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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sorry caps were on didnt realise it.
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99L's cloud tops are cooling. It's getting really close to TD status.
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YES ON YOUR COMMENT.....
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i know just trying to rang ya up

lol
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Quoting KerryInNOLA:
Our analysis indicates that 99L will slowly organize but will not make it to hurricane strength. We feel it is too late in the season and the atmospherics are not present.
wha ! who ! we ho ho hoh oh ohohohohoho LoL
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Out for now.
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Quoting KEEPEROFTHEGATE:
relax JFV it not coming your way anyway


What is the story behind JFV? I hear his name mentioned all the time. Would someone care to explain now that the blog is completely dead?
Member Since: October 5, 2010 Posts: 0 Comments: 269
Quoting CybrTeddy:
550. The last vortex had 38 sustained.


Glad I'm not the only one that saw it.

Also interesting is the portion in bold below:

Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 19th day of the month at 21:49Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 303)
Mission Purpose: Investigate eight suspect area (flight in the North Atlantic basin)
Mission Number: 1
Observation Number: 19
A. Time of Center Fix: 19th day of the month at 21:15:30Z
B. Center Fix Coordinates: 1727'N 8326'W (17.45N 83.4333W) (View map)
B. Center Fix Location: 186 miles (299 km) to the SW (226) from George Town, Cayman Islands (GBR).
C. Minimum Height at Standard Level: Not Available
D. Estimated (by SFMR or visually) Maximum Surface Wind: 15kts (~ 17.3mph)
E. Location of the Estimated Maximum Surface Wind: 23 nautical miles (26 statute miles) to the SE (141) of center fix
F. Maximum Flight Level Wind Inbound: From 197 at 14kts (From the SSW at ~ 16.1mph)
G. Location of Maximum Flight Level Wind Inbound: 34 nautical miles (39 statute miles) to the SE (139) of center fix
H. Minimum Sea Level Pressure: 1008mb (29.77 inHg) - Extrapolated
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 23C (73F) at a pressure alt. of 306m (1,004ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 23C (73F) at a pressure alt. of 307m (1,007ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 22C (72F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Not Available
M. Eye Shape: Not Available
N. Fix Determined By: Penetration, Wind and Pressure
N. Fix Level: 1,500 feet
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 5 nautical miles
Remarks Section:
Maximum Flight Level Wind: 26kts (~ 29.9mph) in the northeast quadrant at 19:50:50Z
Maximum Flight Level Wind Outbound: 26kts (~ 29.9mph) in the northwest quadrant at 21:26:30Z
Sea Level Pressure Extrapolation From: Below 1,500 feet
Maximum Surface (likely estimated by SFMR) Wind Outbound: 27kts (~ 31.1mph) in the northwest quadrant at 21:25:30Z


Oh well.
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Quoting TropicalMan2010:
we know its 70% just go back to the previous pages
relax JFV it not coming your way anyway
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550. VAbeachhurricanes

Thanks for that. They changed it. Must have just been a glitch, because I copy and pasted 32kts (~ 36.8mph) from the same page. Wish I hadn't removed the full message. Oh, well.

Interesting, that it dropped that much from the last vortex message, for sure.
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Good evening...

I see we're at 70% now... not looking so bad.
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Quoting tkeith:
Taz should get a name for 99L before it's all said and done.

That will complete round three for him.
If he does it will be the only time 99L has developed this year according to Taz.
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550. The last vortex had 38 sustained.
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BUOY 4257

4:50 pm SSE ( 156 deg ) 22.5 kts
4:40 pm SSE ( 157 deg ) 22.5 kts
4:30 pm SSE ( 155 deg ) 21.8 kts
4:20 pm SSE ( 154 deg ) 20.6 kts
4:10 pm SSE ( 152 deg ) 22.1 kts
4:00 pm SSE ( 152 deg ) 22.7 kts


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Taz should get a name for 99L before it's all said and done.

