[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 122355
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST MON NOV 12 2012

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...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 2245 UTC.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA TO THE COAST OF
GUINEA-BISSAU AT 12N16W CONTINUING ALONG 7N22W 8N28W. THE ITCZ
BEGINS NEAR 8N28W TO 11N36W AND THEN ALONG 11N38W TO 8N59W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 9N-12N
BETWEEN 17W-31W...AND FROM 9N-14N BETWEEN 35W-41W. SOME OF THIS
ACTIVITY IS NEAR A WEAK SURFACE TROUGH EMBEDDED WITHIN THE ITCZ
ALONG 15N37W TO 12N37W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS ALSO INLAND OVER NORTHERN GUYANA AND EASTERN
VENEZUELA FROM 5N-9N BETWEEN 59W-62W.

...DISCUSSION...

THE GULF OF MEXICO...
A DEEP LAYER TROUGH AND ASSOCIATED COLD FRONT ARE IMPACTING A
GOOD PORTION OF THE GULF OF MEXICO. THE COLD FRONT CURRENTLY
EXTENDS FROM THE FLORIDA PANHANDLE NEAR 31N86W TOWARDS MEXICO
ALONG 27N89W 25N96W 21N97W 24N101W...AS OF 2100 UTC. STRONG NE
WINDS UP TO 25 KTS ARE BEHIND THE FRONT...AND WILL INCREASE TO
30 KT IN THE SW GULF IN THE NEXT 24 HOURS. A LINE OF HEAVY
SHOWERS/POSSIBLE THUNDERSTORMS IS ALONG THE IMMEDIATE AXIS OF
THE FRONT WITH LIGHTER SHOWERS EXTENDING UP TO 120 NM TO EITHER
SIDE. RADAR IMAGERY ALSO INDICATES ISOLATED SHOWERS ARE ACROSS
THE SOUTHERN HALF OF THE FLORIDA PENINSULA. STRONG DRY AIR IS
SINKING INTO THE FAR NW CORNER OF THE GULF AROUND THE BASE OF
THE UPPER TROUGH THAT SUPPORTS THE FRONTAL BOUNDARY AND EXTENDS
FROM THE GREAT LAKES TO THE NW GULF. AN UPPER LEVEL RIDGE STILL
COVERS THE FAR EASTERN GULF EXTENDING JUST EAST OF FLORIDA. THE
FRONT IS EXPECTED TO CONTINUE MOVING SE THROUGH THE NEXT 24-48
HOURS BEFORE IT STALLS OVER THE SOUTHERN GULF.
SHOWERS/THUNDERSTORMS WILL BE LIKELY ALONG THE BOUNDARY.

THE CARIBBEAN SEA...
AN UPPER LEVEL RIDGE OVER THE FAR EASTERN GULF OF MEXICO EXTENDS
INTO THE NW CARIBBEAN ALONG WITH DRY AIR ALOFT. THE DRY AIR
WRAPS AROUND THE UPPER RIDGE AND CONTINUES AROUND AN UPPER LEVEL
TROUGH OVER THE CENTRAL CARIBBEAN EXTENDING FROM HISPANIOLA TO
THE SW CARIBBEAN. THIS DRY AIR IS HELPING PROVIDE MOSTLY FAIR
CONDITIONS ACROSS THE NW AND CENTRAL CARIBBEAN. A FEW SCATTERED
SHOWERS/POSSIBLE THUNDERSTORMS ARE IN THE SW CARIBBEAN FROM
10N-14N BETWEEN 80W-85W AROUND THE BASE OF THE UPPER TROUGH.
MOIST SWLY FLOW AND DIFFLUENCE ALOFT COVER THE EASTERN CARIBBEAN
WHERE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS RANGE FROM
13N-18N BETWEEN 60W-65W...AND ACROSS PORTIONS OF PUERTO
RICO...HISPANIOLA AND THE MONA PASSAGE. THIS ACTIVITY IS ALSO
BEING ENHANCED BY A SURFACE TROUGH ALONG 20N65W TO 12N65W...AND
THE TAIL END OF A SHEAR AXIS IN THE CENTRAL ATLC THAT EXTENDS
INTO THE MONA PASSAGE. THE SURFACE TROUGH IS EXPECTED TO MOVE
WESTWARD AND WILL DRAW MOISTURE WITH IT PRODUCING
SHOWERS/THUNDERSTORMS.

THE ATLANTIC OCEAN...
AN UPPER LEVEL RIDGE COVERS THE FLORIDA PENINSULA AND THE
EASTERN UNITED STATES SEABOARD SUPPORTING A 1033 MB HIGH EAST OF
NEW ENGLAND WITH A RIDGE AXIS EXTENDING TOWARDS THE GULF OF
MEXICO. THIS PATTERN IS HELPING PROVIDE MOSTLY FAIR CONDITIONS
ACROSS THE FAR WEST ATLC INCLUDING THE BAHAMAS. AN UPPER LEVEL
TROUGH COVERS THE REMAINDER OF THE WEST ATLC ALONG 71W
SUPPORTING A DISSIPATING STATIONARY FRONT ALONG 31N52W 24N62W
WHERE IT BECOMES A SHEAR AXIS TO THE MONA PASSAGE AT 18N68W.
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 180 NM
EITHER SIDE OF THE AXIS. AN UPPER LEVEL RIDGE IS ALONG 54W
PROVIDING WEAK SURFACE RIDGING AND FAIR CONDITIONS BETWEEN
43W-55W. A WEAK SURFACE TROUGH IS ALONG 16N50W TO 12N50W...BUT
IS NOT PRODUCING ANY SHOWER ACTIVITY. AN UPPER LEVEL LOW IS
IMPACTING THE EASTERN ATLC CENTERED NEAR 22N37W WITH AXIS
EXTENDING SOUTH TO NEAR 11N32W. THE UPPER LOW SUPPORTS A LARGER
SURFACE TROUGH ALONG 27N40W TO 20N37W. SCATTERED
SHOWERS/POSSIBLE THUNDERSTORMS ARE EAST AND SOUTHEAST OF THE
AXIS FROM 13N-24N BETWEEN 28W-33W...AND FROM 21N-25N BETWEEN
35W-38W. THE UPPER TROUGH IS ALONG ENHANCING CONVECTION NEAR THE
ITCZ/MONSOON TROUGH. BOTH THE FRONTAL BOUNDARY IN THE
CENTRAL/WEST ATLC AND THE SURFACE TROUGH IN THE EAST ATLC ARE
EXPECTED TO DRIFT WEST WITH CONTINUED SHOWERS/THUNDERSTORMS NEAR
THEM.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
WALTON






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