[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 101150
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST MON DEC 10 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC

...SPECIAL FEATURE...
THE AREA OF DISTURBED WEATHER ASSOCIATED WITH A BROAD AREA OF LOW
PRESSURE CENTERED ABOUT 250 NM EAST OF PUERTO RICO REMAINS
FAIRLY WELL-ORGANIZED. AS OF 0600 UTC...A 1010 MB SFC LOW IS
ANALYZED NEAR 19N60W. THIS SYSTEM IS MOVING WESTWARD NEAR 15 KT
AND IS PRODUCING HEAVY SQUALLS WITH GALE FORCE WINDS TO THE
NORTH OF THE SHOWER ACTIVITY. ENVIRONMENTAL CONDITIONS ARE ONLY
MARGINALLY FAVORABLE FOR DEVELOPMENT...BUT A TROPICAL OR
SUBTROPICAL CYCLONE COULD STILL FORM DURING THE NEXT 24 HOURS.
REGARDLESS OF FURTHER DEVELOPMENT...THIS SYSTEM COULD PRODUCE
HEAVY SQUALLS AND GUSTY WINDS ACROSS THE VIRGIN ISLANDS...PUERTO
RICO...AND HISPANIOLA TODAY AND TONIGHT AS IT MOVES WESTWARD AT
ABOUT 20 MPH. INTERESTS IN THESE AREAS SHOULD CONTINUE TO
MONITOR THE PROGRESS OF THIS SYSTEM.. CONVECTION HAS SLIGHTLY
INCREASED EARLY THIS MORNING. NUMEROUS MODERATE TO STRONG
CONVECTION IS FROM 19N-22N BETWEEN 58W-62W. TIGHT PRES GRADIENT
BETWEEN THIS LOW AND HIGH PRES N OF AREA IS PRODUCING GALE FORCE
WINDS IN THE ATLANTIC JUST N OF THE LEEWARD ISLANDS FROM 19N TO
23N BETWEEN 55W AND 65W. A GALE WARNING IS IN EFFECT IN THIS
AREA. THE GFS COMPUTER MODEL HAS MOISTURE FROM THIS SYSTEM
SPREADING OVER THE LEEWARD ISLANDS AS WELL AS OVER THE UK/US
VIRGIN ISLANDS AND PUERTO RICO TODAY BRINGING AN INCREASE IN
SHOWER/TSTM ACTIVITY WITH LOCALLY HEAVY RAIN...PARTICULARLY OVER
THE MOUNTAINOUS AREA.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 5N10W 4N25W 5N35W 3N53W. CLUSTERS OF
SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE WITHIN 100 NM
EITHER SIDE OF AXIS BETWEEN 34W-42W. WIDELY SCATTERED MODERATE
CONVECTION IS FROM 2N-7N BETWEEN 17W-32W. A DIFFLUENT PATTERN
ALOFT IS ENHANCED ALL THIS ACTIVITY.

DISCUSSION...
GULF OF MEXICO...
HIGH PRES REMAINS IN CONTROL OF THE WEATHER PATTERN ACROSS THE
GULF GIVING THE AREA LIGHT TO MODERATE E TO SE WINDS AND MOSTLY
FAIR WEATHER. FRAGMENTS OF LOW LEVEL MOISTURE ARE SEEN OVER THE
CENTRAL GULF ALONG 90W AND MAINLY N OF 24N ASSOCIATED WITH A
MOIST ONSHORE RETURN FLOW. BROAD UPPER-LEVEL RIDGE EXTENDS FROM
THE CARIBBEAN THROUGH THE YUCATAN CHANNEL INTO THE SE U.S.
COVERING THE ENTIRE GULF. MODERATE TO STRONG UPPER LEVEL
SUBSIDENCE AND IMPLIED DRY/STABLE AIR MASS IS NOTED WITHIN THE
RIDGE AXIS. LOOKING AHEAD...A COLD FRONT WILL APPROACH E TEXAS
WED...AND MOVE ACROSS THE NW CORNER OF THE GULF LATE WED AND
THURSDAY.

CARIBBEAN SEA...
BROAD UPPER RIDGE COVERS CENTRAL AMERICA AND THE W CARIBBEAN W
OF 80W ANCHORED BY AN UPPER HIGH LOCATED IN THE EPAC JUST SOUTH
OF PANAMA. BROAD UPPER TROUGH COVERS THE REMAINDER OF THE
CARIBBEAN EXTENDING SOUTH FROM A CUT-OFF LOW LOCATED N OF PUERTO
RICO NEAR 20N67W. UPPER DIFFLUENCE BETWEEN THIS LOW AND AN UPPER
RIDGE E OF THE LESSER ANTILLES IS ENHANCED THE CONVECTION
ASSOCIATED WITH THE SPECIAL FEATURE. LOW LEVEL NELY FLOW AHEAD
OF THIS SYSTEM COMBINED WITH THE UPPER LOW MENTIONED ABOVE IS
GENERATING QUICK MOVING SHOWERS AND ISOLATED TSTMS OVER PUERTO
RICO AND HISPANIOLA. TYPICAL PATCHES OF LOW LEVEL MOISTURE DOT
THE REMAINDER OF THE BASIN...MORE CONCENTRATED OVER THE CENTRAL
CARIBBEAN SOUTH OF HISPANIOLA AND NEAR THE ATLANTIC COAST OF
NICARAGUA. ISOLATED SHOWERS ARE INLAND AND WITHIN 60 NM ALONG
THE COAST OF PANAMA AND COSTA RICA DUE TO THE CLOSE PROXIMITY OF
THE ITCZ AXIS IN THE E PACIFIC REGION. MODERATE TO STRONG NE TO
E SURFACE WINDS OF 20 TO 25 KT COVER THE CARIBBEAN DUE TO A
DIFFERENCE IN PRES BETWEEN THE STRONG SURFACE RIDGE ACROSS THE W
ATLC AND THE LOW LOCATED E OF PUERTO RICO.

ATLANTIC OCEAN...
THE MOST SIGNIFICANT FEATURE ACROSS THE FORECAST AREA IS THE
BROAD AREA OF LOW PRESSURE CENTERED ABOUT 330 NM EAST OF PUERTO
RICO WITH A SFC TROUGH EXTENDING SOUTH ALONG 60W. SEE SPECIAL
FEATURE ABOVE FOR MORE DETAILS. BROAD UPPER RIDGE COVERS THE
REMAINDER OF THE ATLC WITH A WEAKNESS ALONG THE SURFACE TROUGH.
IN THE UPPER LEVELS...BROAD UPPER RIDGE EXTENDING FROM THE
CARIBBEAN OVER THE GULF OF MEXICO COVERS THE FAR W ATLC W OF
75W. A SHORT WAVE TROUGH IS OVER THE W ATLC AND RUNS FROM 31N68W
TO THE NW BAHAMAS. THERE IS ISOLATED SHOWERS ALONG THE TROUGH
AXIS. AN UPPER-LEVEL RIDGE DOMINATES MOST OF THE CENTRAL ATLC.
A CUT-OFF LOW IS IN THE E ATLC NEAR 31N29W. AN UPPER HIGH IS IN
THE TROPICAL ATLC NEAR 2N38W COVERING THE AREA S OF 19N BETWEEN
THE LESSER ANTILLES AND THE AFRICAN COAST. A JET STREAM BRANCH
IS RIDING ON THE N PERIPHERY OF THIS ANTICYCLONE DRAWING UPPER
LEVEL MOISTURE FROM N SOUTH AMERICA NE AND E ACROSS THE ATLANTIC
OCEAN.

$$
GR




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