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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So I guess 99L can go through 30-40kts of shear as a TD or TS with no problems?
Member Since: May 22, 2010 Posts: 0 Comments: 907
Quoting tennisgirl08:
I say 50% at 8pm. Looks fairly impressive for DMIN.


+1 Everyone doing ok this evening?
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Again, I'm sticking with 40% tonight.
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That 83 knot wind on SW coast of DR has to be an error one would think so anyway!
Member Since: April 29, 2007 Posts: 0 Comments: 8123
Quoting tennisgirl08:
I say 50% at 8pm. Looks fairly impressive for DMIN.


It does look fairly impressive considering what it looked like 24hrs ago.
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I think 99L/PRE-TD5 does not have shear to worry about and the trade winds I think will not be a problem either I think people are overestimating the trades
Member Since: June 13, 2009 Posts: 2 Comments: 12697
Quoting biloxibob:
I dont know but been watching these things for 40 yrs. Looks like a TD to me.do y'all agree?


Agreed. But the NHC won't call it that until it fully breaks from the ITCZ.
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Quoting tennisgirl08:


Yes....this is what Dr. Masters is referring to in his update. I think the trade winds in the Caribbean are being grossly overestimated here.
And if that's the case oh boi...
Member Since: August 14, 2010 Posts: 10 Comments: 17492
1212. ncstorm
Quoting Pocamocca:

Damned if you do, damned if you don't!! LOL

The nogaps really dug quite a hole for itself!!


Yep..the last frame but I will always still be a supporter over here even if its wrong this time..

Member Since: August 19, 2006 Posts: 13 Comments: 16083
I dont know but been watching these things for 40 yrs. Looks like a TD to me.do y'all agree?
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I say 50% at 8pm. Looks fairly impressive for DMIN.
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Quoting tennisgirl08:


Yes....this is what Dr. Masters is referring to in his update. I think the trade winds in the Caribbean are being grossly overestimated here.

Going to have to agree with you there.
Member Since: July 6, 2010 Posts: 113 Comments: 32566
Quoting tennisgirl08:


Yes....this is what Dr. Masters is referring to in his update. I think the trade winds in the Caribbean are being grossly overestimated here.


no its just in a better position to stay west till its in the deep caribbean than it is if it lifts NW now to FL
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Quoting washingtonian115:
The WRF shows favorable shear in the caribbean and a more hostile environment if 99L goes north of the caribbean..Hmmmm.Other meteorologist are starting to point this out as well...


Yes....this is what Dr. Masters is referring to in his update. I think the trade winds in the Caribbean are being grossly overestimated here.
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Quoting CybrTeddy:


Honestly, I'd be surprised with anything above 30%.


40%* typo.
Member Since: July 8, 2005 Posts: 259 Comments: 24512
1204. ncstorm
I tell you what..the Nogaps is still calling for that NW track..18z still running...if its wrong, this blog will never give it any props but if its right, this blog will never give it any props..



Member Since: August 19, 2006 Posts: 13 Comments: 16083
Quoting ilovehurricanes13:
i am going with 40%




I guess I'll be the pessimist and stick with 30% throughout tonight, perhaps an upgrade in the early morning hours tomorrow morning.


Reasoning is flighty convection and organization issues with the southern part of the LLC.

Member Since: June 24, 2012 Posts: 0 Comments: 1546
Quoting stormpetrol:


I'll go out on a limb and say we could see a 60% red alert at 8pm est, if not at 8 and organization continues red alert at 2 am.


Honestly, I'd be surprised with anything above 30%.
Member Since: July 8, 2005 Posts: 259 Comments: 24512
1201. robert88
10:30 PM GMT on July 31, 2012
Quoting quasistationary:


The TUTT is way over by Cuba



It has to go through the TUTT

Member Since: May 22, 2010 Posts: 0 Comments: 907
1197. DataNerd
10:26 PM GMT on July 31, 2012



GFS at 48 hours: Link
Member Since: June 24, 2012 Posts: 0 Comments: 1546
1196. CybrTeddy
10:25 PM GMT on July 31, 2012
Quoting 19N81W:
99l does not look all that impressive...still something to watch but so far not doing much quickly...as it is moving into a slightly less favourable area in the next couple days you cant help but suspect it will not turn into a TS.....maybe a Depression...maybe


We'll have to see then. Given all the factors out there, it's fairly obvious it won't be a strong system at all but I see potential for development if it can get going quick.
Member Since: July 8, 2005 Posts: 259 Comments: 24512
1195. TropicalAnalystwx13
10:24 PM GMT on July 31, 2012
Quoting AllStar17:


Huh?

