[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 112356
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST THU 11 NOV 2004

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
1715 UTC.

...SPECIAL FEATURES...
A BROAD AREA OF LOW PRESSURE ASSOCIATED WITH A SURFACE TROUGH IN
THE E CARIBBEAN SEA EXTENDS FROM THE ABC ISLANDS TO ABOUT
ANTIGUA. WHILE PERSISTENT...THIS AREA HAS SHOWN LITTLE
INDICATION OF ORGANIZATION AND SIGNIFICANT DEVELOPMENT APPEARS
LESS AND LESS LIKELY. THE STRONGEST/DEEPEST CONVECTION CONTINUES
TO TREND EWD AS DRY AIR ASSOCIATED WITH A MIDDLE TO UPPER LEVEL
TROUGH MOVES INTO THE E CARIBBEAN.  THE MAIN AXIS OF ACTIVITY
NOW EXTENDS ACROSS THE WINDWARD ISLANDS WITH STRATIFORM RAIN AND
WIDELY SCATTERED THUNDERSTORMS ACROSS THE LEEWARD
ISLANDS...VIRGIN ISLANDS...AND PUERTO RICO. LOCALLY HEAVY
RAINFALL AND FLOODING IS POSSIBLE OVER BOTH THE WINDWARD AND
LEEWARD ISLAND TONIGHT ESPECIALLY FROM GUADELOUPE SWD TO
GRENADA.

NON-TROPICAL 1000 MB LOW OVER THE E ATLC SEVERAL HUNDRED MILES
SSW OF THE AZORES NEAR 30N34W.  SURFACE PRESSURES HAVE BEEN
STEADILY FALLING DURING THE LAST 24 HOURS DESPITE THE LOW BEING
VERTICALLY STACKED WITH A MIDDLE TO UPPER LEVEL LOW.
ADDITIONALLY...DEEP CONVECTION IS PRESENT NEAR THE CENTER OF THE
LOW WITH SOME INDICATION OF THIS ACTIVITY WRAPPING AROUND THE N
SEMICIRCLE. IF THIS TREND CONTINUES...THE SYSTEM COULD GRADUALLY
ACQUIRE SUBTROPICAL CHARACTERISTICS DURING THE NEXT DAY OR SO.
HOWEVER...THE WINDOW OF OPPORTUNITY APPEARS TO BE SHRINKING AS
WATER VAPOR IMAGERY SHOWS STRONG NLY FLOW BEGINNING TO IMPINGE
UPON THE SYSTEM.

...ITCZ...
ITCZ AXIS IS ALONG 10N10W 4N30W 3N45W 6N65W 7N80W. SCATTERED
MODERATE CONVECTION FROM 3N-10N BETWEEN 20W-32W.  SCATTERED
STRONG CONVECTION FROM 3N-7N BETWEEN 65W-70W.

...DISCUSSION...
GULF OF MEXICO...
NEAR ZONAL FLOW ALOFT EXTENDS OVER THE GLFMEX WITH A SHORTWAVE
TROUGH BYPASSING THE AREA TO THE NORTH PRODUCING AN AREA OF
WIDELY SCATTERED SHOWERS/TSTMS ALONG A OLD FRONTAL BOUNDARY
EXTENDING FROM THE YUCATAN PENINSULA TO THE FLORIDA PANHANDLE.
WIDELY SCATTERED SHOWERS ARE ALSO NOTED ALONG A COLD FRONT
MOVING ACROSS THE NW GLFMEX FROM LOUISIANA SWD OVER THE S TIP OF
TEXAS NEAR BROWNSVILLE THEN INLAND OVER MEXICO ALONG THE SIERRA
MADRE ORIENTAL MOUNTAINS. THIS FRONT WILL SWEEP QUICKLY EWD
ACROSS THE GLFMEX EXTENDING FROM THE FLORIDA PANHANDLE TO THE SW
GLFMEX BY TOMORROW AFTERNOON.  MIDDLE TO UPPER LEVEL
DYNAMICS/LIFT LOOK FAVORABLE FOR SCATTERED SHOWERS/THUNDERSTORMS
ALONG THE FRONT ESPECIALLY N OF 26N.  ELSEWHERE...RATHER DRY
CONDITIONS WILL PREVAIL IN THE MID/UPPER LEVELS WITH NO
SIGNIFICANT WEATHER.  AT THE SURFACE...STRONG HIGH PRESSURE OFF
THE UNITED STATES E COAST IS PRODUCING BRISK ELY FLOW OVER
FLORIDA AND THE E GLFMEX. THE AIRMASS REMAINS GENERALLY COOL/DRY
COURTESY OF A BACKDOOR COLD FRONT WHICH MOVED OVER THE AREA A
COUPLE OF DAYS AGO.

