000
AXNT20 KNHC 181054
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT WED APR 18 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...
CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...
NORTHEASTERN SECTIONS OF SOUTH AMERICA...AND THE 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1015 UTC.

...THE ITCZ...
7N7W 3N20W...CROSSING THE EQUATOR AT 27W...TO 3S36W AND FINALLY
TO 4S44W IN NORTHEASTERN BRAZIL. STRONG SHOWERS AND THUNDERSTORMS
IN INDIVIDUAL CELLS WITHIN 30 NM RADIUS OF 1N6W AND 1N10W. OTHER 
ISOLATED MODERATE SHOWERS ARE FROM 3N TO 5N BETWEEN 6W AND 12W.
ISOLATED MODERATE SHOWERS FROM THE EQUATOR TO 6N BETWEEN 13W AND 
40W. 

...DISCUSSION...

THE GULF OF MEXICO...
GRADUAL AND EVER-SO-SLIGHT UPPER LEVEL ANTICYCLONIC WIND FLOW 
COVERS THE GULF WATERS...AS THE LATEST MIDDLE TO UPPER LEVEL 
TROUGH MOVES ARKANSAS/LOUISIANA/MISSISSIPPI. THE COLD FRONT 
BEING SUPPORTED BY THE MIDDLE TO UPPER LEVEL TROUGH WAS STILL 
INLAND AT 18/0600 UTC...AND IT HAS REACHED THE NORTHWESTERN GULF 
OF MEXICO WATERS AT 18/0900 UTC. VIRTUALLY NO SURFACE PRESSURE 
GRADIENT EXISTS IN THE GULF AT THIS TIME AS NO ISOBAR WAS DRAWN 
THERE ON THE SURFACE MAP ANALYSIS. A 1012 MB HIGH PRESSURE 
CENTER IS NEAR 22N82W BETWEEN CUBA AND THE ISLE OF YOUTH.

THE CARIBBEAN SEA...
MIDDLE TO UPPER LEVEL DRY AIR ALREADY IS IN PLACE IN THE 
CARIBBEAN SEA. BROAD UPPER LEVEL ANTICYCLONIC WIND FLOW COVERS 
THE AREA. MIDDLE TO UPPER LEVEL DRY AIR/SUBSIDENCE IS 
EVERYWHERE. THE SOUTHERNMOST POINT OF THE ATLANTIC OCEAN COLD 
FRONT PASSES THROUGH 22N60W TO THE VIRGIN ISLANDS TO 
17N73W...BECOMING A TROUGH FROM 17N73W TO 17N80W...TO THE 
NORTHERN HONDURAS COAST NEAR 16N86W TO SOUTHERN GUATEMALA NEAR 
15N91W. THIS TROUGH WAS NOT INCLUDED IN THE 18/0900 UTC SURFACE 
MAP ANALYSIS. BROKEN TO OVERCAST LOW TO MIDDLE LEVEL CLOUDS AND 
POSSIBLE PRECIPITATION ARE WITHIN 60 TO 90 NM ON EITHER SIDE OF 
23N56W 20N61W...AND FROM THE VIRGIN ISLANDS TO PUERTO RICO 
WESTWARD TO HISPANIOLA.

THE ATLANTIC OCEAN...
DEEP LAYER CYCLONIC FLOW COVERS THE AREA NORTH OF 20N WEST OF 50W
WITH THE DEEP LAYER CYCLONIC CIRCULATION CENTER AND TROUGH THAT 
HAVE BEEN BRINGING STORMY WEATHER FROM THE U.S.A. EAST COAST 
INTO THE ATLANTIC OCEAN. THE WESTERN ATLANTIC OCEAN CYCLONIC 
CENTER AND TROUGH ARE SUPPORTING THE COLD FRONT THAT PASSES 
THROUGH 32N52W TO 22N60W TO THE VIRGIN ISLANDS...SOUTHEASTERN 
PUERTO RICO...AND EVENTUALLY 17N73W. ISOLATED MODERATE SHOWERS 
AND POSSIBLE THUNDERSTORMS ARE WITHIN 30 TO 60 NM ON EITHER SIDE 
OF 23N56W 27N51W...AND WITHIN 60 TO 90 NM ON EITHER SIDE OF  
27N51W BEYOND 32N47W. BROKEN TO OVERCAST LOW TO MIDDLE LEVEL 
CLOUDS AND POSSIBLE PRECIPITATION ARE WITHIN 60 TO 90 NM ON 
EITHER SIDE OF 23N56W 20N61W...AND FROM THE VIRGIN ISLANDS TO 
PUERTO RICO WESTWARD TO HISPANIOLA. A SHORTWAVE MIDDLE TO UPPER 
LEVEL TROUGH GOES FROM A 33N28W CYCLONIC CIRCULATION CENTER TO 
28N30W. THE DEEP LAYER CYCLONIC CIRCULATION CENTER AND TROUGH 
FROM 24 HOURS AGO HAVE MOVED EASTWARD QUITE A BIT AND NOW ARE IN 
NORTHERN AFRICA. AN UPPER LEVEL TROUGH IS IN THE TROPICAL JET 
STREAM. BROAD WESTERLY FLOW FROM VENEZUELA AND GUYANA/SURINAME/ 
AND FRENCH GUIANA TO 2N43W 5N39W 20N30W BEYOND 24N20W. MIDDLE TO 
UPPER LEVEL DRY AIR/SUBSIDENCE IS WITHIN 120 TO 240 NM NORTHWEST 
OF THE JET STREAM EAST OF 33W...AND WITHIN 180 TO 240 NM WEST OF 
THE JET STREAM BETWEEN 33W AND 44W.

$$
MT