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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HAZARDOUS WEATHER OUTLOOK FOR SOUTH FLORIDA
NATIONAL WEATHER SERVICE MIAMI FL
928 AM EDT TUE JUL 31 2012

AMZ610-630-650-651-670-671-FLZ063-066>075-168-172 >174-GMZ656-657-676-
010430-
LAKE OKEECHOBEE-BISCAYNE BAY-
COASTAL WATERS FROM JUPITER INLET TO DEERFIELD BEACH, FL OUT 20 NM-
COASTAL WATERS FROM DEERFIELD BEACH TO OCEAN REEF, FL OUT 20 NM-
WATERS FROM JUPITER INLET TO DEERFIELD BEACH, FL EXTENDING FROM
20 NM TO 60 NM-
WATERS FROM DEERFIELD BEACH TO OCEAN REEF, FL EXTENDING FROM 20 NM
TO THE TERRITORIAL WATERS OF THE BAHAMAS-GLADES-HENDRY-
INLAND PALM BEACH-METRO PALM BEACH-COASTAL COLLIER-INLAND COLLIER-
INLAND BROWARD-METRO BROWARD-INLAND MIAMI DADE-METRO MIAMI DADE-
MAINLAND MONROE-COASTAL PALM BEACH-COASTAL BROWARD-
COASTAL MIAMI DADE-FAR SOUTH MIAMI DADE-
COASTAL WATERS FROM CHOKOLOSKEE TO BONITA BEACH, FL OUT 20 NM-
COASTAL WATERS FROM EAST CAPE SABLE TO CHOKOLOSKEE, FL OUT 20 NM-
GULF WATERS FROM CHOKOLOSKEE TO BONITA BEACH, FL EXTENDING FROM
20 TO 60 NM-
928 AM EDT TUE JUL 31 2012

...ISOLATED TO SCATTERED THUNDERSTORMS POSSIBLE INTERIOR THIS AFTERNOON...
...HEAT INDICES 103 TO 108 OVER INTERIOR AREAS...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH FLORIDA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS: ISOLATED TO SCATTERED THUNDERSTORMS ARE POSSIBLE
THIS AFTERNOON AND EARLY EVENING ACROSS SOUTH FLORIDA. THE
PRIMARY THREATS FROM THE STRONGEST STORMS WILL BE FREQUENT
LIGHTNING STRIKES ALONG WITH BRIEF HEAVY RAINFALL, GUSTY WINDS, AND
SMALL HAIL.

WIND: THE STRONGEST STORMS MAY PRODUCE WIND GUSTS UP TO 50 MPH.

HAIL: HAIL TO THE SIZE OF DIMES MAY OCCUR WITH A FEW OF THE
STRONGEST THUNDERSTORMS THIS AFTERNOON AND THIS EVENING.

TEMPERATURES: AFTERNOON TEMPERATURES WILL CLIMB INTO THE LOWER AND
MID 90S ACROSS MUCH OF SOUTH FLORIDA TODAY. THIS COMBINED WITH
THE HUMIDITY WILL RESULT IN HEAT INDICES REACHING THE RANGE OF 103
TO 108 DEGREES ACROSS THE INTERIOR. CLOSER TO THE COAST...THESE VALUES
ARE FORECAST TO RANGE FROM THE UPPER 90S TO AROUND 100.


.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

HEAT INDEX VALUES AROUND 105 DEGREES ARE POSSIBLE EACH DAY,
ESPECIALLY ACROSS INTERIOR PORTIONS OF THE REGION DURING THE
AFTERNOON HOURS.

SCATTERED THUNDERSTORMS ARE POSSIBLE EACH DAY INTO THE UPCOMING
WEEKEND. THE STRONGEST STORMS WILL BE CAPABLE OF PRODUCING
FREQUENT LIGHTNING STRIKES AND GUSTY WINDS.


.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED.

FOR MORE INFORMATION...VISIT THE NATIONAL WEATHER SERVICE IN
MIAMI WEBSITE AT WWW.WEATHER.GOV/MIAMI.
Member Since: August 6, 2011 Posts: 4 Comments: 37044
Quoting ncstorm:


GREAT! they can get some quality data to feed into the models


But that first mission is for Friday.
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Quoting xtremeweathertracker:
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
II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.
JWP





GREAT! they can get some quality data to feed into the models
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Member Since: August 6, 2011 Posts: 4 Comments: 37044
Quoting TropicalAnalystwx13:
I was really surprised to see they still have this at 20%.

There has been progress.

DATE/TIME LAT LON CLASSIFICATION STORM
31/1145 UTC 9.2N 40.6W T1.0/1.0 99L
31/0545 UTC 9.3N 38.5W TOO WEAK 99L
30/2345 UTC 9.0N 37.7W TOO WEAK 99L
30/1745 UTC 9.0N 37.1W TOO WEAK 99L
30/1145 UTC 8.9N 35.1W TOO WEAK 99L



That should be 40% and the wave behind it should be at 20%. NHC definitely isn't quick to pull the trigger on these waves this year.
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Member Since: July 17, 2009 Posts: 69 Comments: 25421
Quoting TropicalAnalystwx13:

B.

Maybe I am overexaggerating on the intensity.
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Quoting Articuno:
If 99L becomes a Depression, what do you think it will peak at?

A. Tropical Depression
B. Tropical Storm
C. Category 1
D. Category 2
E. Category 3
F. Category 4
5. Category 5


I choose D.

B
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Quoting quasistationary:


Neg. on the low level winds ghost rider





Negative on your last, Quasi.

Those are still mid to low level winds. Im referring to the 925-850. Also, I'd use a GOES sounder when analyzing winds. EWALL's are based off the GFS.



Member Since: June 9, 2007 Posts: 4 Comments: 15790
Quoting TropicalAnalystwx13:
I was really surprised to see they still have this at 20%.



Considering that SSD Dvorak went up,I would have put 30% at 8 AM.


31/1145 UTC 9.2N 40.6W T1.0/1.0 99L -- Atlantic
Member Since: Posts: Comments:
Quoting Articuno:
If 99L becomes a Depression, what do you think it will peak at?

A. Tropical Depression
B. Tropical Storm
C. Category 1
D. Category 2
E. Category 3
F. Category 4
5. Category 5


I choose D.

B.
Member Since: July 6, 2010 Posts: 113 Comments: 31537
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
II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.
JWP



Member Since: Posts: Comments:
If 99L becomes a Depression, what do you think it will peak at?

A. Tropical Depression
B. Tropical Storm
C. Category 1
D. Category 2
E. Category 3
F. Category 4
5. Category 5


I choose D.
Member Since: Posts: Comments:
I was really surprised to see they still have this at 20%.

There has been progress.

DATE/TIME LAT LON CLASSIFICATION STORM
31/1145 UTC 9.2N 40.6W T1.0/1.0 99L
31/0545 UTC 9.3N 38.5W TOO WEAK 99L
30/2345 UTC 9.0N 37.7W TOO WEAK 99L
30/1745 UTC 9.0N 37.1W TOO WEAK 99L
30/1145 UTC 8.9N 35.1W TOO WEAK 99L

Member Since: July 6, 2010 Posts: 113 Comments: 31537
Wave behind 99L IMO has the potential to become at least a T.D.Could surprise us either way.
Member Since: August 14, 2010 Posts: 10 Comments: 16437
104. 7544
and yet another day the antilis pr wave does well holding together could this become 90l soon
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NOAA research on South Asian monsoon honored by World Meteorological Organization
Member Since: September 30, 2007 Posts: 9 Comments: 15932
Quoting Eyewall07:


I was looking at the beach behind her

Yeah. SURE u were....
lol
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...Well this storm system IS going into the gulf..into that 86 degree water...boom...lets see what happens later today..bet there will be a watch out in the gulf for this
Member Since: August 6, 2011 Posts: 4 Comments: 37044
Quoting GeorgiaStormz:


funny i can't see past her...
and neither can admin!!

but on a weather note, models aren't enthusiastic about the next wave so im not so into its development at this time


Takes some effort to look away doesn't it?

Well, I find her amazing and have that problem with the photo of her in casual wear.

She has great eyes and facial features, and I don't think the camera captures her. I get the impression she sort of captures the camera. That looks cornier than it sounds, but oh well.
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Quoting TropicalAnalystwx13:
Maybe the trade winds aren't as strong as I thought they were. It struck me as odd last night that buoys were only reporting 10-15 knot surface winds when you could see the winds racing from east to west on false visible satellite loops yesterday morning. But now there's more proof...

So far the vorticity maximum associated with the wave in front has not been weakened much.



And wind shear is already beginning to lower in the East Caribbean.
Which is why the GFS doesn't dissipate it as fast as it originally was..Hmmmm.Really do hope conditions continue to be unfavorable in the caribbean.Because if anyone storm reaches those untapped waters it's game on for someone.


Floridat I don't want no arguing :).Just nice civilized discussions like whats going on now.Keep it up blog.
Member Since: August 14, 2010 Posts: 10 Comments: 16437
Quoting GeorgiaStormz:


dude really?
admins a'comin for you :)


I was looking at the beach behind her
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Quoting parlee:
I notice the high temp forecast for weather station can be significantly different even when they are with in 1 km of each other. For example, Carter Lake (kiacarter) shows a high of 104 on thursday but Omaha )KOMA) shows a high of 93. 11 degrees difference, what's going on?

Not sure what you are referring to. I looked up both sites on Wunderground and they both had a forecast high on Thursday of 104.
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Quoting biff4ugo:
Blobs to the East of me (Alabama and Off the Carolinas) Blobs to the West (Puerto Rico and 99L)

August is comming in like a Lion!

'Bama is going to hit Florida first though.

How is 99l WEST of u?
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good morning alot seems to be cooking out there, let the forecasting, wishcating, guesscasting and arguing begin.
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Member Since: August 6, 2011 Posts: 4 Comments: 37044
Quoting ncstorm:


Yes, a lot of people have expressed their displeasure to me about the frontal systems but that is what homegrown is about..I will be watching it though..I think all three waves will surprise most on here..PR wave is looking better and better..
We're all experts on trough splits now.Lol.
Member Since: August 14, 2010 Posts: 10 Comments: 16437

Quoting Tropicsweatherpr:
Here is a good candidate South of CV islands for Invest if it persists.


Impressive,probably will put 99l to shame.
Member Since: August 2, 2011 Posts: 0 Comments: 1781
Maybe the trade winds aren't as strong as I thought they were. It struck me as odd last night that buoys were only reporting 10-15 knot surface winds when you could see the winds racing from east to west on false visible satellite loops yesterday morning. But now there's more proof...

So far the vorticity maximum associated with the wave in front has not been weakened much.



And wind shear is already beginning to lower in the East Caribbean.
Member Since: July 6, 2010 Posts: 113 Comments: 31537
Quoting JrWeathermanFL:

NHC?
Y u no start advisories?!

[This content has been censored by TWC amd the NHC]
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Quoting washingtonian115:
While we're watching 99L the disturbance behind it is interesting as well.
race.for.90l...hispanola.vrs.cape.verde
Member Since: September 11, 2010 Posts: 1 Comments: 4358
Quoting washingtonian115:
I guess no one cares like that really ncstorm is because we've had so many of these system this year it's not even countable anymore XD.And I see that the GFS has a closed isobar with the wave behind 99L south of the cape verde island.


Yes, a lot of people have expressed their displeasure to me about the frontal systems but that is what homegrown is about..I will be watching it though..I think all three waves will surprise most on here..PR wave is looking better and better..
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Quoting Tropicsweatherpr:
Here is a good candidate South of CV islands for Invest if it persists.



NHC?
Y u no start advisories?!
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Quoting Stormchaser2007:


24 knots of shear in the heart of the Caribbean. This doesn't even account for the low level winds, which are screaming.

The way conditions are looking now, things are a bit dim for 99L in the extended range.


SHEAR (KT) 7 5 3 7 4 4 8 7 11 14 14 20 24

LAT (DEG N) 9.3 9.6 9.8 10.0 10.2 10.5 10.9 11.3 11.8 12.7 13.5 14.7 15.7
LONG(DEG W) 39.6 40.9 42.1 43.3 44.5 46.7 48.9 51.0 53.5 56.0 58.8 61.6 64.3


Neg. on the low level winds ghost rider



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BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE BIRMINGHAM AL
908 AM CDT TUE JUL 31 2012

THE NATIONAL WEATHER SERVICE IN BIRMINGHAM HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
NORTHEASTERN CHILTON COUNTY IN ALABAMA...
COOSA COUNTY IN EAST CENTRAL ALABAMA...
SOUTHERN SHELBY COUNTY IN ALABAMA...
SOUTHWESTERN TALLADEGA COUNTY IN EAST CENTRAL ALABAMA...

* UNTIL 945 AM CDT

* AT 905 AM CDT...THE NATIONAL WEATHER SERVICE INDICATED A LINE OF
SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN EXCESS
OF 60 MPH. THESE STORMS WERE LOCATED ALONG A LINE EXTENDING FROM
PELHAM TO CHILDERSBURG...AND MOVING SOUTHEAST AT 40 MPH.

* LOCATIONS IMPACTED INCLUDE...
WILSONVILLE...COLUMBIANA...SYLACAUGA...TALLADEGA SPRINGS...
CALERA...STEWARTVILLE...WEOGUFKA AND ROCKFORD.

WINDS OF 60 TO 70 MPH WILL BREAK LARGE TREE LIMBS AND CAUSE SOME
DAMAGE...ESPECIALLY TO SMALLER STRUCTURES.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

FOR YOUR PROTECTION...MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF
YOUR HOME OR BUSINESS.
Member Since: August 6, 2011 Posts: 4 Comments: 37044
Quoting 19N81W:
amazing the clarity of the water around her....
:)


funny i can't see past her...
and neither can admin!!

but on a weather note, models aren't enthusiastic about the next wave so im not so into its development at this time
Member Since: February 11, 2012 Posts: 0 Comments: 9721
Quoting biff4ugo:
Blobs to the East of me (Alabama and Off the Carolinas) Blobs to the West (Puerto Rico and 99L)

August is comming in like a Lion!

'Bama is going to hit Florida first though.
..yes im afraid so..and alot of northern florida is still cleaning up after Debby...this is not good at all
Member Since: August 6, 2011 Posts: 4 Comments: 37044
I notice the high temp forecast for weather station can be significantly different even when they are with in 1 km of each other. For example, Carter Lake (kiacarter) shows a high of 104 on thursday but Omaha )KOMA) shows a high of 93. 11 degrees difference, what's going on?
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Quoting Tropicsweatherpr:
Here is a good candidate South of CV islands for Invest if it persists.



Whoa.. WTF I know it's not but it looks like an eye.
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............this storm is going to be the big story today and maybe for the next few days,a huge amount of rain and wind and lightning etc and would not be surprised at tornado's and water spouts AND if it does cross over into the atlantic as NC said..oh boy....remember ..watch for homegrown storms the NWS said
Member Since: August 6, 2011 Posts: 4 Comments: 37044
Blobs to the East of me (Alabama and Off the Carolinas) Blobs to the West (Puerto Rico and 99L)

August is comming in like a Lion!

'Bama is going to hit Florida first though.
Member Since: Posts: Comments:
Quoting ncstorm:
I know everyone is focus on 99l but there are several models predicting development off of SC/NC from the disturbance currently located in GA/Alabama..its supposed to enter into the Atlantic off either the NC or SC coast and ride up both coasts depending on where it exits off

on the verge of warm core..could be subtropical

GFS

NOGAPS

CMC
I guess no one cares like that really ncstorm is because we've had so many of these system this year it's not even countable anymore XD.And I see that the GFS has a closed isobar with the wave behind 99L south of the cape verde island.
Member Since: August 14, 2010 Posts: 10 Comments: 16437
Here is a good candidate South of CV islands for Invest if it persists.


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amazing the clarity of the water around her....
:)
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Quoting GeorgiaStormz:


dude really?
admins a'comin for you


It's weather related, honest! Erm, well, it could be...

Look at that beautiful...ocean!
The rainbow theme.
The sky.

What lovely WEATHER they had there that day!
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Quoting ncstorm:
I know everyone is focus on 99l but there are several models predicting development off of SC/NC from the disturbance currently located in GA/Alabama..


Yah, i looked at those but there is too much shear for tropical development in spite of their tropical airmass origins. Wet, mild and maybe a little breezy for Nova Scotia next couple of days. One always havs to be careful with convective feedback in high PW systems - models tend to overdo convection which, in turn, overdoes vorticity.
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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.