000 AXNT20 KNHC 210534 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SAT JUN 21 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0445 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 29W/30W S OF 11N MOVING W NEAR 20 KT. BROAD MID LEVEL INVERTED-V CURVATURE IS SHOWN ON SATELLITE IMAGERY AND THE MIMIC-TPW ANIMATION DEPICTS A MOISTURE SURGE BETWEEN 27W-32W. THE UPPER LEVEL FLOW IS KEEPING ANY CONVECTION TO THE W OF THE WAVE AXIS. TROPICAL WAVE IS IN THE E CARIBBEAN ALONG 68W/69W S OF 20N MOVING W NEAR 20 KT. SATELLITE IMAGERY SHOWS A BROAD LOW LEVEL INVERTED-V CURVATURE WITH THE MIMIC-TPW ANIMATION DEPICTS A MOISTURE SURGE 72W TO THE LESSER ANTILLES. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE FROM 14N-18N BETWEEN 67W-73W. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 7N10W 7N25W 5N34W 2N52W. THE ITCZ IS ACTIVE THIS EVENING W OF THE TROPICAL WAVE WHILE E OF THE WAVE IS RATHER TRANQUIL. CLUSTERS OF SCATTERED MODERATE/STRONG CONVECTION ARE FROM THE EQUATOR TO WITHIN 180 NM N OF THE AXIS BETWEEN 29W-40W AND CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM THE EQUATOR TO WITHIN 180 NM N OF THE ITCZ BETWEEN 40W-50W. ...DISCUSSION... GULF OF MEXICO... BROAD UPPER RIDGE REMAINS ANCHORED OVER NW MEXICO COVERING THE FAR W GULF WITH AN UPPER LEVEL SHORTWAVE TROUGH EXTENDING FROM THE LOWER MISSISSIPPI VALLEY TO THE BAY OF CAMPECHE. AN UPPER RIDGE ANCHORED IN THE W CARIBBEAN EXTENDS N OVER THE E GULF. MODERATE SUBSIDENCE ALONG THE MOST OF THE UPPER TROUGH AXIS MAINTAINING MOSTLY CLEAR CONDITIONS IN THE W GULF. UPPER LEVEL DIVERGENCE BETWEEN THIS TROUGH AND A RIDGE TO THE SOUTH IS GENERATING AN AREA OF SCATTERED SHOWERS/THUNDERSTORMS IN MAINLY IN THE E BAY OF CAMPECHE S OF 21N E OF 93W AND WITHIN 90 NM ALONG THE NW COAST OF CUBA BETWEEN 81W-85W. SCATTERED SHOWERS/ ISOLATED THUNDERSTORMS DOT THE NE GULF BETWEEN 26N29N BETWEEN 83W-89W. A WEAK PRESSURE PATTERN IS PROVIDING LIGHT WINDS ACROSS THE REGION. CARIBBEAN... AN UPPER RIDGE COVERS THE W CARIBBEAN ANCHORED BY AN UPPER HIGH INLAND OVER HONDURAS AND EXTENDS N INTO THE GULF OF MEXICO. AN UPPER TROUGH FROM THE W/CENTRAL ATLC EXTENDS ACROSS THE GREATER ANTILLES NEAR THE MONA PASSAGE TO JUST OFF THE COLOMBIAN COAST. MODERATE/STRONG SUBSIDENCE BETWEEN THE UPPER TROUGH AND RIDGE IS KEEPING THE CENTRAL CARIBBEAN RELATIVELY CLOUD FREE. THE TIGHTER PRESSURE GRADIENT BETWEEN THE SURFACE RIDGE OVER THE ATLC AND THE LOWER PRESSURE OVER SOUTH AMERICA IS PRODUCING MODERATE/ STRONG EASTERLY TRADE WINDS ACROSS THE BASIN WITH THE STRONGEST WINDS UP TO 30 KT JUST OFF THE COLOMBIAN COAST. ATLANTIC... THE BROAD UPPER TROUGH IS OVER THE E US JUST CLIPPING THE NW PORTION OF THE REGION WITH THE ASSOCIATED FRONTAL BOUNDARY NOT ENTERING THE REGION. AN UPPER LEVEL TROUGH EXTENDS FROM THE CENTRAL ATLC NEAR 32N36W SW TO A WEAK UPPER LOW NW OF LEEWARD ISLANDS THROUGH THE MONA PASSAGE INTO THE CARIBBEAN. THE RESULTING WEAK UPPER RIDGE BETWEEN THESE UPPER TROUGHS IS PROVIDING UPPER LEVEL DIFFLUENCE TO GENERATE CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS COVERING A BROAD AREA FROM WITHIN 120/150 NM OF LINE FROM 22N55W 26N63W TO 27N68W. THE ONLY LIMITING FACTOR IS THE RELATIVE DRY STABLE UPPER AIR ACROSS THE CENTRAL ATLC BETWEEN 30W-65W. AN UPPER HIGH IN THE E TROPICAL ATLC NEAR 10N27W IS KEEPING ANY CONVECTION THAT MIGHT BE ASSOCIATED WITH THE TROPICAL WAVE W OF THE WAVE AXIS. THE ATLC IS DOMINATED BY A SURFACE RIDGE THAT COVERS THE ENTIRE BASIN INTO THE E GULF OF MEXICO AND ANCHORED BY A SERIES OF HIGHS N OF THE REGION. $$ WALLACE