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
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 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 — Blog Index
AL, 91, 2010080200, 03, LBAR, 96, 177N, 602W, 0, 0, , 0, , 0, 0, 0, 0,
AL, 91, 2010080200, 03, LGEM, 0, 101N, 374W, 25, 0, , 0, , 0, 0, 0, 0,
AL, 91, 2010080200, 03, LGEM, 12, 108N, 401W, 27, 0, , 0, , 0, 0, 0, 0,
AL, 91, 2010080200, 03, LGEM, 24, 118N, 431W, 32, 0, , 0, , 0, 0, 0, 0,
AL, 91, 2010080200, 03, LGEM, 36, 131N, 462W, 39, 0, , 0, , 0, 0, 0, 0,
AL, 91, 2010080200, 03, LGEM, 48, 147N, 495W, 47, 0, , 0, , 0, 0, 0, 0,
AL, 91, 2010080200, 03, LGEM, 60, 164N, 528W, 54, 0, , 0, , 0, 0, 0, 0,
AL, 91, 2010080200, 03, LGEM, 72, 183N, 557W, 59, 0, , 0, , 0, 0, 0, 0,
AL, 91, 2010080200, 03, LGEM, 84, 201N, 583W, 61, 0, , 0, , 0, 0, 0, 0,
AL, 91, 2010080200, 03, LGEM, 96, 220N, 601W, 60, 0, , 0, , 0, 0, 0, 0,
AL, 91, 2010080200, 03, LGEM, 108, 235N, 614W, 57, 0, , 0, , 0, 0, 0, 0,
AL, 91, 2010080200, 03, LGEM, 120, 248N, 622W, 54, 0, , 0, , 0, 0, 0, 0,
Invest91
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)
Dynamic Models (More sophisticated models)
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0048 UTC MON AUG 2 2010
DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.
ATLANTIC OBJECTIVE AIDS FOR
DISTURBANCE INVEST (AL912010) 20100802 0000 UTC
...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
100802 0000 100802 1200 100803 0000 100803 1200
LAT LON LAT LON LAT LON LAT LON
BAMS 10.1N 37.4W 10.9N 39.6W 12.2N 42.6W 13.7N 46.2W
BAMD 10.1N 37.4W 10.8N 39.8W 11.9N 42.5W 13.1N 45.3W
BAMM 10.1N 37.4W 10.8N 40.1W 11.8N 43.1W 13.1N 46.2W
LBAR 10.1N 37.4W 10.7N 39.8W 11.6N 42.7W 12.5N 46.1W
SHIP 25KTS 30KTS 38KTS 48KTS
DSHP 25KTS 30KTS 38KTS 48KTS
...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
100804 0000 100805 0000 100806 0000 100807 0000
LAT LON LAT LON LAT LON LAT LON
BAMS 15.5N 50.0W 19.7N 57.8W 23.4N 64.2W 25.9N 68.1W
BAMD 14.4N 48.1W 16.7N 53.2W 18.8N 57.1W 19.9N 58.9W
BAMM 14.7N 49.5W 18.3N 55.7W 22.0N 60.1W 24.8N 62.2W
LBAR 13.6N 49.6W 15.3N 55.9W 17.7N 60.2W .0N .0W
SHIP 56KTS 68KTS 69KTS 65KTS
DSHP 56KTS 68KTS 69KTS 65KTS
...INITIAL CONDITIONS...
LATCUR = 10.1N LONCUR = 37.4W DIRCUR = 289DEG SPDCUR = 7KT
LATM12 = 9.6N LONM12 = 35.8W DIRM12 = 287DEG SPDM12 = 7KT
LATM24 = 9.2N LONM24 = 34.7W
WNDCUR = 25KT RMAXWD = 50NM WNDM12 = 25KT
CENPRS = 1007MB OUTPRS = 1010MB OUTRAD = 150NM SDEPTH = S
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM
AL, 91, 201008012345, 10, DVTS, CI, , 1020N, 3720W, , 3, 35, 2, , , , , , , , , , , , , , , , , , TAFB, WB, I, 5, 2525 /////, , , MET8, CSC, T, DT = 2.5 BASED ON 0.4 BANDING. NLINEMET= 1.0 PAT=
Due to the way ATCF has been picking coordinates, I still don't quite buy how northerly the models have the initial motion. It doesn't look that far north of due west to me in the short term.
Invest91
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)
Dynamic Models (More sophisticated models)
****************************************************
18z Early Cycle NHC model tracks
Invest91
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)
Dynamic Models (More sophisticated models)
Agatha, east Pacific, earlier this year. It makes me glad that they really are going to utilize the full range of percentages.
Where did you get the TCFA track from?
WOW
I do see some broad and weak spin. It also appears to be the demarcation of the westward moving tongue of dry air intrusion N of 15N.
A TUTT breaker already exists in the form of the E coast trough. Not sure if this feature can trump that.
Thanks for giving us the free "skinny" on his thoughts. 91L looks like it will find a way to develop-one way or the other over the next 3-4 days!
Dynamic Models (More sophisticated models)
18z
No point....it's way too old. Might try the new one:
with that being said the nhc could make this a TD or TS
yeah, things are pretty much fine, if i forget about my back problems.
Could our NICARAGUA twave develop in the EPAC?
Hey there Storm. Thanks for all of your info. The class reunion was wonderful aside from a few tropical showers on Saturday evening from Bonnie. Had really nice weather. Hope this one doesn't come our way, that's for sure.
vary un likey wind shear is too strong look what shear dont too 97E
ok
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN AUG 01 2010
TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.
BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2230 UTC.
...SPECIAL FEATURES...
TROPICAL WAVE EXTENDS ALONG 22N39W TO 11N36W MOVING W NEAR 15
KT. THE WAVE IS EMBEDDED WITHIN AN AREA OF ENHANCED DEEP LAYER
MOISTURE EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY FROM 5N-28N
BETWEEN 35W-42W. A 1007 MB LOW IS CENTERED NEAR THE SRN EXTENT
OF THE WAVE AXIS NEAR 10N36W. CLUSTERS OF STRONG CONVECTION HAVE
DEVELOPED NEAR THE CENTER FROM 10N-12N BETWEEN 35W-38W.
SCATTERED STRONG CONVECTION IS ALSO FROM 9N-12N BETWEEN 32W-35W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 5N-14N
BETWEEN 38W-43W. DUE TO FAVORABLE ENVIRONMENTAL
CONDITIONS...THIS SYSTEM HAS A HIGH CHANCE OF FURTHER
ORGANIZATION INTO A TROPICAL CYCLONE OVER THE NEXT COUPLE OF
DAYS.
will do...
MARK
10.39N/37.03W
Viewing: 2501 - 2551
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 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 — Blog Index