I want some of what he has!
Member Since: July 6, 2010 Posts: 113 Comments: 32566
1194. stormpetrol
10:24 PM GMT on July 31, 2012
Quoting Pocamocca:

I wasn't so sure earlier today before lunch but now I'm onboard with a 40% solution. We'll see what 8pm brings.


I'll go out on a limb and say we could see a 60% red alert at 8pm est, if not at 8 and organization continues red alert at 2 am.
Member Since: April 29, 2007 Posts: 0 Comments: 8123
1193. washingtonian115
10:24 PM GMT on July 31, 2012
The WRF shows favorable shear in the caribbean and a more hostile environment if 99L goes north of the caribbean..Hmmmm.Other meteorologist are starting to point this out as well...
Member Since: August 14, 2010 Posts: 10 Comments: 17492
1192. DataNerd
10:23 PM GMT on July 31, 2012
Howdy all!


Structure is looking better today, seeing some early banding features on the surface in visible imagery particularly in the northern quadrant.

That said, the surface circulation still appears to be open and although its more concise, the southern half of the llc appears somewhat un-organized as yet. Despite this I think if the present trend continues and it keeps firming up its structure we may see a td in 36 hrs.




As to guidance, as I thought the guidance has shifted southward and westward in its latest runs, reflecting a more likely development timeline and depth. Shear at the end of the runs would be the large factor in determining strength at 120 hrs and that would also tell us if we had a storm entering the gulf or not.


Trough scenario is now also firming up better with the larger global models for next week, and that will be the other factor on effecting a turn or not towards the end of the period.


Will be interested to see if we have a cyclone tomorrow, but I am liking the structure so far.
Member Since: June 24, 2012 Posts: 0 Comments: 1546
1191. robert88
10:22 PM GMT on July 31, 2012
Quoting quasistationary:


The TUTT is all the way over by Cuba at the moment




Member Since: May 22, 2010 Posts: 0 Comments: 907
1190. OrchidGrower
10:21 PM GMT on July 31, 2012
So what about the wave crossing through the Leewards today? And the low which exited the Panhandle into the Gulf today? We are dry as a bone here in SW FL in what I thought was supposed to be the heart of our rainy season! Are we stuck in a dry-air sandwich for days to come?
Member Since: September 24, 2002 Posts: 0 Comments: 395
1189. AllStar17
10:20 PM GMT on July 31, 2012
Quoting 19N81W:
99l does not look all that impressive...still something to watch but so far not doing much quickly...as it is moving into a slightly less favourable area in the next couple days you cant help but suspect it will not turn into a TS.....maybe a Depression...maybe


Huh?
Member Since: June 29, 2009 Posts: 13 Comments: 5315
1188. RussianWinter
10:19 PM GMT on July 31, 2012
Quoting wunderkidcayman:
anyway the Hurricane hunters are to fly on the 3rd to 99L

000
NOUS42 KNHC 311315
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
0915 AM EDT TUE JULY 31 2012
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 01/1100Z TO 02/1100Z AUGUST 2012
TCPOD NUMBER.....12-074

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.
3. ADDITIONAL DAY OUT LOOK: PROBABLE LOW LEVEL
INVEST AT 03/1800Z NEAR 12.5N 57.5W


WOOT! HELL ITS ABOUT TIME!

