000 AXNT20 KNHC 181758 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SAT JUL 18 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 31W S OF 19N MOVING W NEAR 15 KT. ALTHOUGH THE WAVE LACKS ANY SIGNIFICANT DEEP CONVECTION DUE TO THE PRESENCE OF SAHARAN DUST TO THE NORTH AND EAST OF THE WAVE AXIS...SLIGHT LOW TO MIDDLE LEVEL CYCLONIC TURNING OF THE CLOUD FIELD IS NOTED IN THE SATELLITE CLOUD DRIFT WINDS WITH THIS WAVE. A TROPICAL WAVE IS ALONG 44W S OF 16N MOVING W NEAR 20 KT. THIS WAVE COINCIDES WITH A LOW TO MIDDLE LEVEL CYCLONIC CIRCULATION ALONG THE WAVE AXIS NEAR 12N. SCATTERED MODERATE CONVECTION IS FROM 10N-14N BETWEEN 43W-47W. A TROPICAL WAVE EXTENDS ALONG 21N58W 15N61W TO 10N62W MOVING W NEAR 18 KT. THIS WAVE COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. WATER VAPOR IMAGERY INDICATES THE WAVE IS BEGINNING TO MOVE BENEATH AN UPPER LEVEL RIDGE ACROSS THE ERN CARIBBEAN AND THE NRN PORTION OF THE WAVE IS COMING UNDER THE IMPACTS OF AN UPPER LOW CENTERED NE OF PUERTO RICO NEAR 23N58W. UPPER LEVEL DIFFLUENCE BETWEEN THESE TWO FEATURES ARE ENHANCING SCATTERED MODERATE CONVECTION FROM 13N-18N BETWEEN 55W-62W. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 10N14W 9N29W 10N34W 11N42W 8N46W 13N60W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM OF A LINE FROM 10N12W TO 6N24W. SIMILAR CONVECTION IS FROM 6N-9N BETWEEN 47W-52W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL RIDGE IS PRESENT ACROSS THE NRN FLORIDA PENINSULA AND THE NRN GULF N OF 25N...WITH A SURFACE RIDGE ACROSS THE CENTRAL GULF AND SRN GULF ANCHORED ON A 1020 MB HIGH NEAR 26N83W. STABLE ATMOSPHERIC CONDITIONS AND SUBSIDENCE ASSOCIATED WITH THE SURFACE HIGH AND SURFACE RIDGE ARE RESULTING IN GENERALLY FAIR WEATHER ACROSS THE SRN GULF S OF 25N. HOWEVER... ACROSS THE NRN GULF COAST AND NRN FLORIDA...UPPER LEVEL MOISTURE IS INTERACTING WITH ATMOSPHERIC LIFT ASSOCIATED WITH AN UPPER LEVEL TROUGH PROGRESSING ACROSS THE SE CONUS THAT IS SUPPORTING A COLD FRONT OVER SRN GEORGIA...THE FLORIDA PANHANDLE AND THE GULF COAST TO NEAR NEW ORLEANS LOUISIANA. A PRE-FRONTAL TROUGH IS ALSO ANALYZED FROM PANAMA CITY FLORIDA W-SW TO 29N94W. DOPPLER RADAR AND LIGHTNING DATA INDICATES SCATTERED SHOWERS AND TSTMS ARE OCCURRING N OF 26N BETWEEN 81W-96W. ANTICYCLONIC FLOW AROUND THE SURFACE RIDGE IS SUPPORTING GENERALLY E TO SE WINDS OF 10-15 KT ACROSS A MAJORITY OF THE SRN GULF. CARIBBEAN SEA... FRESH TO STRONG TRADE WINDS ARE OCCURRING BETWEEN THE SUBTROPICAL RIDGE OVER THE CENTRAL ATLC AND A BROAD TROUGH OVER NWRN SOUTH AMERICA...WITH THE STRONGEST FLOW NEAR THE COAST OF COLOMBIA. AN EARLIER SCATTEROMETER PASS AROUND 1100 UTC DEPICTED A LARGE AREA OF NE TO E WINDS OF 20 TO 30 KT ACROSS THE CENTRAL AND SW CARIBBEAN. THESE TRADE WINDS ARE FORECAST TO REMAIN FRESH TO STRONG THROUGH MONDAY AS THE SUBTROPICAL RIDGE REMAINS IN PLACE. HOWEVER...THIS SURFACE WIND REGIME WILL FLUCTUATE WITH THE APPROACH OF THE TROPICAL WAVE BEGINNING TO IMPACT THE LESSER ANTILLES THIS AFTERNOON AND EVENING. SCATTERED SHOWERS AND TSTMS ARE CONCENTRATED MAINLY E OF 64W AND ARE BEING ENHANCED BY AN UPPER LEVEL DIFFLUENT PATTERN DUE TO AN UPPER HIGH CENTERED NEAR 14N66W. IN THE FAR SW CARIBBEAN AND ACROSS WRN PANAMA...COSTA RICA AND ERN NICARAGUA...SCATTERED SHOWERS AND TSTMS ARE S OF A LINE FROM 9N80W TO 14N83W AND ALSO THE RESULT OF DIVERGENT FLOW ALOFT. ATLANTIC OCEAN... DEEP LAYER MOISTURE IS COMBINING WITH UPPER LEVEL DIFFLUENCE E OF AN UPPER LEVEL TROUGH ACROSS THE SE CONUS TO RESULT IN SCATTERED SHOWERS AND TSTMS ACROSS NRN FLORIDA AND A PORTION OF THE SW NORTH ATLC WATERS FROM 28N-32N BETWEEN 74W-78W. ELSEWHERE ACROSS THE SW NORTH ATLC...SUBSIDENCE AND GENERALLY FAIR WEATHER ARE PRESENT AS A SURGE RIDGE OF HIGH PRESSURE EXTENDS FROM THE BAHAMAS NEWD TO BEYOND 32N50W. THE CENTRAL ATLC WATERS ARE BEING INFLUENCED BY THE NRN EXTENT OF A TROPICAL WAVE S OF 21N ALONG APPROXIMATELY 60W WITH AN UPPER LEVEL LOW CENTERED NEAR 23N58W THAT IS ENHANCING SCATTERED SHOWERS AND TSTMS FROM 13N-18N BETWEEN 55W-62W. ALSO...UPPER DIFFLUENCE E OF THE UPPER TROUGH IS GENERATING POSSIBLE SCATTERED SHOWERS FROM 18N-25N BETWEEN 48W-56W. ELSEWHERE ACROSS THE CENTRAL AND E ATLC...A BROAD SURFACE RIDGE ASSOCIATED WITH A 1034 MB HIGH IS CENTERED NEAR THE AZORES. ACROSS THE TROPICAL ATLC...AN UPPER LEVEL RIDGE EXTENDS FROM THE CAPE VERDE ISLANDS NEAR 16N25W TO AN UPPER LEVEL HIGH NEAR 17N47W TO 14N54W. UPPER LEVEL DIVERGENCE ASSOCIATED WITH THE UPPER LEVEL RIDGE IS SUPPORTING THE CONVECTION ALONG THE ITCZ AND IN THE VICINITY OF THE TROPICAL WAVE IMPACTING THE LESSER ANTILLES. $$ HUFFMAN