That will complete round three for him.
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000
ABNT20 KNHC 192039
TWOAT
SPECIAL TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
440 PM EDT TUE OCT 19 2010

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

OBSERVATIONS FROM AN AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT
INVESTIGATING THE AREA OF LOW PRESSURE...ABOUT MIDWAY BETWEEN
HONDURAS AND THE CAYMAN ISLANDS...INDICATE THAT A BROAD LOW-LEVEL
CIRCULATION HAS FORMED. CONDITIONS APPEAR CONDUCIVE FOR SOME
DEVELOPMENT...AND ANY INCREASE IN THE ORGANIZATION OF THE
ASSOCIATED SHOWERS AND THUNDERSTORMS COULD LEAD TO THE FORMATION OF
A TROPICAL DEPRESSION. INTERESTS IN THE NORTHWEST CARIBBEAN SEA
SHOULD MONITOR THE PROGRESS OF THIS SYSTEM. THERE IS A HIGH
CHANCE...70 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS AS IT MOVES TOWARD THE NORTH AT 5 TO 10
MPH.

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

$$
FORECASTER PASCH


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up to 70% now
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Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 19th day of the month at 21:49Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 303)
Mission Purpose: Investigate eight suspect area (flight in the North Atlantic basin)
Mission Number: 1
Observation Number: 19
A. Time of Center Fix: 19th day of the month at 21:15:30Z
B. Center Fix Coordinates: 17°27'N 83°26'W (17.45N 83.4333W)
B. Center Fix Location: 186 miles (299 km) to the SW (226°) from George Town, Cayman Islands (GBR).
C. Minimum Height at Standard Level: Not Available
D. Estimated (by SFMR or visually) Maximum Surface Wind: 15kts (~ 17.3mph)
E. Location of the Estimated Maximum Surface Wind: 23 nautical miles (26 statute miles) to the SE (141°) of center fix
F. Maximum Flight Level Wind Inbound: From 197° at 14kts (From the SSW at ~ 16.1mph)
G. Location of Maximum Flight Level Wind Inbound: 34 nautical miles (39 statute miles) to the SE (139°) of center fix
H. Minimum Sea Level Pressure: 1008mb (29.77 inHg) - Extrapolated
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 23°C (73°F) at a pressure alt. of 306m (1,004ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 23°C (73°F) at a pressure alt. of 307m (1,007ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 22°C (72°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Not Available
M. Eye Shape: Not Available
N. Fix Determined By: Penetration, Wind and Pressure
N. Fix Level: 1,500 feet
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 5 nautical miles
Remarks Section:
Maximum Flight Level Wind: 26kts (~ 29.9mph) in the northeast quadrant at 19:50:50Z
Maximum Flight Level Wind Outbound: 26kts (~ 29.9mph) in the northwest quadrant at 21:26:30Z
Sea Level Pressure Extrapolation From: Below 1,500 feet
Maximum Surface (likely estimated by SFMR) Wind Outbound: 27kts (~ 31.1mph) in the northwest quadrant at 21:25:30Z

got some work to do
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Just my thoughts after looking at the Water Vapor Loops. There is serious amount of dry air to the West/Northwest of 99L and it has a bulging easterly component to it, (moving to the East, I should say)... For 99L to become Richard, it will have to fight off this entraining area of dry air, which I think is inhibiting development on the West side of this system. Slowing down and meandering, maybe a slight southerly movement, also, will help 99L duck below this dry air. It has right side bias as far as convection, as mentioned before. The more North 99L moves in the short term will inhibit development, IMO. My name is Richard BTW....
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Member Since: August 25, 2009 Posts: 20 Comments: 6785
We did get one more Vortex. Down to 1008mb. Still 32kts (~ 36.8mph).

