000 AXNT20 KNHC 171816 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT TUE JUL 17 2007 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 1745 UTC. ...TROPICAL WAVES... A TROPICAL WAVE HAS BEEN ADDED ALONG 24W EXTENDING THROUGH THE CAPE VERDE ISLANDS. A 1010 MB LOW IS ALONG THE WAVE AXIS NEAR 15N MOVING W NEAR 18 KT. THE DAKAR RAOB SHOWED THE WAVE PASSAGE WELL YESTERDAY MORNING. NO DEEP CONVECTION IS IN THE VICINITY OF THE LOW...THOUGH SCATTERED MODERATE/ISOLATED STRONG IS EMBEDDED IN THE ITCZ FROM 9N-12N BETWEEN 20W-24W. TROPICAL WAVE IS ALONG 47W/48W S OF 17N. THIS WAVE WAS ADJUSTED SLIGHTLY TO THE E TO COINCIDE WITH THE MOST POLEWARD INFLECTION OF THE ITCZ...WHICH ALSO MESHES UP WELL WITH THE CREST OF HIGHER MOISTURE AS DENOTED BY THE UW-CIMSS SSMI DERIVED TOTAL PRECIPITABLE WATER PRODUCT. THIS WAVE PASSED DAKAR EARLY ON JULY 12 WHICH IMPLIES AN OVERALL WWD MOTION OF 6 DEGREES PER DAY...OR 15 KT. SCATTERED MODERATE CONVECTION IS WITHIN 150NM EITHER SIDE OF THE AXIS FROM 5N-9N. THE WAVE MAY ALSO BE ENHANCING THE CONVECTION ALONG THE ITCZ FURTHER W AS DESCRIBED BELOW. TROPICAL WAVE IS OVER THE CARIBBEAN ALONG 75/76W S OF 20N MOVING W 15-20 KT. THIS WAVE MAY NEED TO BE NUDGED FURTHER W AS PER THE WWD MOVING SURGE OF SHOWERS AND TSTMS MOVING INTO THE WRN CARIBBEAN BETWEEN 77W-84W. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 11N16W 10N22W 7N35W 11N45W 11N50W 6N58W. ISOLATED MODERATE CONVECTION IS WITHIN 60NM N AND 120NM S OF THE AXIS E OF 20W. IN ADDITION...A SMALL CLUSTER OF STRONG CONVECTION IS MOVING OFF THE AFRICAN COAST NEAR 14N17W. SCATTERED MODERATE WITHIN 90NM EITHER SIDE OF AXIS BETWEEN 38W-42W. NUMEROUS MODERATE...POSSIBLY ENHANCED BY THE APPROACHING TROPICAL WAVE...IS WITHIN 150 NM N/30NM S OF THE AXIS W OF 49W. ...DISCUSSION... GULF OF MEXICO... THE MOST ACTIVE WEATHER IN THE GULF THIS AFTERNOON LIES IN THE WRN PORTION JUST OFF THE TEXAS/MEXICO COAST. LIGHTNING DATA SUPPORTS SCATTERED TO NUMEROUS TSTMS N OF 20N W OF 92W. THIS ACTIVITY IS BEING SUPPORTED BY DIFFLUENCE AHEAD OF THE MID TO UPPER LEVEL LOW/TROUGH OVER NE MEXICO. IN ADDITION...SOME SUBTLE LOW LEVEL CONFLUENCE NOTED IN SATELLITE IMAGERY AND THIS MORNINGS QUIKSCAT PASS. DEBRIS MOISTURE OVER THIS CONVECTION IS SPREADING NE N OF 23N WITH UPPER SW FLOW...AND TO THE E/SE S OF 23N AROUND RIDGING. ELSEWHERE...A FEW ISOLATED SHOWERS/TSTMS NOTED IN THE FAR SE GULF. ON THE LARGE SCALE AT THE SFC...THE WRN PORTION OF AN ATLC SFC RIDGE CONTINUES TO DOMINATE AND IS GENERALLY EXPECTED TO PERSIST OVER THE NEXT COUPLE OF DAYS. CARIBBEAN SEA... SCATTERED SHOWERS/ISOLATED TSTMS ARE MOVING INTO THE WRN CARIBBEAN AND CENTRAL AMERICA BETWEEN 78W-85W. THIS ACTIVITY IS BEING SUPPORTED BY UPPER DIFFLUENCE SW OF AN UPPER LOW BETWEEN JAMAICA AND ERN CUBA AND LOW LEVEL SPEED CONVERGENCE. FURTHER UPPER DIFFLUENCE BETWEEN THE UPPER LOW AND UPPER RIDGING OVER THE ERN CARIBBEAN IS ALSO SUPPORTING THE SCATTERED MODERATE CONVECTION NEAR PUERTO RICO AND ADJACENT WATERS FROM 18N-21N BETWEEN 65W-70W. OTHERWISE MODERATE TO FRESH TRADES ARE IN PLACE ON THE SW PORTION OF AN ATLC SFC RIDGE AND EXPECTED TO PERSIST OVER THE NEXT COUPLE OF DAYS. UW-CIMSS SAHARAN AIR LAYER PRODUCT DEPICTS FAIRLY DENSE REGION OF AFRICAN DUST OVER THE E/CENTRAL CARIBBEAN. THE DUST MAY HAVE BEEN WHY ST. CROIX WAS REPORTING HAZE EARLIER THIS MORNING. ATLANTIC OCEAN... ISOLATED TSTMS ARE OVER THE FAR WRN ATLC W OF 77W UNDERNEATH AN UPPER HIGH. OVERALL THOUGH SFC RIDGING DOMINATES SW OF A 1030 MB HIGH PRES CENTER NEAR 35N49W. INVERTED SFC TROUGHING EMBEDDED IN THIS RIDGE IS ALONG 29N58W 23N61W 20N66W. THIS...ALONG WITH LIFT AHEAD OF THE MID TO UPPER LOW NEAR 29N63W...IS SUPPORTING SCATTERED SHOWERS/ISOLATED TSTMS N OF 20N BETWEEN 56W-63W. THE ACTIVITY NEAR PUERTO RICO IS DESCRIBED IN CARIB SECTION. THE AREA N OF 18N AND E OF 55W IS WIDELY DOMINATED BY FAIR WEATHER...SCATTERED LOW TO MID CLOUDS AND MODERATE TRADES. AN UPPER RIDGE AXIS IS EXTENDING N ALONG 55W WITH ANOTHER UPPER RIDGE OVER THE FAR ERN ATLC IN BETWEEN IS A WEAK UPPER TROUGH N OF 19N BETWEEN 35W-45W. DENSE AREA OF AFRICAN DUST NOTED OVER MUCH OF THE AREA E OF 40W. $$ WILLIS