000 AXNT20 KNHC 272340 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT FRI MAR 27 2009 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND 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. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 4N8W 2N20W DIPPING TO S OF THE EQUATOR NEAR 27W...THEN CONTINUING W TO JUST S OF THE EQUATOR TO S AMERICA NEAR 47W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION WITHIN 240 NM N OF THE AXIS BETWEEN 41W-45W. SIMILAR CONVECTION IS WITHIN 180 NM S OF THE AXIS BETWEEN 13W-18W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM N OF THE AXIS BETWEEN 26W-30W AND 31W-34W. ...DISCUSSION... GULF OF MEXICO... BROAD ANTICYCLONIC FLOW ALOFT ACROSS THE AREA IS GRADUALLY SHIFTING EASTWARD AS A RATHER LARGE DEEPEN UPPER LEVEL TROUGH OVER THE CENTRAL U.S. CONTINUES TO DIG FAR S INTO WRN TEXAS. A DIFFLUENT PATTERN TO THE SE OF THE TROUGH AS SEEN ON SATELLITE WATER VAPOR IMAGERY IS INDUCING SCATTERED TSTM ACTIVITY JUST N OF THE OF THE FAR NW GULF OVER TEXAS. A SHORTWAVE TROUGH IS EMBEDDED WITHIN THE LARGE TROUGH OVER THE SE U.S. THIS IN COMBINATION WITH STRONG LOW-LEVEL INFLOW...AND LOW LEVEL FORCING DUE TO A WEAK BOUNDARY JUST INLAND THE NE GULF IS TRIGGERING OFF AREAS OF RAIN WITH EMBEDDED SCATTERED SHOWERS AND TSTMS N OF 28N E OF ABOUT 89W. SOME OF THESE TSTMS MAY REACH SEVERE LIMITS WITH STRONG GUSTY WINDS. SURFACE ANALYSIS SHOWS BROAD LOW PRES COVERING THE WRN GULF WITH A 995 MB LOW ALONG THE COAST OF MEXICO JUST N OF TAMPICO MEXICO...AND ANOTHER LOW OF 997 MB JUST E OF CORPUS CHRISTI TEXAS. THE TIGHT PRES GRADIENT CREATING THE STRONG LOW-LEVEL INFLOW IS RESULTING IN SE TO S WINDS OF 20-25 KT ACROSS MUCH OF THE MIDDLE AND ERN GULF SECTIONS AS NOTED IN LATEST BUOY OBSERVATIONS AND IN A QUIKSCAT PASS FROM THIS MORNING. LATEST MODEL FORECAST INDICATE THAT THE SURFACE COLD FRONT ASSOCIATED WITH THE UPPER LEVEL TROUGH WILL MOVE INTO THE NW GULF WATERS OVERNIGHT REACHING FROM THE MISSISSIPPI DELTA TO CENTRAL BAY OF CAMPECHE BY SAT AFTERNOON...AND FROM TAMPA BAY TO NE YUCATAN PENINSULA EARLY SUN...AND SHIFT SE OF THE GULF SUN NIGHT. NW TO N GALE FORCE WINDS IN THE RANGE OF 30-40 KT ARE FORECAST BEHIND THE FRONT WITH SEAS BUILDING UP TO 8-11 FT. A LINE OF SCATTERED SHOWERS AND TSTMS IS LIKELY TO DEVELOP OUT AHEAD OF THE FRONT. CARIBBEAN SEA... THE AREA OF BROAD ANTICYCLONIC FLOW NOTED ABOVE UNDER THE GULF OF MEXICO SECTION COVERS THE WRN PORTION OF THE SEA W OF 77W WITH A MEAN RIDGE AXIS EXTENDING FROM THE SE GULF SW TO THE YUCATAN PENINSULA. TO THE E OF THIS AREA OF ANTICYCLONIC FLOW...THE SOUTHERN TIER OF A CENTRAL ATLC DEEP LAYER TROUGH STRETCHES FROM THE FAR NE CARIBBEAN SEA SW TO 15N70W TO NEAR 11N77W. CONFLUENT FLOW INTO THE BASE OF THE TROUGH IS RESULTING IN ABUNDANT MODERATE SUBSIDENCE PRODUCING DRY STABLE AIR SUPPRESSING MOISTURE AND ANY DEEP CONVECTION FROM FORMING OVER MIDDLE AND WRN PORTIONS OF THE SEA. ONLY VERY NARROW LINES OF LOW CLOUDS WITH POSSIBLE ISOLATED SHOWERS MOVING QUICKLY W TO NW ARE NOTED OVER THE MIDDLE AND WRN CARIBBEAN. A JET STREAM BRANCH...WITH WINDS IN THE RANGE OF 40-60 KT...EXTENDS FROM NORTHERN COLOMBIA TO ALONG