000 AXNT20 KNHC 140532 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT TUE JUL 14 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 31W S OF 16N MOVING W 15-20 KT. THIS WAVE COINCIDES WITH A LOW AMPLITUDE MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. SATELLITE-DERIVED WINDS INDICATE CYCLONIC CURVATURE IN THE FLOW WITHIN THE 800-600 MB LAYER. THE QUIKSCAT PASS AROUND 13/2015 UTC INDICATED E WINDS AT 10-15 KT AHEAD OF THE WAVE FOLLOWED BY E TO SE WINDS AT 15-20 KT BEHIND THE WAVE. THIS WAVE IS ASSOCIATED WITH SCATTERED MODERATE CONVECTION FROM 8N-15N BETWEEN 29W-32W. A TROPICAL WAVE IS E OF THE LESSER ANTILLES AND EXTENDS FROM 19N57W TO 5N53W MOVING W 15-20 KT. THE STRONG LOW LEVEL EASTERLY JET FOLLOWING THE N PORTION OF THE WAVE IS CONTRIBUTING TO THE NW-SE TILT OF THE WAVE. A WELL-DEFINED INVERTED V PATTERN IS EVIDENT IN THE COVERAGE OF LOW-LEVEL CLOUDS BASED ON RECENT SATELLITE IMAGERY. THE RELATIVELY SHORT WAVELENGTH OF THE TROPICAL WAVE IS CURRENTLY PRECLUDING AN EVEN FASTER WESTWARD WAVE MOTION. THE WAVE ALSO COINCIDES WITH A WELL-AMPLIFIED MOISTURE MAXIMUM OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY. THE WAVE IS LEADING ABUNDANT DRY LOW/MID-LEVEL SAHARAN AIR THAT IS INHIBITING DEEP CONVECTION NEAR THE WAVE. NEVERTHELESS... SCATTERED SHOWERS ARE OCCURRING FROM 8N-12N BETWEEN 54W-56W...AND THE DRY AIR IS LIKELY CONTRIBUTING TO STRONG DOWNDRAFTS AND GUSTY OUTFLOW WINDS WITH THESE SHOWERS. THE GFS APPEARS TO HAVE A GOOD HANDLE ON THIS FEATURE AND SHOWS IT MOVING INTO THE LESSER ANTILLES DURING THE NEXT DAY. A TROPICAL WAVE IS ALONG 92W MOVING W NEAR 15-20 KT. THE WAVE POSITION IS MAINLY BASED ON A MOISTURE MAXIMUM IN TOTAL PRECIPITABLE WATER AS FEW ADDITIONAL SIGNATURES ARE APPARENT IN SATELLITE IMAGERY OR OBSERVATIONS. SCATTERED MODERATE CONVECTION IS FROM 17N-20N BETWEEN 91W AND 95W INCLUDING PORTIONS OF THE BAY OF CAMPECHE. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 14N17W 11N28W 9N38W 8N47W 8N60W. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 8N-13N BETWEEN 17W-23W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 6N-12N BETWEEN 25W-28W. SCATTERED MODERATE CONVECTION IS FROM 8N-12N BETWEEN 34W-44W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL RIDGE EXTENDS SOUTHEASTWARD INTO THE GULF OF MEXICO AND IS ASSOCIATED WITH A SURFACE RIDGE ALONG 26N AND A 1016 MB SURFACE HIGH NEAR 26N91W. GENERALLY FAIR WEATHER IS PRESENT ACROSS THE GULF. ONE EXCEPTION IS OVER THE BAY OF CAMPECHE...WHERE SCATTERED MODERATE CONVECTION IS OCCURRING NEAR THE TROPICAL WAVE ALONG 92W S OF 20N. THIS ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN THE AFOREMENTIONED UPPER LEVEL RIDGE AND AN UPPER LEVEL LOW OVER THE N CARIBBEAN SEA. ALSO...WEAKENING SCATTERED SHOWERS AND THUNDERSTORMS... WHICH DEVELOPED EARLIER OVER THE SE UNITED STATES NEAR A SURFACE TROUGH...ARE IMPACTING LOCATIONS IN THE GULF OF MEXICO N OF 28N E OF 87W. WINDS ARE LIGHT AND VARIABLE IN THE VICINITY OF THE SURFACE RIDGE ACROSS THE N GULF...WITH ANTICYCLONIC FLOW AROUND THE RIDGE SUPPORTING A BROAD SWATH OF E WINDS OF 10-15 KT ACROSS THE S HALF OF THE GULF. LITTLE CHANGE IS EXPECTED OVER THE NEXT DAY OR TWO AS BOTH THE UPPER AND SFC RIDGE REMAIN IN PLACE. CARIBBEAN SEA... FRESH TO STRONG TRADE WINDS ARE OCCURRING BETWEEN THE SUBTROPICAL RIDGE OVER THE CENTRAL ATLC AND A BROAD TROUGH OVER NORTHERN SOUTH AMERICA...WITH THE STRONGEST FLOW NEAR THE COAST OF COLOMBIA. THESE WINDS WILL REMAIN STRONG OVER THE NEXT SEVERAL DAYS AS THE SUBTROPICAL RIDGE REMAINS IN PLACE AND A TROPICAL WAVE MOVES INTO THE AREA. IN FACT...GALE CONDITIONS ARE FORECAST FOR THE LATTER HALF OF THE WEEK...AS THE LOW LEVEL FLOW STRENGTHENS ACROSS THE CARIBBEAN. ALOFT...INSTABILITY ASSOCIATED WITH AN UPPER LEVEL LOW OVER THE N CENTRAL CARIBBEAN CENTERED NEAR 19N79W IS RESULTING IN SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS N OF 18N BETWEEN 78W-82W INCLUDING PORTIONS OF JAMAICA AND CUBA. DEEP LAYER DRY AIR IS RESULTING IN GENERALLY FAIR WEATHER ACROSS THE E CARIBBEAN. ATLANTIC OCEAN... DEEP LAYER MOISTURE IS COMBINING WITH UPPER LEVEL DIFFLUENCE IN NORTHWESTERLY FLOW ALOFT TO RESULT IN SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE SW NORTH ATLC N OF 28N W OF 77W. ALSO...SCATTERED SHOWERS AND ISOLATED TSTMS ARE FARTHER E WITHIN 90 NM EITHER SIDE OF A SURFACE TROUGH EXTENDING FROM 28N65W TO E PORTIONS OF THE DOMINICAN REPUBLIC NEAR 19N69W. THIS ACTIVITY IS ALSO SUPPORTED BY DIFFLUENCE ALOFT BETWEEN AN UPPER TROUGH OVER THE SW NORTH ATLC AND AN UPPER RIDGE FARTHER TO THE E. SUBSIDENCE AND GENERALLY FAIR WEATHER ARE PRESENT ACROSS MUCH OF THE CENTRAL AND E ATLC AROUND A BROAD SURFACE RIDGE WITH A 1031 MB HIGH NEAR 34N44W. A SURFACE TROUGH FROM 31N34W TO 28N35W TO 26N39W IS PERTURBING THE RIDGE...THOUGH ASSOCIATED CLOUDINESS AND SHOWERS ARE SHALLOW IN NATURE AND LIMITED TO LOCATIONS WITHIN 60 NM EITHER SIDE OF THE SURFACE TROUGH. ACROSS THE TROPICAL N ATLC...AN UPPER LEVEL RIDGE IS ALONG 14N E OF 37W WITH ASSOCIATED UPPER LEVEL DIVERGENCE ENHANCING THE CONVECTION NEAR THE ITCZ. $$ COHEN