000 AXNT20 KNHC 062345 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SAT OCT 06 2012 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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2245 UTC. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 17N28W TO 9N27W MOVING W AT 15 KT. THE WAVE IS EMBEDDED WITHIN BROAD CYCLONIC FLOW AROUND THE MONSOON TROUGH THAT IS CENTERED NEAR THE SOUTHERN EXTENT OF THE WAVE WHERE A SPOT 1010 MB SURFACE LOW HAS BEEN ANALYZED. THE WAVE LIES ON THE WESTERN SIDE OF A SURGE OF DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. CONVECTION IS CURRENTLY RESTRICTED TO THE MONSOON TROUGH REGION NEAR THE LOW PRESSURE CENTER. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 3N-9N BETWEEN 24W-28W...AND FROM 7N-11N BETWEEN 28W-34W. TROPICAL WAVE IN THE CENTRAL CARIBBEAN IS FROM 18N69W TO 12N70W MOVING W AT 15-20 KT. THE WAVE IS LARGELY AN EXTENSION OF LOW-LEVEL TROUGHING FROM A 1007 MB SURFACE LOW CENTERED NORTH OF THE MONA PASSAGE NEAR 22N67W COMBINED WITH ENERGY THAT HAS ROTATED AROUND THE PERIPHERY OF A MID-LEVEL RIDGE ANCHORED OVER THE SW NORTH ATLC DURING THE PAST WEEK. ONLY A FEW SHOWERS/THUNDERSTORMS ARE OVER HISPANIOLA AT THE NORTHERN EXTENT OF THE WAVE. LARGE CLUSTERS OF STRONG CONVECTION ARE TO THE SOUTH OVER VENEZUELA. TROPICAL WAVE EXTENDS FROM THE NW CARIBBEAN AT 19N84W TO THE SW CARIBBEAN AT 11N78W MOVING W AT 15-20 KT. THE WAVE IS EMBEDDED WITHIN AN AREA OF DEEP LAYER MOISTURE ACROSS THE SW CARIBBEAN MOSTLY SOUTH OF 14N AS INDICATED BY TOTAL PRECIPITABLE WATER IMAGERY. THE SOUTHERN PORTION OF THE WAVE IS ALSO EMBEDDED WITHIN BROAD MONSOONAL FLOW AS THE E PACIFIC MONSOON TROUGH EXTENDS ACROSS COSTA RICA TO THE BASE OF THE WAVE. SCATTERED MODERATE CONVECTION IS FROM 10N-12N BETWEEN 77W-81W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA TO THE COAST OF GUINEA-BISSAU AT 12N16W CONTINUING TO THE BASE OF A TROPICAL WAVE AT 9N27W AND ALONG 10N36W 9N42W. MOST OF THE CONVECTION NEAR THE MONSOON TROUGH HAS BEEN TIED TO THE TROPICAL WAVE. A LARGE CLUSTER OF MODERATE/STRONG CONVECTION IS ALSO MOVING OFF THE COAST OF AFRICA FROM 7N-11N BETWEEN 9W-14W. A CLUSTER OF STRONG CONVECTION IS ALSO FROM 4N-6N BETWEEN 19W-21W. ...DISCUSSION... GULF OF MEXICO... MAINLY WESTERLY FLOW ALOFT COVERS THE MAJORITY OF THE GULF OF MEXICO AROUND THE BASE OF A BROAD UPPER LEVEL TROUGH COVERING MUCH OF THE UNITED STATES. A WEAK SHORTWAVE TROUGH EXTENDS DOWN THE EXTREME WESTERN EDGE OF THE BASIN NEAR THE MEXICO COAST SUPPORTING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS IN THE SW GULF FROM 18N-22N BETWEEN 91W-96W. SIMILAR ACTIVITY ALSO COVERS MUCH OF THE SOUTHEASTERN GULF AS WELL DUE TO MORE MOIST SOUTHWESTERLY FLOW ALOFT ACROSS THIS PORTION OF THE BASIN. SOME STRONGER SHOWERS/THUNDERSTORMS ARE ACROSS THE FLORIDA PENINSULA NEAR A DIURNAL SURFACE TROUGH THAT HAS FORMED OVER THE PENINSULA DUE TO SEABREEZE CONVERGENCE. THE NORTHERN GULF IS MOSTLY DRY AND CLEAR DUE TO STRONG DRY AIR AND SUBSIDENCE ALOFT. DESPITE BROAD SURFACE RIDGING ACROSS MUCH OF THE UNITED STATES...A FRONTAL BOUNDARY IS APPROACHING THE