[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 232357
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT 23 APR 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING
INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER
OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2345 UTC.

...THE ITCZ...

ITCZ AXIS IS ALONG 7N11W 4N20W 1N35W 3N50W. SCATTERED MODERATE
ISOLATED STRONG CONVECTION IS NOTED WITHIN 60 NM OF THE AXIS
BETWEEN 14W AND 17W AND BETWEEN 28W AND 38W AND WITHIN 75 NM OF
3N45W. SCATTERED MODERATE ELSEWHERE WITHIN 60 NM OF AXIS BETWEEN
17W AND 28W.

...DISCUSSION...

THE GULF OF MEXICO...
A 1013 MB HIGH PRESSURE IS CENTERED NEAR 23N84W BUT IS WEAKENING
WITH TIME AND EXPECTED TO DISSIPATE TONIGHT. A BROAD COLD FRONT
LIES ALONG 31N81W 25N90W 25N98W AT 2100 UTC...THE LEADING EDGE
DEFINED BY A LINE OF TOWERING CUMULUS OVER THE GULF WATERS. A
PRE-FRONTAL TROUGH...ACCOMPANIED BY HEAVY SHOWERS... HAS MOVED E
OVER CENTRAL FLORIDA BUT STILL EXTENDS INTO THE GULF JUST W OF
TAMPA BAY. A SECONDARY SURGE IS OBSERVED E OF 90W WHERE FAIR
WEATHER STRATOCUMULUS IS MOVING SE ACROSS THE COASTAL PLAINS E
OF 90W. ALOFT...THE FLOW IS NW INTO UPPER TROUGH E OF FLORIDA.
UPPER DRY AIR IS NOTED S OF 24N E OF 90W. AN UPPER MOISTURE
PLUME IS SPREADING E ACROSS THE WATERS N OF 24N AND S OF 24N W
OF 90W.

THE CARIBBEAN SEA...
AT THE SURFACE THE SOUTHERN END OF FRONTAL TROUGH IS STILL
LIES ACROSS HISPANIOLA. ALOFT AN UPPER TROUGH AXIS EXTENDS S
ALONG 20N75W TO 13N84W. W OF THE TROUGH AXIS STRONG DRY AIR
ALOFT IS SUPPRESSING CONVECTION AND ONLY FAIR WEATHER CUMULUS
IS NOTED. UPPER LEVEL DIFFLUENCE E OF THE UPPER TROUGH IS
ENHANCING CONVECTION OVER THE E CARIBBEAN WITH THE HEAVIEST
CONCENTRATION N OF 15N E OF 65W AT THE MOMENT. THE STRONGER
CONVECTIVE CELLS MAY TRAIN ECHO ACROSS THE SAME ISLANDS TONIGHT
AND INTO SUN AND MAY RESULT IN LOCALIZED FLOODING AND MUDSLIDES.
UPPER SOUTHERLY WINDS E OF THE TROUGH IS ADVECTING DEBRIS
MOISTURE...FROM CONVECTION OVER VENEZUELA...NE ACROSS THE E
CARIBBEAN INTO THE SUBTROPICAL CENTRAL ATLC.

THE ATLANTIC OCEAN...
AT THE LOW LEVELS...A BROAD COLD FRONT HAS MOVED OFF THE SE
UNITED STATES WITH ITS PRE-FRONTAL TROUGH EXTENDING FROM 32N76W
TO CENTRAL FLORIDA. A BROAD DISSIPATING FRONTAL TROUGH EXTENDS
FROM 32N50W TO 28N65W TO HISPANIOLA. ALOFT...AN UPPER TROUGH
EXTENDS S ALONG 32N70W TO 21N74W. AN UPPER ANTICYCLONE IS
ANCHORED NEAR 11N51W WITH ITS ENVELOPE OF ANTICYCLONIC FLOW
DOMINATING THE WATERS BETWEEN 64W AND 30W. UPPER DIFFLUENCE E OF
THE UPPER TROUGH AND UNDER THE NW PERIPHERY OF THE ASSOCIATED
UPPER RIDGE IS ENHANCING CLOUDS AND CONVECTION WITHIN 600 NM E
OF THE SURFACE TROUGH. DEBRIS MOISTURE FROM THIS CONVECTION IS
ADVECTED NE AND E ALONG AN UPPER WIND MAXIMA...ROUGHLY COVERING
THE ATLC FROM 20N TO 36N BETWEEN 65W AND 25W. THE UPPER FLOW
SPLITS NEAR 25N22W WITH THE SOUTHERN BRANCH DIVING CYCLONICALLY
SE INTO AN UPPER TROUGH DESCRIBED NEXT. THE NORTHERN BRANCH
CONTINUE NE TO BEYOND 32N12W.

THE E ATLC IS DOMINATED BY AN UPPER TROUGH EXTENDING ALONG
30N19W TO A BASE AT 7N25W. DRY AIR ALONG THE TROUGH IS
SUPPRESSING THE ITCZ TO S OF 6N. ELSEWHERE ONLY BROKEN
STRATOCUMULUS IS NOTED N OF 15N E OF 40W.

$$
NELSON


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