Little change to 99L, which remains very close to tropical depression status

By: Dr. Jeff Masters , 7:11 PM GMT on October 20, 2010

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A tropical disturbance (Invest 99L) centered 160 miles southwest of the Cayman Islands is moving south to southeast at 5 - 10 mph. A Hurricane Hunter flight arrived in the storm at about 11am this morning, and found a closed circulation with top winds at flight level (700 feet) of 33 mph. A closed circulation and 30 mph surface winds are necessary conditions for a tropical depression to exist, but the storm must also have a great deal of heavy thunderstorm activity near the center that persists for many hours. In the judgment of NHC, 99L does not qualify as a tropical depression in that regard. The storm is bringing heavy rain to the Cayman Islands; 4.14" inches has fallen over the past 2 1/2 days at Savannah on Grand Cayman Island. Heavy rains have diminished over the Cayman Islands, but have spread to western Jamaica and west-central Cuba this afternoon. Recent satellite imagery shows that the surface circulation center is exposed to view, and 99L has a relatively meager amount of heavy thunderstorm activity. The center is more than 80 miles west of the heaviest thunderstorm activity, and it is likely that 99L's center will relocate itself to the east to be more underneath the heaviest thunderstorms. Wind shear is marginal for development, 15 - 20 knots, due to the clockwise flow of air around an upper-level high pressure system near the coast of Honduras. The high is bringing strong upper-level winds out of the southwest to 99L. Water vapor satellite loops show considerable dry air to the west and north of 99L, and the strong southwesterly winds over the storm are bringing some of this dry into into the core of the storm, keeping all the heavy thunderstorm development confined to the east side of the center. The waters beneath 99L are very warm, 29°C, but 99L will not be able to take advantage of these warm waters until the shear relaxes. A new hurricane hunter aircraft will be in the storm tonight near 8pm EDT.

Forecast for 99L
The current southward movement of 99L is carrying the storm into a region of lower wind shear, and we should see 99L accumulate more heavy thunderstorm activity near its center beginning tonight. The latest SHIPS model forecast predicts that wind shear over the Western Caribbean will decline below 15 knots Thursday afternoon through Saturday afternoon, which should allow the storm to become a tropical depression by Thursday. Steering currents will be weak today through Friday in the Western Caribbean, making it difficult to predict where 99L may go. The models are split into two camps, with the GFDL and HWRF models taking 99L to the west-northwest over the western tip of Cuba or the Yucatan Peninsula on Sunday as a hurricane. The rest of the models take 99L to the south over Honduras on Sunday, and keep the storm below hurricane strength. Given 99L's current southward motion and the possibility that the center will relocate farther to the east later today, this makes a track to the southwest towards Honduras more likely, I predict. NHC is giving 99L a 70% chance of developing into a tropical depression by Friday, which is a reasonable forecast. I expect this will become Tropical Storm Richard by Friday.


Figure 1. Afternoon satellite image of Invest 99L.

Death toll from Super Typhoon Megi in the Philippines remarkably low
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 full extent of the destruction wrought by the great storm is still unclear. However, the death toll from the great storm stands at only 19, reflecting the superior effort Philippines officials made to evacuate low-lying areas and get people out of locations prone to flash flooding and mudslides. Previous major typhoons to strike the Philippines have nearly always killed hundreds, and sometime thousands, so the preparation and evacuation efforts for Megi likely saved hundreds of lives. 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. Severe damage was done to Isabela Province in northern Luzon, and media reports indicate that 200,000 people are homeless.


Figure 2. Visible MODIS satellite image of Megi from NASA's Aqua satellite taken at 1:30am EDT October 20, 2010. At the time, Megi was a Category 4 typhoon with 135 mph winds. Image credit: NASA.

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 intensified into a formidable Category 3 typhoon with 125 mph winds. 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 remain a very dangerous major typhoon through Friday. 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 north of 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, or as a strong Category 2, bringing a significant storm surge, high winds, and widespread torrential rains that will likely make this a multi-billion dollar disaster for China. The outer rain bands of Megi are already affecting the coast of China north of Hong Kong, as seen on Hong Kong radar and Taiwan radar.


Figure 3. Still frame of damage to NE Luzon Island from a video posted to YouTube by storm chaser James Reynolds of typhoonfury.com.

Next update
I'll have an update Thursday morning.

Jeff Masters

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Quoting shikori:
Link
HWRF and GFDL would both be bad news for us.
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2010 Storms
All Active Year


Atlantic

East Pacific

Central Pacific

West Pacific
98W.INVEST
95W.INVEST
15W.MEGI

Indian Ocean
98B.INVEST

Southern Hemisphere
Member Since: July 15, 2006 Posts: 174 Comments: 54639
navy took down 99l and may be about to upgrade to 19l soon
Member Since: July 15, 2006 Posts: 174 Comments: 54639
Quoting pilotguy1:


It's highly unlikely in spite of some of the more hyper members of this blog.


I think it could impact the West Coast of Florida but not nearly as strong as the most robust model runs from today have been predicting.

If this scenario plays out, it would be in about a week from today. And it could turn out to be a blessing because we have been desert-dry for weeks.
Member Since: October 15, 2010 Posts: 0 Comments: 727
Has the Us aver been hit on halloween? Also Magi looks like he got his act together, that huge eye is going to cause problems though
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0z dynamical model envelop have come into much better agreement.

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Quoting pilotguy1:


It's highly unlikely in spite of some of the more hyper members of this blog.
...possible,not probable imo
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Quoting caneswatch:


Taz, don't get going with him, he always does that.



oh ok
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Quoting Tazmanian:




am gussing where this going too have too look back at some storms that made land fall on this date or later its going too be a long night


Taz, don't get going with him, he always does that.
Member Since: October 8, 2008 Posts: 14 Comments: 4553
Quoting Levi32:
NAM now coming onboard with a reasonable track idea, as well as the 18z GFDL. The models are finally catching on to what's really happening.





Well, that makes more sense. A minimal Cat 2 hurricane making landfall in about five days in CA.

By this model run, it would be moving WNW at the time of landfall. Afterwards, it would likely bend slowly back to the north and possibly reemerge into the GOM in a much weakened state. Then it would have to try to reorganize there with lower TCHP and probably less favorable upper level winds.
Member Since: October 15, 2010 Posts: 0 Comments: 727
Quoting KerryInNOLA:
It just won't happen. not this close to Halloween. Won't happen.




am gussing where this going too have too look back at some storms that made land fall on this date or later its going too be a long night
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Quoting sebastianflorida:
I'd guess 99L has a few TRICKS up its sleeves, and will give Florida a Treat that is not so good, like when you were a kid and came home fro trick or treating and found a bunch of pennies and tootsie rolls and some hard candy in your bag.


Exactly. For some reason, recently I had the feeling this 'Richard' dude will come and get us I just wasn't too sure when exactly but I think we may have our man.
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Quoting Tazmanian:




dont all way be too sure about that
Quoting Tazmanian:




dont all way be too sure about I think this part of florida would be safe from a Hurricane this time of year. Considering that the gulf has dropped below 80 degrees.that
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According to the ATCF, 99L's pressure has decreased 2mb to 1006mb. That's a pretty good hint as to classification.
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NHC reevaluated&revised the 20Oct,06pmGMT ATCF coordinates in a manner
such that Invest 99L had been traveling nearly Eastward
rather than nearly SouthSouthEastward as reported previously
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
20Oct 12pmGMT - 17.7n82.5w - 30knots - 1008mb - ATCF*1007mb
20Oct 06pmGMT - 17.6n81.6w - 30knots - 1008mb - ATCF *17.1n82.2w
21Oct 12amGMT - 17.6n81.2w - 30knots - 1006mb - ATCF
* Before NHC reevaluated&revised the ATCF numbers
20knots=~37km/h _ 25knots=46.3km/h _ 30knots=~55.6km/h

Copy&paste 15.3n82.8w, 16.0n83.1w, 16.7n83.3w, 17.4n83.4w, 17.7n83.2w-17.8n82.9w, 17.8n82.9w-17.7n82.5w, 17.7n82.5w-17.6n81.6w, 17.6n81.6w-17.6n81.2w, pnd, mbj into the GreatCircleMapper for a look at the last 24^hours
Member Since: August 21, 2007 Posts: 0 Comments: 4860
stormwatcherci here is a better linkLink
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Quoting Pensa2woodtx:
Sorry but there is some scary stuff about 99l....be safe....gulf coast area
I'd guess 99L has a few TRICKS up its sleeves, and will give Florida a Treat that is not so good, like when you were a kid and came home fro trick or treating and found a bunch of pennies and tootsie rolls and some hard candy in your bag.
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Quoting KerryInNOLA:
The Northern GC is COMPLETELY safe from preRichard. It can NOT move in our direction. The season is OVER for us. Fla Pen may get wacked but not us.




dont all way be too sure about that
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Quoting KerryInNOLA:
The Northern GC is COMPLETELY safe from preRichard. It can NOT move in our direction. The season is OVER for us. Fla Pen may get wacked but not us.


