African tropical wave 99L slowly organizing

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

Share this Blog
38
+

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

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: 171 - 121

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48Blog Index

Quoting AussieStorm:
@spann Car completely underwater at Lakeshore exit I-65 S

..huge rainmaker alright
Member Since: August 6, 2011 Posts: 4 Comments: 37831
Quoting RitaEvac:


Didn't see it, lol


We cross?
Member Since: Posts: Comments:
Why??
Quoting floridaboy14:
looks like the carribean is becoming more favorable....
Member Since: Posts: Comments:
Quoting GeorgiaStormz:


farmer's almanac said there will be an august 16-19 hurricane threat in TX/LA coast :)
lol


lol, yea I remember you posting that
Member Since: Posts: Comments:
Quoting GeoffreyWPB:


I think XTRP has the best track.
Member Since: Posts: Comments:
@spann Car completely underwater at Lakeshore exit I-65 S

Member Since: September 30, 2007 Posts: 9 Comments: 15935
Flooding at Warrior Park in Alabaster

Scott McClellan
@alastormspotter
Member Since: September 30, 2007 Posts: 9 Comments: 15935
Quoting RitaEvac:
Does a Wet July suggest an increased threat of Texas tropical activity in August and September?

Chris Hebert of Impact Weather recently completed a study looking at the effects of the top 20 wettest and top 20 driest July’s and the impacts of tropical activity on the upper TX coast in August-November of that year. The results are seen in the graphic below and are fairly dramatic. For the 20 wettest July’s, 13 tropical storms impacted the NW Gulf following that wet July versus 9 in the top 20 dry years. Even more astounding is that 11 hurricanes impacted following a wet July with only 4 in the dry years and 8 major hurricanes impacted the NW Gulf versus none following a dry July. To sum up the data following a wet July, there is a greater than 50% chance a hurricane will strike the TX/LA coast.



The reasoning of this makes sense, as a wet July strongly indicates a lack of strong high pressure over TX (much like this summer) usually with a weakness or trough in the height field aloft in this region. Tropical systems approaching from the south and east will flow toward this weakness in the ridge…hence unlike in 2011 when Texas was strongly protected by strong high pressure, this year we are not and we will need to keep a very close eye on developments over the next 2 months.



farmer's almanac said there will be an august 16-19 hurricane threat in TX/LA coast :)
lol
Member Since: Posts: Comments:
looks like the carribean is becoming more favorable....
Member Since: Posts: Comments:
not a EYE lol
Quoting ilovehurricanes13:
look like a eye!! wow
Member Since: Posts: Comments:


Member Since: Posts: Comments:
I wonder if the NHC will mention the tropical wave by the cape verde islands.They'll probably wait.
Member Since: August 14, 2010 Posts: 10 Comments: 16679
TX/LA you've been warned......
Member Since: Posts: Comments:
156. yoboi
Quoting RitaEvac:
Does a Wet July suggest an increased threat of Texas tropical activity in August and September?

Chris Hebert of Impact Weather recently completed a study looking at the effects of the top 20 wettest and top 20 driest July’s and the impacts of tropical activity on the upper TX coast in August-November of that year. The results are seen in the graphic below and are fairly dramatic. For the 20 wettest July’s, 13 tropical storms impacted the NW Gulf following that wet July versus 9 in the top 20 dry years. Even more astounding is that 11 hurricanes impacted following a wet July with only 4 in the dry years and 8 major hurricanes impacted the NW Gulf versus none following a dry July. To sum up the data following a wet July, there is a greater than 50% chance a hurricane will strike the TX/LA coast.



The reasoning of this makes sense, as a wet July strongly indicates a lack of strong high pressure over TX (much like this summer) usually with a weakness or trough in the height field aloft in this region. Tropical systems approaching from the south and east will flow toward this weakness in the ridge…hence unlike in 2011 when Texas was strongly protected by strong high pressure, this year we are not and we will need to keep a very close eye on developments over the next 2 months.



interesting.....
Member Since: Posts: Comments:
Quoting galvestonhurricane:


Hey! I posted that last week! Are you trying to copy me? Lol


Didn't see it, lol
Member Since: Posts: Comments:



My Shangri-La beneath the summer moon, I will return again
Like the dust that lufts high in June, when moving through Kashmir.
Member Since: Posts: Comments:
Quoting RitaEvac:
Does a Wet July suggest an increased threat of Texas tropical activity in August and September?

Chris Hebert of Impact Weather recently completed a study looking at the effects of the top 20 wettest and top 20 driest July’s and the impacts of tropical activity on the upper TX coast in August-November of that year. The results are seen in the graphic below and are fairly dramatic. For the 20 wettest July’s, 13 tropical storms impacted the NW Gulf following that wet July versus 9 in the top 20 dry years. Even more astounding is that 11 hurricanes impacted following a wet July with only 4 in the dry years and 8 major hurricanes impacted the NW Gulf versus none following a dry July. To sum up the data following a wet July, there is a greater than 50% chance a hurricane will strike the TX/LA coast.



The reasoning of this makes sense, as a wet July strongly indicates a lack of strong high pressure over TX (much like this summer) usually with a weakness or trough in the height field aloft in this region. Tropical systems approaching from the south and east will flow toward this weakness in the ridge…hence unlike in 2011 when Texas was strongly protected by strong high pressure, this year we are not and we will need to keep a very close eye on developments over the next 2 months.



Hey! I posted that last week! Are you trying to copy me? Lol
Member Since: Posts: Comments:
Quoting Stormchaser2007:
Issued this morning (early)


Going to have to watch that tropical wave.
Member Since: July 6, 2010 Posts: 113 Comments: 31858
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.


If it goes through the Caribbean, then E or F.
Member Since: Posts: Comments:
Is that a Hurricane lol jk!!
Member Since: Posts: Comments:
Does a Wet July suggest an increased threat of Texas tropical activity in August and September?

Chris Hebert of Impact Weather recently completed a study looking at the effects of the top 20 wettest and top 20 driest July’s and the impacts of tropical activity on the upper TX coast in August-November of that year. The results are seen in the graphic below and are fairly dramatic. For the 20 wettest July’s, 13 tropical storms impacted the NW Gulf following that wet July versus 9 in the top 20 dry years. Even more astounding is that 11 hurricanes impacted following a wet July with only 4 in the dry years and 8 major hurricanes impacted the NW Gulf versus none following a dry July. To sum up the data following a wet July, there is a greater than 50% chance a hurricane will strike the TX/LA coast.



The reasoning of this makes sense, as a wet July strongly indicates a lack of strong high pressure over TX (much like this summer) usually with a weakness or trough in the height field aloft in this region. Tropical systems approaching from the south and east will flow toward this weakness in the ridge…hence unlike in 2011 when Texas was strongly protected by strong high pressure, this year we are not and we will need to keep a very close eye on developments over the next 2 months.

Member Since: Posts: Comments:
The National Weather Service in Lincoln has issued a

* Severe Thunderstorm Warning for...
northeastern Champaign County in east central Illinois...
northwestern Vermilion County in east central Illinois...

* until 1015 am CDT.

* At 933 am CDT... National Weather Service meteorologists detected a
severe thunderstorm capable of producing quarter size hail... and
damaging winds in excess of 60 mph. This storm was located near
Rankin... or 9 miles east of Paxton... and moving south at 30 mph.

* Locations impacted include...
Gifford... Potomac... Armstrong... Middle Fork wildlife area...
Collison... Royal and Kickapoo State Park.
Member Since: Posts: Comments:
Quoting JrWeathermanFL:
My favorite Invest # is 92L
Whats yalls?
A. 90
B. 91
C. 92
D. 93
E. 94
F. 95
G. 96
H. 97
I. 98
J. 99


94L
Member Since: Posts: Comments:
Quoting AussieStorm:

I choose F5. lol.
Cat. 2 the most...
Member Since: Posts: Comments:
Issued this morning (early)

Member Since: Posts: Comments:
Shear is favorable in the eastern caribbean.In the middle and western not so much.
Member Since: August 14, 2010 Posts: 10 Comments: 16679
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.


Strong tropical storm or maybe a minimall hurricane... (75-80mph)
Member Since: Posts: Comments:
Lordy,

Member Since: Posts: Comments:

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE MOBILE AL
932 AM CDT TUE JUL 31 2012

THE NATIONAL WEATHER SERVICE IN MOBILE HAS ISSUED A

* FLASH FLOOD WARNING FOR...
WESTERN AND CENTRAL WILCOX COUNTY IN SOUTH CENTRAL ALABAMA...

* UNTIL 330 PM CDT TUESDAY

* AT 924 AM CDT...VERY HEAVY RAINFALL CONTINUES TO MOVE INTO WESTERN
AND CENTRAL WILCOX COUNTY FROM THE NORTHWEST. RAINFALL TOTALS OF 2
TO 3 INCHES HAS ALREADY FALLEN OVER PORTIONS OF WILCOX COUNTY OVER
THE PAST 1 TO 2 HOURS...ESPECIALLY THE NORTHWEST SECTION OF THE
COUNTY. AN ADDITIONAL 2 TO 4 INCHES OF RAIN IS EXPECTED OVER THE
NEXT COUPLE OF HOURS WHICH WILL LIKELY RESULT IN FLASH FLOODING.

* LOCATIONS IMPACTED INCLUDE...
BOYKIN... YELLOW BLUFF... PINE HILL...
CATHERINE... CAMDEN...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FLASH FLOOD WARNING MEANS FLOODING IS IMMINENT OR OCCURRING. SEEK
HIGHER GROUND IMMEDIATELY. DO NOT DRIVE OR WALK INTO AREAS WHERE
WATER CROSSES A ROAD. TURN AROUND - DON'T DROWN!

IF YOU ARE IN DANGER FROM THE FLOOD WATERS AND NEED RESCUE ASSISTANCE
CALL 911. TO REPORT FLOODING TO THE NATIONAL WEATHER SERVICE CALL
(800) 284-9059.
Member Since: August 6, 2011 Posts: 4 Comments: 37831
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 F5. lol.
Member Since: September 30, 2007 Posts: 9 Comments: 15935
My favorite Invest # is 92L
Whats yalls?
A. 90
B. 91
C. 92
D. 93
E. 94
F. 95
G. 96
H. 97
I. 98
J. 99
Member Since: Posts: Comments:
Quoting StormTracker2K:


D or E is possible if conditions are right once 99L gets into the Caribbean. Caribbean has basically be untouched for several years now so plenty of potential energy sitting out there.


Not with the winds out there....
you need light shear for D or E
Member Since: Posts: Comments:
Quoting Grothar:


The one I've been posting the last 3 days? Pretty good chance with this one. But look at Central Africa I just posted.
Lol.I'm thinking at least T.D or maybe even weak T.S status.That's one big kahuna coming off Gro.Should bring the dry stable air to it's knees.
Member Since: August 14, 2010 Posts: 10 Comments: 16679
Can you guys tell me how to find the source code or url to post satellite loops!!
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.


mid-B
Member Since: Posts: Comments:
THIS OUTLOOK IS FOR NORTHEAST FLORIDA...SOUTHEAST GEORGIA AND THE
ADJACENT COASTAL WATERS.

.DAY ONE...TODAY AND TONIGHT...
STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED TO MOVE SOUTHEASTWARD
DURING THE EARLY AFTERNOON HOURS ACROSS SOUTHEAST GEORGIA...WITH
ACTIVITY REACHING THE INTERSTATE 10 CORRIDOR IN NORTHEAST FLORIDA
DURING THE LATE AFTERNOON OR EARLY EVENING HOURS. SCATTERED
THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS THE REMAINDER OF
NORTHEAST FLORIDA DURING THE AFTERNOON AND EVENING HOURS. THE
STORM PREDICTION CENTER HAS PLACED ALL OF SOUTHEAST GEORGIA AND
MOST OF NORTHEAST FLORIDA IN A SLIGHT RISK FOR SEVERE
THUNDERSTORMS FOR THIS AFTERNOON AND EVENING...WITH ENHANCED
PROBABILITIES FOR DAMAGING WIND GUSTS. STRONGER THUNDERSTORMS
WILL ALSO HAVE THE CAPABILITY TO PRODUCE FREQUENT AND DEADLY
LIGHTNING STRIKES AND LOCALLY HEAVY RAINFALL.
Member Since: Posts: Comments:
Quoting stormchaser19:


Strong B or Weak C lol


D or E is possible if conditions are right once 99L gets into the Caribbean. Caribbean has basically be untouched for several years now so plenty of potential energy sitting out there.
Member Since: October 26, 2011 Posts: 0 Comments: 2651
Member Since: August 6, 2011 Posts: 4 Comments: 37831
12z Early Cycle NHC model tracks
Invest99
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)



Dynamic Models (More sophisticated models)




Early Model Wind Forecasts

Member Since: Posts: Comments:
In addition, the UKMET (from the Monterey Pouch Guidance) has been consistently showing that 99L will have trouble with supporting it's own moist enviorment once it seperates from the monsoon trof. That TUTT could really knock in some dry air if 99L drifts too far north.

Happy pouch:


Not happy:

Member Since: Posts: Comments:
Quoting washingtonian115:
Gro what is your opinion on the blob south of the cape verde islands?.And wow that's one huge moisture field.


The one I've been posting the last 3 days? Pretty good chance with this one. But look at Central Africa I just posted.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Member Since: August 6, 2011 Posts: 4 Comments: 37831
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting Grothar:
Gro what is your opinion on the blob south of the cape verde islands?.And wow that's one huge moisture field.
Member Since: August 14, 2010 Posts: 10 Comments: 16679
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.


Strong B or Weak C lol
Member Since: Posts: Comments:
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: 37831

Viewing: 171 - 121

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48Blog 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.

Local Weather

Overcast
68 °F
Overcast