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

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

Share this Blog
2
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 926 - 876

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24Blog Index

Quoting stormwatcherCI:


ty. i am reading too fast as i am also flipping between internet tabs watching loops and models. lol my fault sorry but ty for the graphic, it's useful to everyone :)
Member Since: Posts: Comments:
Quoting SweetHomeBamaGOM:



they are calling 99L a 10% chance of development?
Member Since: October 9, 2008 Posts: 0 Comments: 8242
Quoting stormwatcherCI:
No. An area sw of the Cape Verde Islands.


oh oops my mind somehow skipped over that. lol sorry my bad.
Member Since: Posts: Comments:
Quoting stormwatcherCI:
A BROAD LOW PRESSURE SYSTEM LOCATED ABOUT 350 MILES SOUTH-SOUTHEAST
OF THE CAPE VERDE ISLANDS IS PRODUCING A LARGE AREA OF CLOUDINESS
AND THUNDERSTORMS OVER THE FAR EASTERN TROPICAL ATLANTIC. EVEN
THOUGH THIS IS HISTORICALLY NOT A FAVORABLE AREA FOR TROPICAL
CYCLONE FORMATION IN LATE OCTOBER...THIS SYSTEM IS SHOWING SOME
SIGNS OF ORGANIZATION...AND ENVIRONMENTAL CONDITIONS ARE MARGINALLY
CONDUCIVE FOR SOME ADDITIONAL DEVELOPMENT TO OCCUR. THERE IS A LOW
CHANCE...10 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS AS IT MOVES TO THE WEST-NORTHWEST OR
NORTHWEST AT 10 TO 15 MPH. LOCALLY HEAVY RAINFALL IS POSSIBLE OVER
THE SOUTHERN CAPE VERDE ISLANDS TODAY AND TONIGHT.

Yep. Been watching that one (future Shary?) since it slid off the coast yesterday. Healthy-looking specimen:

Click for larger image:

Appropriate tropical weather-related image
Member Since: November 8, 2009 Posts: 4 Comments: 13306
Quoting SweetHomeBamaGOM:



they are calling 99L a 10% chance of development?
No. An area se of the Cape Verde Islands.
Member Since: October 9, 2008 Posts: 0 Comments: 8242
Quoting stormwatcherCI:
A BROAD LOW PRESSURE SYSTEM LOCATED ABOUT 350 MILES SOUTH-SOUTHEAST
OF THE CAPE VERDE ISLANDS IS PRODUCING A LARGE AREA OF CLOUDINESS
AND THUNDERSTORMS OVER THE FAR EASTERN TROPICAL ATLANTIC. EVEN
THOUGH THIS IS HISTORICALLY NOT A FAVORABLE AREA FOR TROPICAL
CYCLONE FORMATION IN LATE OCTOBER...THIS SYSTEM IS SHOWING SOME
SIGNS OF ORGANIZATION...AND ENVIRONMENTAL CONDITIONS ARE MARGINALLY
CONDUCIVE FOR SOME ADDITIONAL DEVELOPMENT TO OCCUR. THERE IS A LOW
CHANCE...10 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS AS IT MOVES TO THE WEST-NORTHWEST OR
NORTHWEST AT 10 TO 15 MPH. LOCALLY HEAVY RAINFALL IS POSSIBLE OVER
THE SOUTHERN CAPE VERDE ISLANDS TODAY AND TONIGHT.



they are calling 99L a 10% chance of development?
Member Since: Posts: Comments:
Quoting SweetHomeBamaGOM:


no...according to the link below it has moved north above the storm. that may keep it south even longer and may help with venting of the tropics creating the feedback loop around the storm in the caribbean.

if trends hold true this could moisten up rather quickly as it appears convection is banding up and the sw shear has died, thus less dry air into the core.

Link
The COC must have moved with the convection then, because it is displaced from the current coordinates. It also looks like the convection has waned some.
Member Since: Posts: Comments:
Quoting SweetHomeBamaGOM:
it appears a trend of convection is starting in the se quad bands. we may be seeing the beginning of r.i. as this storm continues to vertically align and it begins to wrap convection.

also, moisture moving into the gulf so dry air is dissipating.