I am reallyyyyyyy starting to think you are trying to jinx us lol!
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hummm


Decoded recon data in the last 30 minutes:

No decoded data could be found.
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Levi, do you honestly think this storm could impact the West coast of Florida?
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I wounder if i will get my full house
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Hmm...doesn't today mark the 90th anniversary of the formation of the last major hurricane to hit the Tampa Bay area? Historically, the 2nd half of October is precisely when it is most likely. Seems shear will be extreme though, maybe next Tuesday "Richard" could be between systems...so to speak, and shoot the gap. Otherwise, just can't see the expected shear not taking a heavy toll on it.
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Quoting Levi32:
NAM now coming onboard with a reasonable track idea, as well as the 18z GFDL:




If that model comes true, it would be the THIRD time a storm hit Belize this year.
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ATCF says 30 knots/1006mb @ 17.6N / 81.2W:

AL, 99, 2010102100, , BEST, 0, 176N, 812W, 30, 1006, LO, 34, NEQ, 0, 0, 0, 0, 1011, 220, 70, 0, 0, L, 0, , 0, 0, INVEST, M,
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Quoting shikori:
HWRF run is some scary stuff isn't it stormwatcher?
I haven't seen it. Can you post the link ?
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Lots of work ahead if it wants to grow up, but it seems to be trying!
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NAM now coming onboard with a reasonable track idea, as well as the 18z GFDL. The models are finally catching on to what's really happening.



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Quoting all4hurricanes:
I think TD 19 will form by 5 tomorrow morning and since most people sleep during the 11 and 5pm updates I really don't think it matters which one. As for the rest of the season we still have 40 days left even after Richard dies I'd still expect something from November If I were to guess I'd say 2-3 more storms before we're done.
I know you meant am. LOL
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gfs takes weak system into honduras
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99L has a closed surface circulation; it's the convective organization that is impeding upon the system from becoming a tropical depression. Just a minor increase in organization will likely result in the development of a tropical depression and I wouldn't be surprised if it became one by 11p.m EDT tonight.
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Sorry but there is some scary stuff about 99l....be safe....gulf coast area
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Quoting Twinkster:



why doesn't it make sense now. Wilma hit florida as a cat 3 in late october. A major hurricane as depicted by HWRF is not entirely out of question


Wilma hit in 2005 when there had been no cold fronts and no dry air over the Gulf prior to its arrival.

The weather patterns and temperature regime in that year were 2-3 weeks behind the average for that time of year in that year, unlike this year when the reverse has been true. This year, we spent nearly three whole weeks enjoying very dry and cool conditions here in Central Florida and the SSTs are much lower as a result.

Also, Wilma hit in extreme SW Florida, not just south of Tampa. As it turned out, the first significant cold front of the season followed Wilma's passage. That was a blessing to people who were without power across many areas of S. FL, because at least they did not have to suffer through days upon days of heat and humidity.

In 2005, the upper air patterns right through until just after Wilma came through were also much more favorable for tropical cyclones to venture as far north as the Florida Peninsula. This year they have been very hostile and the subtropical jet has made an early appearance. That also was not the case in '05 until after Wilma.

Wind shear may relax a bit over the Gulf next week but I doubt that it will be nonexistent, which it would just about have to be to support such a powerful hurricane as depicted by the HWRF model.
Member Since: October 15, 2010 Posts: 0 Comments: 727
I think TD 19 will form by 5 tomorrow morning and since most people sleep during the 11 and 5pm updates I really don't think it matters which one. As for the rest of the season we still have 40 days left even after Richard dies I'd still expect something from November If I were to guess I'd say 2-3 more storms before we're done.
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Quoting shawn26:
I missed the last couple of hours, are the hurricane hunters flying in tonight?
They were scheduled to but doesn't seem like they have taken off yet so I don't really know.
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BLOG UPDATE
99L likely to become Tropical Storm Richard 10/20/10
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alright i'll be back later on.
Tropical Update From Texas!
Tropical Update: Invest 99L Likely to become Richard; Shary Possible; Western Pacific Firing Up, With Video!
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18z GFDL ?
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e
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Quoting FLWaterFront:


That would make sense, if this were a month ago.



why doesn't it make sense now. Wilma hit florida as a cat 3 in late october. A major hurricane as depicted by HWRF is not entirely out of question
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Quoting HurricaneDean07:

looks like td 19 on its way.
Poll Time:
Do you think 99L will be TD Nineteen at the
(A) 8 PM today
(B) 11 PM tonight
(C) 2 AM tomorrow morning
(D) 5 PM tomorrow morning
(E) Not until late tomorrow


B
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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.