BASIN AND IS CURRENTLY JUST INLAND OF THE GULF COAST. IT IS STATIONARY FOR THE TIME BEING DUE TO THE BROADNESS OF THE UPPER TROUGH. HOWEVER...AS A SHORTWAVE TROUGH MOVES THROUGH THE LONGWAVE IT WILL GIVE THE FRONT ENOUGH PUSH TO MAKE INTO THE BASIN LIKELY IN THE OVERNIGHT HOURS. IT MOST LIKELY WILL NOT BE A VERY MOIST FRONT DUE TO THE ABUNDANCE OF DRY AIR IN THE AREA...BUT STRONGER WINDS ARE EXPECTED BEHIND THE FRONT. SURFACE RIDGING WILL BUILD IN BEHIND IT. CARIBBEAN SEA... AN UPPER LEVEL RIDGE COVERS THE NW CARIBBEAN CENTERED OVER HONDURAS AND NICARAGUA NEAR 15N84W. THE RIDGE IS DRAWING MOIST AIR AROUND ITS WESTERN SIDE...WHILE DRY AIR REMAINS OVER THE EASTERN SIDE. THIS PATTERN IS PRODUCING ISOLATED SHOWERS/THUNDERSTORMS ACROSS MUCH OF CENTRAL AMERICA...BUT IS INHIBITING CONVECTION NEAR THE NORTHERN HALF OF A TROPICAL WAVE THAT EXTENDS FROM THE NW CARIBBEAN INTO THE SW CARIBBEAN. THE SOUTHERN HALF OF THE WAVE IS PRODUCING SHOWERS/THUNDERSTORMS AS IT IS EMBEDDED WITHIN THE BROAD CYCLONIC FLOW AROUND THE MONSOON TROUGH THAT EXTENDS FROM SOUTHERN COSTA RICA TO THE BASE OF THE WAVE. SEE TROPICAL WAVE SECTION FOR MORE DETAILS. A SECOND TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN...BUT IS NOT CAUSING MUCH SIGNIFICANT WEATHER. BROAD UPPER TROUGHING COVERS THE REMAINDER OF THE BASIN...BUT IT IS DRAWING IN DRY AIR AROUND ITS EASTERN SIDE...WHICH IS KEEPING MUCH OF THE CENTRAL AND EASTERN CARIBBEAN UNDER FAIR CONDITIONS. HOWEVER...STRONG CONVECTION CONTINUES OVER NORTHERN COLOMBIA AND NORTHERN VENEZUELA. ONLY A FEW ISOLATED SHOWERS HAVE POPPED UP OF THE LESSER ANTILLES. BOTH WAVES WILL CONTINUE WESTWARD. ATLANTIC OCEAN... MOIST DIFFLUENT FLOW IS ACROSS THE FAR WESTERN ATLC SUPPORTING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WEST OF 74W TO THE FLORIDA COAST AND NORTH OF 26N. A WEAK UPPER RIDGE EXTENDS ACROSS THE BAHAMAS...BUT A SMALL SHORTWAVE TROUGH IS IMMEDIATELY TO THE EAST ASSOCIATED WITH AN UPPER LEVEL LOW NE OF THE LESSER ANTILLES NEAR 22N60W. THE SHORTWAVE IS SUPPORTING A 1007 MB SURFACE LOW NEAR 22N67W ALONG WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 21N-27N BETWEEN 66W-72W. A WEAK SURFACE TROUGH IS ANALYZED UNDERNEATH THE UPPER LOW FROM 22N58W TO 19N61W. SCATTERED SHOWERS/THUNDERSTORMS ARE FROM 20N-22N BETWEEN 58W-60W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE FROM 17N-21N BETWEEN 52W-57W. AN UPPER LEVEL RIDGE COVERS THE MAJORITY OF THE TROPICAL ATLC CENTERED NEAR 16N42W. IT SUPPORTS A WEAK 1012 MB SURFACE HIGH CENTERED NEAR 17N50W. THE PRESENCE OF THIS RIDGE IS ALSO INHIBITING THE PRESENCE OF AN ATLANTIC ITCZ AT THIS TIME. A BROAD UPPER LEVEL TROUGH COVERS MUCH OF THE NE ATLC SUPPORTING A COLD FRONT THAT ENTERS THE DISCUSSION AREA NEAR 32N26W AND CONTINUES ALONG 23N40W 24N50W. IT THEN BECOMES STATIONARY TO 26N60W AND DISSIPATING TO 24N66W AS IT WRAPS AROUND THE UPPER LOW NORTH OF THE CARIBBEAN. ISOLATED SHOWERS ARE WITHIN 120 NM AHEAD OF THE COLD PORTION OF THE FRONT...AND WITHIN 90 NM EITHER SIDE THE AXIS ALONG THE REMAINDER OF THE FRONT. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON