000 AXNT20 KNHC 072355 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT THU AUG 07 2008 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...TROPICAL WAVES... A LOW AMPLITUDE TROPICAL WAVE IS JUST SOUTH OF THE CAPE VERDE ISLANDS ALONG 25W/26W WITH A 1009 MB LOW ALONG THE WAVE AXIS NEAR 12N MOVING W 10-15 KT. 850 MB SATELLITE DERIVED VORTICITY AND THE MIMIC-TPW FROM CIMSS ALSO SUPPORT THE WAVE POSITION. SCATTERED MODERATE CONVECTION IS MAINLY AHEAD OF THE WAVE AND NEAR THE INTERSECTION OF THE WAVE AND THE ITCZ FROM 8N-10N BETWEEN 26W-32W. SCATTERED SHOWERS ARE AROUND THE LOW CENTER. A HIGH AMPLITUDE TROPICAL WAVE IS ALONG 44W/45W FROM 12N-25N MOVING W NEAR 15 KT. THE WAVE CONTINUES TO SHOW A WELL DEFINED INVERTED-V CURVATURE ON SATELLITE IMAGERY. NO DEEP CONVECTION IS ASSOCIATED WITH THIS FEATURE. MAINLY LOW/MID CLOUDS AND ISOLATED SHOWERS ARE EITHER SIDE OF THE WAVE AXIS. THE TROPICAL WAVE PREVIOUSLY LOCATED ALONG 59W IS RELOCATED FURTHER E ALONG 55W S OF 13N BASED ON OBSERVATIONS...THE TPW PRODUCT AND 850 MB SATELLITE DERIVED VORTICITY. THIS IS A LOW AMPLITUDE TROPICAL WAVE. THE GFS MODEL SHOWS AN INCREASE IN MOISTURE ASSOCIATED WITH THE WAVE AS IT MOVES WWD ACROSS THE WINDWARD ISLANDS TOMORROW. MOISTURE WILL CONTINUE TO BUILD UP AS THE WAVE CROSSES THE E CARIBBEAN ON SAT. SCATTERED SHOWERS ARE NEAR THE INTERSECTION OF THE WAVE AN THE ITCZ. THE WAVE IS ALSO ENHANCING SOME SHOWER ACTIVITY OVER THE GUYANAS. TROPICAL WAVE IS ALONG 78W/79W S OF 20N MOVING W 10-15 KT. THE SAHARAN AIR LAYER FROM CIMSS REVEALS THAT THE WAVE IS AT THE LEADING EDGE OF A SURGE OF AFRICAN DUST WHICH COVERS THE E CARIBBEAN AND N OF THE GREATER ANTILLES MOVING INTO THE TURKS AND CAICOS. THE WAVE COUPLED WITH UPPER DIFFLUENCE IS ENHANCING CONVECTION OVER E CUBA...JAMAICA AND THE SW CARIBBEAN. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 13N16W 13N24W 10N30W 10N46W 8N58W. BESIDES THE CONVECTION MENTIONED ON THE TROPICAL WAVE SECTION... A CLUSTER OF MODERATE CONVECTION IS MOVING OFF THE AFRICAN COAST BETWEEN 13N-16N. SIMILAR CONVECTION IS FROM 5N-9N BETWEEN 45W-50W. ...DISCUSSION... GULF OF MEXICO... AN UPPER-LEVEL RIDGE ANCHORED OVER THE FOUR CORNER REGION DOMINATES THE N GULF WATERS WHILE AN UPPER-LEVEL TROUGH IS AMPLIFYING OVER THE EASTERN US. THIS TROUGH IS SUPPORTING A COLD FRONT THAT IS FORECAST TO REACH THE GULF COAST ON SATURDAY AND STALL SUN BEFORE DISSIPATING MON. THE SE GULF IS DOMINATED BY AN UPPER-LEVEL LOW CENTERED OVER THE WESTERN TIP OF CUBA. UPPER DIFFLUENCE BETWEEN THESE UPPER LEVEL FEATURES IS SUPPORTING THE DEVELOPMENT OF SCATTERED SHOWERS AND TSTMS OVER THE EASTERN PORTION OF THE GULF MAINLY S OF 26N AND OVER THE YUCATAN PENINSULA. SHOWERS AND TSTMS ARE ALSO AFFECTING THE SE U.S. AHEAD OF THE AFOREMENTIONED COLD FRONT THAT CURRENTLY EXTENDS ACROSS THE CAROLINAS AND THE TENNESSEE VALLEY. AT THE SURFACE... A RIDGE CENTERED ON A 1017 MB HIGH NEAR 28N93W AT 2100 UTC DOMINATES THE ENTIRE GULF REGION. AS THE FRONTAL BOUNDARY DIPS INTO THE SE U.S. LATE TONIGHT/FRI MORNING THE SURFACE RIDGE WILL WEAKEN AND MOVE S ACROSS THE CENTRAL GULF DURING THE UPCOMING WEEKEND. CARIBBEAN SEA... AN UPPER-LEVEL LOW IS SPINNING OVER WESTERN CUBA COVERING THE SE GULF AND THE NW CARIBBEAN. BROAD UPPER-LEVEL HIGH IS CENTERED JUST SOUTH OF HISPANIOLA WHILE ANOTHER UPPER-LEVEL LOW IS NE OF THE LEEWARD ISLANDS NEAR 19N56W. THE CYCLONIC FLOW ASSOCIATED WITH THIS SECOND UPPER LOW REACHES THE FAR E CARIBBEAN. UPPER LEVEL DIFFLUENCE COUPLED WITH THE CLOSE PROXIMITY OF THE EPAC ITCZ IS GENERATING SCATTERED SHOWERS AND THUNDERSTORMS OVER THE SW CARIBBEAN S OF 13N W OF 80W TO INLAND OVER COSTA RICA AND NICARAGUA. CONVECTION HAS FLARED UP OVER CUBA DUE TO THE PRESENCE OF THE ABOVE MENTIONED UPPER LOW. A DRIER AIR MASS COVERS THE E CARIBBEAN. MODERATE TO STRONG EASTERLY TRADE WINDS ARE BLOWING ACROSS THE BASIN. A TROPICAL WAVE NOW ALONG 55W WILL MOVE ACROSS THE WINDWARD ISLANDS TOMORROW BRINGING AN INCREASE IN THE LIKELIHOOD OF RAIN. ATLANTIC OCEAN... A WEAK 1015 MB LOW HAS DEVELOPED OVER THE CENTRAL BAHAMAS NEAR 25N76W ALONG THE SURFACE TROUGH THAT EXTENDS FROM 27N75W TO 24N78W. THIS LOW IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS OVER THAT AREA. ALOFT...THERE IS AN UPPER-LEVEL LOW OVER THE BAHAMAS COVERING THE W ATLC W OF 70W. A SECOND UPPER-LEVEL LOW IS CENTERED NEAR 19N56W. A BAND OF MULTILAYERED CLOUDS WITH POSSIBLE SHOWERS IS ON THE WESTERN SIDE OF THE LOW. THIS BAND OF MOISTURE MAY REACH THE N LEEWARD ISLANDS TOMORROW. A THIRD UPPER LOW IS OVER THE CENTRAL ATLC NEAR 27N44W. AN UPPER-LEVEL HIGH SITUATED NEAR 19N40W DOMINATES THE TROPICS AND IS SUPPORTING SOME CONVECTION ALONG THE ITCZ. OTHERWISE..THE ATLC IS DOMINATED BY MODERATE/STRONG SUBSIDENCE AND DRY SOMEWHAT STABLE AIR WITH A SURFACE RIDGE EXTENDING SW FROM A 1024 MB HIGH LOCATED NE OF THE AZORES. THE COMBINATION OF THE RIDGE AND LOWER PRES OVER AFRICA IS PRODUCING A SWATH OF NELY WINDS OF 20-25 KT BETWEEN THE MADEIRA/CANARY ISLANDS AND THE AFRICAN COAST. $$ GR