000 AXNT20 KNHC 181037 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT SUN JUL 18 2010 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1000 UTC... ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 56W FROM 9N TO 20N MOVING W NEAR 15 KT. A BROAD AREA OF LOW PRESSURE IS ASSOCIATED WITH THIS WAVE CENTERED ABOUT 565 NM EAST OF THE WINDWARD ISLANDS. CURRENTLY... THIS SYSTEM IS PRODUCING LIMITED SHOWER ACTIVITY...AND ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE UNFAVORABLE FOR SIGNIFICANT DEVELOPMENT DURING THE NEXT COUPLE OF DAYS AS THE AREA OF LOW PRES MOVES WEST-NORTHWESTWARD. THE WAVE REMAINS EMBEDDED WITHIN AN AREA OF DEEP LAYER MOISTURE AS DEPICTED ON THE TOTAL PRECIPITABLE WATER ANIMATION. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS WITHIN ABOUT 120 NM EITHER SIDE OF AXIS PARTICULARLY FROM 15N TO 20N. THIS WAVE WILL ENTER THE CARIBBEAN SEA TONIGHT BRINGING AN INCREASE IN SHOWER AND TSTM ACTIVITY ESPECIALLY ACROSS THE LEEWARD ISLANDS AND THEN OVER PUERTO RICO AND THE US/UK VIRGIN ISLANDS BY MON. EARLY THIS MORNING...SHOWERS AHEAD OF THE TROPICAL WAVE ARE BEGINNING TO REACH THE LEEWARD ISLANDS. 24-HOUR PRESSURE CHANGE IS 2 MB JUST E OF THE LEEWARD ISLANDS IN ASSOCIATION WITH THIS TROPICAL WAVE. TROPICAL WAVE IS OVER THE EASTERN CARIBBEAN ALONG 70W/71W WITH AXIS EXTENDING FROM EASTERN DOMINICAN REPUBLIC TO WESTERN VENEZUELA NEAR 10N70W MOVING W ABOUT 10 KT. THE WAVE IS HELPING TO INDUCE CONVECTION JUST SOUTH OF HISPANIOLA AND OVER WESTERN VENEZUELA. THIS WAVE WILL MOVE THROUGH THE CENTRAL CARIBBEAN TODAY AND THROUGH THE W CARIBBEAN MON AND TUE. TROPICAL WAVE IS OVER THE WESTERN CARIBBEAN ALONG 80W/81W FROM 11N TO 21N MOVING W AT ABOUT 5 KT. THE WAVE IS GENERATING SCATTERED SHOWERS AND TSTMS OVER THE CAYMAN ISLANDS...AND THE SW CARIBBEAN WHERE A BROAD AREA OF LOW PRES IS ALSO NOTED. THE WAVE WILL REACH THE YUCATAN PENINSULA LATE TONIGHT. ...ITCZ... THE ITCZ AXIS IS ALONG 11N15W 7N30W 8N40W 10N52W INTO FAR NE VENEZUELA. A WEAK 1009 MB LOW PRES...LIKELY ASSOCIATED WITH THE NEXT TROPICAL WAVE...IS MOVING OUT OF AFRICA THROUGH SENEGAL. CURRENTLY...DAKAR IS REPORTING NE WINDS AND LIGHT RAIN. THE HOVMOLLER DIAGRAM SHOWS THE WESTWARD PROPAGATION OF THIS SYSTEM DURING THE PAST FEW DAYS. CLUSTERS OF MODERATE TO ISOLATED STRONG CONVECTION ARE FROM 9N-13N E OF 12W...AND FROM 4N-9N BETWEEN 20W-25W. ...DISCUSSION... GULF OF MEXICO... THE SURFACE TROUGH THAT HAS BEEN GENERATING SOME