000 AXPZ20 KNHC 270928 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC MON MAY 27 2013 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0900 UTC. ...SPECIAL FEATURE... A 1008 MB LOW PRES EMBEDDED WITHIN THE MONSOON TROUGH IS LOCATED NEAR 13N95W...OR SEVERAL HUNDRED MILES SOUTH OF THE GULF OF TEHUANTEPEC MOVING WEST AT 6 KT. THIS SYSTEM IS SHOWING SOME SIGNS OF ORGANIZATION. CONVECTION HAS INCREASED NEAR AND TO THE NORTH OF THE LOW WHERE SATELLITE IMAGERY REVEALS A BANDING FEATURE. THERE IS A MEDIUM PROBABILITY OF TROPICAL CYCLONE FORMATION WITH THIS SYSTEM DURING THE NEXT 48 HOURS AS IT MOVES SLOWLY WEST-NORTHWESTWARD OR NORTHWESTWARD...FOLLOWED BY A TURN TOWARD THE NORTH OR NORTHEAST. REGARDLESS OF DEVELOPMENT... HEAVY RAINS ARE LIKELY OVER PORTIONS OF SOUTHERN MEXICO AND NORTHERN CENTRAL AMERICA DURING THE NEXT FEW DAYS DUE TO SEVERAL DAYS OF PERSISTENTLY STRONG ONSHORE FLOW MEETING THE ELEVATED TERRAIN. THESE RAINS COULD PRODUCE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES. SEE LATEST TROPICAL WEATHER OUTLOOK FOR MORE INFORMATION. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH AXIS EXTENDS FROM FROM 08N78W TO 10N86W TO LOW PRES NEAR 13N95W 1008 MB TO 14N107W TO LOW PRES NEAR 11.5N112W 1009 MB TO 08N118W...THEN ITCZ TO 09N128W TO 07N140W. NUMEROUS MODERATE TO ISOLATED STRONG CONVECTION IS NOTED FROM 06N TO 12N BETWEEN 126W AND 132W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS FROM 07N TO 11N BETWEEN 134W AND 138W. ...DISCUSSION... ALOFT...AN UPPER TROUGH EXTENDS ACROSS THE NW PART OF THE AREA FROM 30N134W TO BEYOND 24N140W. SWLY FLOW AHEAD OF THE TROUGH CONTINUES TO ADVECT DEEP TROPICAL MOISTURE FROM THE CENTRAL PACIFIC NEWD TO ACROSS THE FAR WRN AND N CENTRAL PORTIONS OF THE DISCUSSION AREA TOWARDS SRN CALIFORNIA. TO THE SE OF THE TROUGH...BROAD ANTICYCLONIC FLOW COVERS THE AREA BETWEEN 105W- 125W WITH THE ASSOCIATED ANTICYCLONE CENTERED NEAR 13N120W. AN UPPER LEVEL TROUGH IS ACROSS EASTERN MEXICO WITH THE BASE OF THE TROUGH REACHING 18N100W. OVER THE ERN PORTION...ANOTHER ANTICYCLONE CENTERED OVER GUATEMALA COVERS SE MEXICO AND NORTHERN CENTRAL AMERICA. UPPER DIFFLUENCE ASSOCIATED WITH THIS RIDGE IS HELPING TO SUSTAIN INCREASING CLUSTERS OF MODERATE TO STRONG CONVECTION OVER PARTS OF SE MEXICO...NORTHERN CENTRAL AMERICA AND AROUND THE LOW PRES DESCRIBED ABOVE IN THE SPECIAL FEATURE. FARTHER WEST...A 1009 MB LOW PRES IS ALSO EMBEDDED WITHIN THE MONSOON TROUGH NEAR 11.5N112W. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THIS SYSTEM REMAIN POORLY ORGANIZED...AND MAINLY AWAY FROM THE CENTER. THE 0428 UTC ASCAT PASS INDICATES THAT THIS LOW IS RATHER ILL-DEFINED...AND IS PRODUCING ONLY LIGHT TO GENTLE WINDS. GLOBAL MODELS CONTINUE TO SUGGEST THAT BOTH MENTIONED LOWS WILL DEVELOP OVER THE NEXT 48 HRS...WITH THE GFS MODEL STILL QUITE AGGRESSIVE IN DEVELOPING THE ERN MOST LOW PRES AREA. ELSEWHERE AT THE SURFACE...A 1032 MB HIGH PRES LOCATED NEAR 32N139W EXTENDS A RIDGE SE ACROSS THE FORECAST WATERS TO NEAR 18N115W. RECENT SCATTEROMETER DATA VERIFIED THE EXISTENCE OF FRESH TO STRONG TRADE WINDS BETWEEN THE SRN PERIPHERY OF THE RIDGE AND THE ITCZ...COVERING THE AREA FROM 09N TO 17N W OF 124W. DUE TO A TIGHT PRES GRADIENT BETWEEN THE RIDGE AND LOWER PRES OVER NW MEXICO...WINDS ARE ALSO EXPECTED TO INCREASE OVER THE NE PART OF THE FORECAST REGION N OF ABOUT 25N AND E OF 122W TO THE COAST OF BAJA CALIFORNIA DURING THE NEXT 12-24 HOURS. EXPECT NW WINDS OF 20-25 KT AND BUILDING SEAS TO 10-11 FT IN THAT AREA. THESE MARINE CONDITIONS WILL PERSIST THROUGH 48 HOURS. LONG PERIOD CROSS EQUATORIAL SW SWELLS AT 14-16 SECONDS DOMINATE MOST OF THE FORECAST WATERS E OF 115W. THESE SWELLS ARE MERGING WITH NW SWELLS THAT COVER THE REMAINDER OF THE FORECAST WATERS. WAVEWATCH GUIDANCE SUGGESTS THAT THESE SWELLS WILL SLOWLY SUBSIDE ON TUE...EXCEPT FOR THE NE PORTION OF THE AREA WHERE A NEW SET OF NW SWELLS IS FORECAST TO IMPACT THAT REGION. $$ GR