000 AXNT20 KNHC 182345 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT MON JUN 18 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 2315 UTC. ...SPECIAL FEATURES... AN UPPER LEVEL TROUGH OVER THE W ATLC ALONG 65W SUPPORTS A 1004 MB OCCLUDED SURFACE LOW CENTERED NEAR 38N61W. THE LOW IS GENERATING GALE FORCE WINDS...BUT LACKS MUCH CONVECTION NEAR THE LOW CENTER. IT WOULD ONLY TAKE A SLIGHT INCREASE IN CONVECTION NEAR THE CENTER FOR A TROPICAL CYCLONE OR SUBTROPICAL CYCLONE TO FORM. THERE IS A HIGH CHANCE OF FORMATION IN TO A TROPICAL OR SUBTROPICAL CYCLONE DURING THE NEXT 48 HOURS. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 13N40W TO 5N42W MOVING W AT 15-20 KT. THE WAVE IS LOW-AMPLITUDE AND ALIGNS WITH A EQUALLY LOW-AMPLITUDE SURGE IN DEEP LAYER MOISTURE. THERE IS ALSO A CLEARING IN AN AREA OF AFRICAN DUST TO THE N AND E OF THE WAVE INDICATING ITS PRESENCE. DUE TO THE ABUNDANCE OF DRY AIR SURROUNDING THE WAVE TO THE N AND E...ONLY AN AREA OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS W OF THE AXIS FROM 7N-11N BETWEEN 43W-50W. TROPICAL WAVE IS ALONG 13N55W TO 4N57W MOVING W NEAR 15-20 KT. THE WAVE LIES ON THE WRN LEADING EDGE OF A SURGE IN DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. THE WAVE ALSO LIES UNDERNEATH A DRY UPPER LEVEL TROUGH. THE UPPER TROUGH IS LIKELY DRAWING ENERGY TO THE N...WHICH IS WHY THERE IS AN ELONGATION IN THE DEEP LAYER MOISTURE FIELD. CURRENTLY ONLY A SMALL AREA OF MODERATE CONVECTION IS FROM 7N-8N BETWEEN 53W-56W...AND FROM 5N-6N BETWEEN 55W-58W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF SENEGAL AT 15N17W TO 8N26W. THE ITCZ CONTINUES AT 8N26W ALONG 7N41W 4N55W. CONVECTION ALONG THE AXIS IS LIMITED DUE TO A LARGE AREA OF SAHARAN DUST EXTENDING FROM THE COAST OF AFRICA TO THE ERN MOST TROPICAL WAVE. ONLY A SMALL AREA OF MODERATE CONVECTION IS NOTED FROM 6N-7N BETWEEN 21W-24W. ...DISCUSSION... GULF OF MEXICO... SURFACE RIDGING IS ACROSS THE GULF OF MEXICO TODAY AROUND A 1020 MB HIGH OVER GEORGIA. SE-S WINDS OF 10-15 KTS ARE PRESENT AROUND THE RIDGE. HOWEVER...AN UPPER LEVEL LOW OVER OVER SRN TEXAS NEAR 27N98W IS CAUSING SHOWER/THUNDERSTORM ACTIVITY ACROSS THE NW GULF. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE N OF 26N W OF 90W. AN UPPER TROUGH AXIS EXTENDS FROM THE UPPER LOW CENTER TO THE NRN TIP OF THE YUCATAN PENINSULA. THE TROUGH IS HELPING SUPPORT SCATTERED SHOWERS FROM 23N-26N BETWEEN 87W-91W...AS WELL AS SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE NRN YUCATAN PENINSULA. SURFACE RIDGING WILL REMAIN ACROSS MOST OF THE BASIN FOR THE NEXT 24 HOURS...BUT A LARGE AREA OF BROAD LOW PRESSURE IN THE NW CARIBBEAN IS EXPECTED TO DRIFT INTO THE SE GULF