SHOWER ACTIVITY ACROSS THE REGION OVER THE PAST FEW DAYS IS BEGINNING TO WEAKEN OVER THE SW GULF AS HIGH PRES FROM THE ATLC CONTINUES TO BUILD WWD ACROSS THE N GULF WATERS. AT 18/0900 UTC...THE TROUGH EXTENDS FROM 24N95W TO 18N94W. A FEW SHOWERS ARE NEAR THE TROUGH AXIS HEADING TO THE COAST OF MEXICO S OF TAMPICO. SCATTERED SHOWERS AND ISOLATED TSTMS ARE NEAR THE SOUTHERN END OF THE TROUGH AXIS BETWEEN VERACRUZ AND COATZACOALCOS. ABUNDANT MID/UPPER LEVEL MOISTURE IS NOTED ON WATER VAPOR IMAGERY ACROSS MUCH OF THE GULF REGION. A DRYER AIR MASS IS SEEN W OF THE SURFACE TROUGH EXPECTED TO DISSIPATE TONIGHT. AN UPPER-LEVEL LOW REMAINS CENTERED NEAR SW FLORIDA GENERATING SCATTERED SHOWERS AND TSTMS ACROSS THE STRAITS OF FLORIDA AND PORTIONS OF WESTERN CUBA. ANOTHER TROUGH IS FORECAST TO ENTER THE EASTERN GULF LATE MON. CARIBBEAN SEA... VERY UNSTABLE ATMOSPHERIC CONDITIONS PERSIST OVER THE CARIBBEAN SEA DUE TO A PAIR OF TROPICAL WAVES AND THE PRESENCE OF A BROAD AREA OF LOW PRES OVER THE SW CARIBBEAN. SEE TROPICAL WAVE SECTION FOR MORE DETAILS. A DIFFLUENT PATTERN ALOFT BETWEEN AN UPPER LEVEL RIDGE OVER THE CENTRAL CARIBBEAN AND AN UPPER-LEVEL LOW SPINNING N OF PUERTO RICO IS HELPING TO INDUCE CONVECTION ACROSS THE AREA...PARTICULARLY BETWEEN TROPICAL WAVES. A WEAK SURFACE TROUGH IS ALONG THE YUCATAN/BELIZE COASTLINES. SOME SHOWER ACTIVITY IS OVER BELIZE. E TO SE WINDS OF 15 KT ARE BLOWING ACROSS THE GULF OF HONDURAS BEHIND THE TROUGH AXIS. ATLANTIC OCEAN... ALOFT...AN UPPER-LEVEL LOW IS SPINNING NEAR SW FLORIDA WITH THE CYCLONIC FLOW COVERING THE PENINSULA AND THE NW BAHAMAS. ANOTHER UPPER-LEVEL LOW IS N OF PUERTO RICO NEAR 26N66W. MOST OF THE CONVECTIVE ACTIVITY ASSOCIATED WITH THIS SYSTEM HAS MOVED N AND AWAY FROM PUERTO RICO LEAVING THE ISLAND UNDER A MORE STABLE AND LESS HUMID ATMOSPHERE. BETWEEN LOWS...THERE IS AN UPPER-LEVEL RIDGE EXTENDING S TO ACROSS EASTERN CUBA AND INTO THE CENTRAL CARIBBEAN. A RIDGE...ANCHORED ON AN UPPER-LEVEL HIGH LOCATED NEAR 21N53W DOMINATES THE TROPICAL ATLC W OF 34W. AN INVERTED TROUGH IS NOTED OVER THE CAPE VERDE ISLANDS. AT THE SURFACE... THE BERMUDA-AZORE HIGH DOMINATES THE BASIN WITH THE RIDGE EXTENDING SW ACROSS THE ATLANTIC OCEAN THEN MAINLY W TO THE SE CONUS INTO THE EASTERN GULF OF MEXICO. TRADE WINDS ON THE SOUTHERN PERIPHERY OF THE RIDGE ARE IN THE 15 TO 20 KT RANGE TRANSPORTING PATCHES OF LOW LEVEL MOISTURE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GR