[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 161750
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST WED JAN 16 2008

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...
THE ITCZ AXIS IS CENTERED ALONG 8N13W 4N20W ALONG THE EQUATOR
BETWEEN 30W AND 35W TO 2S45W. SCATTERED MODERATE CONVECTION IS
WITHIN 170 NM N OF AXIS BETWEEN 27W-40W.

...DISCUSSION...

GULF OF MEXICO...
STRONG UPPER-LEVEL DIVERGENCE...RIGHT REAR QUADRANT JET
DYNAMICS...AND POSITIVE VORTICITY ADVECTION ASSOCIATED WITH
A SHORTWAVE TROUGH MOVING INTO THE TENNESSEE VALLEY HAVE
HELPED IN THE FORMATION OF A GALE CENTER LOCATED NEAR 27N
92W...WHICH IS MOVING RAPIDLY ENE AT 25-30 KTS.  SURFACE
OBSERVATIONS INDICATE A BROAD AREA OF GALE FORCE WINDS IN THE
NORTHERN SEMICIRCLE...WITH A PEAK WIND OF 49 KTS GUSTING TO 53
KTS AT BUOY FGBL1 AT 13Z. SATELLITE AND RADAR IMAGERY REVEALS A
WELL-ORGANIZED COMMA HEAD OF CLOUDS AND PRECIPITATION MOVING
ONSHORE THE UPPER TX/LA COASTS NEAR AND NORTH OF THE SFC
CYCLONE...WHILE A WELL-DEVELOPED CONVECTIVE BAND AHEAD OF THE
ASSOCIATED COLD FRONT IS SHIFTING EWD INTO THE CENTRAL GULF OF
MEXICO. FARTHER EAST...OVERRUNNING LOW/MID-LEVEL MOISTURE ARE
CONTRIBUTING TO A LARGE SHIELD OF CLOUDS AND LIGHT TO MODERATE
RAINS AHEAD OF THE ASSOCIATED WARM FRONT OVER THE CENTRAL AND
EASTERN GULF OF MEXICO.  WINDS OVER THE NORTH CENTRAL AND
NORTHEASTERN GULF ARE ALSO APPROACHING GALE FORCE IN RESPONSE TO
THE STRONG PRESSURE GRADIENT BETWEEN HIGH PRESSURE CENTERED OVER
THE NORTHERN APPALACHIANS AND LOW PRESSURE OVER THE GULF.
GLOBAL MODELS INDICATE THAT THE GALE CENTER SHOULD BEGIN
WEAKENING AS ITS UPPER-LEVEL SUPPORT OUTRACES IT...AND THE
CENTER SHOULD COME ASHORE FLORIDA PANHANDLE THURS MORNING BEFORE
RE-EMERGING ALONG THE SE CONUS COAST LATER IN THE DAY.
IN THE WAKE OF THIS SYSTEM...STRONG COLD-AIR ADVECTION ON A N TO
NE WIND SHOULD OVERTAKE MOST OF THE GULF OF MEXICO BY
FRIDAY...AS HIGH PRESSURE FROM THE ROCKIES BUILDS INTO THE
SOUTHERN PLAINS.

CARIBBEAN SEA...
A MID-LEVEL HIGH LOCATED JUST NE OF DOMINICAN REPUBLIC CONTINUES
TO DOMINATE MOST OF THE CARIBBEAN SEA WITH A VERY DRY AND STABLE
AIR MASS WHICH IS LIMITING THE DEVELOPMENT OF DEEP CONVECTION.
HOWEVER...THERE ARE SOME POCKETS OF LOW-LEVEL CLOUDS WITH
EMBEDDED SHOWERS MOVING WWD ACROSS THE AREA UNDER THE INFLUENCE
OF A PREVAILING ELY FLOW. IN FACT...THE SAN JUAN DOPPLER RADAR
SHOWS SHOWERS CROSSING FROM THE N LEEWARD ISLANDS TO THE UK/US
VIRGIN ISLANDS AND PUERTO RICO. STREAKS OF CLOUDS AND A FEW
SHOWERS COVER PARTS OF THE CENTRAL AND WESTERN CARIBBEAN
SEA...LIKELY RELATED TO THE SHEAR OF THE LOW-LEVEL WIND/SPEED
CONVERGENCE.  THE SPEED CONVERGENCE OVER THIS REGION IS A RESULT
OF STRONG TRADE WINDS OVER THE CENTRAL CARIBBEAN SEA TO THE
COLOMBIA COAST...WITH WEAKER TRADES TO THE WEST. ELSEWHERE...A
DYING FRONTAL BOUNDARY LIES OVER NORTH CENTRAL CUBA AND IS
GENERATING SCATTERED CLOUDINESS AND SOME LIGHT SHOWERS. THE NEXT
COLD FRONT IS FORECAST TO REACH THE YUCATAN CHANNEL/WESTERN CUBA
LATE SAT WITH STRONG NORTHERLY WINDS BEHIND IT. FINALLY...TO THE
EAST...A BROAD UPPER-LEVEL RIDGE DOMINATING NRN SOUTH AMERICA IS
ADVECTING MOISTURE/HIGH CLOUDS INTO THE SE CARIBBEAN AND THE
TROPICAL ATLC.

ATLANTIC OCEAN...
A COLD FRONT STRETCHES FROM A DEVELOPING STORM OVER THE WESTERN
ATLC NEAR 39N58W TO 28N68W THEN CONTINUES AS A STATIONARY FRONT
LYING ACROSS THE CENTRAL BAHAMAS/CUBA. A BROKEN BAND OF MAINLY
LOW CLOUDS AND POSSIBLE SHOWERS ARE ASSOCIATED WITH THE
FRONT...MAINLY NE OF THE BAHAMAS. FARTHER EAST...A WWD-MOVING
SFC TROUGH IS LOCATED OVER THE TROPICAL ATLC ALONG 47W/48W FROM
10N-17N WITH SCATTERED SHOWER AND THUNDERSTORMS EAST OF THE N
END OF THE TROUGH AXIS. FARTHER NORTH...A 1030 MB SURFACE HIGH
CENTERED NEAR 33N25W CONTINUES TO DOMINATE MUCH OF THE ERN ATLC.
MODERATE TO STRONG EASTERLY TRADES SOUTH OF THIS FEATURE
CONTINUE TO PRODUCE A REGION OF FAIRLY DENSE STRATOCUMULUS
CLOUDS GENERALLY N OF 20N AND EAST OF 40W. FINALLY...AT UPPER
LEVELS...A RIDGE/TROUGH/RIDGE PATTERN DOMINATES THE ERN PART OF
ATLC. WITHIN THE BROAD LONGWAVE TROUGH ALONG 40W...A CUT-OFF LOW
IS LOCATED IN THE CENTRAL ATLC NEAR 22N56W WITH A TROUGH
EXTENDING SW TO ANOTHER DEVELOPING UPPER-LEVEL LOW WHICH
CENTERED NEAR 13N50W. A STRONG 70- TO 90-KT JET DIGGING INTO THE
BASE OF THE TROUGH MEETING ANTICYCLONIC FLOW TO THE SOUTH IS
CREATING STRONG UPPER-LEVEL CONVERGENCE FROM THE LESSER ANTILLES
EWD TO ABOUT 40W.  THE RESULT IS LITTLE IN THE WAY OF ORGANIZED
LOW CLOUDS...THOUGH A STREAM OF THIN CIRRUS CONTINUES TO FLOW
FROM NORTHERN SOUTH AMERICA TO THE NW COAST OF AFRICA.

$$
TK/GR




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