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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1913 ilovehurricanes13: weakening invest 99L UP 1012mb!
Nope, down to 1009millibars
1920 ilovehurricanes13: invest 99L IS MOVING WNW...NOW
99L has been headed between 273.7degreesWest and 278.3degreesWest for quite a while now.
Exactly WestNorthWest is 292.5degrees: so WNW generally describes a direction in the octant between 281.25degrees and 303.75degrees

1) Posting nonsense only gets you Ignored
2) CAPITALIZing or embolding everything within a comment just makes people skip reading that comment, and gets you Ignored.

So I gotta ask, why do you wanna to be ignored by others?

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Quoting Grothar:
Who was the idiot who said 99L would be a depression by late Tuesday or Wednesday?


Twas the Guru
Member Since: September 18, 2010 Posts: 0 Comments: 5237
Quoting wxchaser97:
small typhoon and big typhoon in here we can clearly see how small and how big the systems in the WPAC can be.
Member Since: October 15, 2011 Posts: 0 Comments: 4450
00Z EURO is interesting

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EURO + NOGAPS + CMC = Northward movement
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AL, 99, 2012073112, 93N, 398W, 20, 1010, LO
AL, 99, 2012073118, 94N, 414W, 25, 1009, LO
AL, 99, 2012080100, 96N, 428W, 25, 1009, LO
AL, 99, 2012080106, 97N, 440W, 25, 1009, LO
In other words...
1August12amGMT's 9.3n39.6w - 9.5n41.3w - 9.7n43.0w was re-evaluated&altered to
1August06amGMT's 9.3n39.8w - 9.4n41.4w - 9.6n42.8w - 9.7n44.0w

Copy&paste 9.3n39.6w-9.5n41.3w, 9.5n41.3w-9.7n43.0w, 9.3n39.8w-9.4n41.4w,
9.4n41.4w-9.6n42.8w, 9.6n42.8w-9.7n44.0w into the GreatCircleMapper for more information
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Euro is farther north and out of the Caribbean in 120 hours:
Member Since: August 31, 2009 Posts: 0 Comments: 5628
1909. JLPR2
Now the strongest vort area is clearly at 10N.



It's doing it slowly, but 99L is pulling itself together.


Well I'm off to bed too, night all!
Member Since: September 4, 2007 Posts: 7 Comments: 8747
1908. JLPR2
Quoting ProgressivePulse:


Oh to have the QuikScat Back....


I miss that satellite so much!

:\
Member Since: September 4, 2007 Posts: 7 Comments: 8747
99L hitting warmer SSTs now.
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Wake me up in 2 more weeks when the MJO comes back and the real fireworks begin. 99L is going to get it's head chopped off. The Caribbean is a graveyard. You can see on satellite how quickly the TUTT is dissipating the TW near the DR.
Member Since: May 22, 2010 Posts: 0 Comments: 907
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Quoting ilovehurricanes13:
200 AM EDT WED AUG 1 2012

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH AN AREA OF LOW PRESSURE
LOCATED ABOUT 1100 MILES EAST-SOUTHEAST OF THE WINDWARD ISLANDS
HAVE NOT BECOME ANY BETTER ORGANIZED DURING THE PAST SEVERAL HOURS..

yes but,you failed in the forecast
Member Since: June 20, 2012 Posts: 0 Comments: 2169
1814 wunderkidcayman: [inre the page37comment1807 mapping] about time you show up

Nah. 99L's still an Invest, and still far away from populated areas.
Timeliness becomes important when an Invest becomes a TropicalCyclone that interacts more strongly with the steering currents, etc. Or its fringes come close enough to shore for land interactions, which can change a storm's strength and travel-direction&speed extremely quickly.

Still make a mapping for myself every 6hours. But eg the 31July6pmGMT had 99L heading toward southernmost Carriacou. Then 6hours later, the 1August12amGMT report re-evaluated&altered that 31July6pmGMT position so that 99L had been heading for Tobago all along.

Nobody missed much from me not posting that 31July6pmGMT map.
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pass, happy rest of the night to all
Member Since: June 20, 2012 Posts: 0 Comments: 2169
Quoting KoritheMan:
50%.


My head told me 60%, instinct told me 50%. Always go with your instinct, I guess. Didn't help that Stewart wasn't in the house.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
50%.
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Stays at 50%...not really unexpected.

Have a great night, everyone.
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And it stays the same, night everyone.
000
ABNT20 KNHC 010538
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT WED AUG 1 2012

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH AN AREA OF LOW PRESSURE
LOCATED ABOUT 1100 MILES EAST-SOUTHEAST OF THE WINDWARD ISLANDS
HAVE NOT BECOME ANY BETTER ORGANIZED DURING THE PAST SEVERAL HOURS.
ENVIRONMENTAL CONDITIONS ARE MARGINALLY CONDUCIVE FOR GRADUAL
DEVELOPMENT OF THIS LOW OVER THE NEXT FEW DAYS. THIS SYSTEM HAS A
MEDIUM CHANCE...50 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS AS IT MOVES WESTWARD AT 15 TO 20 MPH.

DISORGANIZED SHOWERS AND THUNDERSTORMS OVER HISPANIOLA...PUERTO
RICO...AND THE CENTRAL CARIBBEAN SEA ARE ASSOCIATED WITH A
WESTWARD-MOVING TROPICAL WAVE. DEVELOPMENT OF THIS WAVE IS NOT
EXPECTED AND IT HAS A LOW CHANCE...NEAR 0 PERCENT...OF BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS. HOWEVER...LOCALLY HEAVY
RAINFALL AND GUSTY WINDS ASSOCIATED WITH THIS WAVE WILL SPREAD
ACROSS EASTERN CUBA AND THE SOUTHEASTERN BAHAMAS DURING THE NEXT
DAY OR TWO.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER CANGIALOSI
Member Since: March 16, 2012 Posts: 127 Comments: 7958
Quoting JLPR2:


It's pretty much luck.
As you can see 99L happened to be where the hole in the OSCAT readings are.



Oh to have the QuikScat Back....
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Quoting KoritheMan:


That would only happen if the wave became the stronger of the two. Somehow I don't think that's likely with all the westerly shear.


I should have been more clear. My thinking is more long term. If the area develops in the Bahamas it may exaggerate the COL area allowing 99L to turn more NW or Nward in time. Path into the South and Central Caribbean is a pretty sure thing.
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1890. JLPR2
Quoting stormchaser19:


Because, why do you think he missed?


It's pretty much luck.
As you can see 99L happened to be where the hole in the OSCAT readings are.

Member Since: September 4, 2007 Posts: 7 Comments: 8747
Quoting wxchaser97:
After the TWO I'm going to bed.


Me too.
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Quoting JLPR2:
OSCAT completely missed 99L, instead it caught the mess in front of it.



Because, why do you think he missed?
Member Since: June 20, 2012 Posts: 0 Comments: 2169
After the TWO I'm going to bed.
Member Since: March 16, 2012 Posts: 127 Comments: 7958
Quoting wxchaser97:
The poll is closed, lets see the results:
A= 1 vote
B= 6 votes
C= 3 votes

50% is the consensus here, thanks for all who participated!


No prob.
Member Since: June 20, 2012 Posts: 0 Comments: 2169
1885. JLPR2
OSCAT completely missed 99L, instead it caught the mess in front of it.

Member Since: September 4, 2007 Posts: 7 Comments: 8747
The poll is closed, lets see the results:
A= 1 vote
B= 6 votes
C= 3 votes

50% is the consensus here, thanks for all who participated!
Member Since: March 16, 2012 Posts: 127 Comments: 7958
Quoting wxchaser97:
Gradual development as the NHC would say but yeah could be better and its getting there.


Agreed. I actually think this has a high chance of developing over the next 48 hours (as opposed to medium).
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Quoting AllStar17:


Still looks ragged to me, but it is still making progress in organization.


Yes, And we need to remember the system is getting out of the (ITCZ)
Member Since: June 20, 2012 Posts: 0 Comments: 2169
I'm glad some of us have seen the northward movement of convection with 99L. Well it's detaching from the itcz.. but jumping from 9.8 to nearly 11N in just a few hours is pretty significant..
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Quoting AllStar17:


Still looks ragged to me, but it is still making progress in organization.
Gradual development as the NHC would say but yeah could be better and its getting there.
Member Since: March 16, 2012 Posts: 127 Comments: 7958
Quoting wxchaser97:
Hey AllStar, it does look like convection is increasing with 99L.


Still looks ragged to me, but it is still making progress in organization.
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Member Since: March 16, 2012 Posts: 127 Comments: 7958
Quoting AllStar17:
99L appears to be recovering after a brief period of waning convection. New popcorn-like convection is already firing, which should further aid its development process.
Hey AllStar, it does look like convection is increasing with 99L.
Member Since: March 16, 2012 Posts: 127 Comments: 7958
Damry expected to become a Hurricane despite Saola to its Southwest and looks headed towards China.



Saola expected to become a Major Hurricane as it grazes the island of Taiwan and also heads on a course towards China.



Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting sunlinepr:


The tail of the typhoon is pounding this islands
Member Since: June 20, 2012 Posts: 0 Comments: 2169
99L appears to be recovering after a brief period of waning convection. New popcorn-like convection is already firing, which should further aid its development process.
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Saola is really starting to look good and people in it's path are in trouble.
Member Since: March 16, 2012 Posts: 127 Comments: 7958
Quoting GTcooliebai:
I'm impressed at how close these two systems are because usually the larger system kills the smaller one when its this close together due to the outflow from the larger system that would induce shear on the smaller one.


The smaller one is about to get slung into China by Saola. Maybe a small Fujiwara Effect.
Member Since: July 15, 2006 Posts: 17 Comments: 10284

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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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