I expect models to change on the 3rd.
Member Since: August 21, 2011 Posts: 0 Comments: 666
1186. pcola57
10:14 PM GMT on July 31, 2012
Member Since: August 13, 2009 Posts: 13 Comments: 6895
1185. KEEPEROFTHEGATE (Mod)
10:12 PM GMT on July 31, 2012
XX/INV/99L
MARK
9.95n/43.33w


Member Since: July 15, 2006 Posts: 175 Comments: 54893
1184. 19N81W
10:11 PM GMT on July 31, 2012
99l does not look all that impressive...still something to watch but so far not doing much quickly...as it is moving into a slightly less favourable area in the next couple days you cant help but suspect it will not turn into a TS.....maybe a Depression...maybe
Member Since: August 24, 2008 Posts: 0 Comments: 436
1182. wunderkidcayman
10:08 PM GMT on July 31, 2012
anyway the Hurricane hunters are to fly on the 3rd to 99L

000
NOUS42 KNHC 311315
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
0915 AM EDT TUE JULY 31 2012
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 01/1100Z TO 02/1100Z AUGUST 2012
TCPOD NUMBER.....12-074

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.
3. ADDITIONAL DAY OUT LOOK: PROBABLE LOW LEVEL
INVEST AT 03/1800Z NEAR 12.5N 57.5W
Member Since: June 13, 2009 Posts: 2 Comments: 12697
1180. pcola57
10:07 PM GMT on July 31, 2012
Member Since: August 13, 2009 Posts: 13 Comments: 6895
1179. TideWaterWeather
10:07 PM GMT on July 31, 2012
Quoting TropicalAnalystwx13:

Send them to me.


A passage from what you JUST posted... practice what you preach sport.

"your verbal jousts consume the space and time everyone else is sharing"
Member Since: September 12, 2008 Posts: 0 Comments: 178
1178. KEEPEROFTHEGATE (Mod)
10:06 PM GMT on July 31, 2012

XX/INV/99L
MARK
9.95n/43.33w


Member Since: July 15, 2006 Posts: 175 Comments: 54893
1177. Hurricane1956
10:00 PM GMT on July 31, 2012
Quoting washingtonian115:
No the one the one south of the cape verde islands.See post 1163.
Thank you for your response!.
Member Since: August 28, 2006 Posts: 0 Comments: 635
1176. sunlinepr
9:59 PM GMT on July 31, 2012
Member Since: August 2, 2010 Posts: 21 Comments: 9874
1175. washingtonian115
9:59 PM GMT on July 31, 2012
Quoting Hurricane1956:
Link please!,is the impressive wave you are talking about that the GFS is trying to develop is the one over Puerto Rico & Espanola,thank you!!!.
No the one south of the cape verde islands.See post 1163.
Member Since: August 14, 2010 Posts: 10 Comments: 17492
1174. pcola57
9:58 PM GMT on July 31, 2012
Quoting weathermanwannabe:


And mentions Dr. Neil Frank's research to boot in the cites....He was as much of a pioneer in the area as Dr. Gray.

Have a good one.............Heading home..... :)


Dr. Neil Frank did alot for the weather community.. :)
Member Since: August 13, 2009 Posts: 13 Comments: 6895
1173. quasistationary
9:58 PM GMT on July 31, 2012
Quoting robert88:


Yeah either way it has to go through the TUTT. At this point i'm not sure which would be the better route for it to be a more significant system in the long term??? The longer it hangs around the more time Atmospheric conditions can change...so who knows. :)


The TUTT is all the way over by Cuba at the moment

Member Since: May 3, 2012 Posts: 0 Comments: 83
1172. tropicfreak
9:58 PM GMT on July 31, 2012
Wow, I leave for 3 hours come back to a much better organized system. I expect a bump up to 40, maybe 50% at 8pm. Could see Ernesto/ TD 5 as early as tomorrow 11am.
Member Since: September 2, 2006 Posts: 110 Comments: 6878
1171. robert88
9:57 PM GMT on July 31, 2012
Quoting Pocamocca:

Yeah, the TUTT is quite the force. I agree it has to start moving further north. I think in the short term that's probably the way to go for it. I know Dr. Master's mentioned it encountering more adverse conditions the more northerly route it would take. But I think he was more or less referring to the longer term solution...

But yeah, it has it's obstacles to overcome. Not going to disagree with you there!


Yeah either way it has to go through the TUTT. At this point i'm not sure which would be the better route for it to be a more significant system in the long term??? The longer it hangs around the more time atmospheric conditions can change...so who knows. :)
Member Since: May 22, 2010 Posts: 0 Comments: 907

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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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