[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 261749
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST WED DEC 26 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC

...THE ITCZ...

ITCZ AXIS IS CENTERED ALONG 7N12W 3N25W 4N35W EQUATOR AT 48W...
INTO NE BRAZIL. WIDELY SCATTERED MODERATE CONVECTION IS WITHIN
60 NM EITHER SIDE OF AXIS BETWEEN 16W-19W. SCATTERED SHOWERS AND
ISOLATED TSTMS ARE FROM 2N-5N BETWEEN 31W-37W.

...DISCUSSION...

THE GULF OF MEXICO...
AS OF 1500 UTC...A NEW COLD FRONT HAS ENTERED THE NW CORNER OF
THE GULF. DOPPLER RADAR DEPICTS A WELL DEFINED LINE OF STRONG
SHOWERS AND TSTMS ALONG THE COLD FRONT THAT TRAILS ACROSS
EASTERN TEXAS...THE NW PORTION OF THE GULF AND NE MEXICO. THE
FRONT IS ATTACHED TO A 1007 MB LOW LOCATED OVER SE TEXAS. THIS
FRONTAL SYSTEM WILL EXTEND FROM THE MISSISSIPPI COAST TO NEAR
TAMPICO MEXICO TONIGHT. THE FRONT IS FORECAST TO WEAKEN AND
BECOME DIFFUSE ON THURSDAY. AT THE SAME TIME...A SFC HIGH IS
SETTLING OVER SOUTH GEORGIA/N FLORIDA USHERING A COOL AND DRIER
AIRMASS OVER FLORIDA AND THE EASTERN GULF. THE LEADING EDGE OF
THIS AIRMASS IS A COLD FRONT THAT CROSSES JUST N OF LAKE
OKEECHOBEE. A MID/UPPER-LEVEL TROUGH WITH AXIS ALONG THE TEXAS
PANHANDLE SUPPORTS THE AFOREMENTIONED COLD FRONT. TROPICAL
MOISTURE IS SEEN STREAMING NORTHEASTWARD BY A JETSTREAM BRANCH
FROM THE E PACIFIC NE ACROSS THE CENTRAL MEXICO AND THE GULF
REACHING TO ACROSS NORTH-CENTRAL FLORIDA INTO THE W ATLC.
SATELLITE-DERIVED WINDS INDICATE A CORE WINDS OF 70-110 KT
ASSOCIATED WITH THIS JETSTREAM. LOOKING AHEAD...ANOTHER COLD
FRONT WILL ENTER THE NW GULF LATE THURSDAY NIGHT.

THE CARIBBEAN SEA...
AMPLIFIED MID TO UPPER LEVEL RIDGING IS PRESENT OVER THE NW AND
CENTRAL PORTIONS OF THE SEA CREATING ABUNDANT MODERATE TO STRONG
SUBSIDENCE IN THESE AREAS. THE TAIL END OF A MID/UPPER LEVEL
TROUGH EXTENDS FROM THE E ATLC SW ENTERING THE EASTERN CARIBBEAN
THROUGH THE LESSER ANTILLES. PRETTY QUIET CONDITIONS ARE FOUND
ACROSS THE BASIN UNDER THE INFLUENCE OF THIS STABLE ENVIRONMENT.
TYPICAL PATCHES OF LOW LEVEL CLOUDS WITH LIGHT RAIN SHOWERS DOT
THE AREA. BRISK NELY WINDS ARE TRANSPORTING PATCHES OF LOW LEVEL
MOISTURE WITH SHALLOW CONVECTION ACROSS THE CARIBBEAN PLAINS OF
NICARAGUA AND COSTA RICA. FRAGMENTS OF MOISTURE IN THE TRADE
WIND FLOW ARE ALSO MOVING ACROSS THE NE CARIBBEAN AFFECTING THE
NORTHERN LEEWARD ISLANDS. THIS CLOUDINESS IS SPREADING ACROSS
THE UK/US VIRGIN ISLANDS AND PUERTO RICO WHERE ISOLATED TO
SCATTERED SHOWER ACTIVITY IS EXPECTED. MODERATE EASTERLY WINDS
WILL PERSIST ACROSS THE BASIN THIS AFTERNOON THROUGH SUNDAY.

THE ATLANTIC OCEAN...
A COLD FRONT ENTERS THE AREA NEAR 31N76W THEN CONTINUES SW TO
OVER N-CENTRAL FLORIDA. AN INVERTED SFC TROUGH REMAINS JUST OFF
THE SE COAST OF FLORIDA GENERATING ISOLATED SHOWERS ACROSS THE
STRAITS OF FLORIDA. A RIDGE IS BUILDING BEHIND THE FRONT ACROSS
THE SE U.S. AND THE FLORIDA PENINSULA BRINGING IN A COOL AND
DRIER ATMOSPHERE. A 1025 MB HIGH LOCATED NEAR 31N55W EXTENDS A
RIDGE INTO THE DISCUSSION AREA BETWEEN 50W AND 75W. ALOFT...A
RIDGE/TROUGH/RIDGE PATTERN DOMINATES THE FORECAST REGION. A
BROAD UPPER RIDGE COVERS W OF 60W ACCOMPANIED BY DRY UPPER AIR.
A DEEP LAYERED TROUGH REMAINS STUCK OVER THE CENTRAL ATLC
EXTENDING SW TO THE EASTERN CARIBBEAN. AMPLE UPPER LEVEL
MOISTURE IS EVIDENT WITHIN 600 NM E OF THE TROUGH. A CUT-OFF LOW
HAS DEVELOPED ALONG THE TROUGH AXIS NEAR 27N40W. THESE UPPER
FEATURES SUPPORT AN OCCLUDED 1014 MB SFC LOW THAT HAS A COLD
FRONT EXTENDING ALONG 31N37W 23N40W 20N52W. A 120-140 NM WIDE
BAND OF SHOWERS WITH ISOLATED TSTMS IS RELATED TO THE FRONTAL
BOUNDARY N OF 23N WHILE A BAND OF BROKEN LOW CLOUDS IS
ASSOCIATED WITH THE TAIL END OF THE FRONTAL SYSTEM. TIGHT PRES
GRADIENT BETWEEN THIS FRONT AND THE RIDGE TO THE W OF THE FRONT
IS PRODUCING MODERATE TO STRONG NLY WINDS OF 25 TO 30 KT OVER
THE OCEAN...WITHIN 240 NM W SEMICIRCLE OF LOW. RIDGING ALSO
DOMINATES THE E ATLC ANCHORED ON A 1033 HIGH LOCATED WEST OF
PORTUGAL. THE UPPER FLOW IS GENERALLY ZONAL OVER THE TROPICAL
ATLC W OF 45W. STRONG SWLY FLOW TO THE E AND SE OF THE
FRONT/TROUGH IS ADVECTING UPPER LEVEL MOISTURE NEWD E OF
45W...REACHING THE CAPE VERDE ISLANDS.

$$
GR




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