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 Jeff9641:


It is moving east and is evident of sat. The center you are looking at is the old one.
...been sattionary alllll day,lol...
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Quoting CyclonicVoyage:



First Vortex
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) (View map)

Latest Vortex
Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 20th day of the month at 17:04Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 309)
Mission Purpose: Investigate eight suspect area (flight in the North Atlantic basin)
Mission Number: 2
Observation Number: 11
A. Time of Center Fix: 20th day of the month at 16:47:40Z
B. Center Fix Coordinates: 17°20'N 81°31'W (17.3333N 81.5167W) (View map)


Exactly my point. Those fixes are 19 hours apart.
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Quoting kmanislander:


Perhaps because in the time interval that has passed the low center went from a position farther West, up to the North, drifted East and then back down to the South to the last reported position. In essence, the low is today just East of where it was yesterday due to the inverted "U" shaped track it has executed since this time yesterday.

The recon does not depict the track of the low continously but more so where it started one day and where it has finished up today without the intermediate trip to the North and East.



First Vortex
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) (View map)

Latest Vortex
Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 20th day of the month at 17:04Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 309)
Mission Purpose: Investigate eight suspect area (flight in the North Atlantic basin)
Mission Number: 2
Observation Number: 11
A. Time of Center Fix: 20th day of the month at 16:47:40Z
B. Center Fix Coordinates: 17°20'N 81°31'W (17.3333N 81.5167W) (View map)
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Quoting Jeff9641:


It is moving east and is evident of sat. The center you are looking at is the old one.


Wind direction at buoy 42057 all day, and as recent as less than an hour ago, does not support that proposition.
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At least for right now, everyone is backing down on their intensity.

I don't see the CAT 4-5's we had earlier.

1800:


1200:


0600:
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Quoting CyclonicVoyage:


Then why does recon show east?


Perhaps because in the time interval that has passed the low center went from a position farther West, up to the North, drifted East and then back down to the South to the last reported position. In essence, the low is today just East of where it was yesterday due to the inverted "U" shaped track it has executed since this time yesterday.

The recon does not depict the track of the low continously but more so where it started one day and where it has finished up today without the intermediate trip to the North and East.
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Quoting lightningbolt73:
Hello everybody I have another question. How do I set my account up so I can view all of the comments posted? I really enjoy this blog and if I could good get some help I'd really appreciate it. Thanks!


Where the Reader Comments start, on the right side of the page there is a Filter drop down menu. Choose Show All.

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Quoting scott39:
What shows the remnant going into LA?


12Z EURO


Not much, but the closed isobar near New Orleans is the remnants of 99L.
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Quoting FLWaterFront:


If I had to guess, I'd say it might wind up as a moderate TS that makes landfall somewhere between the Florida Big Bend and Cape Sable. But that is just a shot in the dark, like any other guess at this point.

I'm skeptical about that solution that shows a remnant low going into Louisiana, however. That to me seems even less likely than a hurricane strike on the FL West coast.


It's going to be a headache to track, as most storms this year were. Some like Earl and Igor were fascinating to track. Earl was just one jog off from becoming a classic East Coast Hurricane. Igor neared, and was probably in all reality a Category 5 storm.
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Quoting FLWaterFront:


If I had to guess, I'd say it might wind up as a moderate TS that makes landfall somewhere between the Florida Big Bend and Cape Sable. But that is just a shot in the dark, like any other guess at this point.

I'm skeptical about that solution that shows a remnant low going into Louisiana, however. That to me seems even less likely than a hurricane strike on the FL West coast.
What shows the remnant going into LA?
Member Since: June 13, 2009 Posts: 0 Comments: 6740
Quoting kmanislander:


Here is your motion to the South which has been evident all day in the visible loops

06 GMT 10/20/10 17.8N 82.9W 30 1008 Invest
12 GMT 10/20/10 17.7N 82.5W 30 1007 Invest
18 GMT 10/20/10 17.1N 82.2W 30 1008 Invest


Then why does recon show east?
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Quoting kmanislander:


The visible loop is starting to suggest that the current low center is opening up some and trying to migrate underneath the deep convection nearby to the East. Fascinating to watch this thing evolve


Yes it is fascinating to watch this one. Think it might even be farther N than that. Need some more frames and also see what happens when it does get fully underneath there.
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Quoting CyclonicVoyage:
Anyone care to take a stab at why Dr. Masters said it moved south? Recon fixes clearly show east movement since yesterday.