CARIBBEAN SEA...
A MID/UPPER TROUGH CONTINUES TO BE THE DOMINANT FEATURE
EXTENDING FROM THE CENTRAL ATLC ACROSS HISPANIOLA TO THE SW
CARIBBEAN.  HOWEVER...WATER VAPOR IMAGERY INDICATES THE TROUGH
IS PROGRESSING EWD ALLOWING STRONG SUBSIDENCE AND VERY DRY
MIDDLE TO UPPER LEVEL AIR TO SPREAD EWD OVER THE CENTRAL AND E
CARIBBEAN.  WIDESPREAD SHOWERS/THUNDERSTORMS CONTINUE OVER THE
EXTREME E CARIBBEAN IN ASSOCIATION WITH AN ELONGATED AREA OF LOW
PRESSURE. THE STRONGEST OF THIS ACTIVITY SHOULD SLIDE E OF THE
AREA OVERNIGHT. HOWEVER...A COLD FRONT DROPPING SWD INTO THE
CENTRAL AND E CARIBBEAN FROM THE ATLC WILL PRODUCE SCATTERED
SHALLOW TOPPED CONVECTION OVER HISPANIOLA AND PUERTO RICO
TONIGHT.  THE BOUNDARY WILL WEAKEN AS IT PENETRATES INTO THE
CARIBBEAN BUT AMPLE LOW LEVEL MOISTURE POOLING WILL CONTINUE TO
SPARK SCATTERED SHOWERS AND A FEW ISOLATED THUNDERSTORMS.
BEHIND THE FRONT...DRY/STABLE AIR WILL SPILL SWD FROM THE W
ATLC.

ATLANTIC...
THE VAST MAJORITY OF THE W ATLC CONTINUES TO BE DOMINATED BY
MIDDLE TO UPPER LEVEL SUBSIDENCE AND DRY AIR. BROKEN
STRATOCUMULUS CLOUDS...INDICATING COLD ADVECTION AND STABLE
CONDITIONS...COVER THE ENTIRE AREA W OF A CENTRAL ATLC COLD
FRONT EXTENDING FROM 32N50W SWD TO PUERTO RICO THEN STATIONARY
OVER HISPANIOLA.  A STRONG 1029 MB MIGRATORY SURFACE HIGH
MOVING OFF THE MID-ATLANTIC COAST IS PRODUCING BRISK NE FLOW TO
30 KT BEHIND THE FRONT.  FARTHER E...SHARP MID/UPPER LEVEL
TROUGH FROM 32N53W SWD OVER HISPANIOLA CONTINUES TO PROVIDE THE
SUPPORT FOR WIDESPREAD CLOUDINESS AND SHOWERS/THUNDERSTORMS OVER
THE CENTRAL ATLC.  THE BULK OF THIS ACTIVITY IS FAVORED ALONG
AND TO THE EAST OF A STRONG UPPER LEVEL SUBTROPICAL JET
EXTENDING FROM THE E CARIBBEAN NEWD TO BEYOND 32N50W.  MID/UPPER
RIDGE EXTENDS FROM THE DEEP TROPICAL ATLC NEAR 10N50W NEWD TO
BEYOND 32N42W. THE AFOREMENTIONED SUBTROPICAL JET AND ASSOCIATED
MOISTURE SURGE RIDE UP AND OVER THIS RIDGE LEAVING SUBSIDENCE
AND DRY AIR E OF THE RIDGE...ESPECIALLY S OF 20N.  OVER THE FAR
E ATLC...A DEEP LAYERED LOW CONTINUES TO DRIFT SLOWLY WESTWARD
NEAR 29N33W. SEE SPECIAL FEATURES SECTION FOR MORE DETAILS ON
1000 MB LOW NEAR 30N34W.  ELSEWHERE...THE DEEP LAYERED LOW
TRAILS A TROUGH SWD WELL INTO THE TROPICAL ATLC ALONG 15N35W TO
5N40W.  VERY DRY AIR ALOFT IS PRESENT NEAR AND W OF THE TROUGH
AXIS...SUPPRESSING SIGNIFICANT ITCZ CONVECTION W OF 40W.
HOWEVER THE TROUGH IS ENHANCING CONVECTION OVER THE E ATLC WITH
WIDESPREAD CLOUDINESS AND SHOWERS/THUNDERSTORMS EXTENDING FROM
THE ITCZ NWD TO 25N BETWEEN 20W-30W. DEEP CONVECTION EMBEDDED
WITHIN THIS LARGE AREA IS NOTED JUST NW OF THE CAPE VERDE
ISLANDS AND MOVING SEWD.

$$
RHOME



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