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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i don't know what thing is seeing the HWRF at 96 hour, that develops the system, i think the HWRF is seeing the same thing of us, remember HWRF is one of the best models predicting intensity
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Quoting GeorgiaStormz:


28kts shear isnt too helpful even for a good storm.
30kts is pretty deadly to a moderate TS


I'm saying that the SHIPS/GFS sometimes think they see shear when it's really just being generated by a collocated anticyclone. Look around at the GFS wind shear forecasts on FSU's experimental genesis page, and you will sometimes notice 30 knots of shear directly ahead of a mature hurricane. That's usually not shear from external influences. Obviously 99L is not a mature hurricane, and may not ever be, but the general philosophy still stands.
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1469. wxmod
These are six satellite photos, all depicting fires in Russia. Each non overlapping photo covers an area the size of California. Smoke from these fires covers an area the size of the United States. The smoke is affecting weather all over the world and is making the ice cap melt faster than ever before. Fire season is far from over and the fires are becoming larger every day.






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Quoting ryang:


Where can I find the link to this info?

Link
Member Since: March 16, 2012 Posts: 127 Comments: 7972
TAFB up to Dvorak 1.5


AL 99 201207312345 920N 4300W SAB 1010 /////
AL 99 201208010000 970N 4280W TAFB 1515 /////
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Quoting tennisgirl08:


I would agree with this statement except for the fact that 99L is so low in latitude right now.


Yep, you're right. I think in order to gain lat., it has to build intensity (high cloud towers) to get pulled towards the low. We shall see soon enough.

Trinidad may want to take cover. lol
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1465. Grothar
It looks a little bit like Kilroy



Member Since: July 17, 2009 Posts: 71 Comments: 27211
Quoting VAbeachhurricanes:


REally? I thought the main run was the average of the ensembles?


You may be right. I'm really not sure.
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1463. ryang
Quoting TropicalAnalystwx13:
00Z SHIPS:

SHEAR (KT) 6 3 6 9 6 10 8 13 14 21 16 28 21

Nothing a well developed tropical storm can't handle. Especially a large one like 99L.


Where can I find the link to this info?
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Quoting washingtonian115:
Lol.No Kori.Just don't wanna see a hurricane coming for the gulf..especially after the oil spill.


I was down in Gulfport not too long ago. There was still plenty of oil in the sand. Hate to see the subsurface.
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Quoting KoritheMan:


Some of that might be storm relative as well.


28kts shear isnt too helpful even for a good storm.
30kts is pretty deadly to a moderate TS
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Quoting tennisgirl08:


I would agree with this statement except for the fact that 99L is so low in latitude right now.
I don't think it is actually overly low as Ivan developed below 10N. I think what is hindering it for now is the fact that it is still attached to the ITCZ.
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Quoting KoritheMan:


Uh, that's what they're supposed to do. That's why they're called ensembles.


REally? I thought the main run was the average of the ensembles?
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Quoting wxchaser97:

If you dont mind Im going to make a forecast graphic for 99L.
No problems! I wasn't the one starting the idea anyway :) Beside, I encourages others to do it as well :)
Member Since: August 1, 2011 Posts: 28 Comments: 8075
Quoting KoritheMan:


Are you trying to ruin my chase, wash?
Lol.No Kori.Just don't wanna see a hurricane coming for the gulf..especially after the oil spill.
Member Since: August 14, 2010 Posts: 10 Comments: 17860
1456. Grothar
Quoting GeoffreyWPB:


Geoff, that looks like it wants to go straight for the Cayman Islands. What do you think?
Member Since: July 17, 2009 Posts: 71 Comments: 27211
Quoting washingtonian115:
99L is developing a anti-cyclone.Could help a little with the conditions in the caribbean.Ya'll along the Gulf coast better hope shear stays in place and keep it in check.