Link
http://www.ssd.noaa.gov/goes/flt/t1/flash-rb.html




jsl--

Link
Member Since: Posts: Comments:
Zero wind this hour here in Savannah (G. Cayman) & steady rain
Member Since: Posts: Comments:
A BROAD LOW PRESSURE SYSTEM LOCATED ABOUT 350 MILES SOUTH-SOUTHEAST
OF THE CAPE VERDE ISLANDS IS PRODUCING A LARGE AREA OF CLOUDINESS
AND THUNDERSTORMS OVER THE FAR EASTERN TROPICAL ATLANTIC. EVEN
THOUGH THIS IS HISTORICALLY NOT A FAVORABLE AREA FOR TROPICAL
CYCLONE FORMATION IN LATE OCTOBER...THIS SYSTEM IS SHOWING SOME
SIGNS OF ORGANIZATION...AND ENVIRONMENTAL CONDITIONS ARE MARGINALLY
CONDUCIVE FOR SOME ADDITIONAL DEVELOPMENT TO OCCUR. THERE IS A LOW
CHANCE...10 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS AS IT MOVES TO THE WEST-NORTHWEST OR
NORTHWEST AT 10 TO 15 MPH. LOCALLY HEAVY RAINFALL IS POSSIBLE OVER
THE SOUTHERN CAPE VERDE ISLANDS TODAY AND TONIGHT.
Member Since: October 9, 2008 Posts: 0 Comments: 8242
Quoting scott39:
Has the wind shear picked up over TD 19?


no...according to the link below it has moved north above the storm. that may keep it south even longer and may help with venting of the tropics creating the feedback loop around the storm in the caribbean.

if trends hold true this could moisten up rather quickly as it appears convection is banding up and the sw shear has died, thus less dry air into the core.

Link
Member Since: Posts: Comments:
it appears a trend of convection is starting in the se quad bands. we may be seeing the beginning of r.i. as this storm continues to vertically align and it begins to wrap convection.

also, moisture moving into the gulf so dry air is dissipating.


Link
http://www.ssd.noaa.gov/goes/flt/t1/flash-rb.html

Member Since: Posts: Comments:
Has the wind shear picked up over TD 19?
Member Since: Posts: Comments:
906. IKE
1006.5 mb
(~ 29.72 inHg)
Member Since: June 9, 2005 Posts: 23 Comments: 37858
905. HCW
Model madness


Member Since: Posts: Comments:
904. IKE
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Saltydogbwi1:


Probably waiting for all the kids to get to school first lol ;-) But I agree TS warning possible this am
Yep. It would be strange if they issued it BEFORE the kids got to school.
Member Since: October 9, 2008 Posts: 0 Comments: 8242
Quoting stormwatcherCI:
I thought it was funny that none was issued since it is expected to intensify and begin movement wnw. Not really that far off from us yet. Cayman Prepared said the next update would be at 5 am this morning but nothing yet. Big surprise.


Probably waiting for all the kids to get to school first lol ;-) But I agree TS warning possible this am
Member Since: Posts: Comments:
899. IKE
Lowest pressure so far...1006.8 mb
(~ 29.73 inHg)
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting stormpetrol:
890. stormwatcherCI
Good morning all,I personally think that at 7am Local we should be under a TS warning just in case,quite possibly a hurricane watch also, just my opinion though!
I thought it was funny that none was issued since it is expected to intensify and begin movement wnw. Not really that far off from us yet. Cayman Prepared said the next update would be at 5 am this morning but nothing yet. Big surprise.
Member Since: October 9, 2008 Posts: 0 Comments: 8242
TD 19 looks like its sliding off a plate at the end of the loop. It Doesnt look as impressive as earlier.
Member Since: Posts: Comments:
Quoting clwstmchasr:
Stormwatcher - great minds think alike...
Same thing I was thinking. LOL
Member Since: October 9, 2008 Posts: 0 Comments: 8242
890. stormwatcherCI
Good morning all,I personally think that at 7am Local we should be under a TS warning just in case,quite possibly a hurricane watch also, just my opinion though!
Member Since: April 29, 2007 Posts: 0 Comments: 7506
dr masters acls online is a good idea. but unfornately the hospital associated with does not accept it. just recently blew a big spot on it only to find out its worthless
Member Since: Posts: Comments:
Quoting aislinnpaps:


Understood here. I have mowed once in the last ten weeks. My yard is dead. As you drive down the road all the young pine trees along the side of the road are dead, parts of grown trees are dying and dead. We need a steady drizzle for days, no deluges.


agreed. it has been so dry here i can't remember a foggy morning. and we always have foggy mornings usually in the summer, especially across the bay bridge. it has been so dry i cant remember when we have had fog.

we need drizzle, something to slowly soak in and moisten up for a deeper watering later on.
Member Since: Posts: Comments:
Quoting IKE:
Take it for what it's worth, but Accuweather shows next weekend here in the Florida panhandle as cool to cold....

Friday
Oct 29
Partly sunny, windy and cooler 65°Lo 37°

Saturday
Oct 30
A full day of sunshine 65°Lo 39°

Sunday
Abundant sunshine 65°Lo 40°
Goodmorning, Great-- The power will be out and we will freeze! J/K We need the rain yesterday!
Member Since: Posts: Comments:
From Crown Weather TWD this morning.


One thing that should be noticed is that the trends in the model guidance is definitely further north with each new model cycle and there is a definite consensus now that TD 19 will stay north of Honduras. I think the 5 am ET track forecast from the National Hurricane Center may be too far south and I believe you will see the track shift further north over the next 12 to 24 hours or so.

My thinking is that TD 19 will meander around for the next day or so and strengthen slowly and then start tracking west-northwest across the northwest Caribbean starting Friday night or Saturday. A track to the west-northwest with potential significant strengthening is quite possible this weekend and this system may track very close to or right over Cozumel and Cancun on Monday as a hurricane and possibly a major hurricane. After that, I think we may see TD 19 track into the southeastern Gulf of Mexico Monday night and track north-northeastward towards either the west coast of Florida or the Florida Panhandle by about the middle part of next week (Wednesday/Thursday timeframe). Obviously, it’s way too early to pinpoint exactly where this will impact in the eastern Gulf of Mexico or how strong at that point.

So, all interests in the northwestern Caribbean, especially Cozumel and Cancun should closely monitor the progress of this system. In addition, those of you on the west coast of Florida and the Florida Panhandle should also monitor the progress of this system.
Member Since: October 9, 2008 Posts: 0 Comments: 8242
Quoting SweetHomeBamaGOM:



thank god, my yard is dead. for gosh sakes i live in mobile where we get more annual rain than anyone in the nation and i haven't mowed for over 6 weeks in fear that the yard would burn out. now it is burned out.


i have never seen this dry of a summer in mobile. it has been strange, and that just made the smell of oil burning off and evaporating just that much worse.



we need the rain, badly.....but like they say, not a deluge too quick. the ground is bone dry.


Understood here. I have mowed once in the last ten weeks. My yard is dead. As you drive down the road all the young pine trees along the side of the road are dead, parts of grown trees are dying and dead. We need a steady drizzle for days, no deluges.
Member Since: Posts: Comments:
might become part of the front just north of the yucatan stretch out and transfer the energy northeast
Member Since: Posts: Comments:
886. HCW

Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting IKE:
Mobile,AL...

(MONDAY NIGHT THROUGH NEXT THURSDAY)...VERY INTERESTING. AS THE
AFOREMENTIONED VIGOROUS MID-TROPOSPHERIC SYSTEM MOVES OFF TO
EAST...LOW LEVEL FLOW REMAINS SOUTHERLY...SO GLFMEX REMAINS WIDE
OPEN. PROMINENT UPPER RIDGE PRESENT NEAR CUBA AT BEGINNING OF PERIOD
WITH BROAD FLAT COAST-TO- COAST UPPER TROUGH OVER CONUS. PIECE OF
ENERGY AMPLIFIES WHILE MOVING THROUGH AFOREMENTIONED ON WEST COAST
AND THEN AMPLIFIES GRADUALLY TO BE LOCATED OVER SW U.S. FOUR CORNERS
BY TUE NIGHT. MEANWHILE ...MODELS INSIST ON ADVECTING WEAK SFC LOW
NWD OUT OF TROPICS AND INTO SRN GLFMEX. SPECTRAL MODELS EXHIBIT
DISSENT ON PRECISELY WHERE FEATURE WILL BE LOCATED BUT GENERAL LARGE
SCALE PATTERN IS THE SAME...DEEP LAYER POSITIVE THERMAL AND MOISTURE
ADVECTION. SO...THIS PERIOD WILL FEEL OVERLY MUGGY UNTIL SFC COLD
FRONT CLEANS US OUT SOMETIME NEXT THURSDAY (NEW DAY 7). LATEST
GFS...ECMWF AND GEFS SOLTN`S ALL AGREE WITH THE SCENARIO AND
EVOLUTION OF ADVANCING SW U.S. TROUGH INTO PLAINS AND THEN SHOVING
LARGE SCALE SFC COLD FRONT THROUGH OUR REGION ON THURSDAY. MAIN
CONCERN AT THIS POINT IS THAT RAINFALL COULD BE HEAVY IN THE MIDDAY
WED THROUGH EARLY THU TIME FRAME. EVEN THOUGH ITS BEEN BRUTALLY
DRY...TOO MUCH RAIN TOO FAST IS NOT GOOD EITHER. TOO FAR OUT TO
DISCUSS RAINFALL AMOUNTS UNTIL POSITIONING AND MAGNITUDE OF MAJOR
SYNOPTIC FEATURES BECOMES MORE CERTAIN. HOWEVER...DEEP TROPICAL
MOISTURE TAP AND HIGH PW AIR IN PRESENCE OF STUBBORN RIDGE JUST TO
EAST PORTENDS MUCH UPWARD VERTICAL MOTION WHEN ADVANCING TROUGH
BEGINS TO IMPINGE UPON OUR REGION. SO...CONFIDENCE IS INCREASING IN
THE LARGE SCALE SETUP FOR RECEIVING HEALTHY RAINFALL EVENT AS JUST
DESCRIBED.



thank god, my yard is dead. for gosh sakes i live in mobile where we get more annual rain than anyone in the nation and i haven't mowed for over 6 weeks in fear that the yard would burn out. now it is burned out.


i have never seen this dry of a summer in mobile. it has been strange, and that just made the smell of oil burning off and evaporating just that much worse.



we need the rain, badly.....but like they say, not a deluge too quick. the ground is bone dry.
Member Since: Posts: Comments:
morning all
Member Since: Posts: Comments:
879. code1
G'mornin' Aqua, Ike, et al. Neo, I am one of the "bulk" of FL members. I'm praying it bring the panhandle and other areas of our state much needed rains. Far different than the "bulk" of youngsters/crazy's wishing for more.....

pssst aqua, I'll be your way next weekend.
Member Since: Posts: Comments:
878. IKE
Take it for what it's worth, but Accuweather shows next weekend here in the Florida panhandle as cool to cold....

Friday
Oct 29
Partly sunny, windy and cooler 65°Lo 37°

Saturday
Oct 30
A full day of sunshine 65°Lo 39°

Sunday
Abundant sunshine 65°Lo 40°
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting mcluvincane:


Yep, and will catch a lot of people off gaurd this late in the season. Most will pay little or no attention to it.


The biggest storms have all missed the U.S. and so it seems late in the season and over. Still, this developing storm may cause floods and even some winds in Florida.
Member Since: Posts: Comments:
876. IKE
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
507 AM EDT THU OCT 21 2010

VALID 12Z MON OCT 25 2010 - 12Z THU OCT 28 2010


USED THE 00Z/21 ECMWF FOR THE PRELIMINARY FRONTS AND PRESSURES FOR
DAYS 3 THROUGH 7. THE 12Z/20 ECENS MEAN WAS SUPPORTIVE OF THE
HIGHLY AMPLIFIED DETERMINISTIC ECMWF...WITH THE GEM GLOBAL
DIFFERING ONLY IN TIMING OF THE EASTWARD PROGRESSION OF THE SHARP
POLAR FRONT ACROSS THE TENNESSEE VALLEY BY THE END OF THE PERIOD.
ALL THE MODELS...GFS INCLUDED...ARE NOW HONORING THE SOUTHEAST
RIDGE...DELAYING HEIGHT FALLS INTO THAT REGION UNTIL THE VERY END
OF THE FORECAST. THE EUROPEAN CENTRE GUIDANCE HAS BEEN VERY
CONSISTENT ON THE BIG PICTURE FOR DAYS NOW...WITH THE LATEST
NEARLY CLOSED MID LEVEL TROUGH INDICATED OVER THE PLAINS DAY 7
SIMPLY A VARIATION ON A THEME. THERE IS STILL WIGGLE ROOM FOR THE
ULTIMATE POSITIONS OF THE INTENSE CYCLONES PRODUCED BY THIS
PATTERN...WITH SOME JUMPING NO DOUBT TO COME IN DETERMINISTIC
SOLUTIONS. WHETHER A TROPICAL SYSTEM CAN BE DRAWN NORTHWARD INTO
THE GULF OF MEXICO BY THE EXTREME MERIDIONAL FLOW IS ANOTHER
WILDCARD.


CISCO
Member Since: June 9, 2005 Posts: 23 Comments: 37858

Viewing: 926 - 876

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24Blog Index

Top of Page

About

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