[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211137
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST FRI DEC 21 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
1045 UTC

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 6N9W 5N20W 5N30W 3N40W AND INTO
SOUTH AMERICA NEAR THE EQUATOR AND 50W. CLUSTERS OF MODERATE TO
STRONG CONVECTION ARE WITHIN 60 NM EITHER SIDE OF THE AXIS
BETWEEN 20W-34W. SCATTERED MODERATE CONVECTION IS FROM 4N-7N
AND 33W-40W. UPPER DIFFLUENCE IS ENHANCING CONVECTION ALONG THE
ITCZ.

DISCUSSION...
GULF OF MEXICO...
CONVECTION HAS DECREASED IN THE E GULF AND DIMINISHED IN THE
CENTRAL GULF THIS MORNING AS THE SFC LOW AND ASSOCIATED TROUGH
MOVED E TOWARD FLORIDA. AS OF 09Z...THE LOW WAS CENTERED OVER N
FLORIDA NEAR 30N83W AND THE TROUGH EXTENDED FROM THE LOW ALONG
29N82W 26N85W TO 25N89W. THIS LOW HAS BECOME THE MAIN LOW OF THE
SYSTEM AND THE WEAK COLD FRONT NOW ATTACHES TO IT AND STRETCHES
TO 28N88W THEN BEGINS TO DISSIPATE ALONG 25N93W TO THE COAST OF
MEXICO NEAR 23N98W. THE COLD FRONT IS MARKED BY A DEW POINT
GRADIENT AND ALL OF THE CONVECTIVE ACTIVITY WITH THIS SYSTEM
LIES TO THE EAST OF THE SFC TROUGH. COMPOSITE RADAR IMAGERY
INDICATES THAT MOST OF THE CONVECTION IS NOW OVER CENTRAL
FLORIDA...HOWEVER...A FEW SHOWERS AND ISOLATED TSTMS REMAIN OVER
THE E GULF E OF 85W N OF 25N. MODERATE TO STRONG S WINDS ARE
ALONG THE AXIS OF THE TROUGH. THE REMAINDER OF THE GULF REMAINS
UNDER A WEAK PRESSURE PATTERN RESULTING IN LIGHT WINDS ACROSS
THE REGION. ALOFT...NEAR ZONAL FLOW CONTINUES TO MAINTAIN DRY
AND STABLE CONDITIONS. THE NORTHERN PERIPHERY OF AN UPPER RIDGE
IS DRAWING UPPER-LEVEL MOISTURE FROM THE E PAC OVER THE SW GULF.
A STRONGER COLD FRONT IS EXPECTED TO MOVE INTO THE NW GULF SAT
EVENING. MODERATE TO STRONG NLY WINDS AND BUILDING SEAS CAN BE
EXPECTED BEHIND THE FRONT.

CARIBBEAN SEA...
TRANQUIL WEATHER CONDITIONS PERSIST ACROSS THE CARIBBEAN THIS
MORNING UNDER THE INFLUENCE OF A MID/UPPER-LEVEL RIDGE WHICH IS
PRODUCING STRONG SUBSIDENCE AND A DRY/STABLE AIRMASS.  A FEW
PATCHES OF LOW LEVEL CLOUDS WITH ISOLATED SHOWERS REMAIN OVER
THE AREA. SAN JUAN RADAR SHOWS ISOLATED SHOWERS MOVING SOUTH OF
PUERTO RICO. A SMALL CLUSTER OF SHOWERS AND ISOLATED TSTMS IS
MOVING OFF PANAMA INTO THE SW CARIBBEAN. LIGHT TO MODERATE
TRADES WILL PREVAIL OVER MUCH OF THE AREA THROUGH MONDAY.

ATLANTIC OCEAN...
THE BAND OF CONVECTIVE ACTIVITY ASSOCIATED WITH THE LOW AND SFC
TROUGH OVER THE E GULF OF MEXICO IS BEGINNING TO ENTER THE W
ATLC. THIS CONVECTION WILL CONTINUE TO PUSH EASTWARD AS THE SFC
LOW  MOVES ACROSS FLORIDA AND ENTERS THE W ATLC THIS AFTERNOON.
THE PRESSURE GRADIENT BETWEEN THIS LOW AND HIGH PRESSURE
BUILDING TO THE NORTH WILL TIGHTEN RESULTING IN INCREASED WINDS
AND SEAS. A PRE-FRONTAL TROUGH ASSOCIATED WITH A COLD FRONT
NORTH OF THE DISCUSSION AREA ENTERS THE REGION NEAR 31N62W AND
EXTENDS SW TO 27N68W. A NARROW BAND OF SHOWERS/ ISOLATED
TSTMS LIES ALONG THE TROUGH AXIS. A WEAK 1016 MB LOW IS CENTERED
NEAR 29N52W. A SFC TROUGH EXTENDS FROM THE LOW CENTER ALONG
25N58W TO 23N66W. A BAND OF SHOWERS AND TSTMS EXTENDS UP TO 200
NM AHEAD OF THE TROUGH. A WARM FRONT ALSO EXTENDS FROM THE LOW
CENTER ALONG 31N51W 32N45W TO 31N36W WHERE IT CONNECTS TO A COLD
FRONT AND CONTINUES ALONG 30N30W EXITING THE REGION NEAR 32N23W.
A LARGE SFC RIDGE REMAINS FIXED OVER THE E ATLC TRANSPORTING
FAIR WEATHER STRATOCUMULUS CLOUDS AROUND ITS PERIPHERY. IN THE
TROPICAL ATLC...UPPER DIFFLUENCE IS SUPPORTING CONVECTION ALONG
THE ITCZ. A SFC TROUGH IS ANALYZED JUST EAST OF THE WINDWARD
ISLANDS ALONG 60W FROM 9N-14N. SCATTERED MODERATE CONVECTION IN
THIS AREA IS ENHANCED BY UPPER DIFFLUENCE.

$$
WADDINGTON






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