[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 182353
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST FRI 18 FEB 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
2315 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 5N10W 2N20W 1N40W EQ50W.  SCATTERED
MODERATE TO ISOLATED STRONG CONVECTION IS FROM 1N-3N BETWEEN
17W-19W...FROM EQ-2N BETWEEN 21N-26W...AND FROM 2S-5N BETWEEN
36W-47W.  SCATTERED MODERATE CONVECTION IS FROM 2N-4N BETWEEN
25W-29W.

...DISCUSSION...

GULF OF MEXICO...
IN THE UPPER LEVELS...BROAD RIDGING DOMINATES MEXICO AND THE
GULF OF MEXICO. RIDGE AXIS EXTENDS FROM THE YUCATAN PENINSULA TO
SE TEXAS.  A PLUME OF PACIFIC MOISTURE AND 100-110 KT
SUBTROPICAL JETSTREAM IS OVER N MEXICO N OF 26N...AND OVER THE
SOUTHER UNITED STATES N OF 29N.  STRONG SUBSIDENCE COVERS THE
GULF OF MEXICO S OF 29N.  AT THE SURFACE...A 1030 MB HIGH IS
OVER N LOUISIANA NEAR 32N91W.  A WEAK COLD FRONT IS OVER THE
CENTRAL GULF OF MEXICO FROM THE STRAITS OF FLORIDA TO E MEXICO
ALONG 24N80W 25N90W 23N98W DRIFTING S.  OVER THE NORTHERN
GULF OF MEXICO 15 KT NE-E WINDS ARE N OF THE FRONT.  BROKEN LOW
CLOUDS AND SPARSE SHOWERS ARE ALSO N OF THE FRONT FROM 25N-28N
BETWEEN 84W-96W.  ELSEWHERE...AN AREA OF SCATTERED SHOWERS IS
OVER THE BAY OF CAMPECHE W OF A WEAK TROUGH FROM THE ISTHMUS OF
TEHUANTEPEC TO 23N94W.  OVERCAST LOW CLOUDS ARE ALL ALONG THE
FOOTHILLS OF THE SIERRA MADRE ORIENTAL MOUNTAINS FROM 18N-29N
BETWEEN 95W-102W DUE TO NE WINDS N OF THE FRONT AND E WIND S OF
THE FRONT.  EXPECT SHOWER ACTIVITY OVER THE ENTIRE AREA TO
DIMINISH DURING THE NEXT 24 HOURS AS THE FRONTAL BOUNDARY WASHES
OUT AND LOW LEVEL MOISTURE BECOMES MORE LIMITED.  RELATIVELY DRY
CONDITIONS SHOULD CONTINUE THROUGH MUCH OF SUNDAY PRIOR TO THE
NEXT UPSTREAM SYSTEM APPROACHING THE NW GULF LATE SUN.

CARIBBEAN...
MID/UPPER LEVEL RIDGE REMAINS IN PLACE FROM N VENEZUELA TO THE
YUCATAN PENINSULA.  STRONG SUBSIDENCE AND DRY/STABLE AIR ALOFT
CONTINUES TO DOMINATE THE AREA LIMITING SIGNIFICANT WEATHER TO
ISOLATED SHALLOW TOPPED SHOWERS. NE LOW LEVEL FLOW IS PRODUCING
CLOUDINESS AND SHOWER ACTIVITY ALONG THE WINDWARD FACING SLOPES
OF W PANAMA...COSTA RICA...AND SE NICARAGUA.  THE HIGH PRESSURE
RIDGE BUILDING SWD FROM THE GULF OF MEXICO HAS TIGHTENED THE
PRESSURE GRADIENT OVER THE CARIBBEAN LEADING TO INCREASING ELY
TRADES. LOW LEVEL MOISTURE AND SHOWER ACTIVITY SHOULD REMAIN
MINIMAL THROUGH THE WEEKEND PRIOR TO THE ARRIVAL OF A DIFFUSE
FRONTAL BOUNDARY OVER THE NE CARIBBEAN SUNDAY NIGHT.

ATLANTIC...
PREDOMINATELY ZONAL FLOW IS OVER THE W ATLANTIC N OF 20N AND W
OF 50W.  AN ATTENDANT COLD FRONT ENTERS THE W ATLANTIC E OF OF
BERMUDA ALONG 32N57W AND EXTENDS SW TO 27N70W TO THE STRAITS OF
FLORIDA NEAR 24N80W.  THE FRONT LACKS SIGNIFICANT UPPER SUPPORT
WITH ONLY A NARROW CLOUD LINE AND ISOLATED SHOWERS ALONG THE
LEADING EDGE.  THE FRONT IS QUICKLY LOSING ITS THERMAL GRADIENT
WITH A NOTICEABLE ABSENCE OF THE TYPICAL POST-FRONTAL COLD AIR
STRATOCUMULUS.  OVER THE CENTRAL ATLANTIC...A SHORTWAVE MIDDLE TO
UPPER LEVEL TROUGH IS ALONG 42W PRODUCING AN AREA OF
CLOUDINESS AND SCATTERED SHOWERS/THUNDERSTORMS FROM 20N-32N
BETWEEN 33W-43W.  THIS ACTIVITY SHOULD WEAKEN OVER THE NEXT 24
HOURS AS THE UPPER SHORTWAVE BECOMES SHEARED OUT BY THE MUCH
LARGER SCALE UPSTREAM TROUGH.  OVER THE E ATLANTIC AND W
AFRICA... A MID/UPPER LEVEL TROUGH IS N OF 20N AND E OF 25W.  ON
THE SURFACE... A 1038 MB HIGH W OF FRANCE AT 49N23W IS PRODUCING
A SURGE OF OVERCAST COLD AIR STRATOCUMULUS CLOUDS AND SCATTERED
SHOWERS OFF THE COAST OF W AFRICA NEAR THE CANARY ISLANDS N OF
26N AND E OF 36W.  THE SURGE IS MOVING SW WITH EMBEDDED 20-30 KT
WINDS NOTED.  FURTHER S...VISIBLE SATELLITE IMAGERY CONTINUES TO
INDICATE AN AREA OF AFRICAN DUST MAINLY S AND E OF THE CAPE
VERDE ISLANDS TO THE ITCZ.  THE HIGHEST CONCENTRATION EXTENDS AS
FAR WEST AS 30W WITH LESSER AMOUNTS TO 40W.

$$
FORMOSA



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