Here is your motion to the South which has been evident all day in the visible loops

06 GMT 10/20/10 17.8N 82.9W 30 1008 Invest
12 GMT 10/20/10 17.7N 82.5W 30 1007 Invest
18 GMT 10/20/10 17.1N 82.2W 30 1008 Invest
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BOTTOM LINE, we don't really know where this will go, we have clues and maps showing us the possibilities. This could and is likely to ramp up to a strong storm at best as it stalls in the Western Caribbean. Another thing is we need a TC to develop before we can pinpoint a track.
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Quoting reedzone:


I don't think it will even be a TS if it does go this way. You really call this wishcasting? I'm just going by the pattern, I like the EURO run, a remnant low in the GOM.


If I had to guess, I'd say it might wind up as a moderate TS that makes landfall somewhere between the Florida Big Bend and Cape Sable. But that is just a shot in the dark, like any other guess at this point.

I'm skeptical about that solution that shows a remnant low going into Louisiana, however. That to me seems even less likely than a hurricane strike on the FL West coast.
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Quoting lightningbolt73:
I don't mean to be a pest, but I've asked 2 questions about posting on here and none of them have been answered! I'm not a troll I'm a totally blind new user who wants to enjoy posting just like evryone else!


Your 1st question about setup was answered at lest twice:

"Posts do get eaten on occasion, but always refresh once or twice before reposting because there can also be a delay in it showing up. Happens all the time on the initial "Post Comment." (Seastep)

"No set-up needed.
Click on 'quote' and scroll down to the comments box, add comment and click 'post comment'. (Pottery)
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Quoting Seastep:


I think it already has. If you look at the 1km loop it looks like the center that was being tracked is really just a vortex within a larger circulation and is being pulled into the center (developing center). The tracked llc makes a nice U-shaped arc within that flow. Where exactly that center is is hard to tell. KOTG could be right from his earlier post. Will probably know soon enough.
Yes
Member Since: June 13, 2009 Posts: 0 Comments: 6740
Quoting CybrTeddy:
Watch this loop, check out what the COC has been doing. It has been removed from the convection, and has broadened out and unwinding considerably in the last few frames, but has rapidly been moving southward. There is likely a COC developing where kman thinks it might be.
Link


I think it already has. If you look at the 1km loop it looks like the center that was being tracked is really just a vortex within a larger circulation and is being pulled into the center (developing center). The tracked llc makes a nice U-shaped arc within that flow. Where exactly that center is is hard to tell. KOTG could be right from his earlier post. Will probably know soon enough.
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back later
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99L is going to the N Gulf Coast as a puff of wind and a rain shower.
Member Since: June 13, 2009 Posts: 0 Comments: 6740
Quoting OneDrop:
Jeff, I wasn't hassling you yesterday, just saying not to get overzealous. McLuvincane heckled me for that (and my name LOL). I like the way you word it this time....."maybe a very very real possibility next week" Maybe being the key word. On another note, what is it with the models always throwing Florida into the mix on almost every early run of every model? Sometimes that is a good omen for us because the models change so much that we end up out of the mix in the end. Wilma was a once in a few decades type of storm and the chance of that happening again are low, not impossible but low. I think the front coming to pick up this system is going to be a stronger one than the previous ones and will probably rip it up as it moves NE. Always prepare for the worst and hope for the best!!


There's a T.V. axiom that says "if it bleeds it leads". I think it holds true on weather blogs too. The people posting HWRF today were posting the GFDL yesterday. Now that the GFDL has gone the way everyone in the know has been saying this thing would most likely go it's not the hot model anymore of doom and destruction to SoFla like they want it to be. ie: Wishcasting and Doomcasting, if the GFDL goes back the same way the HWRF is they'll say "see I told you so". It's so ridiculous.

I'm not picking on Jeff specifically with this post or anyone specifically, it's just the way it is or at least the way it seems to be. They can have a feel all they want about any particular model it surely doesn't mean they're right but it's not wrong to have a "feeling" about anything. I just don't agree with getting all alarmed over a model in a computer so far out.
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Quoting lightningbolt73:
I don't mean to be a pest, but I've asked 2 questions about posting on here and none of them have been answered! I'm not a troll I'm a totally blind new user who wants to enjoy posting just like evryone else!


