000 AXNT20 KNHC 271331 RRA TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT THU JUL 27 2006 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN 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...WEATHER OBSERVATIONS...RADAR... AND METEOROLOGICAL ANALYSIS. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1300 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ADDED TO THE 06 UTC SURFACE ANALYSIS ALONG 19W SOUTH OF 18N MOVING WEST NEAR 15 KT. THIS WAVE WAS ADDED BASED UPON THE LOW LEVEL CYCLONIC WIND SHIFT IN THE DAKAR SOUNDINGS BETWEEN 11 UTC AND 23 UTC YESTERDAY AND THE IMPRESSIVE LOW-MID LEVEL TURNING EVIDENT ON THE FIRST FEW VISIBLE PICTURES THIS MORNING. IN ADDITION...GFS HAS A GOOD HANDLE ON THIS WAVE ALREADY AND SUGGESTS THAT IT MAY BECOME HIGH AMPLITUDE IN THE NEXT DAY OR TWO. SCATTERED MODERATE CONVECTION IS EMBEDDED WITHIN THE ITCZ FROM 6N-13N BETWEEN 11W-31W. BASED UPON SATELLITE IMAGERY AND THE AVAILABLE DATA...THE TROPICAL WAVE IN THE EASTERN ATLANTIC PREVIOUSLY ALONG 31W AT 18 UTC YESTERDAY HAS BEEN DROPPED FROM THE SURFACE ANALYSIS. THIS FEATURE DOES NOT APPEAR TO HAVE BEEN A TROPICAL WAVE BUT RATHER SOME INSTABILITY LEFT BEHIND FROM THE BROAD HIGH AMPLITUDE WAVE 600-700 NM TO ITS WEST. A HIGH AMPLITUDE TROPICAL WAVE IS ALONG 46W SOUTH OF 21N MOVING WEST NEAR 20 KT. THIS LARGE WAVE REMAINS WELL DEFINED WITH CLEAR LOW-MID LEVEL TURNING EVIDENT ON SATELLITE IMAGERY. THE WAVE IS ENHANCING CONVECTION EMBEDDED WITHIN THE ITCZ FROM 5N-12N BETWEEN 35W-53W. THE NORTHERN EXTENSION OF THE WAVE HAS LIMITED SHOWER ACTIVITY AS IT IS EMBEDDED IN A DRY/STABLE ENVIRONMENT LIKELY DUE TO SAHARAN DUST. A HIGH AMPLITUDE TROPICAL WAVE IS IN THE EASTERN CARIBBEAN ALONG 66W SOUTH OF 23N MOVING WEST 15-20 KT. THIS WAVE HAS BEEN WELL-DEFINED OVER THE PAST SEVERAL DAYS. SHOWER AND TSTM ACTIVITY HAS INCREASED TODAY WITH PATCHES OF SCATTERED MODERATE CONVECTION MAINLY BEHIND THE WAVE AXIS ACROSS PUERTO RICO...THE VIRGIN ISLANDS...LEEWARD AND WINDWARD ISLANDS FROM 13-23N BETWEEN 60W-69W. AN INCREASE IN WINDS IS EVIDENT BEHIND THE WAVE AXIS BASED ON AN EARLIER QUIKSCAT PASS AND BUOY/SHIP OBS. FURTHER DEVELOPMENT IS NOT LIKELY TO OCCUR AS UPPER LEVEL WINDS ARE HIGHLY UNFAVORABLE. A WESTERN CARIBBEAN SEA TROPICAL WAVE IS ALONG 83W/84W SOUTH OF 18N MOVING WEST NEAR 15 KT. VERY LITTLE WAVE SIGNATURE IS NOTED ON SATELLITE IMAGERY. HOWEVER...THIS WAVE MAY BE AIDING IN TRIGGERING CLUSTERS OF MODERATE/STRONG CONVECTION EMBEDDED IN THE ITCZ ACROSS THE SOUTHERN CARIBBEAN FROM 5N-12N BETWEEN 73W-83W. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 11N15W 10N30W 11N45W TO INLAND OVER SOUTH AMERICA NEAR 10N63W TO PANAMA NEAR 9N82W. ALL OF THE SIGNIFICANT AREAS OF CONVECTION IS ASSOCIATED WITH OR ENHANCED BY TROPICAL WAVES AND IS DISCUSSED IN THE ABOVE SECTION. ...DISCUSSION... GULF OF MEXICO... THE SURFACE LOW THAT HAS BEEN MOVING NORTHWARD ALONG THE MEXICO/TEXAS COAST OVER THE PAST FEW DAYS HAS DISSIPATED. DURING THE OVERNIGHT HOURS...THERE WERE PATCHES OF MODERATE CONVECTION ACROSS PORTIONS OF NRN MEXICO...SOUTH TEXAS...WRN LOUISIANA AND THE COASTAL WATERS. SINCE THEN...MUCH OF THE ACTIVITY HAS WEAKENED CONSIDERABLY LEAVING ONLY SCATTERED SHOWERS AND TSTMS IN THE NW GULF W OF 93W N OF 23N. THESE LEFT OVER SHOWERS ARE CAUSED BY WEAK LOW LEVEL CONVERGENCE AND UPPER DIFFLUENCE BETWEEN AN UPPER HIGH IN THE CENTRAL GULF AND AN UPPER LOW OVER NRN MEXICO. THE UPPER HIGH IS ADVECTING SOME OF THE MOISTURE FROM THE W GULF ACROSS THE