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 poknsnok:


well we will see what it does but that cloud movement beginning just south of Cuba stretching through the straits and into the atlantic is not outflow. not a chance..There is no doubt the system is seriously "right heavy" and I think in the end thats because of shear...we are all entitled to an opinion



again i beg to differ. the initial creation of this storm will be noted for the broad low pressure it has had to work with. when that much low pressure forms and there are pockets of deeper lows there is a competition of sorts when the thing pulls itself together. i think that could be an inhibiting factor for the creation of large storms (many small low pressure pockets in initial formation vying for stronger influence) but the fact that this thing even with that adversity has now pulled itself together into a low level closed circulation things are going to change, and probably quickly.

i have examined many different loops and models and i still can't find the dry air and wind shear you are referencing. for the most part the deep pocket of wind shear that was over the gulf has moved out over the atlantic and the pocket in front of the low trough now over so-cal is not nearly as strong with its westerlies. but as far as a) dry air, and b) wind shear i don't see what you are saying. i would be curious to know what model or map you are extrapolating your data from. here are links to the models i am looking at--



shear tendency

Link



gulf w.v. loop

Link


99L w.v. loop

Link



also, based on the fact that we now have a low level closed circulation i would bet on the chance of major convection springing up all over the place now. at least i would tend to believe there will be a considerable increase in convection now that the circulation has finally wound up in and out, as compared to what this system has looked like over the past few days. i just think it took days to organize the various low pressure pockets into one closed circulation, but by virtue of the fact that it has successfully done that very thing i would tend to favor formation now at this point.
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Also NGP, HWRF present Low S of PR in Experimental forecast Tropical Cyclone Genesis Link
Member Since: August 2, 2010 Posts: 21 Comments: 9648
Okay, my link is working again with TA.
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Quoting kmanislander:


That is also over 100 miles away from the center fix. 99L probably down to 1008 or 1007 mbs now with convection starting to consolidate over the center.


That's what I would expect too, but HH just can't find it. 1008.5mb has been the lowest.
Member Since: September 9, 2008 Posts: 6 Comments: 3412
We should have Tropical Storm Richard by morning.

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Quoting Seastep:
Should see another vortex message any minute now.


I do not see any data from the aircraft on TA. Are they still flying ??
Member Since: August 19, 2006 Posts: 0 Comments: 15671
Quoting Seastep:
Winds now steadily out of the SSE at 42057



That is also over 100 miles away from the center fix. 99L probably down to 1008 or 1007 mbs now with convection starting to consolidate over the center.
Member Since: August 19, 2006 Posts: 0 Comments: 15671
Quoting BLee2333:
Pressure's dropping.

1008.6 mb


They found 1008.5, but that's splitting hairs.

That's been the issue, to me. Plenty of winds, but no real consolidated area of low pressure. Low pressure area still appears to be quite broad.
Member Since: September 9, 2008 Posts: 6 Comments: 3412
Should see another vortex message any minute now.
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circulation certainly looks to be tightening up on visible
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CMC develops in SW Carib/ S PR / Mid Atl
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Pressure's dropping.

1008.6 mb
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Winds now steadily out of the SSE at 42057

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Quoting CybrTeddy:


Paula contended with worse.


I agree
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Quoting weatherman12345:

thats not sheared. thats really good outflow


well we will see what it does but that cloud movement beginning just south of Cuba stretching through the straits and into the atlantic is not outflow. not a chance..There is no doubt the system is seriously "right heavy" and I think in the end thats because of shear...we are all entitled to an opinion
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Quoting Hurricanes101:


yea dry air is a bigger issue for this than shear is right now


Paula contended with worse.
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506. Skyepony (Mod)
99L Average Position Error (nm) for core models
model Error Trend 24hr Error 48hr Error 72hr Error Day 4 Error Day 5 Error
HWRF DECREASING 60.2 85.1 -1 -1 -1
GFDL DECREASING 96.1 96.7 -1 -1 -1
MM5E INCREASING 114.1 193.4 -1 -1 -1
MM5B DECREASING 114.4 178.7 -1 -1 -1
BAMD DECREASING 146.2 219.4 -1 -1 -1
LBAR DECREASING 146.5 163.4 -1 -1 -1
KHRM CONSTANT 170 335.7 -1 -1 -1
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Quoting Bordonaro:

Actually it is dry air. As 99L moistens his environment along with the upward MJO pulse later this week, into next week, 99L will blossom nicely!!!


yea dry air is a bigger issue for this than shear is right now
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There is shear in the Florida Straits, but there is a very pronounced and strenghtening anticylone directly over 99L

In other words, shear should not be a factor right now
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Quoting Hurricanes101:
It amazes me how people see things that are not actually present

current movement is NNW, not West towards the pacific

also there is an anticyclone over 99L and the shear some think is occurring looks more to me like the clouds fanning out

Actually it is dry air. As 99L moistens his environment along with the upward MJO pulse later this week, into next week, 99L will blossom nicely!!!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Dry Air / Shear fight...



