[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 172353
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST THU JAN 17 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 6N11W 3N20W 1N30W 1S40W 2N48W
1N50W. WIDELY SCATTERED MODERATE CONVECTION IS FROM EQ-7N
BETWEEN 44W-52W.  SCATTERED MODERATE CONVECTION IS FROM 1S-1N
BETWEEN 40W-42W.  SCATTERED SHOWERS ARE WITHIN 120NM OF THE AXIS
BETWEEN 20W-40W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 2100 UTC...A WEAKENING SHORTWAVE OVER THE CENTRAL
APPALACHIANS IS PRODUCING A 1011MB LOW CENTERED OVER THE FL
PANHANDLE NEAR 30N84W AND SHOULD MOVE NE IN DEEP SWLY FLOW
ALOFT. A COLD FRONT EXTENDS SOUTHWARD TO THE YUCATAN PENINSULA
ALONG 25N84W 22N88W. THE FRONT BECOMES STATIONARY INTO THE BAY
OF CAMPECHE ALONG 19N96W 23N100W.  AN ASSOCIATED SQUALL LINE
CONTINUES AHEAD OF THE COLD FRONT ALONG 26N83W 23N86W. RADAR
TRENDS INDICATE A GRADUAL WEAKENING OF THIS ACTIVITY DURING THE
PAST SEVERAL HOURS...AS UPPER-LEVEL SUPPORT SHIFTS WELL
NORTHEAST.  A DISSIPATING COLD FRONT LOCATED OVER THE NW GULF OF
MEXICO IS ALONG 29N93W 26N97W. A WEAK 1019MB SFC HIGH IS LOCATED
IN BETWEEN THE TWO FRONTS...JUST SOUTH OF THE MOUTH OF THE
MISSISSIPPI RIVER AT 28N89W.  OF NOTE...A 20-25KT SLY FLOW
CONTINUES AHEAD OF THE SQUALL OVER THE STRAITS OF FLORIDA FROM
23N-26N 80W-85W.  AS THE FIRST SHORTWAVE DEPARTS THE ERN CONUS
TONIGHT...EXPECT THE UPPER-LEVEL FLOW TO REMAIN SWLY OVER THE
GULF WHILE ADDITIONAL NORTHERN STREAM SHORTWAVE ENERGY
REINFORCES THE LONGWAVE TROUGH OVER THE CENTRAL CONUS WITHIN 24
HRS. AS THIS OCCURS...THE FRONTAL BOUNDARY OVER THE GULF SHOULD
STALL OUT AND BEGIN RETURNING AS A WARM FRONT IN RESPONSE TO A
NEW ROUND OF CYCLOGENESIS BEGINNING OVER THE W CNTRL/NWRN GULF
OF MEXICO FRI NIGHT.  UNTIL THEN...OVERRUNNING PACIFIC MOISTURE
SHOULD CONTINUE TO BRING A THIN VEIL OF HIGH CLOUDS FROM MEXICO
INTO THE SERN STATES TONIGHT...WITH CLOUDS AND CONVECTION ON THE
INCREASE OVER THE WRN AND CNTRL GULF OF MEXICO FRI NIGHT.

CARIBBEAN SEA...
A STRONG MID-TO UPPER-LEVEL RIDGE OVER NWRN SOUTH AMERICA WITH
A RIDGE AXIS EXTENDING NWD ALONG 75W THROUGH THE CARIBBEAN SEA
SHOULD CONTINUE TO DOMINATE THE WEATHER THROUGH AT LEAST FRI.
UNDERNEATH THE RIDGE...STRONG SUBSIDENCE IS NOTED IN WATER VAPOR
IMAGERY OVER MOST OF THE CARIBBEAN...ESPECIALLY FROM NRN
VENEZUELA INTO THE SOUTHWESTERN CARIBBEAN SEA.  DESPITE THIS...A
MODERATELY STRONG TRADE WIND FLOW CONTINUES TO PRODUCE SCATTERED
BANDS OF SHOWERS FROM PORTIONS OF THE LESSER ANTILLES TO
JAMAICA.  THE SHOWERS ARE MORE CONCENTRATED IN THE VICINITY OF
THE BRITISH/U.S. VIRGIN ISLANDS...WHERE STREAMERS ARE CARRYING
SHOWERS DOWNSTREAM TO PUERTO RICO.  ADDITIONAL CONCENTRATED
BANDS OF SHOWERS ARE ALSO OBSERVED IN THE W CNTRL CARIBBEAN...
LIKELY RELATED TO THE SHEAR OF THE LOW-LEVEL WIND/SPEED
CONVERGENCE.  THE SPEED CONVERGENCE OVER THIS REGION IS A RESULT
OF STRONG TRADES OVER THE CENTRAL CARIBBEAN...WITH WEAKER TRADES
LYING TO THE WEST. A STRONG COLD FRONT IS EXPECTED TO MOVE INTO
THE NW CARIBBEAN SAT NIGHT ACCOMPANIED BY STRONG N WINDS AND
BUILDING SEAS.

ATLANTIC OCEAN...
A COLD FRONT ENTERS THE AREA NEAR 32N42W AND EXTENDS SW TO E OF
THE BAHAMAS ALONG 27N50W 24N70W.  BROKEN LOW CLOUDS AND A FEW
SHOWERS ARE WITHIN 90NM EITHER SIDE OF THE FRONT.  SCATTERED
MODERATE CONVECTION LIES E OF THE FRONT FROM 30N TO BEYOND 32N
BETWEEN 39W-43W.  BEHIND THE BOUNDARY...A 1025 MB SFC HIGH IS
CENTERED NEAR 33N67W.  IN THE ERN ATL...A 1030 MB IS LOCATED OFF
THE COAST OF PORTUGAL NEAR 36N10W...WITH A RIDGE AXIS EXTENDING
SW TO 27N35W.  IN THE TROPICS...A SFC TROUGH IS NORTH OF THE NRN
COAST OF BRAZIL ALONG 48W FROM 1N-8N. ASSOCIATED CONVECTION IS
WIDELY SCATTERED FROM EQ-7N BETWEEN 44W-52W. AT UPPER LEVELS...A
BROAD LONGWAVE TROUGH LIES EAST OF THE CARIBBEAN HIGH CENTER...
COVERING MUCH OF THE CNTRL AND ERN ATL.  AROUND THE BASE OF THE
TROUGH...A STRONG 70KT-90KT JET IS PUMPING CONSIDERABLE ATLANTIC
MOISTURE EWD INTO THE CNTRL AND ERN TROPICAL ATLANTIC.

$$
TK





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