[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181752
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...THE ITCZ...
ITCZ AXIS EXTENDS FROM 6N9W 3N20W CROSSING THE EQUATOR AT 33W
INTO NE BRAZIL NEAR 4S41W. CLUSTERS OF MODERATE/ISOLATED STRONG
CONVECTION ARE WITHIN 200-300 NM S OF THE AXIS E OF 12W.
ISOLATED MODERATE CONVECTION IS WITHIN 90 NM S OF THE AXIS
BETWEEN 26W-29W. A BAND OF MODERATE TO STRONG CONVECTION EXISTS
ALONG THE COAST OF NE BRAZIL STRETCHING FROM 2S42W TO 7S32W.

...DISCUSSION...

GULF OF MEXICO...
A SHORTWAVE TROUGH OVER THE EAST COAST OF THE US IS SUPPORTING
THE COLD FRONT THAT EXTENDS FROM THE 1006 MB SFC LOW CENTERED
OVER SE LOUISIANA ACROSS THE NW GULF AND INTO TEXAS NEAR CORPUS
CRISTI. A BAND OF LOW/MID CLOUDS WITH EMBEDDED SHOWERS/POSSIBLE
THUNDERSTORMS EXTENDS 60-90 NM AHEAD OF THE FRONT N OF 27N. THE
FRONT IS EXPECTED TO CONTINUE MOVING SE ACROSS THE GULF AND
REACH THE STRAITS OF FLORIDA AND THE YUCATAN CHANNEL BY EARLY
THURS NIGHT. MODERATE SLY WINDS AHEAD OF THE FRONT WILL WEAKEN
TO 10-15 KT AND BECOME NLY FOLLOWING THE FRONTAL PASSAGE. A WEAK
1011 MB HIGH OVER CUBA IS KEEPING THE REMAINDER OF THE GULF
UNDER A DRY AND STABLE AIRMASS WITH FAIR WEATHER STRATOCUMULUS
CLOUDS COVERING THE S GULF AND THE YUCATAN CHANNEL. ALOFT...FLOW
AROUND AN UPPER HIGH CENTERED OVER HONDURAS IS TRANSPORTING A
PLUME OF UPPER LEVEL MOISTURE/HIGH CLOUDS ACROSS N-CENTRAL
MEXICO INTO THE SOUTHERN GULF WATERS.

CARIBBEAN SEA...
THE STRONG COLD FRONT OVER THE ATLANTIC EXTENDS TO JUST S OF
PUERTO RICO AND CONTINUES TO GENERATE SHOWERS OVER THE ISLAND.
AS OF 12Z...THE 24 HR RAINFALL TOTAL IN SAN JUAN WAS 1.71 IN.
THIS MOISTURE IS EXPECTED TO MEANDER ACROSS THE REGION OVER THE
NEXT 24-48 HRS. COLD AIR STRATOCUMULUS CLOUDS REMAIN OVER THE
YUCATAN CHANNEL AND THE NW CARIBBEAN. ALOFT...AN UPPER HIGH
CONTINUES TO DOMINATE THE CARIBBEAN...HOWEVER IT HAS SHIFTED
WEST AND IS NOW CENTERED OVER HONDURAS. THIS IS PROVIDING DRY
AIR AND MODERATE TO STRONG SUBSIDENCE OVER THE ENTIRE CARIBBEAN.
A BAND OF CIRRUS CLOUDS IS BEING TRANSPORTED AROUND THE HIGH AND
IS ENTERING THE NW CARIBBEAN FROM THE GULF. THE TRADES ARE LIGHT
TO MODERATE ACROSS MUCH OF THE AREA DUE TO A WEAK PRES GRADIENT.

ATLANTIC OCEAN...
THE STRONG COLD FRONT CONTINUES TO MARCH EWD ACROSS THE ATLC AND
ENTERS THE REGION NEAR 31N50W EXTENDING SW THROUGH PUERTO RICO.
THE FRONT IS NO LONGER PRODUCING GALE FORCE WINDS...HOWEVER
STRONG WINDS AND HAZARDOUS MARINE CONDITIONS CONTINUE TO
EXIST...PARTICULARLY N OF 24N WITHIN 330 NM AHEAD OF THE
FRONT...AND N OF 26N BEHIND THE FRONT TO 69W. A BROAD BAND OF
MOISTURE WITH EMBEDDED SHOWERS AND POSSIBLE ISOLATED
THUNDERSTORMS EXTENDS 100-200 NM AHEAD OF THE FRONT. A 15Z QSCAT
PASS SHOWS 20-35 KT ON EITHER SIDE OF THE FRONT...WHEREAS 12Z
SHIP OBS WITHIN 100NM OF THE FRONT REPORTED 20-25 KT WINDS.
WINDS OVER THE W-CENTRAL ATLC WILL DIMINISH TO 15 KT AS THE
FRONT CONTINUES TO MOVE EWD. A TROUGH ENTERS THE REGION NEAR
31N25W EXTENDING FROM A COLD FRONT AND SFC LOW WELL NORTH OF THE
AREA. THE TROUGH CONTINUES SW TO NEAR 25N39W WITH A BAND OF
MOISTURE EXTENDING 60-90 NM AHEAD OF THE TROUGH. A SFC HIGH
REMAINS E OF THE TROUGH CENTERED NEAR 26N25W EXTENDING A RIDGE
OVER THE E-CENTRAL ATLC TO NEAR THE LESSER ANTILLES. ALOFT...A
SHORTWAVE TROUGH IS ADVECTING UPPER LEVEL MOISTURE OVER THE NW
ATLC. A DEEP LAYERED TROUGH IS SUPPORTING THE FRONTAL BOUNDARY
OVER THE CENTRAL ATLC. THE RIDGE OVER THE CARIBBEAN EXTENDS ENE
INTO THE S-CENTRAL ATLC THROUGH THE LEEWARD ISLANDS. A SECOND
UPPER TROUGH DOMINATES THE E ATLC WITH THE AXIS EXTENDING SW TO
THE DEEP TROPICS NEAR 2N45W. STRONG SWLY WINDS AHEAD OF THE
TROUGH ARE TRANSPORTING UPPER LEVEL MOISTURE FROM N SOUTH
AMERICA TO THE AFRICAN COAST.

$$
RJW



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