000 AXNT20 KNHC 180539 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 AM EST SUN NOV 18 2007 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN 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...METEOROLOGICAL ANALYSIS... WEATHER OBSERVATIONS...AND RADAR. BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS IN THE E CARIBBEAN ALONG 63W/64W S OF 17N MOVING W 15 KT. NIGHT CHANNEL VIS IMAGES SHOWS A FAINT AREA OF CYCLONIC TURNING IN THE THIN LOW-LEVEL CLOUD FIELD NEAR THE AXIS. SCATTERED SHOWERS TRAIL THE WAVE AXIS OVER THE WINDWARD AND SRN LEEWARD ISLANDS. A STRONGER BURST OF CONVECTION HAS FIRED UP TO THE W OF THE WAVE S OF HISPANIOLA FROM 15N-16N BETWEEN 67W-72W...BUT ITS NOT CLEAR IF THIS IS ASSOCIATED WITH THE WAVE...SOME SORT OF SURGE OR MID-LEVEL INSTABILITY. TROPICAL WAVE IS IN THE W CARIBBEAN ALONG 78W/79W S OF 17N MOVING W 10-15 KT. THE INTERACTION BETWEEN THIS WEAK WAVE...A WEAKENING FRONTAL BOUNDARY AND OVERALL LOW-LEVEL CONFLUENCE NEAR THE ITCZ IS PRODUCING SCATTERED SHOWERS AND TSTMS S OF 17N W OF 80W. ...THE ITCZ... ITCZ IS CENTERED ALONG 7N11W 4N25W 6N40W 8N52W 6N59W. THE ITCZ IS ACTIVE LIKELY AIDED BY AN UPPER JET N OF THE REGION. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM N AND 90 NM S OF THE AXIS BETWEEN 16W-27W. SIMILAR CONVECTION IS WITHIN 180 NM N OF THE AXIS BETWEEN 30W-46W AND 48W-53W. DISCUSSION... THE GULF OF MEXICO... SFC HIGH PRESSURE HAS NOW MOVED E OF THE AREA IN THE W ATLC. THIS HAS ALLOWED WINDS TO SHIFT E TO SE ACROSS THE REGION ...WHICH HAS GREATLY MODIFIED THE VERY COOL AIRMASS THAT WAS IN PLACE OVER THE PAST COUPLE OF DAYS. FAIR WEATHER DOMINATES MUCH OF THE AREA WITH SAT IMAGES ONLY SHOWING A SCATTERED TO BROKEN DECK OF STRATOCUMULUS CLOUDS IN THE CENTRAL AND ERN GULF. DEEPER MOISTURE IS AVAILABLE OVER CENTRAL MEXICO...E TEXAS AND THE FAR WRN GULF ASSOCIATED WITH DIFFLUENCE ALOFT TO THE E OF A SHARP SHORTWAVE TROUGH AND LIKELY AIDED BY MOIST LOW-LEVEL RETURN FLOW. DOPPLER RADAR AND LIGHTNING DATA REVEAL A FAIRLY IMPRESSIVE MCS OVER ERN TEXAS WITH ACTIVITY MORE ISOLATED IN THE WRN GULF WATERS. FLATTENED MID TO UPPER LEVEL RIDGING AND STABLE AIR CONTROL THE PATTERN ALOFT ACROSS THE REMAINDER OF THE REGION. THE CARIBBEAN SEA... A DISSIPATED STALLED FRONT EXTENDS ACROSS THE NW WATERS FROM THE WINDWARD PASSAGE TO BELIZE. THE INTERACTION BETWEEN THIS WEAK BOUNDARY...A TROPICAL WAVE TO THE S AND LOW-LEVEL CONVERGING FLOW NEAR THE COASTS OF COSTA RICA AND NICARAGUA ARE PRODUCING SCATTERED SHOWERS AND ISOLATED TSTMS S OF 17N W OF 80W. SWLY FLOW ALOFT ON THE UPWARD SIDE OF BROAD RIDGING IS ALSO SUPPORTING THAT ACTIVITY. A WEAKENING AREA OF CONVECTION S OF HISPANIOLA FROM 15N-16N BETWEEN 68W-72W COULD BE SOMEWHAT SUPPORTED BY LOW-LEVEL SPEED CONVERGENCE AS NOTED IN RECENT SCATTEROMETER PASSES. THESE PASSES INDICATE WINDS NEAR 25 KT IN THE VICINITY OF THE N COAST OF COLOMBIA. SCATTERED SHOWERS OVER THE WINDWARD AND SRN LEEWARD ISLANDS ARE LIKELY ASSOCIATED WITH A WEAK TROPICAL WAVE...SEE ABOVE FOR DETAILS. SIMILAR SHOWER ACTIVITY IS OVER HISPANIOLA TIED TO THE AFOREMENTIONED FRONT. THE ATLANTIC OCEAN... FAIRLY ZONAL MID TO UPPER FLOW...BETWEEN RIDGING TO THE S AND TROUGHING TO THE N...DOMINATES MUCH OF THE W ATLC. AN UPPER SHORTWAVE DIPS ALONG 54W SUPPORTING A COLD FRONT THAT STRETCHES FROM 32N51W TOWARD THE N COAST OF HISPANIOLA NEAR 21N70W. THE COMBINATION OF SFC HIGH PRES BEHIND THE FRONT AND A VERY DRY ENVIRONMENT ALOFT IS PROVIDING FAIR AND SEASONABLY COOL WEATHER ACROSS THE SW ATLC. SOME ACTIVE WEATHER LIES IN A DIFFLUENT ZONE ALOFT BETWEEN THE TROUGH AND A RIDGE AXIS ALONG 44W/45W. IR IMAGES AND LIGHTNING DATA REVEAL SCATTERED SHOWERS AND ISOLATED TSTMS N OF 24N BETWEEN 47W-54W. VERY NARROW DEEP LAYER RIDGING COVERS A SMALL PART OF THE ATLC BETWEEN 40W-47W. THE PATTERN QUICKLY CHANGES THEME IN THE E ATLC WHERE LARGE SCALE DEEP LAYER TROUGHING IS IN PLACE ANCHORED BY A SLOW MOVING LOW NEAR 35N30W. A 1010 MB SFC LOW HAS ALSO BEEN NEARLY STATIONARY W OF THE MADEIRA ISLANDS NEAR 34N21W WITH A COLD FRONT EXTENDING SW ALONG 24N24W 23N46W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE WITHIN 90 NM OF THE FRONT E OF 26W AND NEAR THE MAIN LOW N OF 29N BETWEEN 25W-32W. A SWLY JET BRANCH EXISTS NEAR THE BASE OF THE TROUGH AND THEN RUNS NE ALONG 11N44W 16N29W 28N14W. DIFFLUENCE TO THE SE OF THE JET IS GENERATING AND ADVECTING MID-HIGH LEVEL CLOUDINESS WITHIN 240 NM AND ENHANCING CONVECTION ALONG THE ITCZ. $$ CANGIALOSI