African tropical wave 99L slowly organizing

By: Dr. Jeff Masters , 1:26 PM GMT on July 31, 2012

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A tropical wave (Invest 99L) near 9°N 41°W, halfway between the Lesser Antilles Islands and the coast of Africa, has the potential to develop into a tropical depression later this week as it moves westward at 10 - 15 mph. Visible satellite loops show that the disturbance now has a moderate amount of poorly-organized heavy thunderstorms that continue to slowly increase in intensity and areal coverage. There is no surface circulation, but some counter-clockwise rotation of the large-scale cloud pattern is evident. Water vapor satellite loops show that 99L has a reasonably moist environment. The latest Saharan air layer analysis shows that the dry air from the Sahara lies to the north of 99L and is currently not affecting the storm. WInd shear over the disturbance is a light 5 - 10 knots, and ocean temperatures are 28°C, (82°F) which is well above the 26.5°C (80°F) threshold typically needed to allow formation of a tropical depression.


Figure 1. Morning satellite image of Invest 99L.

Forecast for 99L
Wind shear is expected to remain light through Friday, and ocean temperatures will remain near 28°C, according to the 8 am EDT run of the SHIPS model. However, a band of high wind shear of 20 - 40 knots associated with the subtropical jet stream lies just to the north of 99L, and it would not be a surprise to see 99L experience some higher shear conditions than are currently forecast. The farther north 99L gets, the higher the shear it will experience, and the SHIPS model is predicting shear in the moderate range, 10 - 20 knots, for Saturday - Sunday, as the storm works its way to 15°N. The disturbance is at 9°N, which is close enough to the Equator that the storm will have some difficultly getting spinning. Most of the models are showing some slow development of 99L. There are some major differences in the predicted forward speed of 99L, with the ECMWF and UKMET models predicting the storm will reach the Lesser Antilles on Friday, and the GFS predicting a later arrival, on Saturday. At 8 am Tuesday, NHC gave 99L a 20% chance of developing into a tropical depression by Thursday morning. I expect the storm will begin having trouble with tendrils of dry air reaching down from the north at times this week, but give 99L a 50% chance of eventually developing into Tropical Storm Ernesto sometime in the next ten days. Residents and visitors to the Lesser Antilles Islands should anticipate heavy rains and strong winds from 99L beginning to affect the islands as early as Friday morning. The long-range fate of 99L next week is uncertain. A track west to west-northwest through the Caribbean, or to the northwest towards the U.S. East Coast are both possible. The storm is less likely to survive if it heads northwest towards the U.S.

Extreme heat in the Central U.S.
The withering heat in America's heartland continued on Monday, with high temperatures of 112° recorded in Winfield, Kansas and Searcy, Arkansas. Little Rock, Arkansas hit 111°, their 3rd hottest temperature ever record, behind the all time record of 114° set just last year on August 3, and the 112° reading of 7/31/1986. Wichita and Coffeyville in Kansas both hit 111° Monday, and in Oklahoma, Enid, Tulsa Jones Airport, and Chandler all topped out at 111°. Carr Creek, Missouri hit 110°, the hottest temperature measured in the state so far this year. Highs temperatures Tuesday and Wednesday in this region could reach 110° again, as the most extreme heat this week will stay focused over Oklahoma and surrounding states.

Jeff Masters

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2371. HurricaneHunterJoe
2:26 PM GMT on August 01, 2012
Quoting Patrap:


Is bearing 340 degrees on that the actual heading now? 340 is NNW?
Member Since: September 18, 2010 Posts: 0 Comments: 5243
2370. PensacolaDoug
2:19 PM GMT on August 01, 2012
Quoting Patrap:
A closed mind sees no Light.

But bulbs are cheap.





So are words.
Member Since: July 25, 2006 Posts: 0 Comments: 639
2369. PensacolaDoug
2:10 PM GMT on August 01, 2012
Quoting hurricanejunky:
Will Ernesto be the next great Cape Verde storm?
The Gulf temps off the Southwest Florida Coast (Fort Myers area)are running at or above 90 degrees right now so let's hope we don't see another Charley scenario or it could get UGLY!




Caribe will be hard on this system,
Member Since: July 25, 2006 Posts: 0 Comments: 639
2368. hurricanejunky
2:09 PM GMT on August 01, 2012
Quoting TropicalAnalystwx13:

99L's too far from Cape Verde and the East Atlantic to be considered a Cape Verde tropical cyclone.


Oh quit being such a stickler, I'm working on my dramatization skills! LOL
Member Since: August 28, 2006 Posts: 6 Comments: 2899
2367. HurricaneHunterJoe
2:06 PM GMT on August 01, 2012
Quoting muddertracker:


This is an excellent product! On the shortwave loop you can see it, too.


Link Please
Member Since: September 18, 2010 Posts: 0 Comments: 5243
2366. MississippiWx
2:04 PM GMT on August 01, 2012
I believe 99L is good enough to be classified a TD. The NHC, however, may not be impressed with the convection-less northern quadrant.

Member Since: July 15, 2006 Posts: 17 Comments: 10284
2365. LargoFl
2:02 PM GMT on August 01, 2012
one GOOD thing about 99L....its getting people to THINK..about preparing etc...its been slow for storms so far..and people are relaxed huh....time to prepare..just in case..August is here now
Member Since: August 6, 2011 Posts: 4 Comments: 41550
2364. Patrap
2:02 PM GMT on August 01, 2012
..O the sweet smell of success,

handle me with care..
Member Since: July 3, 2005 Posts: 427 Comments: 129311
2363. WunderAlertBot (Admin)
2:02 PM GMT on August 01, 2012
JeffMasters has created a new entry.
2362. TropicalAnalystwx13
2:01 PM GMT on August 01, 2012
Quoting floridaboy14:
well not exactly... it would need to be declared a depression pretty soon and has to develop at LEAST 100 miles east of the islands but it has cape verde roots

Most tropical cyclones that develop in the Atlantic do. That doesn't make them a Cape Verde system.

Cape Verde hurricane:



Not a Cape Verde hurricane:

Member Since: July 6, 2010 Posts: 113 Comments: 32679
2360. Patrap
2:01 PM GMT on August 01, 2012
A closed mind sees no Light.

But bulbs are cheap.
Member Since: July 3, 2005 Posts: 427 Comments: 129311
2359. washingtonian115
2:00 PM GMT on August 01, 2012
Quoting muddertracker:


You're right! Let's go back to that global warming discussion! Sarcasam Flag: RI

Now that you mentioned it duck here they come!!.Lol.
Member Since: August 14, 2010 Posts: 10 Comments: 17585
2358. unknowncomic
1:59 PM GMT on August 01, 2012
Quoting Patrap:
Wave coming off africa looks massive.
Member Since: August 2, 2011 Posts: 0 Comments: 2108
2357. Stormchaser2007
1:59 PM GMT on August 01, 2012
*12z SHIPS could be unreliable.

It was run off of the BAMM track due to the Camp Springs, MD computer issues. Last cycle was off the OPFI which was much further south and faster.

Might get an official track later.
Member Since: June 9, 2007 Posts: 4 Comments: 15947
2356. floridaboy14
1:58 PM GMT on August 01, 2012
Quoting TropicalAnalystwx13:

99L's too far from Cape Verde and the East Atlantic to be considered a Cape Verde tropical cyclone.
well not exactly... it would need to be declared a depression pretty soon and has to develop at LEAST 100 miles east of the islands but it has cape verde roots
Member Since: July 25, 2011 Posts: 0 Comments: 1102
2354. Patrap
1:58 PM GMT on August 01, 2012
Member Since: July 3, 2005 Posts: 427 Comments: 129311
2353. LargoFl
1:57 PM GMT on August 01, 2012
Quoting jascott1967:
As a Kemah, Texas resident I am a bit less concerned about 99L today than I was on Monday. Wind shear appears to be effecting 99L and hopefully will rip it apart before it gets a real chance to develope.
..I am with you on that..we dont need any hurricane this year doing alot of damage to any area
Member Since: August 6, 2011 Posts: 4 Comments: 41550
2352. Patrap
1:57 PM GMT on August 01, 2012
Member Since: July 3, 2005 Posts: 427 Comments: 129311
2351. washingtonian115
1:57 PM GMT on August 01, 2012
A storm has to be at least 600 miles in the area of the Cape verde islands to be considered one.
Member Since: August 14, 2010 Posts: 10 Comments: 17585
2350. muddertracker
1:57 PM GMT on August 01, 2012
Quoting CybrTeddy:
Whether 99L becomes Tropical Depression 5 today or not is all dependent on if it can manage to sustain it's convection while being able to increase organization in banding. The continued northern motion by 99L is telling that it has separated from the ITCZ, TAFB and SAB are both at 1.5, and latest SCAT pass reveals that there is a circulation on the NW edge of the convection. I'm still not sold on this happening today as I've seen for a long time systems that look impressive in the day then take a swig of dry air and become less organized as the day progresses before developing. Let's see what happens.


