[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 231804
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST TUE DEC 23 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
1715 UTC.

...THE ITCZ...
ITCZ IS CENTERED ALONG 7N12W 5N20W 4N35W 3N45W EQUATOR AT 53W.
SCATTERED MODERATE CONVECTION IS WITHIN 50 NM EITHER SIDE OF THE
AXIS BETWEEN 20W-28W. SIMILAR CONVECTION IS N OF 2N TO THE SW
COAST OF AFRICA BETWEEN THE PRIME MERIDIAN AND 12W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 1500 UTC...A 1014 MB SFC LOW IS INLAND OVER TEXAS NEAR
29N96W. A COLD FRONT EXTENDS FROM THE LOW ACROSS THE FAR NW GULF
ENTERING NE MEXICO JUST SOUTH OF BROWNSVILLE/MATAMOROS. A WARM
FRONT ALSO STRETCHES FROM THE LOW ACROSS THE UPPER TEXAS COAST
THEN CONTINUES AS A STATIONARY FRONT ALONG THE LOUISIANA COAST
TO NEAR 29N89W. A SECOND STATIONARY FRONT THAT WAS PREVIOUSLY
OVER THE GULF REGION HAS DISSIPATED. A SFC RIDGE DOMINATES THE
SE CONUS AND MUCH OF THE EASTERN HALF OF THE GULF. TIGHT PRES
GRADIENT BETWEEN THE RIDGE AND THE SFC LOW IS PRODUCING MAINLY
E TO SE WINDS OF 20 TO 25 KT ACROSS MUCH OF THE AREA. THE LOW
PRES WILL CONTINUE TO LIFT N INTO TEXAS AND MERGE WITH A WEAK
COLD FRONT THAT IS FORECAST TO MOVE OFF THE COAST OF TEXAS COAST
ON WED. BROKEN STRATOCUMULUS LOW CLOUDS WITH ISOLATED SHOWERS
COVER A GOOD PORTION OF THE REGION BUT ARE BEGINNING TO PUSH N
DUE TO THE RETURN FLOW AROUND THE SURFACE RIDGE. MODERATE/STRONG
SUBSIDENCE AND DRY STABLE AIR ARE NOTED ACROSS S FLORIDA AND THE
S GULF WATERS MAINLY S OF 25N. WLY FLOW ALOFT IS TRANSPORTING
MID/UPPER LEVEL MOISTURE ACROSS THE N GULF WATERS AND N FLORIDA.

CARIBBEAN SEA...
THE CARIBBEAN REMAINS UNDER THE INFLUENCE OF A BROAD UPPER HIGH
CENTERED NEAR THE ABC ISLANDS AND ENCOMPASSES THE ENTIRE BASIN
WITH STRONG SUBSIDENCE IN DRY AIR. THIS UPPER LEVEL FEATURE ALSO
ENVELOPS CENTRAL AMERICA AND THE N PORTION OF SOUTH AMERICA.
HOWEVER...AREAS OF SHALLOW LOW-LEVEL MOISTURE WITH EMBEDDED
SHOWERS CONTINUE TO STREAM ACROSS THE CARIBBEAN USHERED IN ON
NE-E TRADE WIND FLOW. THESE PATCHES OF MOISTURE ARE MORE
CONCENTRATED OVER THE EASTERN CARIBBEAN...JUST WEST OF THE ABC
ISLANDS AND OVER THE NW CARIBBEAN. LOOKING AHEAD...STRONG HIGH
PRESSURE IS
FORECAST TO BUILD N OF AREA WITH INCREASING TRADE WINDS EXPECTED
OVER THE TROPICAL ATLC AND MUCH OF THE CARIBBEAN SEA THROUGH THE
REST OF THE WEEK.

ATLANTIC OCEAN...
A DEEP LAYERED TROUGH OVER THE W ATLC N OF 30N SUPPORTS A COLD
THAT ENTERS THE FORECAST AREA NEAR 31N56W AND EXTENDS ACROSS THE
CENTRAL BAHAMAS TO CENTRAL CUBA NEAR 23N80W. STRONG HIGH PRES...
ANALYZED 1040 MB...OVER THE MIDDLE ATLANTIC STATES IS IN THE
WAKE OF THE FRONT PRODUCING MODERATE TO STRONG NELY WINDS ACROSS
THE W ATLC AND THE NW BAHAMAS JUST BEHIND THE FRONT. COLD AIR
ADVECTION OVER THE RELATIVELY WARM OCEAN WATERS IS GENERATING A
LARGE AREA OF BROKEN/OVERCAST STRATOCUMULUS LOW CLOUDS BETWEEN
THE FRONT AND THE EASTERN SEABOARD. THE HIGH PRES WILL MOVE EWD
ACROSS THE W ATLC DURING THE NEXT 24 HOURS. A BROAD UPPER LEVEL
RIDGE EXTENDS FROM THE CARIBBEAN WITH AXIS ACROSS THE VIRGIN AND
LEEWARD ISLANDS NE TO BEYOND 32N45W. MOSTLY FAIR WEATHER
CONDITIONS ARE OBSERVED E OF THE COLD FRONT TO 30W WITH A WEAK
SFC RIDGE DOMINATING THE CENTRAL ATLC. A SURFACE TROUGH IS ALSO
IN THE CENTRAL ATLC EXTENDING ALONG 49W FROM 16N-26N SUPPORTED
BY UPPER LEVEL TROUGHING WHICH EXTENDS FROM A STRONG UPPER-LEVEL
LOW LOCATED MIDWAY BETWEEN THE MADEIRA AND THE AZORES ISLANDS TO
20N36W TO 10N53W. UPPER DIFFLUENCE AHEAD OF THIS UPPER TROUGH
ALONG WITH AN UPPER RIDGE AMPLIFIED ALONG THE W AFRICAN COAST IS
HELPING TO INDUCE CONVECTION ALONG AND NEAR THE ITCZ AXIS. NE TO
E WINDS HAVE INCREASED ACROSS THE TROPICS AND WILL CONTINUE
THROUGH FRI.

$$
GR






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