Member Since: August 2, 2010 Posts: 21 Comments: 9648
looks.like we'll have another invest-TS status,again,skipping the td stage...whats that 3for3...iguess their no longer a need for td's anymore,just invests,ts's and canes,lol...
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Quoting weatherman12345:

thats not sheared. thats really good outflow


I was thinking the same thing, but it is not super clear on Sat to me.
Member Since: September 9, 2008 Posts: 6 Comments: 3412
It amazes me how people see things that are not actually present

current movement is NNW, not West towards the pacific

also there is an anticyclone over 99L and the shear some think is occurring looks more to me like the clouds fanning out
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Quoting BLee2333:
RAMMB has a new feature on it's site incorporating GFDL and HWRF model data.

Pretty cool.

If these models pan out, Richard will do a loop in the western CARIB and hit somewhere between Belize and south of Cancun as a pretty serious storm close to the weekend.

If you're in that area, you may definately want to keep an eye on it.

Here's a direct link to the 99L runs...

Link

Invest 99L is Westward bound.

Onward to the Pacific.

Check out MIMIC-TPW

http://cimss.ssec.wisc.edu/tropic/real-time/tpw2/natl/main.html


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Quoting mcluvincane:


Caa, caa, caa....... 30%. Why in the world would u have thought 30%?


well, its easy. Every satellite presentation I look at shows the system being "Right Heavy". The Clouds are being sheared to the east. in fact a low level center has formed and there is a teardrop shaped convection ball over that. Thinner at the bottom, fatter at the top. Because its being sheared to the NE.There are no thunderstorms at all west of the center (shear) Look just N of Cuba. the ULW must be 50 kts. Look near Andros. Thats the LLC from Paula still producing TS activity being wickedly sheared. There is very dry air just NW od the system. very dry. is my reasoning relatively sound??

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RAMMB has a new feature on it's site incorporating GFDL and HWRF model data.

Pretty cool.

If these models pan out, Richard will do a loop in the western CARIB and hit somewhere between Belize and south of Cancun as a pretty serious storm close to the weekend.

If you're in that area, you may definately want to keep an eye on it.

Here's a direct link to the 99L runs...

Link
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So far this season, an invest labeled 99 has never made it to storm status.
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Quoting tkeith:
LOL


why is that funny?
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Quoting WillandGrace:
Hello every one! I´m brand new here and not a weather literate, just a regular person learning from all of you. I live in Cancun, Yucatan Peninsula in Mexico, and I was looking to the coments of today´s 5th aniversary of Willma... not a pleasent memory for must of the people that live here (it was Category 4, but it felt like 5 for over 2 days!!)... anyway, I follow you almost since then (although I suscribed myself to the blog a month ago, before I was just reading). Today here is sunny, yesterday little rain... extrange weather, but is not as warm as it was back on 2005, that kind of give me some peeace... Thank you for let me include my coment.

Welcome regular person :) (I am one too). This blog is very informative with some interesting discussions but it has been several weeks that I have gotten a question answered so I mostly lurk...
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Quoting PSLFLCaneVet:


One more in the bank!
lol....it's a cash cow! Gotta' prime the pump a bit....lol
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Quoting CosmicEvents:
I say we have a TD at 11.
LOL
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Quoting poknsnok:


there is dry air but if its up to 70% i eat crow... ooopsie!!! go shear!!! I got Wilma Whipped once and once was enough



downcasting (even if for all the best of intents) can do more harm than good. if you had the power of god to stop a storm with your words then a) you would never have to downcast, and b) no hurricanes would ever form.

no harm intended i am sure but it can be dangerous because if someone sees what you downcast and they believe in you instead of others that know better you are creating potential peril for that person with your hearsay and misinformation.
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Quoting CosmicEvents:
I say we have a TD at 11.


One more in the bank!
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Quoting TropicalMan2010:
ha i called that special two ehhh


Good job. You nailed it.
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hey guys I just came back from work and nice they up the percentages to 70% I say maybe TD 19 by 5pm or 8pm or at 11pm and maybe TS watches for us and the Yucatan at that time
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Quoting poknsnok:


Im right here I owe you a nickle


LOL
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Quoting poknsnok:


there is dry air but if its up to 70% i eat crow... ooopsie!!! go shear!!! I got Wilma Whipped once and once was enough


Caa, caa, caa....... 30%. Why in the world would u have thought 30%?
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Quoting mcluvincane:
Where's that 30% Guy?


Im right here I owe you a nickle
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Quoting Bordonaro:

469. Bordonaro


See my post 426. :)
Member Since: September 9, 2008 Posts: 6 Comments: 3412

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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.