Set the filter to show all, then you'll see everything.
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Anyone care to take a stab at why Dr. Masters said it moved south? Recon fixes clearly show east movement since yesterday.



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the latest HWRF showing a Charley track
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Quoting FLWaterFront:


More realistic but still not highly realistic.

Remember what Levi said. The GFDL and HWRF both have a poleward bias in the early model runs. That will likely be altered once this officially becomes a TC.

And the earlier runs for both models were showing no land interaction at all.

I'm thinking that both models have other biases in their program and which come out in a situation like this, where a system is in the early formative stages.

You may call me a downcaster but if this were mid-August through late September or if it were 2005 I'd be likely keeping quiet on these points.


GFDL moved south on the 12Z, joining the EURO which now has a decent storm, along with the BAMS and other model consensus. It's much more possible then the last run and the current HWRF run.
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Took Physics I and II, aced them both! Still have my books. yes, books.
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Quoting reedzone:


I don't think it will even be a TS if it does go this way. You really call this wishcasting? I'm just going by the pattern, I like the EURO run, a remnant low in the GOM.


it could be stronger than that
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Quoting kmanislander:


The visible loop is starting to suggest that the current low center is opening up some and trying to migrate underneath the deep convection nearby to the East. Fascinating to watch this thing evolve
I agree. Its obvious on the Loop.
Member Since: June 13, 2009 Posts: 0 Comments: 6740
Quoting scooster67:

Reed: Don't woory about the dowmcasting Reed haters. You are my Favorite Wishcaster. That is a complament.

Do you think it will go into FL?


I don't think it will even be a TS if it does go this way. You really call this wishcasting? I'm just going by the pattern, I like the EURO run, a remnant low in the GOM.
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136. HadesGodWyvern (Mod)
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Quoting Seastep:
Sorry, missed the commentary. Graphical version.



The visible loop is starting to suggest that the current low center is opening up some and trying to migrate underneath the deep convection nearby to the East. Fascinating to watch this thing evolve
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Quoting OneDrop:
Jeff, I wasn't hassling you yesterday, just saying not to get overzealous. McLuvincane heckled me for that (and my name LOL). I like the way you word it this time....."maybe a very very real possibility next week" Maybe being the key word. On another note, what is it with the models always throwing Florida into the mix on almost every early run of every model? Sometimes that is a good omen for us because the models change so much that we end up out of the mix in the end. Wilma was a once in a few decades type of storm and the chance of that happening again are low, not impossible but low. I think the front coming to pick up this system is going to be a stronger one than the previous ones and will probably rip it up as it moves NE. Always prepare for the worst and hope for the best!!
...the reason fl's been being thrown.inthe mix is climatology,one of the parameters put inzsome of the models is climatology,that and overstregthening a system because of improper wind sheer parameters, sending a stronger system more poleward jmo...
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Sorry, missed the commentary. Graphical version.

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Quoting johnnyascat:


Smile when u say dem words 'round here, pardner!



That was totally uncalled for, but still funny.
Member Since: July 7, 2010 Posts: 0 Comments: 474
Quoting SouthDadeFish:
Sorry I was judging WSW by the elongated inflow I'm seeing on satellite. Since the reading has been like that since this morning, you are correct. I think a relocation is coming farther east though.


42057 just updated. pressure down to 1006.8 and still out of the WSW

Wind Direction (WDIR): WSW ( 240 deg true )
Wind Speed (WSPD): 13.6 kts
Wind Gust (GST): 15.5 kts
Wave Height (WVHT): 3.3 ft
Dominant Wave Period (DPD): 6 sec
Average Period (APD): 4.0 sec
Atmospheric Pressure (PRES): 29.73 in
Pressure Tendency (PTDY): -0.09 in ( Falling )
Air Temperature (ATMP): 82.0 °F
Water Temperature (WTMP): 84.2 °F
Dew Point (DEWP): 75.6 °F
Heat Index (HEAT): 89.1 °F
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127. JLPR2
99L looking interesting but still only an invest and this disturbance in the Eastern Atl is looking healthy. O.o

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Quoting Waltanater:
Excellent! Good luck to you and your studies there. FIU is a great university and is it ever growing!
Thank you! speaking of studies, that's what i'm going to do now. Physics exam tomorrow.... Gross. Later everyone.
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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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