Lesser Antilles may see a tropical storm late this week
A concentrated area of intense thunderstorms near 9N 36W, midway between Africa and the Lesser Antilles Islands, has become more organized this morning. NHC has labeled this system Invest 91L, and is giving it a 60% chance of developing into a tropical depression by 8am Tuesday. Wind shear is a moderate 10 - 20 knots, sea surface temperatures are at record highs, and the dust and dry air of the Saharan Air Layer (SAL) are far enough to the north of 91L to potentially allow further development. The main negatives for development are the current phase of the Madden-Julian Oscillation, which favors downward motion over the tropical Atlantic, and the fact that 91L is too close to the Equator to take much advantage of the Earth's spin to get spinning. Last night's ASCAT pass of the region did show a large region of westerly winds south of 91L, indicating that a surface circulation is trying to form. Satellite imagery shows that the intensity and areal extent of 91L's heavy thunderstorms is increasing. However, there are no signs of a surface circulation, and low-level spiral bands and upper-level outflow are not apparent yet.
Forecast for 91L
There is strong model support for 91L developing into a tropical depression. The GFS, ECMWF, NOGAPS, and UKMET models all develop 91L into a tropical depression by Tuesday or Wednesday. A west to west-northwest motion is predicted, and residents of the Lesser Antilles Islands should anticipate the possibility of a tropical storm arriving in the islands as early as Thursday. It is possible that 91L would pass northeast of the islands, as predicted by the UKMET model, and it is too early to speculate on which of the islands is at most risk. As the storm approaches the Lesser Antilles late this week, 91L will encounter a strong upper-level low pressure system centered north of Puerto Rico. This upper-level low will likely bring high levels of wind shear to the waters just north of Puerto Rico and Hispaniola. Thus, if 91L stays to the south, in the Caribbean, it is far more likely to attain hurricane status than if it pushes north of the Caribbean. As always, long range forecasts of this sort are speculative, and it is too early to reliably say what the long-term risks of 91L becoming a hurricane are. The latest intensity forecast from the SHIPS model shows 91L peaking in strength four days from now, then weakening as it encounters the high wind shear area north of Puerto Rico.
Figure 1. Morning satellite image of Invest 91L.
Next update
I'll have an update Monday morning.
Jeff Masters
Reader Comments
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MARK
10.31N/36.89W
Or I might add pro aviation met briefings done by NWS. Levi is my go to guy.
Oops, sorry. Here's the clickable link for the Times story featuring Dr. Masters.
On another note , looks like only one didn't affect land or hit somewhere, I must say Levi you're a very brilliant young man, I imagine you must have a very high IQ.
That sounds great I live in Pensacola and on the 12th I will be in Boston. Yeah cooler temps.
yes but it's nice to see the 3 models for comparison along with the different heights laid out in that format for a time verses time loops of one height..also the resolution is better...
I would love to see one with a pressure overlay too..
As far as track goes it's all computer models..
You can't estimate track 3 days from now with Sat Loops
Most who have been here a few years or more will answer whatever they can usually, within reason and it's what we do best here.
Also wu-mail is a good way to communicate out of the blog traffic view.
Esp when things get closer to a Landfall.
Um no I don't think so LOL.
You're right Pat! That's how a lot of us learned.
And for SSI, this is one of the ways you can get a Georgia landfall:
Can I get a Amen?
Hey. FloridaHeat. I'm another newbie here but have been living on the MS Gulf Coast for a number of years. To answer your question, a storm is named when it becomes a Tropical Storm, at about 35 mph windspeed.
91L seems to be settling down on a WNW course which should prevail for several days unless something comes along to weaken it significantly.
The center of the steering high is all the way up at 45N and 32W. As such 91L is already working its way around the South Western periphery and the forecast for low and mid level steering out thru 48 hrs both show the weakness remaining East of the Bahamas.
This should allow 91L to make steady progress to pass to the NE of the Leewards barring some unexpected change in the upper level pattern.
????? I thought they didn't update until 8p?
Feeling more "Westerly" after the rest?
i just moved to florida so that is why i am curious about hurricanes now i did not have to worry about them in oklahoma so much
A. TROPICAL DISTURBANCE 92C (SE OF HAWAII)
B. 01/2030Z
C. 11.0N
D. 142.1W
E. SIX/GOES11
F. T1.5/1.5/D0.5/21HRS STT: D0.5/03HRS
G. IR/EIR/VIS/MSI
H. REMARKS: 40A/PBO SBC/ANMTN. CNVCTN WRAP OF .25 ON LOG10
SPIRAL YIELDS A DT OF 1.5. PT AND MET AGREE. CNVCTN APPEARS TO
BE IMPROVING WITH SOME BANDING EVIDENT ON MULTISPECTRAL IMAGERY.
CORRECTED TO ADD DVORAK VALUE TO THIS FIX TO INDICATE
REPRESENTATIVE DEVELOPMENT OF THE SYSTEM.
I. ADDITIONAL POSITIONS:
01/1555Z 11.0N 142.2W AMSU
01/1700Z 11.0N 142.0W SSMS
UEHARA
go to the blog of stormw he has a lot of those codes decoded if u will lol
How far or close do you think kman?
Thanks in advance.
NMFC Norfolk Tropical Feed
No Active Tropical Warnings in the Atlantic, Caribbean, or Gulf of Mexico
By Maritime.CDO@navy.mil (NMFC CDO) from Naval Maritime Forecast Center Norfolk Virginia. Published on .
As of Sun 01 Aug 2010 21:30:02Z
2010 Storms
All Active Year
Atlantic
91L.INVEST
East Pacific
NONE
Central Pacific
92C.INVEST(T.C.F.A.)
West Pacific
NONE
Indian Ocean
NONE
Southern Hemisphere
NONE
97E is gone and yes they do update at 8pm
My eyes felt like someone kicked sand in them when I woke up but much better now.
There is a mid/upper level high to it's NE and big upper level low to it's NW which models have heading west over us. There is the trough from the cold front that came off the east coast of the US a few days ago that has put a weakness in the MAR/BAH and the 1016MB line is farther north ,around 20N than it has been all summer.
These 4 things along with the natural tendency to "climb" north should pull/push it on a more northerly course than it's drift along the ITCZ has been..
Although being in the Northern Antillies I am NOT thinking we are out of the possible path at all...but it's developing at a good pace and already above 10N so...
there is so much uncertainty in the forecast for 91L....... that you can determine who the idiots are....... the ones who make definitive statements!
It is ok to post your opinion...... just stay away from saying you know what is going to happen...... because you don't!
I like that H right over Florida...
I was just going to direct him there: Link
When I first came here, all the acronyms confused the hell out of me. StormW's blog page is a good key for all that stuff. :-)
Levi, Will PR be a direct target or you see it skipping it?
kman ill give you one guess who that is
92C.INVEST(T.C.F.A.)
11.1N/142.3W
he is traveling but suggesting its a us problem
That's strange that 92C has a TCFA, when the CPHC is only giving it a 10% chance within the next 48 hours:
Issued: Aug 01, 2010 8:13 am HST
For the central north Pacific, between 140°W and 180.
1. A surface trough located about 1060 miles southeast of Hilo, Hawaii has disorganized showers and isolated thunderstorms associated with it. Strong upper level winds are not conducive for any significant development of this system as it moves westward at 5 to 10 mph during the next couple of days. There is a low chance, 10 percent, of this system becoming a tropical cyclone during the next 48 hours.
Elsewhere, no tropical cyclones are expected through Tuesday morning.
I know they are separate agencies though. And it WAS at a code orange 40% earlier.
This is my exact line of thought
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