SE U.S. AND NRN GULF...HOWEVER MUCH OF IT IS MAINLY IN THE UPPER LEVELS. MOISTURE IS SLIGHTLY DEEPER WITH EMBEDDED SCATTERED SHOWERS/TSTMS ACROSS FLORIDA AND THE SE GULF AS THERE IS SOME UPPER DIFFLUENCE BETWEEN THE GULF OF MEXICO HIGH AND A TROUGH OFF THE SE U.S. AT THE SURFACE...RIDGING HAS BUILT ACROSS THE REGION FROM THE BERMUDA-AZORES HIGH TO A 1018 MB HIGH OVER THE FL/GA BORDER. SFC FLOW IS LIGHT ACROSS FLORIDA AND THE E GULF...STRONGER W OF 87W WHERE SE WINDS OF 15-20 KT ARE COMMON. THE REMNANT MOISTURE IN THE W GULF WILL CONTINUE TO DRIFT NWD AND BECOME ISOLATED. COMPUTER MODELS INCREASE MOISTURE SLIGHTLY OVER FLORIDA AND THE E GULF LATER TODAY ASSOCIATED WITH THE DIGGING UPPER TROUGH OFF THE U.S. EAST COAST. LITTLE CHANGE IN THE SURFACE PATTERN IS EXPECTED OVER THE NEXT FEW DAYS AS SFC RIDGING IS LIKELY TO REMAIN ESTABLISHED. CARIBBEAN SEA... TWO TROPICAL WAVES ARE IN THE CARIBBEAN SEA THIS MORNING. THE WESTERN-MOST WAVE IS ALONG 83W/84W ENHANCING CONVECTIVE ACTIVITY IN THE ITCZ ACROSS THE SOUTHERN CARIBBEAN. SEE THE TROPICAL WAVES SECTION FOR MORE DETAILS. THE OTHER WAVE...ALONG 66W...IS MORE IMPRESSIVE INTERACTING WITH AN UPPER LEVEL LOW IN THE ATLC TO PRODUCE A RATHER WIDE AREA OF SHOWERS AND TSTMS ACROSS THE LESSER ANTILLES AND PUERTO RICO FROM 13N-23N BETWEEN 60W-69W. PUERTO RICO DOPPLER RADAR SHOWS BANDS OF SHOWERS AND TSTMS MOVING WWD TO THE N OF THE ISLAND WITH A MUCH LARGER SHIELD OF MODERATE TO HEAVY RAIN OVER THE EASTERN PORTION OF PUERTO RICO AND THE VIRGIN ISLANDS. THIS WAVE WILL CONTINUE TO MOVE QUICKLY TO THE WEST...STEERED BY THE STRONG SFC HIGH...SPREADING MOISTURE ACROSS THE CENTRAL CARIBBEAN LATER TODAY AND WESTERN CARIBBEAN ON FRI. AN UPPER LOW IS MOVING TO THE WSW IN THE WRN CARIBBEAN CENTERED NEAR 18N86W. WEAK UPPER DIFFLUENCE BETWEEN THIS UPPER LOW AND THE GULF OF MEXICO UPPER HIGH IS TRIGGERING SCATTERED SHOWERS/ISOLATED TSTMS OVER SOUTH CUBA AND THE CAYMAN ISLANDS FROM 19N-21N BETWEEN 76W-86W. TRADE WINDS ARE GENERALLY IN THE 15-20 KT RANGE WITH SOME SLIGHTER STRONGER WINDS OFF THE COAST OF COLOMBIA AND POSSIBLY IN THE CONVECTION ACROSS THE LESSER ANTILLES. ATLANTIC OCEAN... A BERMUDA-AZORES SURFACE RIDGE RUNS FROM A 1027 MB HIGH PRESSURE CENTER OVER THE AZORES TO A 1030 MB HIGH IN THE CENTRAL ATLC NEAR 34N54W ACROSS BERMUDA INTO THE CENTRAL GULF OF MEXICO. A WEAK BENIGN 1021 MB SURFACE LOW PRESSURE CENTER IS CONTAMINATING THE RIDGE NEAR 30N31W AS IT DRIFTS SWD. IN THE UPPER LEVELS...A TROUGH OFF THE SE U.S. INTERACTING WITH AN UPPER HIGH IN THE GULF IS PRODUCING A CONSIDERABLE AMOUNT OF UPPER LEVEL MOISTURE W OF 72W N OF 24N. ONLY SCATTERED SHOWERS AND ISOLATED TSTMS ARE EMBEDDED IN THIS MOISTURE PLUME. A WELL-DEFINED UPPER LOW IS CENTERED NEAR 27N65W. THIS UPPER LOW IS INTERACTING WITH THE EASTERN CARIBBEAN TROPICAL WAVE TO PRODUCE A LARGE AREA OF SCATTERED MODERATE CONVECTION. SEE THE CARIBBEAN SECTION FOR MORE DETAILS. A VERY WEAK DRY UPPER LOW IS MOVING NWD OUT OF THE DISCUSSION AREA NEAR 33N56W. A BROAD UPPER RIDGE COVERS A LARGE PORTION OF THE ATLC N OF 10N BETWEEN 18W AND 55W. MIDDLE TO UPPER LEVEL DRY/STABLE AIR IS NORTH OF 14N BETWEEN 25W AND 55W. AN UPPER TROUGH CLIPS THE AREA E OF 18W N OF 27N. A WIDESPREAD AREA OF DENSE SAHARAN DUST EXTENDS OUT TO ABOUT 65W...BEHIND THE E CARIBBEAN TROPICAL WAVE. THE COMBINATION OF THE DRY/STABLE ATMOSPHERE FROM THE SAHARAN DUST AND SUBSIDENCE FROM UPPER RIDGING IS SUPPRESSING ANY SIGNIFICANT CONVECTION IN THE ATLC N OF THE ITCZ. $$ CANGIALOSI