[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 161802
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE SEP 16 2008

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1745 UTC.

...SPECIAL FEATURES...
NONE.

...TROPICAL WAVES...
AN ATLANTIC OCEAN LOW AMPLITUDE TROPICAL WAVE IS ALONG 36W
SOUTH OF 13N MOVING WEST NEAR 10 KT. SCATTERED SHOWERS ARE
NEAR THE INTERSECTION OF THE WAVE AXIS AND THE ITCZ.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 61W SOUTH OF 20N MOVING
WEST 15 KT. THE MIMIC TOTAL PRECIPITABLE WATER PRODUCT FROM
CIMMS DEPICTS ENHANCED DEEP LAYER MOISTURE JUST EAST OF THE WAVE
AXIS...WITH ISOLATED MODERATE CONVECTION WITHIN AN AREA 150 NM
EAST OF THE WAVE AXIS.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 77W/78W SOUTH OF 20N
MOVING WEST 10-15 KT. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS NEAR AND SOUTH OF THE INTERSECTION OF THE WAVE
AXIS AND THE ITCZ...PARTICULARLY WITHIN AN AREA 100 NM WEST OF
THE WAVE AXIS.

A TROPICAL WAVE IS ALONG 88W FROM THE YUCATAN PENINSULA SOUTH
OF 20N INTO THE EASTERN PACIFIC OCEAN MOVING WEST NEAR 10 KT.
VISIBLE SATELLITE IMAGERY DEPICTS LOW LEVEL TURNING AND AN
INVERTED-V STRUCTURE IN THE CLOUD ELEMENTS ASSOCIATED WITH THIS
WAVE. ISOLATED MODERATE CONVECTION IS MAINLY SOUTH OF 17N WITHIN
AN AREA 100 NM EITHER SIDE OF THE WAVE AXIS.

...THE ITCZ...
ITCZ AXIS IS ANALYZED ALONG 10N15W 8N35W 9N55W 11N70W 9N81W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 7N-14N
BETWEEN 14W-27W NEAR THE WEST AFRICAN COAST. SCATTERED MODERATE
CONVECTION IS FROM 8N-21N BETWEEN 49W-60W. CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ARE FROM 4N-12N BETWEEN
79W-85W.

...DISCUSSION...

GULF OF MEXICO...
A WEAKENING COLD FRONT EXTENDS FROM THE WEST COAST OF FLORIDA
NEAR 29N84W WESTWARD TO THE CENTRAL GULF...AND THEN CURVES
SOUTHWARD TOWARD THE NORTHWESTERN BAY OF CAMPECHE. NORTH TO
NORTHEASTERLY SURFACE WINDS...WITH SPEEDS UP TO 25 KTS PER A
RECENT QUIKSCAT PASS WEST OF 95W...ARE OCCURRING BEHIND THE COLD
FRONT...WITH MORE EASTERLY WINDS AHEAD OF THE FRONT. SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS CONTINUE TO DEVELOP IN THE
VICINITY OF THE FRONT...ESPECIALLY OFF THE EAST COAST OF MEXICO
AND OVER THE NORTHWESTERN GULF. THIS CONVECTIVE ACTIVITY IS IN
RESPONSE TO WEAK UPPER LEVEL DIFFLUENCE TO THE EAST OF AN UPPER
LEVEL ANTICYCLONE OVER CENTRAL MEXICO. ACROSS THE CENTRAL AND
EASTERN GULF...A WEAK SURFACE PRESSURE GRADIENT AHEAD OF THE
COLD FRONT WAS SUPPORTING LIGHT EASTERLY WINDS GENERALLY UNDER
10 KT FROM A RECENT QUIKSCAT PASS. OTHERWISE...MOSTLY FAIR
CONDITIONS WERE IMPACTING THE CENTRAL AND EASTERN GULF...THOUGH
SOME MOISTURE TO THE EAST OF AN UPPER LEVEL TROUGH OVER THE
CENTRAL GULF WAS ENHANCING SOME CLOUDINESS OVER THE SOUTHEASTERN
GULF. THE AFOREMENTIONED FRONT WILL CONTINUE TO WEAKEN AND
BECOME STATIONARY OVER THE NEXT 24 HOURS...THOUGH IT COULD SURGE
SOUTHWARD TOWARD THE BAY OF CAMPECHE OVER THE WESTERN GULF.
SCATTERED SHOWERS WILL REMAIN POSSIBLE NEAR THE
FRONT...ESPECIALLY NEAR THE EASTERN MEXICAN COAST.