THE BASE OF THE TROUGH REACHING NE TO WELL INTO THE CENTRAL ATLC OCEAN. THE JET IS TRANSPORTING BROKEN TO TO SCATTERED HIGH LEVEL CLOUDS FROM S AMERICA NE TO ACROSS THE FAR ERN CARIBBEAN SEA. THE JET SEPARATES A DRY STABLE ENVIRONMENT OVER THE WRN CARIBBEAN FROM ONE WHICH CONTAINS MOISTURE IN THE FORM OF PATCHES OF BROKEN LOW/MID CLOUDS WITH ISOLATED SHOWERS AS OBSERVED IN THE FAR ERN CARIBBEAN...MOSTLY ATTRIBUTE TO A WEAKENING ATLC FRONTAL TROUGH ANALYZED ABOUT 250-420 NM E OF THE WINDWARD ISLANDS. THE TROUGH IS FORECAST TO DRIFT N AND WEAKEN OVER THE NEXT 48 HOURS... DIMINISHING THE CHANCES OF PRECIPITATION OVER THE WINDWARD ISLANDS AND ERN CARIBBEAN SEA. WITH RESPECT TO SURFACE MARINE CONDITIONS...STRONG SE WINDS IN THE RANGE OF 20-30 KT ARE BEING OBSERVED OVER THE NW CARIBBEAN W OF ABOUT 83W DUE TO THE TIGHT PRES GRADIENT BETWEEN HIGH PRES CENTERED N OF THE SEA OVER THE ATLC NEAR 30N67W...AND THE AREA OF BROAD LOW PRES OVER THE SRN CONUS AND GULF OF MEXICO. THESE WINDS ARE ALSO BEING FURTHER ENHANCED BY THE ADJACENT TOPOGRAPHY OF LAND. ATLANTIC OCEAN... OVER THE W ATLC...DEEP LAYER RIDGING...THE EWD EXTENSION OF THE BROAD ANTICYCLONIC FLOW OVER THE GULF OF MEXICO...CONTINUES TO KEEP HOLD OF THE WRN PORTION OF THE ATLC AS IT GRADUALLY TRANSLATES EWD. AN UPPER LEVEL RIDGE AXIS MOVING E EXTENDS FROM 32N68W TO 29N69W. THE ASSOCIATED 1022 MB SURFACE HIGH CENTER IS LOCATED NEAR 30N67W WITH A RIDGE SW TO S CENTRAL FL. A JET STREAM BRANCH WITH MAXIMUM WINDS OF 60 KT POKES SE INTO CENTRAL BAHAMAS FROM THE ERN GULF OF MEXICO. UPPER LEVEL MOISTURE IS BEING CHANNELED EWD INTO THE WRN ATLC BY THIS JET STREAM BRANCH. A SURFACE COLD FRONT IS FORECAST TO MOVE OFF THE SE U.S. AND NE FL COAST SAT NIGHT PRECEDED BY INCREASING SLY WINDS OF 20-30 KT FOLLOWED BY SHIFTING WINDS TO W-NW AT 20-25 KT. OVER THE CENTRAL ATLC...THE DEEP LAYER TROUGH DESCRIBED ABOVE UNDER CARIBBEAN SEA EXTENDS NE TO 22N65W TO 25N63W...THEN TILTS SHARPLY NE TO 28N57W TO NE OF THE AREA AT 32N55W. THE ASSOCIATED SURFACE COLD FRONT ENTERS THE AREA THROUGH 32N41W AND CONTINUES TO 26N44W TO 23N47W WHERE IT BECOMES STATIONARY TO 19N51W...THEN A FRONTAL TROUGH TO NEAR 12N57W. LATEST SATELLITE IMAGERY SHOWS OVERCAST MOSTLY LOW AND MID LEVEL CLOUDS WITH EMBEDDED SCATTERED SHOWERS AND ISOLATED WEAK SMALL TSTMS ALONG AND WITHIN 180 NM E OF THE FRONT N OF 25N. SCATTERED SHOWERS ARE ELSEWHERE WITHIN 100 NM E OF THE FRONT...AND WITHIN 150 NM EITHER SIDE OF THE TROUGH. LONG PERIOD NLY SWELL HAS SPREAD WELL S TOWARD THE ANTILLES ELEVATING SEAS BETWEEN 10-18 FT W OF THE FRONT TO THE BAHAMAS. A FAR ERN ATLC SURFACE LOW IS LOCATED NEAR THE CANARY ISLANDS NEAR 28N18W WITH A TROUGH SW TO 26N20W TO 24N24W. IT IS FORECAST TO DISSIPATE WITHIN THE NEXT 24 HRS. COLD-AIR INSTABILITY PRODUCING SCATTERED SHOWERS AND ISOLATED TSTMS ARE N AND NE OF THE LOW. OVER THE DEEP TROPICS...A LARGE SPRAWLING UPPER HIGH IS CENTERED NEAR 7N30W WITH A RIDGE WNW TO 9N38W TO 10N45W TO 10N58W. THE RIDGE IS ENHANCING CONVECTION NEAR AND ALONG THE ITCZ W OF 31W WHERE SOME DIFFLUENCE IS NOTED. THE HIGH IS FORECAST TO SLIDE E OVER THE NEXT 48 HRS AS THE UPPER TROUGH PRESSES E. $$ AGUIRRE