000 AXNT20 KNHC 050004 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SAT AUG 04 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...TROPICAL WAVES... HIGH AMPLITUDE TROPICAL WAVE EXTENDS ACROSS THE WRN CAPE VERDE ISLANDS ALONG 25W S OF 23N MOVING W NEAR 15 KT. THIS WAVE CONTINUES TO EXHIBIT A LARGE WELL DEFINED AREA OF CYCLONIC TURNING IN THE LOW AND MID LEVEL CLOUDS. THE MOST PRONOUNCED ROTATION IS NOW PUSHING JUST W OF THE CAPE VERDE ISLANDS. DEEP CONVECTION REMAINS MINIMAL NEAR THIS ROTATION THOUGH. THE MORE PERSISTENT SCATTERED SHOWER/TSTM ACTIVITY HAS BEEN ACROSS THE SRN PORTION OF THE WAVE AND THE INTERSECTION OF THE ITCZ FROM 7N-12N BETWEEN 22W-30W. TROPICAL WAVE IS ALONG 42W S OF 18N MOVING W NEAR 15 KT. THIS WEAK WAVE REMAINS DIFFICULT TO LOCATE AS IT IS EMBEDDED IN THE FLOW OF THE LARGER WAVES TO IT'S E AND W. STABLE AIR AND BROKEN STRATOCUMULUS CLOUDS SURROUND THIS FEATURE. ISOLATED SHOWERS AND TSTMS NEAR THE AXIS S OF 12N ARE MORE LIKELY ASSOCIATED WITH THE ITCZ. HIGH AMPLITUDE TROPICAL WAVE IS ALONG 57W/58W MOVING W 15-20 KT. THIS LARGE-SCALE WAVE REMAINS FAIRLY EASILY SEEN WITH A PRONOUNCED INVERTED-V SHAPE NOTED IN THE LOW AND MID LEVEL CLOUD FIELD. ALTHOUGH DEEP CONVECTION REMAINS MINIMAL WITH THIS WAVE...THE FEATURE HAS GAINED MOISTURE COMPARED TO YESTERDAY AS IT IS INTERACTING WITH AN UPPER LOW NEAR 21N59W. THIS IS PRODUCING WIDESPREAD CLOUDINESS WITH SCATTERED SHOWERS N OF 15N WITHIN 250NM EITHER SIDE OF THE AXIS. STRONG TROPICAL WAVE IS MOVING THROUGH THE W CARIBBEAN AND CENTRAL AMERICA ALONG 85W S OF 24N MOVING W NEAR 20 KT. SINCE THE WAVE IS MOVING INLAND OVER CENTRAL AMERICA FURTHER DEVELOPMENT IS NOT ANTICIPATED. HOWEVER...THE WAVE IS EXPECTED TO BRING LOCALLY HEAVY RAINFALL AND GUSTY WINDS OVER PORTIONS OF CENTRAL AMERICA AND THE YUCATAN PENINSULA TONIGHT AND SUNDAY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS CURRENTLY FROM 13N-22N W OF 79W. A RECENT FLARE UP OF MODERATE TO STRONG CONVECTION IS ALSO OVER THE GUANACASTE REGION OF COSTA RICA. THE NRN PORTION OF A TROPICAL WAVE ALONG 95W EXTENDS ACROSS THE BAY OF CAMPECHE S OF 21N MOVING W 15-20 KT. THIS WAVE REMAINS WEAK WITH THE CURRENT PSN BASED MOSTLY ON A MODEST WWD SURGE OF MOISTURE NOTED ON THE UW-CIMSS TPW PRODUCT. SOME OF THE MOISTURE APPEARS TO BE ROTATING MORE NW AROUND THE RIDGING OVER THE GULF. SHOWERS AND TSTMS ARE OVERALL MINIMAL. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 16N15W 11N26W 10N40W 16N56W. BESIDES FOR THE CONVECTION DISCUSSED WITH THE TROPICAL WAVES...SCATTERED MODERATE TO STRONG CONVECTION IS NEAR THE COAST OF AFRICA FROM 11N-14N E OF 19W. SCATTERED MODERATE IS WITHIN 120NM N/150NM S OF THE AXIS BETWEEN 30W-40W. ISOLATED MODERATE IS FROM 8N-11N BETWEEN 46W-55W. ...DISCUSSION... THE GULF OF MEXICO... THE GULF IS FAIRLY QUIET THIS EVENING WITH A 1022 MB SFC HIGH S OF MOBILE NEAR 27N88W. ISOLATED SHOWERS STILL LINGER WITHIN 120 NM EITHER SIDE OF A BROWNSVILLE TO FLORIDA BIG BEND LINE BUT HAVE GENERALLY DIMINISHED OVER THE LAST SEVERAL HOURS. A SWATH OF UPPER MOISTURE NOTED IN THIS