000 AXNT20 KNHC 161809 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT MON JUL 16 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 1715 UTC. ...TROPICAL WAVES... CENTRAL ATLANTIC TROPICAL WAVE IS TILTED ALONG AXIS 18N40W 2N45W...MOVING WEST 20 KT. THIS REMAINS A VERY LARGE AMPLITUDE WAVE WITH VISIBLE SATELLITE IMAGERY INDICATING BROAD TURNING IN THE STRATOCUMULUS FIELD BETWEEN 35W AND 50W. THE WAVE IS PRECEDED BY A LARGE AREA OF SAHARAN DUST AS INDICATED BY CIMSS ANALYSES. SURFACE OBSERVATIONS FROM MARTINIQUE AND DOMINICA INDICATED HAZE AS WELL. THIS DUST WAS INHIBITING DEEP CONVECTION WITH THE EXCEPTION OF SCATTERED MODERATE CONVECTION NEAR THE INTERSECTION OF THE WAVE AXIS AND ITCZ FROM 4N TO 6N BETWEEN 45W AND 51W. TILTED TROPICAL WAVE OVER THE FAR SW ATLANTIC AND EAST-CENTRAL CARIBBEAN ALONG 22N64W 11N70W MOVING WEST 15 KT. THE 1200 UTC RAOB FROM SAN JUAN SUGGESTED THE WAVE HAD JUST PASSED TO THE WEST OF THE STATION WITH INCREASED LOW LEVEL WINDS. IN ADDITION PRECIPITABLE WATER VALUES HAVE INCREASED TO 2.12 INCHES. THE WAVE IS UNDER THE INFLUENCE OF AN UPPER LEVEL TROUGH OVER THE SOUTHWEST NORTH ATLANTIC WITH DIFLUENT FLOW E OF THE TROUGH AXIS MAINTAINING SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 120 NM EITHER SIDE OF THE WAVE AXIS AND NORTH OF 16N. SHOWER AND THUNDERSTORM ACTIVITY HAS ALSO SPREAD TO PORTIONS OF THE DOMINICAN REPUBLIC AS WELL. THE NORTHERN EXTENSION OF AN EAST PACIFIC TROPICAL WAVE ALONG 96W IS OVER THE EXTREME SOUTHERN BAY OF CAMPECHE AND WAS TRIGGERING SCATTERED SHOWER AND ISOLATED THUNDERSTORM ACTIVITY OVER THE BAY OF CAMPECHE. THE PORTION OF THE WAVE WHICH EXTENDED INTO THE EAST PACIFIC WAS MORE ACTIVE WITH WELL DEFINED TURNING IN THE LOW AND MID LEVEL CLOUDS JUST TO THE SOUTHWEST OF THE GULF OF TEHUANTEPEC. ...THE ITCZ... AXIS OF THE ITCZ IS ALONG 11N16W 9N25W 11N41W 5N53W. OTHER THAN THE CONVECTION DESCRIBED IN ASSOCIATION WITH THE TILTED WAVE ALONG 18N40W 2N46W...SCATTERED MODERATE THUNDERSTORMS WERE NOTED ELSEWHERE WITHIN 90-120 NM OF THE WAVE AXIS BETWEEN 26W AND 42W. ...DISCUSSION... THE GULF OF MEXICO... EXTENSION OF AN ATLANTIC SURFACE RIDGE IS FROM SOUTH FLORIDA/FLORIDA STRAITS THROUGH 24N90W TO THE EAST CENTRAL COAST OF MEXICO NEAR TAMPICO. HIGHLY AMPLIFIED FLOW REMAINS OVER THE CONUS WITH THE AXIS OF A SHARP UPPER LEVEL RIDGE ALONG 110W WITH THE DOWNSTREAM TROUGH EXTENDING FROM THE SOUTHERN ILLINOIS SOUTHWARD ALONG THE TEXAS COAST TO NEAR 23N95W. A DEVELOPING CYCLONIC CIRCULATION WAS NOTED OVER SOUTHEAST TEXAS. THE ASSOCIATED SOUTHWESTERLY UPPER LEVEL FLOW AND UPPER DIFFLUENCE COVERED THE NORTHWESTERN HALF OF THE GULF OF MEXICO. AS A RESULT SCATTRED MODERATE TO STRONG THUNDERSTORMS CONTINUED ALONG A SURFACE TROUGH WHICH EXTENDED FROM JUST EAST OF BROWNSVILLE TEXAS TO SOUTHEAST LOUISIANA COAST. THE LIGHTNING DATA HAS REMAINED ACTIVE OVER THE PAST SEVERAL HOURS. A NARROW RIDGE AXIS BETWEEN ANTICYCLONES OVER THE ISTHMUS OF TEHUANTEPEC AND THE NORTH CENTRAL ATLANTIC WAS OVER SOUTH FLORIDA...THE FLORIDA STRAITS AND EXTREME SE GULF. THE CARIBBEAN SEA... A RATHER LARGE MID TO UPPER LEVEL ANTICYCLONE OVER THE ISTHMUS OF TEHUANTEPEC DOMINATED THE FLOW OVER THE CARIBBEAN WEST OF 85W. THIS ANTICYCLONE WAS SEPARATING FROM A MUCH LARGER ANTICYCLONE OVER THE CONNECTED TO THE ANTICYCLONE OVER THE WESTERN ATLANTIC OCEAN. THE BASE OF A MID TO UPPER LEVEL TROUGH WAS SPREADING WESTWARD OVER THE CARIBBEAN AND ENTERED THE BASIN OVER EXTREME EASTERN CUBA AND EXTENDED SOUTHWARD TO 12N81W WITH A FAIRLY LARGE CYCLONIC CIRCULATION NOTED OVER THE WINDWARD PASSAGE NEAR 20N74W. A BROAD SWATH OF AMPLIFYING SOUTHERLY FLOW AT THE MID AND UPPER LEVELS COVERS THE AREA SOUTHEAST OF THE UPPER TROUGH AND 73W. THIS DIFLUENT FLOW REGIME WAS ENHANCING SCATTERED MODERATE TO STRONG CONVECTION ALONG THE TROPICAL WAVE OVER THE EAST CENTRAL CARIBBEAN. AN EASTERLY SURGE IN THE WAKE OF THE TROPICAL WAVE WAS MOVING INTO THE FAR EASTERN CARIBBEAN AND WAS ACCOMPANIED BY SOME SAHARAN DUST. SCATTERED MODERATE THUNDERSTORMS WERE OCCURRING OVER THE EXTREME SOUTHWEST CARIBBEAN SOUTH OF 10N TO THE COAST OF PANAMA. ELSEWHERE ONLY LOW TOPPED SHOWERS AND ISOLATED THUNDERSTORMS WERE NOTED OVER THE CARIBBEAN. THE ATLANTIC OCEAN... A PERSISTENT POSITIVELY TILTED MID TO UPPER LEVEL TROUGH EXTENDS FROM A MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER NEAR 30N59W THROUGH 26N65W TO A SECOND CYCLONIC CENTER OVER THE WINDWARD PASSAGE. WIDELY SCATTERED MODERATE CONVECTION IS NOTED IN ASSOCIATION WITH THE SECOND CYCLONIC CIRCULATION OVER CUBA. AN EXPANDING ANTICYCLONE WAS NOTED OVER THE TROPICAL ATLANTIC NEAR 18N50W WITH A SMALLER ANTICYCLONE NEAR 18N30W. BOTH FEATURES DOMINATED THE AREA BETWEEN THE AFRICAN COAST AND 60W. A SHEARED EASTERN ATLANTIC MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM 32N10W TO 27N27W 27N35W. SURFACE ANTICYCLONIC FLOW IS NORTH OF 20N BETWEEN AFRICA AND 80W. $$ COBB