Good morning CT, can you let me know if the Kelvin wave aids in atmospheric lift or ventilation? TIA
Member Since: August 16, 2007 Posts: 1 Comments: 2351
2348. Skyepony (Mod)
1:56 PM GMT on August 01, 2012
99L struggles on. The disruptive swirl in the front 1/2 of it is about to get tore up on South America. It soon may have a chance to pull together before it hits that area of higher shear where the TUTT is. The little swirl off Africa is coming undone. Another wave is about to step off.
Member Since: August 10, 2005 Posts: 207 Comments: 39016
2347. CybrTeddy
1:56 PM GMT on August 01, 2012
Whether 99L becomes Tropical Depression 5 today or not is all dependent on if it can manage to sustain it's convection while being able to increase organization in banding. The continued northern motion by 99L is telling that it has separated from the ITCZ, TAFB and SAB are both at 1.5, and latest SCAT pass reveals that there is a circulation on the NW edge of the convection. I'm still not sold on this happening today as I've seen for a long time systems that look impressive in the day then take a swig of dry air and become less organized as the day progresses before developing. Let's see what happens.
Member Since: July 8, 2005 Posts: 259 Comments: 24545
2346. Patrap
1:55 PM GMT on August 01, 2012
Member Since: July 3, 2005 Posts: 427 Comments: 129311
2345. muddertracker
1:55 PM GMT on August 01, 2012
Quoting LargoFl:
......................folks just remember....from the NHC............



There are no tropical cyclones at this time.


You're right! Let's go back to that global warming discussion! Sarcasam Flag: RI

Member Since: August 16, 2007 Posts: 1 Comments: 2351
2344. LargoFl
1:55 PM GMT on August 01, 2012
Quoting Houstonweathergrl:
Unknown,
Not entirely sure what impact windows are, but if they're what the name implies, sounds like something I should look into. Just too many windows to board.
..im looking into roof tie downs..if the roof goes..poof goes the windows i guess..my wife says..a cat-3 or higher and we are on I-75 headed north as fast as we can
Member Since: August 6, 2011 Posts: 4 Comments: 41550
2343. GetReal
1:55 PM GMT on August 01, 2012
Quoting hurricanejunky:
Will Ernesto be the next great Cape Verde storm?
The Gulf temps off the Southwest Florida Coast (Fort Myers area)are running at or above 90 degrees right now so let's hope we don't see another Charley scenario or it could get UGLY!



Well there have been several here calling for the NHC to retire the Ernesto name....
Member Since: July 4, 2005 Posts: 204 Comments: 8898
2342. TropicalAnalystwx13
1:54 PM GMT on August 01, 2012
Quoting hurricanejunky:
Will Ernesto be the next great Cape Verde storm?
The Gulf temps off the Southwest Florida Coast (Fort Myers area)are running at or above 90 degrees right now so let's hope we don't see another Charley scenario or it could get UGLY!

99L's too far from Cape Verde and the East Atlantic to be considered a Cape Verde tropical cyclone.
Member Since: July 6, 2010 Posts: 113 Comments: 32679
2340. washingtonian115
1:54 PM GMT on August 01, 2012
Quoting Houstonweathergrl:
Wash....yes it's true. Some areas will never recover. On another note, after Ike, I bought a whole house stand alone generator. Not sure how much good that will do with the windows blown out though.
Quoting Squid28:


Sadly yes, this is my area it is pretty ghost townish in a lot of areas...

Shoreacres
Reminds me of some parts of the lower 9th ward that were never touched again after Katrina.Who would wish this on somebody?.
Member Since: August 14, 2010 Posts: 10 Comments: 17585
2339. Houstonweathergrl
1:53 PM GMT on August 01, 2012
Unknown,
Not entirely sure what impact windows are, but if they're what the name implies, sounds like something I should look into. Just too many windows to board.
Member Since: August 8, 2008 Posts: 0 Comments: 189
2338. HurricaneHunterJoe
1:53 PM GMT on August 01, 2012
Quoting Grothar:
Seems to be gaining a little more latitude.




Agree
Member Since: September 18, 2010 Posts: 0 Comments: 5243
2337. hurricanejunky
1:53 PM GMT on August 01, 2012
Will Ernesto be the next great Cape Verde storm?
The Gulf temps off the Southwest Florida Coast (Fort Myers area)are running at or above 90 degrees right now so let's hope we don't see another Charley scenario or it could get UGLY!
Member Since: August 28, 2006 Posts: 6 Comments: 2899
2336. LargoFl
1:52 PM GMT on August 01, 2012
Quoting GeorgiaStormz:
NWS Key West ‏@NWSKeyWest

This disturbance, about 1,000 miles east of S. Windward Islands, will likely become #Tropical Cyclone #Ernesto. #flwx


key west believes
......................folks just remember....from the NHC............



There are no tropical cyclones at this time.
Member Since: August 6, 2011 Posts: 4 Comments: 41550
2335. hydrus
1:52 PM GMT on August 01, 2012
Quoting GetReal:



99L appears to be close to becoming a TD or TS Ernesto later today. I see there is plenty of speculation as to where this system is going.

The previous runs of the M.O.D. (model of doom) had been pretty consistant on bringing an Ivan type tracking system across the southern Caribbean, before it turned WNW towards the NW Caribbean.

The latest 1300 run of the MOD has shifted slightly northward, and Ernesto tracking west to WNW as a strong Cat 1 hurricane through the central Lesser Antilles. MOD brings Erneato towards, and possibly over Jamaica as a strong Cat 2 as it tracks WNW torwards the Caymans. Ernsto bombs as a Cat 4 in NW Caribbean.

MOD turns Ernesto NW towards the Yucatan Channel, and at the end of the run has a 920 mb hurricane sitting in the central GOM.

MOD is nearly always correct.
I was hoping this system would gain some latitude and have a higher chance at recurvature out to sea. The deep convection has become more centralized since yesterday.
Member Since: September 27, 2007 Posts: 1 Comments: 22223
2334. TropicalAnalystwx13
1:52 PM GMT on August 01, 2012
Quoting GeorgiaStormz:
NWS Key West ‏@NWSKeyWest

This disturbance, about 1,000 miles east of S. Windward Islands, will likely become #Tropical Cyclone #Ernesto. #flwx


key west believes

They're a believer!

If this is any indication of where 99L may go:

Member Since: July 6, 2010 Posts: 113 Comments: 32679
2333. jascott1967
1:52 PM GMT on August 01, 2012
Quoting LargoFl:
....................hmmm do we have to watch something closer to the florida coast?


No.
Member Since: August 16, 2007 Posts: 0 Comments: 614
2332. GeorgiaStormz
1:51 PM GMT on August 01, 2012
NWS Key West ‏@NWSKeyWest

This disturbance, about 1,000 miles east of S. Windward Islands, will likely become #Tropical Cyclone #Ernesto. #flwx


key west believes
Member Since: February 11, 2012 Posts: 0 Comments: 9746
2331. unknowncomic
1:49 PM GMT on August 01, 2012
Quoting Houstonweathergrl:
Wash....yes it's true. Some areas will never recover. On another note, after Ike, I bought a whole house stand alone generator. Not sure how much good that will do with the windows blown out though.

Impact windows?
Member Since: August 2, 2011 Posts: 0 Comments: 2108
2330. jascott1967
1:49 PM GMT on August 01, 2012
As a Kemah, Texas resident I am a bit less concerned about 99L today than I was on Monday. Wind shear appears to be effecting 99L and hopefully will rip it apart before it gets a real chance to develope.
Member Since: August 16, 2007 Posts: 0 Comments: 614
2329. Squid28
1:49 PM GMT on August 01, 2012
Quoting washingtonian115:
Ike was a bad bad.I heard some parts are still deserted.Is that true?.


Sadly yes, this is my area it is pretty ghost townish in a lot of areas...

Shoreacres
Member Since: May 23, 2006 Posts: 0 Comments: 343
2327. LargoFl
1:47 PM GMT on August 01, 2012
....................hmmm do we have to watch something closer to the florida coast?
Member Since: August 6, 2011 Posts: 4 Comments: 41550
2326. Josihua2
1:47 PM GMT on August 01, 2012
it would seem that Typhoon Saola and Typhoon Damrey planned their attack on Taiwan.............
Member Since: December 19, 2009 Posts: 0 Comments: 65
2325. Houstonweathergrl
1:47 PM GMT on August 01, 2012
Wash....yes it's true. Some areas will never recover. On another note, after Ike, I bought a whole house stand alone generator. Not sure how much good that will do with the windows blown out though.
Member Since: August 8, 2008 Posts: 0 Comments: 189
2324. SLU
1:46 PM GMT on August 01, 2012
212

WHXX01 KWBC 011344

CHGHUR

TROPICAL CYCLONE GUIDANCE MESSAGE

NWS NATIONAL HURRICANE CENTER MIAMI FL

1344 UTC WED AUG 1 2012



DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.

PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE

AND SUBTROPICAL CYCLONE INFORMATION.



ATLANTIC OBJECTIVE AIDS FOR



DISTURBANCE INVEST (AL992012) 20120801 1200 UTC



...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...

120801 1200 120802 0000 120802 1200 120803 0000



LAT LON LAT LON LAT LON LAT LON

LBAR 10.7N 46.9W 11.4N 49.9W 11.9N 53.0W 12.3N 56.1W

SHIP 30KTS 36KTS 43KTS 48KTS

DSHP 30KTS 36KTS 43KTS 48KTS



...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...

120803 1200 120804 1200 120805 1200 120806 1200



LAT LON LAT LON LAT LON LAT LON

LBAR 12.6N 59.0W 13.6N 64.9W 14.4N 70.4W .0N .0W

SHIP 51KTS 52KTS 45KTS 44KTS

DSHP 51KTS 52KTS 45KTS 37KTS



...INITIAL CONDITIONS...

LATCUR = 10.7N LONCUR = 46.9W DIRCUR = 280DEG SPDCUR = 19KT

LATM12 = 9.9N LONM12 = 43.2W DIRM12 = 285DEG SPDM12 = 18KT

LATM24 = 9.3N LONM24 = 39.8W

WNDCUR = 30KT RMAXWD = 50NM WNDM12 = 25KT

CENPRS = 1009MB OUTPRS = 1012MB OUTRAD = 150NM SDEPTH = M

RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM



$$

NNNN


Member Since: July 13, 2006 Posts: 13 Comments: 5364
2323. TropicalAnalystwx13
1:45 PM GMT on August 01, 2012
Quoting Bobbyweather:

Today? Nah.
the ATCF doesn't say so. And it has only 60% chance of forming within the next 48 hours.

Just out of curiosity, why doesn't the NHC say 2 days instead of 48 hours and 1 day instead of 24 hours?

The ATCF doesn't say so now...that doesn't mean it won't get upgraded later today. Tropical Storm Bret from last season went from Code Orange 30% to a Tropical Depression in just a few hours, albeit that's because there was a recon out.

99L is organized enough to be declared Tropical Depression Five. It's up to them to decide whether or not to do it later today.
Member Since: July 6, 2010 Posts: 113 Comments: 32679
2322. Houstonweathergrl
1:45 PM GMT on August 01, 2012
Member Since: August 8, 2008 Posts: 0 Comments: 189

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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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