Removed as redundant.
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New vortex answered my question. Thanks!
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Sorry, Cuba's radar was banned....
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709

URNT12 KNHC 192149

VORTEX DATA MESSAGE AL992010

A. 19/21:15:30Z

B. 17 deg 27 min N

083 deg 26 min W

C. NA

D. 15 kt

E. 141 deg 23 nm

F. 197 deg 14 kt

G. 139 deg 34 nm

H. EXTRAP 1008 mb

I. 23 C / 306 m

J. 23 C / 307 m

K. 22 C / NA

L. NA

M. NA

N. 134 / 1

O. 0.02 / 5 nm

P. AF303 01IIA INVEST OB 19

MAX FL WIND 26 KT NE QUAD 19:50:50Z

MAX OUTBOUND FL WIND 26 KT NW QUAD 21:26:30Z

SLP EXTRAP FROM BELOW 1500 FT

MAX OUTBOUND SFC WIND 27 KT NW QUAD 21:25:30Z

;


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Quoting kmanislander:
The aircraft is hunting around on the NW side of the circulation. We will have to wait for another center pass to see how the pressure is doing. Those 1008s we are seeing carry Westerly winds ( NW side )

It appears they're done for this flight; they've finished their final delta, and are on their way home. They found lots of TD (and even some TS) force sustained winds at low flight levels; I have little doubt this will be classified as TD19 this evening, if not TS Richard...so long as that convection at the center increases, or at the very least doesn't fade.
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Anyone look at that last message? Are those anomolous pressures??
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541. unf97
Quoting CybrTeddy:
99L up to 70%.

Might get a TD by 11 tonight, or 5am tomorrow.



I think early Wednesday morning should see an upgrade by NHC.
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See you all later
Member Since: August 19, 2006 Posts: 0 Comments: 15948
Just saw an extrapolated surface pressure of 1003 on the climb out. Not sure if that is valid or not.
Member Since: August 19, 2006 Posts: 0 Comments: 15948
Quoting Seastep:


Correction, already have. Surprised they didn't issue one last vortex.


Aircraft climbing out. No new message probably means none warranted based upon fairly static surface data. 99L has work to do tonight it seems.
Member Since: August 19, 2006 Posts: 0 Comments: 15948
Quoting kmanislander:


No doubt we will see a big convective blow up once the HH has cleared the area LOL


LOL. Murphy's Law.
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Quoting Seastep:


Based on HH, it still appears to be a very broad area of low pressure.

And, unfortunately, they are going to leave soon.


Correction, have left already. Surprised they didn't issue one last vortex.
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Quoting nrtiwlnvragn:






i agree with those model runs for what they are really saying. there are influences on all 4 sides of this development that are going to hold it in place or send it in loop-de-loops.
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Quoting Seastep:


Based on HH, it still appears to be a very broad area of low pressure.

And, unfortunately, they are going to leave soon.


No doubt we will see a big convective blow up once the HH has cleared the area LOL
Member Since: August 19, 2006 Posts: 0 Comments: 15948
Quoting kmanislander:


Sorry, yes, see corrected post.


Based on HH, it still appears to be a very broad area of low pressure.

And, unfortunately, they are going to leave soon.
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Quoting Seastep:


Try the 21:04Z here

Mostly W and WSW.


Sorry, yes, see corrected post.
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Quoting kmanislander:
The aircraft is hunting around on the NW side of the circulation. We will have to wait for another center pass to see how the pressure is doing. Those 1008s we are seeing carry ENE winds ( NW side )


Try the 21:04Z here

Mostly W and WSW.
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Quoting SweetHomeBamaGOM:

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The aircraft is hunting around on the NW side of the circulation. We will have to wait for another center pass to see how the pressure is doing. Those 1008s we are seeing carry Westerly winds ( NW side )
Member Since: August 19, 2006 Posts: 0 Comments: 15948
Quoting kmanislander:


I do not see any data from the aircraft on TA. Are they still flying ??


Yes, found 1008.5 about 20min ago at about 17.3N/83.3W.

Try this.

The "see all of this type" drop-down box page is not working.
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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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