imo . but is really looking like ts richard at this hour . any one agree ?
Member Since: May 6, 2007 Posts: 0 Comments: 6812
1216. pottery
Quoting kmanislander:


Good morning to you as well

Very interesting day on tap today. 99L now much closer to us and continuing to drift this way. I expect we will see this classified as a TD very soon nothwithstanding the sheared appearance.


True.
And the image at post 1212 sums it up pretty well.
Looks to me like it will eventually end up over central/eastern Cuba.
You should be getting some heavy rains....
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Recon

12:23:30Z 27.500N 88.833W 392.5 mb
(~ 11.59 inHg) 7,633 meters
(~ 25,043 feet)

Flight level winds are screaming up there. 64+mph.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
expect 99l to move more westward at the end of 48hr period imo
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Quoting pottery:
Good Morning..
99L looks a lot better than it did last night.
Would be surprised if it moves much today, but it could sit there and get better organized by tonight.
Interesting one....

Raining here. A damp, blustery, grey morning. Nice!


Good morning to you as well

Very interesting day on tap today. 99L now much closer to us and continuing to drift this way. I expect we will see this classified as a TD very soon nothwithstanding the sheared appearance.

Member Since: August 19, 2006 Posts: 0 Comments: 15826
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1211. scott39
Quoting FLstormwarning:


No question this moves NE and when it happens a lot of people on here will be ashamed for bashing me because of the pattern I see. Once in the Gulf it have to go NE no other motion is supportive to the wx pattern early next week and FL better beware.
Wont it be ripped to shreads by the wind shear in the GOM?
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Quoting FLstormwarning:
If anyone should get reported it's P'Doug. Funny JB and most forecasted aree saying the samething the FL could get nailed and people on here for whatever reason can't seem to think that once Richard passes the Tip of Cuba that it would get pulled NE by the trough moving in so I propose a question IF it passes the Tip of Cuba and gets into the Gulf as the models are saying then where do you think it will go? Well climo even says NE from that point. with a trough that deep moving SE then this would get scooped up to the NE.



Mid-October storms in the NW Caribbean should have all Floridians on guard. It's nearly a no-brainer.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
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Quoting 7544:
hwrf agrees with the gfdl now and takes it est of the yucatan look at the end of the run looks like it tries to turn ne at that time sorta like wilma did so we have to wait for the new run latter today could that happen as the high moves east and the trof kicks in to push it ne ? also the clip model has been showing that track for days now and now it shows closer to so fla . tia


The models will get a grip soon.


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1204. 7544
hwrf agrees with the gfdl now and takes it est of the yucatan look at the end of the run looks like it tries to turn ne at that time sorta like wilma did so we have to wait for the new run latter today could that happen as the high moves east and the trof kicks in to push it ne ? also the clip model has been showing that track for days now and now it shows closer to so fla . tia
Member Since: May 6, 2007 Posts: 0 Comments: 6812
Looks like recon has just left. Should have some better info a little later this morning.
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1201. pottery
Good Morning..
99L looks a lot better than it did last night.
Would be surprised if it moves much today, but it could sit there and get better organized by tonight.
Interesting one....

Raining here. A damp, blustery, grey morning. Nice!
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Quoting kmanislander:


Good morning

Good question, no West there at all. The drift to the East and the shear we were talking about
last night have both been confirmed by the NHC update.

99L is on the verge of being classified as a TD. The system looks better today to me than ever before notwithstanding that shear has displaced the convection to the East of the center. The shear tendency map shows that 99L has drifted into an area of relatively low shear and we will likely see the convection begin to close in over the center during the course of the morning.

Here is the real concern for the NW Caribbean that I have been posting about for the past couple of days. Very weak steering.

99L is not going anywhere any time soon and the danger of it sitting and organizing on our door step is quite high. A tense couple of days ahead I think.

I really appreciate your input since I don't know the first thing about it but I do agree we really need to keep a very close eye on it.
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2008 nobody except me expected the disturbance to the south to develop and look what it did Paloma missed grand cayman by 40 miles and ran smack dab into Cayman brac and little Cayman devastating the island, so to all the nay sayers out there about way too early to call any development "go fly a kite" this is my niegborhood and all my islanders know what i am saying the carribean especially in these part of the woods unexpected things happen with weather. GFDL very reliable at this time of year for some reason , in the early part of the season i dont trust it only maybe GFS & HWRF,.
To my fellow cayman bloggers we are gonna get somthing out of this not sure ... maybe more rain and tropical force winds , Cayman brac mmmmmm possible cat 1 .(TIMOHO)
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wow none of those models look good for me HWRF & GFDL the two models that plan to kill us here in Grand Cayman via Richard
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Quoting FLstormwarning:
The Tampa Shield maybe running out. This could very well hit Tampa head on.
no nature is saving that for 2012
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1196. scott39
Could 99L be picked up by a trough, if it tracks into the Yucatan channel?
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Quoting FLstormwarning:


Then you should also report 1177 let me guess the buddy system so what he says is fine.
It's not the buddy system. He used Dick which is a nickname for Richard. NOT the way you used it.
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Morning IKE and PCDoug. Cranked out morning PT this AM an hour before dawn, before I had to do the morning reports. I'm so glad to have some of the moisture back. So are my lungs. Thought I'd pop in here before work to see if you all survived the weekend out there. I see the blog is still having it's rocky moments.
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ATCF says another one millibar pressure drop; winds still at 30 knots. 17.7N/82.5W

AL, 99, 2010102012, , BEST, 0, 177N, 825W, 30, 1007, LO, 34, NEQ, 0, 0, 0, 0, 1011, 190, 70, 0, 0, L, 0, , 0, 0, INVEST, M,
Member Since: November 8, 2009 Posts: 4 Comments: 13537
Quoting superpete:
Morning everyone.Looks like more slow development on 99L in store.I hope that HWRF model run doesn't eventuate Stormwatcher... (needless to say)
I hope not.
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1191. shawn26
GFDL and HWRF look really ugly. I hope that does not pan out.
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Quoting stormwatcherCI:
???????Where u get west from ?


Good morning

Good question, no West there at all. The drift to the East and the shear we were talking about
last night have both been confirmed by the NHC update.

99L is on the verge of being classified as a TD. The system looks better today to me than ever before notwithstanding that shear has displaced the convection to the East of the center. The shear tendency map shows that 99L has drifted into an area of relatively low shear and we will likely see the convection begin to close in over the center during the course of the morning.

Here is the real concern for the NW Caribbean that I have been posting about for the past couple of days. Very weak steering.

99L is not going anywhere any time soon and the danger of it sitting and organizing on our door step is quite high. A tense couple of days ahead I think.

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1187. IKE
1185...reported.

Back away from the computer. Go mow the yard...or go for a walk. It will relieve stress.
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1186. ackee
check out the 06oz HWRF AND the GFDL both devlop 99L very close to west of jamaica then move almost right over caymans as cane the track by both models seem identical to how 99L is moving Eastward now I do buy into both idea shorterm both of models tacks not sure about there intensity thow
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1183. IKE
From Miami discussion....

ONCE THE TROUGH MOVES EAST INTO THE ATLANTIC WATERS ON
THURSDAY...HIGH PRESSURE WILL THEN BUILD INTO THE FLORIDA PENINSULA
FROM THE GULF OF MEXICO FOR FRIDAY INTO THIS WEEKEND. THIS WILL
PUSH THE LOW LEVEL MOISTURE BACK SOUTH AND BRING IN DRY AIR IN ALL
LEVELS OF THE ATMOSPHERE INTO THE CWA. SO WILL REMOVE THE POPS FOR
THURSDAY AND KEEP THE WEATHER DRY FOR FRIDAY INTO THIS WEEKEND.

EXTENDED FORECAST...
THE HIGH OVER THE FLORIDA PENINSULA WILL MOVE EAST INTO THE
ATLANTIC WATERS EARLY NEXT WEEK ALLOWING FOR ANOTHER COLD FRONT TO
APPROACH THE SOUTHEAST UNITED STATES MIDDLE OF NEXT WEEK. THIS
WILL ALLOW FOR THE STEERING FLOW TO SWING FROM A EASTERLY
DIRECTION TO A SOUTHERLY DIRECTION...AND BRING BACK SOME MOISTURE
INTO THE CWA FOR MIDDLE OF NEXT WEEK. SO WILL CONTINUE THE DRY
WEATHER OVER THE CWA FOR EARLY NEXT WEEK...BEFORE INTRODUCING A
SLIGHT CHANCE OF SHOWERS FOR THE MIDDLE OF NEXT WEEK.
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Quoting FLstormwarning:
HWRF and GFDL are similar in track. NOT GOOD! These 2 models nailed Wilma 5 years ago how ironic.


that's actually not an example of irony at all.
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Quoting stormwatcherCI:
I pray this does not occur as it would be very bad for Cayman.
Morning everyone.Looks like more slow development on 99L in store.I hope that HWRF model run doesn't eventuate Stormwatcher... (needless to say)
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1180. scott39
Developing Caribbean TCs are complex and difficult to forecast.
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i think he ment east
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06z Early Cycle NHC Dynamic Model Tracks

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Quoting FLstormwarning:
HWRF and GFDL are similar in track. NOT GOOD! These 2 models nailed Wilma 5 years ago how ironic.



Get a grip. Way to early to start sending out warnings. You don't know "Dick".
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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 ?
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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.