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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The sharp curve to the northeast seems a bit much. Not because the longwave trough might not be strong enough to deflect it from the coast (though that still remains to be seen), but because the trough should begin gaining influence earlier than 144 hours.
caplock caster
Luck.
Well taz that made me laugh. XD
HOSTILE SHEAR caster
18z GFS keeps the current anticyclone above the circulation even as it enters a region of high shear associated with the TUTT.
is a battle cruiser.
Battlecruiser operational?
but would it be considered a Cape Verde Storm, did it pass the distance required to be known as such?
Link
Thanks....I am very sleepy at the moment....Best thing for all concerned (a best case scenario) would be for strong development in the short term which would take it NW and perhaps a fish path....We will have to see what happens;
100%?
Advisories will start at 5am.
that's my take.
yup
What will the percentage for 91L be on the 2 A.M. TWO?
A. 80%
B. 90%
C. 100%
D. O4L - TD
Even if it rapidly develops during the day, the mid- upper-level steering flow is still east-southeasterly, which would take it WNW. This isn't to say that recurvature isn't possible, just that it won't be doing so in the short-term.
oh really? when?
Morning......I don't like the look of this one at the moment; can't wait to see the visible loops in the morning but it looks to me like some banding and outflow is starting to develop.
Yeah... Same here.
Nice meteorological jargon there. XD
A recent TMI microwave satellite overpass would certainly agree with your assessment.
What do you want me to say? Hot towers?
XD
LOL
Wouldn't be the first time.
WTF? Where?
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