000 AXNT20 KNHC 042325 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT TUE JUL 04 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...TROPICAL WAVES... E ATLC TROPICAL WAVE IS ALONG 28W/29W S OF 15N MOVING W 10-15 KT. IT IS DIFFICULT TO PINPOINT ANY AXIS WITHIN A LARGE AREA OF ANOMALOUS LOW-LEVEL CYCLONIC FLOW FROM 20W-35W AND THE WAVE IS PUT AT THE LEADING EDGE OF THICKER MID/UPPER LEVEL CLOUDINESS. ISOLATED MODERATE CONVECTION IS WITHIN 60 NM OF LINE 8N22W 6N32W. THE GFS FORECASTS THE WAVE TO AFFECT THE LESSER ANTILLES ON SUN WITH SHOWERS/TSTMS. CENTRAL ATLC TROPICAL WAVE IS ALONG 43W/44W S OF 13N MOVING W 15 KT. THIS WAVE IS RATHER LOW-AMPLITUDE AND ITS EFFECTS ARE LIMITED TO THE ITCZ WHICH SHOWS A SLIGHT NORTHWARD BEND NEAR THE WAVE AXIS. ISOLATED SHOWERS ARE FROM 5N-10N BETWEEN 42W-48W. MOISTURE FROM THIS WAVE SHOULD BEGIN TO AFFECT THE WINDWARD ISLANDS ON THU AS THE WAVE ACCELERATES WESTWARD UNDER STRONG ELY FLOW OVER THE CENTRAL TROPICAL ATLC. CENTRAL CARIBBEAN TROPICAL WAVE IS ALONG 70W S OF 20N MOVING W 20 KT. WAVE IS RESPONSIBLE FOR WIDELY SCATTERED SHOWERS/TSTMS FROM 15N-23N BETWEEN PUERTO RICO AND 72W AND POSSIBLY FOR AN INCREASE IN TSTMS OVER NW VENEZUELA. AS THE WAVE LEAVES... DRIER CONDITIONS SHOULD BE OBSERVED OVER THE E CARIBBEAN TOMORROW WITH MOST EFFECTS ON WED W OF HISPANIOLA N OF JAMAICA. LOW-AMPLITUDE TROPICAL WAVE IS S OF 12N ALONG 85W OVER CENTRAL AMERICA INCREASING TSTMS IN THE EPAC ITCZ. ...ITCZ... ITCZ AXIS IS ALONG 13N16W 6N50W 9N61W. ISOLATED MODERATE CONVECTION IS FROM 6N-10N BETWEEN 33W-40W AND WITHIN 90 NM OF 6N30W. ISOLATED SHOWERS ARE FROM 4N-8N BETWEEN 47W-53W. ...DISCUSSION... GULF OF MEXICO... UPPER PATTERN HAS RETROGRESSED A BIT FROM YESTERDAY WITH UPPER RIDGING NOW ACROSS THE WESTERN GULF ALONG 93W/94W. DIFFLUENCE ON THE N END OF THE HIGH COMBINED WITH DAYTIME HEATING AND A PERSISTENT LOW OVER CENTRAL TEXAS HAS CAUSED A FEW SHOWERS/TSTMS OVER THE FAR NW GULF N OF 27N W OF 89W WITH MOST OF THE ACTIVITY INLAND. DRIER AIR ALOFT AND SUBSIDENCE IS BEING BROUGHT INTO THE E GULF BY AN UPPER LOW JUST E OF MIAMI WITH A NOTABLE ABSENCE OF TSTMS ACROSS MOST OF FLORIDA TODAY. LIGHT E TO SE WINDS ARE ACROSS THE REGION AND SHOULD REMAIN LIGHT FOR AT LEAST THE NEXT FEW DAYS. RELATIVELY WET CONDITIONS SHOULD REMAIN FOR THE NW GULF STATES FOR AT LEAST THE NEXT FEW DAYS AS THE PATTERN IS FORECAST TO CHANGE LITTLE. A WETTER DAY IS LIKELY FOR FLORIDA ON WED AS THE UPPER LOW MOVES INTO THE STRAITS OF FLORIDA. CARIBBEAN SEA... CYCLONIC FLOW AROUND THE UPPER LOW E OF MIAMI COVERS THE NORTHERN CARIBBEAN AND IS ALLOWING PLENTY OF DIURNAL TSTMS OVER THE GREATER ANTILLES. WEAK RIDGING IS OVER THE NW CARIBBEAN WITH LITTLE MOISTURE FOR SIGNIFICANT PRECIPITATION. UPPER TROUGH EXTENDS FROM THE LEEWARD ISLANDS TO THE SW CARIBBEAN WITH VERY DRY CONDITIONS ALOFT KEEPING THE AREA WITHOUT MANY SHOWERS. THE EXCEPTIONS TO THIS RULE ARE NEAR A TROPICAL WAVE AT 70W AND IN THE FAR SW CARIBBEAN WHERE SOME TSTMS HAVE RETURNED S AND W OF 11N80W. UPPER RIDGING IS EXPANDING NORTHWARD OVER THE E CARIBBEAN WITH LOTS OF HIGH CLOUDS AND A FEW SHOWERS. LARGE AREA OF DRIER AIR/AFRICAN DUST IS SEEN IN VISIBLE SATELLITE PICTURES FILTERING INTO THE E CARIBBEAN AND THIS SHOULD MAKES CONDITIONS LESS UNSTABLE BEHIND THE TROPICAL WAVE AT 70W FOR THE NEXT FEW DAYS.. SAVE A BRIEF WAVE PASSAGE IN THE WINDWARD ISLANDS FOR THU. THE BULK OF THE PRECIP BY LATE THU SHOULD BE IN THE SW AND NW CARIBBEAN WITH PROBABLY ONLY ISOLATED TRADEWIND SHOWERS IN THE NE CARIBBEAN OVER WATER. UPPER CONDITIONS ARE RATHER HOSTILE FOR TROPICAL CYCLONE DEVELOPMENT WITH STRONGER- THAN-AVERAGE WIND SHEAR AND LESS MOISTURE THAN TYPICAL OVER THE AREA. GALE CONDITIONS ARE FORECAST FOR TOMORROW INTO THU OVER THE CENTRAL CARIBBEAN AS THE ATLC RIDGE BUILDS IN STRONGLY BEHIND THE WAVE AT 70W. ATLANTIC OCEAN... GENERALLY UNSETTLED CONDITIONS ARE IN THE W ATLC WITH QUIETER WEATHER FARTHER E. BROKEN MULTI-LAYERED CLOUDINESS AND ISOLATED TSTMS ARE W OF 68W S OF 29N ASSOCIATED WITH A WEAK TROUGH OF LOW PRESSURE FROM CENTRAL CUBA THRU THE NW BAHAMAS AND INSTABILITY PROVIDED BY A MID/UPPER LOW E OF MIAMI. A SLOW SW DRIFT IS LIKELY FOR THE LOW AS UPPER HEIGHTS BUILD OVER THE SE USA. GENERALLY ZONAL FLOW ALOFT IS PRESENT E OF THE 70W WITH A WEAK TROUGH NOTED ALONG 26N56W SW TO THE LEEWARD ISLANDS.. THOUGH HAVING LITTLE EFFECT ON SENSIBLE WEATHER. THE STORY ACROSS MUCH OF THE REST OF THE AREA IS A NOTABLE LACK OF MOISTURE IN THE MID/UPPER LEVELS AS OBSERVED ON WATER VAPOR IMAGES N OF 15N E OF 60W. UPPER LOW IS NEAR 31N46W HEADED NORTHWARD OUT OF THE AREA WITH A HIGH NEAR 24N33W AND WEAK TROUGHING OVER THE NE ATLC. ELY FLOW ALOFT COVERS MUCH OF THE TROPICAL ATLC E OF 40W THOUGH LARGE-SCALE DRYNESS AND A LACK OF INSTABILITY ARE NOT ALLOWING ANY TROPICAL SYSTEM TO EVEN TRY TO GET GOING. SOME CHANGE TO THIS PATTERN SEEMS PLAUSIBLE IN A WEEK OR TWO AS THE CURRENT NEGATIVE MADDEN-JULIAN OSCILLATION (MJO) TYPE CONDITIONS LEAVE THE AREA... THOUGH THE MJO HAS NOT EXACTLY BEEN STRONG THIS SUMMER. FOR NOW HIGHER-THAN-AVERAGE SURFACE PRESSURES AND TRADEWINDS RULE MOST OF THE ATLANTIC. $$ BLAKE