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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I do think that this is trending a bit north still to go directly over Jamaica, so not sure if land interaction will weaken the system. He'd have to begin moving more east to feel the effects of those higher elevations. Anything can happen, but a named storm should be coming any moment as the convection has finally blown up and that was probably the only factor missing for the NHC....
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1072. ackee
Quoting Neapolitan:
I'm not so sure I buy the GFDL track, but it will be very interesting to see what happens with 99L, and when. Too, while I can understand what GFDL is seeing--and what was explained very nicely by NCHurricane2009--it's difficult to look at the LSU WV loop in #1021 and not see the squeeze play being put on. Finally, if it keeps moving east at this latitude, it's going to run into the Jamaican Alps later, and at its slow speed and compact size, that would probably signal its doom.

Having said all, that, however: 99L does look pretty good this morning. Dense and consolidated convection, quickening spin, great inflow on the south and east. I wouuld guess this is aready a TD, if not a TS, and as such may be designated as one or the other at the 8AM TWO.
agress think this is already a I guessing watch or warning will be posted for jamaica or caymans
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agreed Neapolitan
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I'm not so sure I buy the GFDL track, but it will be very interesting to see what happens with 99L, and when. Too, while I can understand what GFDL is seeing--and what was explained very nicely by NCHurricane2009--it's difficult to look at the LSU WV loop in #1021 and not see the squeeze play being put on. Finally, if it keeps moving east at this latitude, it's going to run into the Jamaican Alps later, and at its slow speed and compact size, that would probably signal its doom.

Having said all, that, however: 99L does look pretty good this morning. Dense and consolidated convection, quickening spin, great inflow on the south and east. I wouuld guess this is aready a TD, if not a TS, and as such may be designated as one or the other at the 8AM TWO.
Member Since: November 8, 2009 Posts: 4 Comments: 13611
A very good reason why the center is exposed, shear of 20-30 knots hammering the western side. The anticyclone is not really on top of this yet, could be in a few days. Stuff like this can grow fast in warm waters and ideal conditions, which could be in place for 99L soon. Right now, shear is impacting the system. Dry air is not much of an issue, I disagree with some on here. Shear is the main issue.
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This is a TD


While yes, dry air is inhibiting further development. We all can't forget what Paula did when she was surrounded by dry air, she strengthened into a Category 2 storm. This should be designated by later this morning if trends continue. You see some small, but nice banding northeast of the LLC.
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Megi is leaving:
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1064. ackee
ITS raining here in jamaica looks like SOON TO TD#19 ? or R might rhiard might take us like suprise not met serice had issue flash flood warning hope starts to move by west soon
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99L isn't looking too good at the moment. You can see the center exposed to the W of the convection. That pocket of increasing shear to the N is making it rough on this invest. Going to be a while before this becomes a named storm imo. Shows you why the GFS and ECMWF are not doing much with this system. Link
Member Since: May 22, 2010 Posts: 0 Comments: 907
in addition look at the wind shear tendency.



Link

it shows an increase of wind shear to the north over the yucatan. beyond that north of the small weak pocket there is a considerable decrease in wind shear across the GOM. the wind shear moving west is not necessarily as strong as the wind shear that has been in the GOM for the past 2 weeks.


This may mean that the storm will have an increased period of time to strengthen before it makes its move north. the wind shear isn't so strong it will interfere with development yet it is strong enough to keep it in the caribbean for a while.
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Quoting NCHurricane2009:


Yeah, a really small TD, LOL!



doesn't look too small to me.

Link


jsl shows considerable strengthening is occurring. also keep in mind this storm started with a very broad low pressure area. within that large circumference there were a number of low pressure pockets. it has taken time to organize the different pockets but now that it has low level closed circulation all of those pockets have ceased combating each other for superiority and this appears to now be growing in intensity. the fact that is is creeping due east is also a sign of potential development. it will buy it time to strengthen and avoid land.

don't underestimate this storm. it has a long time to grow before being pulled north by a trough. i agree with the models calling this thing a loop-de-loop for the next 24-36 hrs. however, like i say don't up-cast this but also be careful with it. it has a broad low pressure zone so it's potential to grow into a large hurricane is substantially greater than say a gustav or paula.
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Invest 99L
18Oct 06amGMT - 13.7n81.4w - 20knots - 1010mb - ATCF*14.0n81.8w*14.3n81.8w*13.8n81.5w
18Oct 12pmGMT - 14.1n81.8w - 25knots - 1010mb - ATCF*15.1n82.5w*15.0n82.4w*14.1n81.9w
18Oct 06pmGMT - 14.6n82.3w - 25knots - 1010mb - ATCF*15.7n83.2w*14.5n82.2w
19Oct 12amGMT - 15.3n82.8w - 25knots - 1009mb - ATCF*15.0n82.6w*15.1n82.7w
19Oct 06amGMT - 16.0n83.1w - 25knots - 1009mb - ATCF*15.7n83.0w*1008mb*15.8n82.9w
19Oct 12pmGMT - 16.7n83.3w - 25knots - 1009mb - ATCF*16.5n83.3w*1008mb*16.5n83.0w
19Oct 06pmGMT - 17.4n83.4w - 30knots - 1008mb - ATCF*17.0n83.0w*1009mb
20Oct 12amGMT - 17.7n83.2w - 30knots - 1009mb - ATCF*17.6n83.4w
20Oct 06amGMT - 17.8n82.9w - 30knots - 1008mb - ATCF
* Before NHC reevaluated&revised the ATCF numbers
20knots=~37km/h _ 25knots=46.3km/h _ 30knots=~55.6km/h

Copy&paste 13.7n81.4w, 14.1n81.8w, 14.6n82.3w, 15.3n82.8w, 16.0n83.1w-16.7n83.3w, 16.7n83.3w-17.4n83.4w, 17.4n83.4w-17.7n83.2w, 17.7n83.2w-17.8n82.9w, ctm, cyo into the GreatCircleMapper for a look at the last 24^hours

Looking at the 20Oct,12amGMT coordinate revision, those here who detected a more eastward movement after 20Oct,06pmGMT were apparently correct.
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989 DaaiTouLaam "I think the camel is trying to sneak its nose under the edge of the tent.
[map posted from] 256km radar for Hong Kong Observatory
and no official standby signal for a typhoon! (i.e. not even a hurricane watch posted yet)
"

Considering how unreliable forecasts of over 72hours are, posting a Watch now could easily be considered a bit premature.

Though the numbers should be updated soon (but since JTWC is unreliable on the when), using the coordinates supplied by the WeatherUnderground for 19Oct,12amGMT thru 19Oct,12amGMT
SuperTyphoonMegi

Copy&paste 16.3n119.0e-16.5n118.4e, 16.5n118.4e-16.7n117.9e, 16.7n117.9e-17.0n117.6e, 17.0n117.6e-17.2n117.3e, 17.2n117.3e-21.37n110.73e, zha, 17.2n117.3e-hkg into the GreatCircleMapper for a look at the headings and the distances travelled over the last 24^hours.

^ Each of the 4 eastern line-segments individually spans 6hours of Megi's path.
The westernmost line-segment is a straightline projection of the speed&heading averaged
over the 6hours spanning the last two reported positions extended to landfall:
~5days4hours from now to Wuchuan,Zhanjiang,Guangdong,China

And on a more northward path, ~4days2hours from now to HongKong
Admittedly that 4mph(6.4km/h) is a slow travel speed for a TropicalCyclone.
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Both Megi and 99L are entraining dry air.

""

""

Member Since: May 22, 2010 Posts: 0 Comments: 907
ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT WED OCT 20 2010

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

1. A NEARLY STATIONARY AREA OF LOW PRESSURE IS CENTERED ABOUT 165 MILES
SOUTHWEST OF GRAND CAYMAN. SHOWERS AND THUNDERSTORMS ASSOCIATED
WITH THE LOW HAVE INCREASED TO THE NORTHEAST OF ITS CENTER DURING
THE PAST FEW HOURS. ALTHOUGH UPPER-LEVEL WINDS ARE MARGINALLY
CONDUCIVE FOR DEVELOPMENT...ONLY A SMALL INCREASE IN ORGANIZATION
OF THE THUNDERSTORM ACTIVITY COULD LEAD TO THE FORMATION OF A
TROPICAL DEPRESSION. AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT
IS SCHEDULED TO INVESTIGATE THE LOW LATER THIS MORNING. INTERESTS
IN THE NORTHWEST CARIBBEAN SEA SHOULD CONTINUE TO 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.

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

$$
FORECASTER BROWN
NNNN
Member Since: January 30, 2010 Posts: 0 Comments: 3259
1055. JLPR2
99L will probably gain a name tomorrow since I wont be home till 9pm, :\ LOL!

I'm going to a conference by Stephen Alvarez, a photographer of National Geographic at my university and that's till 9pm.
I'm looking forward to it but suffering about the time chosen for it 6-9pm. :(

Well, night all!
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With that, I'll be signing off now understanding what some of the models do with 99L in the long range. Definetly something to keep us afoot here in the Atlantic basin,

Good night,
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Quoting CyclonicVoyage:


GFDL


Thanks for that. Now I see what at least this model wants to say. In the short-term, it drags 99L ENE toward eastern Cuba thanks to the aftorementioned upper trough. But the upper convergence on the back side of the upper trough supports a new ridge popping up over the central US, with this ridge then turning 99L WNW just in the nick of time before it makes landfall in eastern Cuba. Then, the central US ridge steers 99L WNW parallel to the S coast of Cuba till it makes landfall in the western tip of Cuba.

In short, GFDL is saying that 99L will miss the current ridge weakness and turn back toward the WNW later after missing the weakness.
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Quoting NCHurricane2009:


What's the GDFL showing? LOL, I keep losing my links to computer model sites. And when I do find such sites, they are crummy, LOL.


GFDL
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting CyclonicVoyage:


Yes, just pointing out your correctness. GFDL track is not looking too bad ATM.


What's the GDFL showing? LOL, I keep losing my links to computer model sites. And when I do find such sites, they are crummy, LOL.
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Quoting NCHurricane2009:
Yep, I see that discussion supporting the trough theory:

THE MODELS
SHOW A SHORT WAVE TROUGH OVER THE EASTERN GULF/FLORIDA
PENINSULA...WHICH SLOWLY TRACKS TO THE NORTHEAST. THIS WILL THEN
SET THE STAGE FOR A LONG WAVE TROUGH TO AMPLIFY ACROSS THE EASTERN
USA/WESTERN ATLANTIC TO THE EASTERN GULF OF MEXICO THROUGH 48-60
HRS...
TO THEN MOVE INTO THE WESTERN ATLANTIC BY 72 HRS. AT UPPER
LEVELS...AS THE POLAR TROUGH AMPLIFIES...IT WILL PRESS AGAINST THE
SUBTROPICAL RIDGE
...

MODELS
CONTINUE TO MAKE CYCLE-TO-CYCLE CORRECTIONS TO THIS SYSTEM...AS
THEY TRY TO TAKE INTO ACCOUNT THE EVOLVING MID LEVEL WEAKNESS IN
THE HEIGHT FIELD ACROSS THE WESTERN CARIBBEAN
.


Yes, just pointing out your correctness. GFDL track is not looking too bad ATM.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Yep, I see that discussion supporting the trough theory:

THE MODELS
SHOW A SHORT WAVE TROUGH OVER THE EASTERN GULF/FLORIDA
PENINSULA...WHICH SLOWLY TRACKS TO THE NORTHEAST. THIS WILL THEN
SET THE STAGE FOR A LONG WAVE TROUGH TO AMPLIFY ACROSS THE EASTERN
USA/WESTERN ATLANTIC TO THE EASTERN GULF OF MEXICO THROUGH 48-60
HRS...
TO THEN MOVE INTO THE WESTERN ATLANTIC BY 72 HRS. AT UPPER
LEVELS...AS THE POLAR TROUGH AMPLIFIES...IT WILL PRESS AGAINST THE
SUBTROPICAL RIDGE
...

MODELS
CONTINUE TO MAKE CYCLE-TO-CYCLE CORRECTIONS TO THIS SYSTEM...AS
THEY TRY TO TAKE INTO ACCOUNT THE EVOLVING MID LEVEL WEAKNESS IN
THE HEIGHT FIELD ACROSS THE WESTERN CARIBBEAN
.
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Quoting NCHurricane2009:


Also, I do see the 1022 mb ridge, which looks like it'll impart some norhtward deflection in 99L's track. But look at the red arrow, which forecasts the 1022 mb ridge to shift NE in advance of the big E US upper trough.


This was a good discussion out of CS Maryland.


TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
237 PM EDT TUE OCT 19 2010 Link

FARTHER EAST...THE MODELS ONCE AGAIN INITIALIZE AN UPPER LEVEL
RIDGE THAT EXTENDS ACROSS CENTRAL AMERICA AND MOST OF THE
CARIBBEAN/ GREATER ANTILLES. LIFTING OVER THIS AXIS...THE MODELS
SHOW A SHORT WAVE TROUGH OVER THE EASTERN GULF/FLORIDA
PENINSULA...WHICH SLOWLY TRACKS TO THE NORTHEAST. THIS WILL THEN
SET THE STAGE FOR A LONG WAVE TROUGH TO AMPLIFY ACROSS THE EASTERN
USA/WESTERN ATLANTIC TO THE EASTERN GULF OF MEXICO THROUGH 48-60
HRS...TO THEN MOVE INTO THE WESTERN ATLANTIC BY 72 HRS. AT UPPER
LEVELS...AS THE POLAR TROUGH AMPLIFIES...IT WILL PRESS AGAINST THE
SUBTROPICAL RIDGE...FLATTENING THIS AXIS WHILE DISPLACING IT
SOUTH. AT 500 HPA THE RIDGE WILL SPLIT IN TWO CELLS...THE
AFOREMENTIONED ONE OVER MEXICO/WESTERN GULF AND A NEW ONE ACROSS
THE EASTERN CARIBBEAN-CENTRAL ATLANTIC. THIS WILL FAVOR A WEAKNESS
IN THE HEIGHT FIELD ACROSS THE NORTHWESTERN CARIBBEAN BY THE END
OF THE FORECAST CYCLE.

AT LOW LEVELS A BROAD TROUGH/LOW PRESSURE AREA OVER THE WESTERN
CARIBBEAN CONTINUES TO FAVOR ORGANIZED DEEP CONVECTION...WITH
CELLS BUILDING/TRAINING ACROSS JAMAICA-CAYMAN ISLANDS. MODELS
CONTINUE TO MAKE CYCLE-TO-CYCLE CORRECTIONS TO THIS SYSTEM...AS
THEY TRY TO TAKE INTO ACCOUNT THE EVOLVING MID LEVEL WEAKNESS IN
THE HEIGHT FIELD ACROSS THE WESTERN CARIBBEAN. SO THIS REMAINS A
HIGH UNCERTAINTY FORECAST. ALSO NOTE THAT THE NHC IS EVALUATING
THIS SYSTEM FOR POSSIBILITY OF TROPICAL CYCLONE FORMATION...AND
THEY WILL ISSUE THE OFFICIAL FORECAST. ACROSS JAMAICA TO THE
CAYMAN ISLANDS IT WILL SUSTAIN ACCUMULATION OF 15-20MM/DAY AND
MAXIMA OF 30-60MM/DAY THROUGH 36 HRS...WITH MAXIMA TO SURGE TO
35-70MM/DAY BETWEEN 36-72 HRS. OVER NORTHERN HONDURAS EXPECT
ACCUMULATION OF 15-20MM/DAY AND MAXIMA OF 30-60MM THROUGH 36
HRS...TO DECREASE TO 20-30MM/DAY THROUGH 48-72 HRS. UNDER
INFLUENCE OF THE SUBTROPICAL RIDGE...SOME OF THE MOISTURE WILL
LIFT NORTH ACROSS CUBA TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY
AND MAXIMA OF 20-35MM/DAY THROUGH 24 HRS. BY 24-48 HRS THE MAXIMA
WILL INCREASE TO 35-70MM/DAY.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Yawn, 5-minutes since anyone posted, looks like we're getting sleepy LOL.
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Quoting CyclonicVoyage:


Latest surface analysis.



Also, I do see the 1022 mb ridge, which looks like it'll impart some norhtward deflection in 99L's track. But look at the red arrow, which forecasts the 1022 mb ridge to shift NE in advance of the big E US upper trough.
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Quoting sunlinepr:
Good nite, thanks for your support,,, and keep the Watcher of the skies job....


Good night
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Good nite, thanks for your support,,, and keep the Watcher of the skies job....
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Quoting CyclonicVoyage:


Latest surface analysis.



Yeah, surface anlaysis also confirms the upper trough (LOL, I am probably annoying you know with this upper trough :) ). The divergence along the upper trough is supporting that 1011 mb low along NC, and that cold front (a cold front is a surface band of surface low pressure that features air mass contrasts).

South of the cold front is high air mass contrasts. The air mass contrast at the surface is leading to the subtropical jet you see. The subtropical jet that you highlighted is pretty much parallel to the cold front, right? And this jet wouldn't exist if it weren't for the upper trough and the surface cold front its supporting.
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Quoting sunlinepr:
Interesting fact is that Puerto Rico, has never been more than 12 years without a direct Hurricane landfall..... Our last visit was Georges in 1998 and this year we are "supposed" to break that 12 year period statistic. Well, we will see.....

