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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That's how we learn, though. Right?
hmmm something happen
I see no link to the ITCZ in the MIMIC TPW or TCTrak images. What should I be looking for?
Do you recon the blob to your east will drift up to me or give you another good soaking?
high pressure aloft enhancing the ridge to the north just enough to help keep it on a WNW track and close that door in the weakness
91L is winding up nicely.
Not getting rain yet :P All lightning at this point. I don't think that's gonna keep up for very long tho. I see we're about to kick of the start of our CV season.
Wish I was there....
I agree with you completely.
Don't know what the MM5B and MM5E models are but I noticed the BAMD has done that several runs in a row, slows down the track and takes that left turn.
Exactly. It's farther to the north. With at that location it seems like a sure miss for us here in the northern antilles. I will be going to take a break from following the invest, it's driving me mad. Break time!
you could go camera happy...lol
That is what I do
Earlier this afternoon, I thought B'dos.
But it has kept west all day, mostly.
Looks like between me and you.
Tobago, Grenada.
But I am sure we will all get wetter.....
Strange model
.
Totally agree...they appear to still be tracking the center of the broad low, instead of switching to the developing surface center which will almost certainly become Colin's core.
August 1, 2010 - 10:30 PM EDT - 91L On The Verge Of Becoming A Tropical Depression
I love taking pictures myself but I am not going to go out and get struck knowing my luck (with this bad of a storm)
..now, here to check on the potential mischief to the East.
I said I would leave but.. well... this is addicting =P.
What change in track do you think this could create?
Nice loop, Keeper. Thanks.
I had not seen that.
Ty eyes,,..long time no see.
Im Like BP and Beaches..
Forever
oh, don't go out,,, I can tell you know, it's not worth getting stuck just for the sake of a photo. I am a survivor of being struck.
I will keep you updated :)
Thats what friends are for.
I'd almost guarantee a TD at 5am with the info I'm seeing.
You and Lee Trevino !
It's horrendous!
is this wrong or right??
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