BEGINNING LATE TOMORROW. THIS WILL MEAN MOIST CONDITIONS ACROSS MUCH OF THE SE GULF. CARIBBEAN SEA... BROAD CYCLONIC SURFACE FLOW ALONG WITH A LARGE AREA OF SHOWERS/THUNDERSTORMS COVER PORTIONS OF THE CENTRAL AND WRN CARIBBEAN. CURRENTLY A LARGE CLUSTER OF STRONG SHOWERS/THUNDERSTORMS IS S OF HISPANIOLA FROM 16N-19N BETWEEN 72W-76W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ALSO COVER THE AREA N OF 15N BETWEEN 70W-87W. SHOWERS/THUNDERSTORMS ARE ALSO OVER ERN HISPANIOLA. A SURFACE TROUGH EXTENDS FROM CUBA NEAR 21N77W TO A 1009 MB LOW NEAR 16N83W WHICH DEPICTS THE AXIS OF THE CYCLONIC FLOW. A PORTION OF THE MONSOON TROUGH ALSO EXTENDS FROM THE LOW CENTER WWD ACROSS NRN CENTRAL AMERICA INTO SRN MEXICO. THIS IS HELPING SUPPORT SCATTERED SHOWERS/THUNDERSTORMS ACROSS THESE AREAS. ALOFT...MOIST SWLY FLOW COVERS THE WRN AND CENTRAL CARIBBEAN BETWEEN AN UPPER LEVEL TROUGH OVER THE WRN GULF OF MEXICO AND AN UPPER LEVEL RIDGE OVER THE ERN CARIBBEAN EXTENDING INTO THE CENTRAL ATLC. DRY AIR ALOFT IS WRAPPING AROUND THE E SIDE OF THE UPPER RIDGE PROVIDING FAIR CONDITIONS ACROSS THE ERN CARIBBEAN. THE BROAD AREA OF LOW PRESSURE ACROSS THE WRN CARIBBEAN IS EXPECTED TO GRADUALLY DRIFT NW OVER THE NEXT SEVERAL DAYS. THIS WILL CONTINUE TO BRING THE NW CARIBBEAN RAIN AND THUNDERSTORMS. FLOODING AND MUDSLIDES ARE POSSIBLE IN PORTIONS OF THE NRN CENTRAL AMERICA...CUBA...AND HISPANIOLA IN AREAS THAT HAVE ALREADY RECEIVED HEAVY RAINFALL. ATLANTIC OCEAN... A WEAK UPPER LEVEL RIDGE IS OVER THE FLORIDA PENINSULA AND FAR WRN ATLC SUPPORTING A SURFACE RIDGE AROUND A 1020 MB HIGH OVER GEORGIA PROVIDING FAIR CONDITIONS ACROSS THE FAR W ATLC. AN UPPER LEVEL TROUGH IS TO THE E ALONG 65W. THE UPPER TROUGH SUPPORTS A 1004 MB LOW TO THE N OF THE AREA NEAR 38N61W. SEE SPECIAL FEATURES ABOVE FOR MORE DETAILS. A SURFACE TROUGH IS ALSO SUPPORTED BY THE UPPER TROUGH EXTENDING FROM 31N62W TO THE SE BAHAMAS AT 21N73W. A LARGE CLUSTER OF SHOWERS/THUNDERSTORMS IS E OF THE AXIS FROM 22N-24N BETWEEN 68W-72W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS EXTEND UP TO 500 NM E OF THE TROUGH AXIS ELSEWHERE IN THE AREA OF LARGEST DIFFLUENCE ALOFT. AN UPPER LEVEL RIDGE EXTENDS FROM THE NE CARIBBEAN TO THE CENTRAL ATLC ALONG 52W SUPPORTING A 1027 MB HIGH NEAR 29N44W WHICH IS PROVIDING FAIR CONDITIONS ACROSS THE REMAINDER OF THE BASIN. A SECOND UPPER RIDGE ALSO COVER THE TROPICAL ATLC CENTERED OVER W AFRICA NEAR 18N11W. THE LAST VISIBLE SATELLITE IMAGES OF THE DAY ALONG WITH GOES-R IMAGERY ENHANCEMENTS INDICATE THAT A LARGE AREA OF SAHARAN DUST EXTENDS FROM THE COAST OF AFRICA TO NEAR 50W WITH CLEARING AROUND THE TROPICAL WAVE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON