000 AXNT20 KNHC 192334 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SUN JUL 19 2009 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 2245 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 41W/42W S OF 19N MOVG W NEAR 20 KT. THIS WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. THIS WAVE IS JUST W OF A DRY SAHARAN AIR LAYER. DUE TO THE PRESENCE OF THIS DRY AIR...NO DEEP CONVECTION IS CURRENTLY ASSOCIATED WITH THE WAVE. A TROPICAL WAVE IS ALONG 52W S OF 18N MOVG W NEAR 15 KT. THIS WAVE COINCIDES WITH A LOW TO MIDDLE LEVEL CYCLONIC CIRCULATION NEAR THE WAVE AXIS AT 13N. SCATTERED MODERATE CONVECTION IS FROM 12N-15N BETWEEN 51W-54W. A HIGH AMPLITUDE TROPICAL WAVE IS ALONG 71W S OF 26N MOVG W 20-25 KT. THIS WAVE COINCIDES WITH A HIGH AMPLITUDE MOISTURE MAXIMUM OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY. AN INVERTED-V PATTERN OF LOW CLOUDS IS ALSO EVIDENT ON VISIBLE SATELLITE IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 16N-20N BETWEEN 69W-72W INCLUDING PORTIONS OF CUBA. THIS WAVE MAY FRACTURE OVER THE NEXT DAY WITH THE N PORTION OF THE WAVE FORMING A TROUGH THAT WILL CONTINUE TO THE NW...WHILE THE S PORTION OF THE WAVE CONTINUES TO PROPAGATE WWD. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 12N15W 7N27W 10N40W 10N51W 9N62W. SCATTERED MODERATE CONVECTION IS FROM 9N-13N BETWEEN 13W-17W. A CLUSTER OF NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS FROM 5N-9N BETWEEN 26W-29W. SCATTERED MODERATE CONVECTION IS FROM 7N-14N BETWEEN 60W-64W. ...DISCUSSION... THE GULF OF MEXICO... A STATIONARY FRONT IS OVER THE NRN GULF OF MEXICO ALONG 31N81W 28N88W 29N96W. AN UPPER LEVEL TROUGH EXTENDING DOWN THE ERN CONUS INTO THE GULF TO NEAR 26N90W SUPPORTS THE FRONT. SURFACE CONVERGENCE AHEAD OF THE FRONT ALONG WITH UPPER LEVEL DIFFLUENCE ARE SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM 24N-29N E OF 96W. THE REMAINDER OF THE GULF IS UNDER A BROAD SURFACE RIDGE ANCHORED BY A 1020 MB SURFACE HIGH NEAR 26N87W BRINGING GENERALLY FAIR WEATHER S OF 24N. A MID-LEVEL DRY SAHARAN AIR LAYER IS ACROSS THE SRN GULF OF MEXICO SUPPORTING THE NOTED FAIR WEATHER. LIGHT ANTICYCLONIC FLOW IS AROUND THE SURFACE RIDGE WITH E-SE WINDS UP TO 15 KT PRESENT ACROSS THE SRN GULF...EXCEPT FOR A SMALL PORTION OF NE WINDS UP TO 20 KT NEAR THE YUCATAN PENINSULA COAST. EXPECT THE FRONT TO STALL TONIGHT AND BECOME DIFFUSE TOMORROW. THE CARIBBEAN SEA... FAIR WEATHER IS NOTED IN THE FAR NW PORTION OF THE CARIBBEAN AS IT IS UNDER THE INFLUENCE OF A MID-LEVEL DRY SAHARAN AIR LAYER. HOWEVER...ATMOSPHERIC INSTABILITY IS CAUSING A FEW ISOLATED SHOWERS TO FLARE UP OVER CUBA AND THE YUCATAN PENINSULA. AN UPPER LEVEL RIDGE DOMINATES THE MAJORITY OF THE CARIBBEAN CENTERED NEAR 14N75W. UPPER LEVEL DIFFLUENCE AND THE PROXIMITY OF THE E PACIFIC ITCZ ARE SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS OVER CENTRAL AMERICA S OF 14N W OF 80W INCLUDING PORTIONS OF NICARAGUA...COSTA RICA...AND PANAMA. SURFACE CONVERGENCE AROUND A 1008 MB SURFACE LOW OVER COLUMBIA NEAR 8N76W IS SUPPORTING SCATTERED SHOWER/THUNDERSTORMS S OF 10N BETWEEN 75W-78W. UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL RIDGE OVER THE CARIBBEAN AND AN UPPER LEVEL LOW IN THE ATLC NEAR 27N55W IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS OVER THE ERN CARIBBEAN N OF 14N BETWEEN 63W-69W. THIS SHOWER ACTIVITY IS PROBABLY BEING ENHANCED BY THE TROPICAL WAVE ALONG 71W. SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO AFFECTING THE SRN LESSER ANTILLES S OF 14N W OF 62W DUE TO UPPER LEVEL DIFFLUENCE AND THE PROXIMITY OF THE ATLC ITCZ. EXPECT A SECOND TROPICAL WAVE TO REACH THE ERN CARIBBEAN EARLY TUE. THE ATLANTIC OCEAN... SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS S FLORIDA ENTERING THE ATLC AND APPROACHING THE BAHAMAS FROM 25N-29N W OF 79W. THIS SHOWER ACTIVITY IS SUPPORTED BY A SMALL UPPER LEVEL LOW OVER THE BAHAMAS NEAR 25N77W. UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL TROUGH OVER THE ERN CONUS AND AN UPPER LEVEL RIDGE CENTERED AROUND 39N54W IS SUPPORTING ISOLATED SHOWERS/THUNDERSTORMS ACROSS THE SW NORTH ATLC N OF 24N BETWEEN 68W-75W. THE REMAINDER OF THE ATLC IS DOMINATED BY A BROAD RIDGE ANCHORED BY A 1029 MB SURFACE HIGH N OF THE DISCUSSION AREA NEAR 35N46W BRINGING GENERALLY FAIR WEATHER ACROSS THE MAJORITY OF THE CENTRAL AND ERN ATLC. HOWEVER...A LINE OF SHOWERS ARE FROM 17N58W TO 24N50W DUE TO UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL HIGH NEAR 15N50W AND AN UPPER LEVEL LOW NEAR 27N55W. $$ WALTON