Are you trying to ruin my chase, wash?
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Quoting etxwx:
Sometimes when reading the news...you find odd weather related things...hammers?
Survival kit sales peak following floods
Survival kits have been flying off shelves following the deadly floods in North and Southwest China. Hammers are the most popular items online. Sales of multifunction key chains, first aid kits, protective masks, life jackets, and even band-aids and emergency glow sticks have also increased sharply. During the last several days, online sales of hammers rose nearly six times over the previous month and online searches for emergency flashlights have jumped 20 times, according to data from e-Commerce search engine Etao.com. 28% of consumers who buy hammers online are from Beijing.



re Flood.... trapped in a car... electric windows... must break window to escape
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Quoting TropicalAnalystwx13:
00Z SHIPS:

SHEAR (KT) 6 3 6 9 6 10 8 13 14 21 16 28 21

Nothing a well developed tropical storm can't handle. Especially a large one like 99L.


Some of that might be storm relative as well.
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99L is developing a anti-cyclone.Could help a little with the conditions in the caribbean.Ya'll along the Gulf coast better hope shear stays in place and keep it in check.
Member Since: August 14, 2010 Posts: 10 Comments: 17860
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00Z SHIPS:

SHEAR (KT) 6 3 6 9 6 10 8 13 14 21 16 28 21

Nothing a well developed tropical storm can't handle. Especially a large one like 99L.
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Quoting RetainingH2O:
Have you ever noticed that tropical storms seem to form in Alphabetical order each year?
This has to be more than a coincidence. Every year... a list of names is created and the storms somehow manage to form in order. It's almost uncanny!




How do they know!!!!
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1448. SLU
126

WHXX01 KWBC 010041

CHGHUR

TROPICAL CYCLONE GUIDANCE MESSAGE

NWS NATIONAL HURRICANE CENTER MIAMI FL

0041 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 0000 UTC



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

120801 0000 120801 1200 120802 0000 120802 1200



LAT LON LAT LON LAT LON LAT LON

BAMS 9.7N 43.0W 10.5N 46.4W 11.0N 49.7W 11.2N 53.2W

BAMD 9.7N 43.0W 10.2N 45.1W 10.6N 47.0W 10.8N 48.8W

BAMM 9.7N 43.0W 10.3N 45.4W 10.8N 47.6W 11.2N 49.7W

LBAR 9.7N 43.0W 10.2N 45.9W 10.8N 48.9W 11.2N 52.1W

SHIP 25KTS 32KTS 39KTS 45KTS

DSHP 25KTS 32KTS 39KTS 45KTS



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

120803 0000 120804 0000 120805 0000 120806 0000



LAT LON LAT LON LAT LON LAT LON

BAMS 11.1N 56.5W 10.7N 63.0W 11.5N 68.1W 13.6N 72.8W

BAMD 11.0N 50.6W 12.1N 54.6W 13.8N 58.7W 15.4N 62.0W

BAMM 11.7N 51.9W 13.3N 57.0W 15.5N 62.7W 17.4N 68.8W

LBAR 11.5N 55.2W 11.8N 61.4W 12.4N 66.5W .0N .0W

SHIP 50KTS 56KTS 55KTS 53KTS

DSHP 50KTS 56KTS 55KTS 53KTS



...INITIAL CONDITIONS...

LATCUR = 9.7N LONCUR = 43.0W DIRCUR = 280DEG SPDCUR = 17KT

LATM12 = 9.3N LONM12 = 39.6W DIRM12 = 277DEG SPDM12 = 16KT

LATM24 = 8.9N LONM24 = 36.6W

WNDCUR = 25KT RMAXWD = 50NM WNDM12 = 20KT

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

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



$$

NNNN


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Quoting Bluestorm5:
My forecast for 99L:


If you dont mind Im going to make a forecast graphic for 99L.
Member Since: March 16, 2012 Posts: 127 Comments: 7972


850 vort looking better with every update!
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00z Best Track

AL, 99, 2012080100, , BEST, 0, 97N, 430W, 25, 1009, LO
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Quoting washingtonian115:
RetainingH2O


I thought there was some sort of joke he was trying to convey, but did so rather poorly. Either way, I wasn't giving him a hard time (considering I didn't even respond :P). I have self-confidence issues as it is, so I hate to knock others down.
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Quoting Clearwater1:
We have a stationary high over the western gulf, a stationary low north of FL and the A/B high (currently bridged). So, if the trade winds and or shear does not take a toll and it can gain some intensity, it should take the path of least resistance . . . and that is towards the conus, east coast, around the Bermuda high. I'm using the 18z surface analyses for this amateur's observation.


I would agree with this statement except for the fact that 99L is so low in latitude right now.
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Quoting washingtonian115:
RetainingH2O

Why would we do that? He/she was just joking...
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1440. etxwx
Sometimes when reading the news...you find odd weather related things...hammers?
Survival kit sales peak following floods
Survival kits have been flying off shelves following the deadly floods in North and Southwest China. Hammers are the most popular items online. Sales of multifunction key chains, first aid kits, protective masks, life jackets, and even band-aids and emergency glow sticks have also increased sharply. During the last several days, online sales of hammers rose nearly six times over the previous month and online searches for emergency flashlights have jumped 20 times, according to data from e-Commerce search engine Etao.com. 28% of consumers who buy hammers online are from Beijing.
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RetainingH2O
Member Since: August 14, 2010 Posts: 10 Comments: 17860
Member Since: March 16, 2012 Posts: 127 Comments: 7972
Quoting washingtonian115:
Guys leave that person alone.


Huh?
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Quoting MAweatherboy1:
Generally Caribbean shear isn't that bad... The only questionable area is around Jamaica as I said... That 40 doesn't look too friendly:



Looks here, the shear over jamaica go away when the system is passing in the north of veneuela, and the shear looks good in west carribean and why the gfs weakens the system ?

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Quoting washingtonian115:
Guys leave that person alone.

What person?
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good night guys


too trided too say uip any more


long day
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
Guys leave that person alone.
Member Since: August 14, 2010 Posts: 10 Comments: 17860
1431. JLPR2
Quoting Pocamocca:

How often do they come out? Been wondering that...


Not exactly sure, but would say more or less 12hrs apart.
Member Since: September 4, 2007 Posts: 7 Comments: 8747
My forecast for 99L:

Member Since: August 1, 2011 Posts: 28 Comments: 8075
1429. yqt1001
Quoting TropicalAnalystwx13:

If you want mine, Will:



Thanks, I'll be back home about this time tomorrow so make sure to make an update for me. :P

Also I see Saola is either rapidly intensifying or close. It's expected to make landfall on China as a strong category 3 strength typhoon.

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1427. JLPR2
Waiting for new OSCAT and ASCAT passes.
Crossing my fingers they hit 99L again.
Member Since: September 4, 2007 Posts: 7 Comments: 8747
Quoting RetainingH2O:
Have you ever noticed that tropical storms seem to form in Alphabetical order each year?
This has to be more than a coincidence. Every year... a list of names is created and the storms somehow manage to form in order. It's almost uncanny!


I'm sorry but this made me LMAO
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Quoting RetainingH2O:
Have you ever noticed that tropical storms seem to form in Alphabetical order each year?
This has to be more than a coincidence. Every year... a list of names is created and the storms somehow manage to form in order. It's almost uncanny!

This has to be post of the year, I'm still laughing right now.
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1424. wxmod
North Shore Alaska to Greenland appears to be open water. MODIS today

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Quoting washingtonian115:
Banned?.

Nope.

Link
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I said earlier that 99L should at least be 50% at 8PM.
NHC....I said AT LEAST!
More?
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Quoting yqt1001:
I've been away for a few days and am tethering so I don't want to use tons of data loading other pages. I see 99L at 50% on NHC and would like some more information on what it may do and how strong it will be in the future.

If you want mine, Will:

Quoting TropicalAnalystwx13:
My thinking is that this is designated as a tropical depression tomorrow afternoon. It further intensifies to become a tropical storm on Thursday, and approaches hurricane status by the time it reaches the Leeward Islands over the weekend. After entering the Caribbean, it weakens slightly to a midgrade tropical storm and enters the West Caribbean.

To be continued...
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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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