VICINITY AS WELL. VERY DRY MID TO UPPER AIR IS OVER THE GULF FROM 24N-28N E OF 90W THROUGH SOUTHERN FLORIDA...CONTRIBUTING TO THE NICE WEATHER THERE. INCREASING MOISTURE...CLOUDINESS...AND SHOWERS ARE NOW AFFECTING THE FAR ERN BAY OF CAMPECHE AND THE SRN GULF S OF 23N BETWEEN 84W-92W. THIS IS ASSOCIATED WITH THE NRN EXTENT OF THE STRONG TROPICAL WAVE MOVING THROUGH THE NW CARIBBEAN. THIS MOISTURE IS EXPECTED TO CONTINUE SPREADING INTO THE BAY OF CAMPECHE LATE TONIGHT AND TOMORROW AS THE WAVE CONTINUES W. HI PRES OVER THE NE GULF WILL KEEP WINDS LIGHT TO MODERATE OTHERWISE. THE CARIBBEAN SEA... THE MAIN FEATURE IN THE CARIB IS THE ACTIVE TROPICAL WAVE MOVING OVER THE NW PORTION AND CENTRAL AMERICA. FOR DETAILS REFER TO THE TROPICAL WAVES SECTION ABOVE. OTHERWISE...THIS REGION REMAINS RATHER TRANQUIL WITH UPPER NELY FLOW DRAWING DRIER AIR INTO MUCH OF THE CENTRAL AND ERN PORTIONS. THE ATMOSPHERE IS A LITTLE MORE MOIST ACROSS THE NRN LEEWARD ISLANDS AND PUERTO RICO...CLOSER TO AN UPPER LOW CENTER. RADAR DATA FROM SAN JUAN SHOWS QUICK MOVING STREAMS OF SHOWERS MOVING THROUGH THE AREA FROM THE ENE...LIKELY ASSOCIATED IN PART WITH LIFT FROM THE UPPER LOW IN ADDITION TO NORMAL LOW LEVEL TRADE WIND MOISTURE. AN INCREASE IN MOISTURE IS LIKELY OVER THE ERN CARIB OVER NEXT COUPLE OF DAYS AS THE LARGE TROPICAL WAVE IN THE TROPICAL ATLC APPROACHES. OTHERWISE MODERATE TO FRESH TRADES ARE IN PLACE AND EXPECTED TO PERSIST OVER THE NEXT COUPLE OF DAYS. THE ATLANTIC OCEAN... ON THE LARGE SCALE THE WRN ATLC IS QUIET THIS EVENING IN RESPONSE TO VERTICALLY STACKED RIDGING. A THIN CONVERGENCE LINE OF SHOWERS BETWEEN 27N79W AND 31N76W HAS MOSTLY DIMINISHED...BUT ANOTHER SIMILAR FEATURE HAS DEVELOPED FROM JUST OFFSHORE ST. AUGUSTINE TO NEAR 31N76W. THESE SHOWERS ARE DEVELOPING WITH CONFLUENT FLOW AHEAD OF THE WEAK SFC LOW PUSHING E FROM THE SOUTH CAROLINA COAST. DEEP MOISTURE HAS PERSISTED OVER THE ATLC BETWEEN 53W-69W. SOME OF THIS IS STILL ASSOCIATED WITH NLY UPPER FLOW DRAWING MOISTURE DOWN FROM AN OLD FRONTAL BOUNDARY N OF THE AREA...THOUGH THE LARGE AMPLITUDE TROPICAL WAVE ALONG 58W IS INCREASING THE MOISTURE IN THE VICINITY AS IT INTERACTS WITH THE UPPER LOW NE OF THE LEEWARD ISLANDS NEAR 21N59W. A WEAK 1016 MB SFC LOW IS S OF THE OLD FRONTAL BOUNDARY NEAR 31N62W. SCATTERED MODERATE CONVECTION IS JUST AHEAD OF THIS FEATURE FROM 30N-32N BETWEEN 58W-61W. THE REMAINDER OF THE UPPER PATTERN IS RATHER BENIGN WITH OVERALL LITTLE SIGNIFICANT MOISTURE BEING PRODUCED. OUTSIDE OF THE LARGE TROPICAL WAVES...THE REMAINDER OF THE SFC PATTERN IS DOMINATED BY A RIDGE EXTENDING FROM A 1027 MB HIGH NEAR 35N37W TO A 1020 MB CENTER NEAR 26N70W CONTINUING W INTO THE GULF. THE COMBINATION OF THIS HIGH PRES AND A LARGE AREA OF STABLE AIR ALOFT IS PRODUCING WIDESPREAD FAIR WEATHER N OF 18N E OF 50W. TYPICAL STABLE SCATTERED STRATOCUMULUS ARE THE MAIN SOURCE OF CLOUD COVER ACROSS THIS REGION. TRADES ARE MODERATE...EXCEPT NEAR THE CARIB ISLANDS AND THE COAST OF NW AFRICA WHERE THE TIGHTENED PRES GRAD IS PRODUCING SLIGHTLY STRONGER WINDS. $$ WILLIS