000 AXNT20 KNHC 182359 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS IN THE CARIBBEAN ALONG 70W S OF 18N MOVING W 15-20 KT. LAST FEW SATELLITE PICTURES FOR THE DAY SHOWS AN INVERTED-V LOW LEVEL CLOUD SIGNATURE ASSOCIATED WITH THE WAVE JUST SOUTH OF HISPANIOLA. SCATTERED SHOWERS ARE BETWEEN DOMINICAN REPUBLIC AND THE ABC ISLANDS. A TROPICAL WAVE IS OVER THE NW CARIBBEAN AND CENTRAL AMERICA ALONG 84W/85W S OF 20N MOVING W NEAR 10 KT. THE INTERACTION BETWEEN THIS WAVE AND REMNANT TROUGHING FROM AN OLD FRONTAL BOUNDARY IS PRODUCING A CLUSTER OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION FROM 16N-19N BETWEEN 82W-86W. LIGHTNING DATA SUPPORTS SCATTERED TSTMS IN THIS AREA. POCKETS OF SCATTERED MODERATE CONVECTION AREA OVER THE SW CARIBBEAN. UPPER DIFFLUENCE IN ENHANCING ALL THIS ACTIVITY. ...THE ITCZ... ITCZ IS CENTERED ALONG 10N15W 5N35W 6N50W 7N62W. THE ITCZ IS SOMEWHAT ACTIVE AIDED BY UPPER DIFFLUENCE. CLUSTERS OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION ARE MOVING OUT OF THE AFRICAN COAST THROUGH SIERRA LEONE AND LIBERIA. SIMILAR CONVECTION IS WITHIN 80-120 NM NORTH OF THE AXIS BETWEEN 23W-32W. WIDELY SCATTERED MODERATE CONVECTION IS WITHIN 80-100 NM N OF AXIS BETWEEN 39W-50W. DISCUSSION... THE GULF OF MEXICO... A RIDGE ANCHORED ON A 1024 MB HIGH OVER SOUTH GEORGIA DOMINATES THE GULF. PATCHES OF LOW/MID CLOUDS ARE NOTED OVER THE E GULF AND THE N PORTION OF THE YUCATAN PENINSULA. CONVECTION HAS FLARED UP OVER CENTRAL MEXICO WHILE A BAND OF SHOWERS WITH EMBEDDED TSTMS IS CROSSING THE NW QUADRANT OF THE GULF EXTENDING ROUGHLY FROM SE LOUISIANA TO JUST SOUTH OF BROWNSVILLE TEXAS. THIS MOISTURE IS ASSOCIATED WITH DIFFLUENCE ALOFT TO THE E OF A SHARP SHORTWAVE TROUGH LOCATED OVER CENTRAL TEXAS AND NORTHERN MEXICO...AIDED BY MOIST LOW-LEVEL RETURN FLOW. A COASTAL TROUGH WAS ANALYZED OVER NE MEXICO ON THE 2100 UTC MAP. A MID TO UPPER LEVEL RIDGE CONTROLS THE REMAINDER OF THE GULF WITH DRY AIR. CHANGES IN THE WEATHER PATTERN ARE IN STORE FOR THE GULF THIS WEEK. THE NEXT COLD FRONT IS FORECAST TO MOVES ACROSS THE AREA ON THU. GALE CONDITIONS ARE EXPECTED BEHIND THE COLD FRONT OVER THE SW PORTION OF THE GULF WED NIGHT AND THU. THE CARIBBEAN SEA... TWO TROPICAL WAVES ARE MOVING WWD ACROSS THE BASIN GENERATING SOME SHOWER/TSTM ACTIVITY. SEE TROPICAL WAVE SECTION. MODERATE TO STRONG TRADE WINDS OF 20-25 KT ARE NOTED BETWEEN THE WAVES AND MAINLY OFFSHORE THE COLOMBIAN COAST. N TO NE WINDS IN 20 KT RANGE ARE BLOWING ACROSS THE NW CARIBBEAN. THE REMNANTS OF AN OLD FRONTAL BOUNDARY STRETCHING ACROSS THE CENTRAL ATLC INTO DOMINICAN REPUBLIC IS STILL GENERATING SOME SHOWER ACTIVITY OVER HISPANIOLA AND NORTHERN COASTAL WATERS. THIS FEATURE IS FORECAST TO PUSH SOUTH ACROSS PUERTO RICO AND THE UK/US VIRGIN ISLANDS TONIGHT THROUGH MONDAY INCREASING THE CHANCE OF SHOWERS. THE SAN JUAN DOPPLER RADAR CURRENTLY DEPICTS SCATTERED SHOWERS AND ISOLATED TSTMS MAINLY N OF THOSE ISLANDS. ALOFT...BROAD RIDGE COVERS MOST THE CARIBBEAN SEA WITH A SHORT WAVE TROUGH ALONG 65W. ABUNDANT MID/UPPER LEVEL MOISTURE IS SEEN OVER THE BASIN WITH SUBSIDENCE AND IMPLIED DRY AIR OVER CENTRAL AMERICA. HIGH PRES N OF THE AREA WILL MAINTAIN BRISK TRADE WINDS NEAR THE COLOMBIAN COAST THROUGH MID WEEK. THE ATLANTIC OCEAN... FAIRLY ZONAL MID TO UPPER FLOW...BETWEEN A RIDGE OVER THE CARIBBEAN SEA AND AN UPPER TROUGH TO THE N...DOMINATES THE STATE OF FLORIDA AND MUCH OF THE W ATLC. DRY AIR RESULTING IN MODERATE TO STRONG SUBSIDENCE IS NOTED SOUTH OF 29N...INCLUDING THE BAHAMAS. AN UPPER SHORTWAVE TROUGH ALONG 49W/50W SUPPORTS THE THE STATIONARY FRONT THAT ENTERS THE REGION NEAR 31N47W THEN CONTINUES SW TO DOMINICAN REPUBLIC. A 1024 MB HIGH IS BEHIND THE FRONT CENTERED W OF BERMUDA NEAR 32N67W. A CLUSTER OF MODERATE CONVECTION IS AHEAD OF THE FRONT NEAR 28N47W. VERY NARROW DEEP LAYERED RIDGE IS OVER THE CENTRAL ATLC BETWEEN 40W-46W. EAST OF THIS RIDGE...A LARGE UPPER-LEVEL LOW IS SPINNING NEAR 33N30W. A COUPLE OF SFC LOWS WERE ANALYZED ON THE 1800 UTC MAP N OF AREA WITH A COLD FRONT EXTENDING ACROSS THE E ATLC ALONG 31N19W 24N23W 18N31W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE BETWEEN THE MADEIRA AND THE CANARY ISLANDS RELATED TO THE FRONT. MOSTLY ZONAL FLOW IS OVER THE TROPICAL ATLANTIC S OF 20N FROM THE LESSER ANTILLES TO W AFRICA. WV IMAGERY SHOWS A BAND OF TRANSVERSE HIGH CLOUDS ASSOCIATED WITH JET STREAM BRANCH WITH CORE WINDS OF NEAR 70 KT OVER THE TROPICAL ATLANTIC BETWEEN THE LESSER ANTILLES AND THE W COAST OF AFRICA. $$ GR