CARIBBEAN SEA...
ONE TROPICAL WAVE IS ALONG 61W SOUTH OF 20N MOVING WEST 15 KT.
ISOLATED MODERATE CONVECTION WITHIN AN AREA 150 NM EAST OF THE
WAVE AXIS. A SECOND TROPICAL WAVE IS ALONG 77W/78W SOUTH OF 20N
MOVING WEST 10-15 KT. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS NEAR AND SOUTH OF THE INTERSECTION OF THE WAVE
AXIS AND THE ITCZ...PARTICULARLY WITHIN AN AREA 100 NM WEST OF
THE WAVE AXIS. A THIRD TROPICAL WAVE IS ALONG 88W FROM THE
YUCATAN PENINSULA SOUTH OF 20N INTO THE EASTERN PACIFIC OCEAN
MOVING WEST NEAR 10 KT. ISOLATED MODERATE CONVECTION IS MAINLY
SOUTH OF 17N WITHIN AN AREA 100 NM EITHER SIDE OF THE WAVE AXIS.
EASTERLY SURFACE TRADE WINDS AT 15 TO 20 KT ARE BLOWING ACROSS
MUCH OF THE CARIBBEAN. ISOLATED SHOWERS ARE DEVELOPING OVER
HISPANIOLA AND PUERTO RICO...AND ARE DRIFTING SOUTHWARD OVER THE
NORTHERN CARIBBEAN. THESE SHOWERS ARE DEVELOPING IN RESPONSE TO
UPPER LEVEL DIFFLUENCE ON THE WESTERN PERIPHERY OF AN UPPER
LEVEL CYCLONE LOCATED NEAR 16N67W. UNSTABLE CONDITIONS BENEATH
AN UPPER LEVEL CYCLONE EAST OF THE YUCATAN PENINSULA...NEAR
17N85W...ARE SUPPORTING SCATTERED MODERATE/ISOLATED STRONG
CONVECTION OVER CENTRAL AMERICA AND THE ADJACENT CARIBBEAN
WATERS. NORTHERLY FLOW ALOFT IS OCCURRING ACROSS THE CENTRAL
CARIBBEAN...AND THIS FLOW IS RELATIVELY DRY AND CONFLUENT...
RESULTING IN MOSTLY FAIR WEATHER ACROSS THE CENTRAL CARIBBEAN.
SCATTERED CONVECTION WILL REMAIN POSSIBLE OVER THE WESTERN
CARIBBEAN FOR THE NEXT DAY...ESPECIALLY NEAR CENTRAL AMERICA...
WITH THE APPROACH OF THE NEXT TROPICAL WAVE.

ATLANTIC OCEAN...
LOW LEVEL CONVERGENCE ASSOCIATED WITH A WEAK SURFACE TROUGH WAS
GENERATING SCATTERED MODERATE CONVECTION FROM 26N-31N BETWEEN
54W-61W. THIS CONVECTION IS PROPAGATING SOUTHWARD AT 20-25 KT
BENEATH WEAK DIFFLUENT UPPER LEVEL SOUTHERLY FLOW. THE SURFACE
TROUGH IS EXPECTED TO SLIDE NORTHWESTWARD OVER THE NEXT DAY OR
SO...WITH CONVECTION REMAINING POSSIBLE PARTICULARLY EAST OF THE
TROUGH. A 1018 MB SURFACE HIGH TO THE WEST OF THIS TROUGH IS
RESULTING IN MOSTLY FAIR WEATHER OVER THE WESTERN ATLANTIC.
ISOLATED SHOWERS AND THUNDERSTORMS ARE FORECAST TO OCCUR OVER
THE EAST COAST OF FLORIDA THIS AFTERNOON AND EVENING WITH SEA
BREEZE CONVERGENCE ZONES. VISIBLE SATELLITE IMAGERY DEPICTS
A SMALL CYCLONIC CIRCULATION CENTER IN THE MOTION OF LOW LEVEL
CLOUD ELEMENTS NEAR 18N37W...WHERE A SURFACE LOW HAS BEEN PLACED
ON THE 12Z MAP. THIS LOW IS EXPECTED TO MOVE WEST-SOUTHWESTWARD
DURING THE NEXT 24 HOURS. NO SUBSTANTIAL CONVECTION HAS BEEN
NOTED WITH THIS LOW THUS FAR...AS THIS SURFACE LOW REMAINS
EMBEDDED WITHIN A DEEP-LAYER RIDGE THAT COVERS MUCH OF THE
EASTERN ATLANTIC OCEAN. THIS RIDGE EMANATES WESTWARD FROM AN
UPPER LEVEL ANTICYCLONE LOCATED NEAR 11N36W. A LARGE PORTION OF
THE REST OF THE CENTRAL AND EASTERN ATLANTIC IS DOMINATED BY
A SURFACE RIDGE THAT EXTENDS SOUTHWESTWARD FROM A 1031 MB
SURFACE HIGH NEAR 47N27W. ITCZ CONVECTION NEAR THE WEST COAST
OF AFRICA IS EXPECTED TO CONTINUE MOVING WESTWARD AT 10 TO 20 KT
OVER THE FAR EASTERN ATLANTIC OVER THE NEXT DAY.

$$
COHEN/MT



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