[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202356
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE OCT 20 2009

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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS TILTED FROM 19N24W TO 8N28W DRIFTING WESTWARD.
WAVE AXIS IS OBSERVED ON THE VISIBLE SATELLITE IMAGERY AND IN
THE SATELLITE DERIVED WINDS. THE DEEP LAYER MOISTURE MAXIMUM AS
OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY APPEARS TO BE
WEAKENING AND MAY ACCOUNT FOR THE REAL LACK OF MOVEMENT IN THE
WAVE AXIS AS WELL AS THE LACK OF ANY DEEP CONVECTION. ISOLATED
SHOWERS ARE FROM 12N-18N BETWEEN 23W-28W WHICH INCLUDES ALL OF
THE CAPE VERDE ISLANDS.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 10N12W 6N20W 13N37W 9N53W 8N60W. A
1009 MB SURFACE LOW IS EMBEDDED WITHIN THE AXIS CENTERED NEAR
13N38W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN
60 NM OF LINE FROM 6N34W TO 8N36W. CLUSTERS OF ISOLATED MODERATE
CONVECTION DOT THE AREA FROM 3N-8N BETWEEN 15W-27W.

...DISCUSSION...

GULF OF MEXICO...
BROAD SURFACE RIDGE DOMINATES THE GULF ANCHORED OVER GEORGIA BY
A 1026 MB HIGH. A BROAD UPPER RIDGE ANCHORED OVER SW MEXICO
COVERS THE W GULF WHILE A STRONG DEEP LAYERED TROUGH COVERS
THE REMAINDER OF THE GULF. THIS UPPER TROUGH IS ASSOCIATED WITH
THE FRONTAL BOUNDARY THAT PASSED THROUGH THE GULF OVER THE
WEEKEND PROVIDING DRY STABLE AIR OVER THE E GULF. HOWEVER...
MOIST TROPICAL AIR IS NOW BEING DRAWN ACROSS THE W GULF BY THE
UPPER RIDGE AND WITH EASTERLY SURFACE FLOW IS BANKING LOW LEVEL
CLOUDS WITH POSSIBLE ISOLATED SHOWERS OVER THE W GULF AGAINST
THE E SLOPES OF THE SIERRA MADRE MOUNTAINS. THE SURFACE RIDGE IS
EXPECTED TO SHIFT E AS ANOTHER FRONT MOVES INTO THE GULF ON THU.

CARIBBEAN SEA...
THE DEEP LAYERED TROUGH OVER THE E GULF OF MEXICO DIPS S OVER
THE NW CARIBBEAN WITH THE REMNANT DISSIPATING STATIONARY FRONT
EXTENDING ACROSS CENTRAL CUBA NEAR 21N77W S OF THE CAYMAN
ISLANDS TO 18N82W. A 1007 MB LOW IS CENTERED NEAR 12N82W MOVING
W TO INLAND OVER NICARAGUA AT 2100 UTC WITH A 1011 MB LOW IN THE
GULF OF HONDURAS NEAR ROATAN ISLAND DRIFTING NW. A NARROW UPPER
RIDGE IS JUST TO THE E EXTENDING FROM COLOMBIA NEAR 10N75W TO
12N78W THEN NE THROUGH THE WINDWARD PASSAGE INTO THE W ATLC
PROVIDING DIFFLUENCE ALOFT TO ENHANCE A BROAD AREA OF SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS THAT COVERS THE W CARIBBEAN W OF
A LINE FROM PANAMA NEAR 9N78W TO JAMAICA THEN NE OVER HAITI. A
BROAD UPPER TROUGH COVERS THE E CARIBBEAN EXTENDING FROM AN
UPPER LOW IN THE CENTRAL ATLC PROVIDING DRY STABLE AIR E OF 70W.

ATLANTIC OCEAN...
THE BROAD DEEP LAYERED TROUGH THAT COVERS THE E GULF OF MEXICO
EXTENDS OVER THE FLORIDA PENINSULA INTO THE W ATLC WITH THE
ASSOCIATED COLD FRONT ENTERING THE REGION NEAR 32N59W SW TO
25N71W WHERE IT BECOMES STATIONARY ACROSS THE BAHAMA ISLANDS TO
22N76W WHERE IT DISSIPATES IN THE W CARIBBEAN WITH ISOLATED
SHOWERS WITHIN 60 NM EITHER SIDE OF THE FRONT. A NARROW UPPER
RIDGE EXTENDS FROM THE CARIBBEAN THROUGH THE WINDWARD PASSAGE
ALONG 25N69W TO 32N58W PROVIDING DIFFLUENCE ALOFT TO ENHANCE
SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS MAINLY S
OF 24N BETWEEN 70W-78W. A WEAK SURFACE TROUGH IS TO THE E ALONG
67W FROM 21N-24N. BROAD UPPER LOW IS IN THE CENTRAL ATLC NEAR
24N50W WITH AN UPPER TROUGH EXTENDING SW TO COVER THE E
CARIBBEAN AND SUPPORTING A SURFACE TROUGH THAT EXTENDS ALONG 54W
FROM 21N-27N. BROAD UPPER RIDGE OVER THE TROPICAL ATLC ANCHORED
NEAR 10N38W EXTENDS A RIDGE AXIS N TO 27N30W PROVIDING
DIFFLUENCE ALOFT TO ENHANCE SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS WITHIN 120/150 NM OF LINE FROM 18N52W TO 29N41W.

$$
WALLACE



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