(Georges made landfall on the island on September 22 1998 as a Category 3-hurricane. Georges caused $2 billion)



You guys came darn close to breaking that "quiet" period with Jeanne in 2004. It made landfall across Puerto Rico just below hurricane force, and then became a hurricnae right after leaving Puerto Rico.
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Quoting NCHurricane2009:


Isn't that jet generated by the temperature contrasts associated with the upper trough? There is cold air beneath the upper trough, with warmth over the tropics to the south of the upper trough. Surface contrasts in temperature lead to upper-level wind jets. So, isn't that subtropical jet due to the fact that the upper trough exists?


Latest surface analysis.

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1039. JRRP
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Interesting fact is that Puerto Rico, has never been more than 12 years without a direct Hurricane landfall..... Our last visit was Georges in 1998 and this year we are "supposed" to break that 12 year period statistic. Well, we will see.....

(Georges made landfall on the island on September 22 1998 as a Category 3-hurricane. Georges caused $2 billion)

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Quoting JLPR2:
Well 99L is starting to look TD-ish XD



Yeah, a really small TD, LOL!
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Quoting sunlinepr:
25N 40W Spin Area, Interesting Shape keeps on going....



Yeah, neat little disturbance it is. I have been watching it for a few days. I am still a little confused as to whether it came from an African tropical wave or not. Right now, thinking this was not the case. My rough draft report on that system:

"An enhanced area of thunderstorms developed in the open tropical Atlantic Ocean, in the vicinity of 35 west longitude and 10 north latitude beginning on October 15. Although disturbed weather in this region is typically associated with tropical waves of African origin, it appears this activity was supported by a combination of surface convergence from the ITCZ (intertropical convergence zone) coupled with divergence from a large mid-ocean upper trough. The storm activity weakened as the supportive divergence left the area while the upper trough lifted northeastward. However, a weak surface low was leftover from the storm activity, and the low began drifting westward while deep-layered subtropical ridging became established to the north."
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1035. JLPR2
Well 99L is starting to look TD-ish XD

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Quoting NCHurricane2009:


Check out this water vapor loop of the entire North Atlantic Basin:

http://www.ssd.noaa.gov/goes/east/natl/flash-wv.html


That's a good point of view; sometimes we concentrate in local satellite images (micro view), forgeting that the macro has also a very influencing effect and should be considered....
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Quoting sunlinepr:
25N 40W Spin Area, Interesting Shape keeps on going....



Yep, 1009 mb low on TAFB surface analysis at the location:

http://www.nhc.noaa.gov/tafb/ATSA_18Z.gif
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1032. JLPR2
Quoting sunlinepr:
well, .....Not much convection, but some spin in this area...



Not just spin but an elongated closed area of low pressure.

But lacking convection, but as you pointed out it is interesting to watch.
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Complete Update



AOI
AOI AOI AOI

AOI AOI AOI

TS BUSTED FORECAST ALIBI
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Quoting CyclonicVoyage:


200HPA (SubTropical Jet)



Isn't that jet generated by the temperature contrasts associated with the upper trough? There is cold air beneath the upper trough, with warmth over the tropics to the south of the upper trough. Surface contrasts in temperature lead to upper-level wind jets. So, isn't that subtropical jet due to the fact that the upper trough exists?
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25N 40W Spin Area, Interesting Shape keeps on going....

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Quoting sunlinepr:
well, .....Not much convection, but some spin in this area...



Yeah, watching that area of spin just for fun, this area was actually mentioned in the NHC tropical weather outlook a couple of days ago, and then was removed from the outlook when its storm activity did a disappearing act.

Quoting jasoniscoolman2010xo:
invest 99l looking better then the yankees are!!!!hahaha,.,


You think 99L looks swank? Typhoon Megi looks swanker! Wow, God Bless the folks in the Philippines who got the brunt of that monster!
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Quoting NCHurricane2009:


Check out this water vapor loop of the entire North Atlantic Basin:

http://www.ssd.noaa.gov/goes/east/natl/flash-wv.html

During the loop, click on the HDW-H (upper-level wind vectors) check box and the Lat/Lon check boxes. There is a very massive upper trough across eastern North America between 100W and 70W longitude. This can be seen by the v-shape in the water vapor motions and the massive collection of HDW-H wind vectors. The massive trough is moving eastward.

Any standard upper trough in the westerlies has upper divergence on its east side, which reduces surface pressure below. As the upper trough's divergence overspreads the low-level ridge, the ridge will gradually weaken (erode). So, I am wondering how that low-level ridge will be strong enough to deflect 99L NW or WNW when the ridge is struggling due the massive trough over eastern N America.


200HPA (SubTropical Jet)

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well, .....Not much convection, but some spin in this area...

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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.