000 AXPZ20 KNHC 121003 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC THU MAR 12 2015 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 0945 UTC. ...SPECIAL FEATURES... GULF OF TEHUANTEPEC GALE WARNING...A RIDGE ASSOCIATED WITH A 1024 MB LOCATED JUST NW OF TAMPICO CONTINUES TO SURGE SEWD ALONG THE E SIDE OF THE SIERRA MADRE ORIENTAL MOUNTAINS AND TO SOUTHEASTERN MEXICO IN THE WAKE OF WESTERN GULF OF MEXICO STATIONARY FRONT ALONG 94W. THE RESULTANT TIGHT PRES GRADIENT HAS INDUCED GALE FORCE WINDS OF 30-35 KT THROUGH THE GULF AS WAS NICELY CAPTURED IN THE 0358 UTC HIGH RESOLUTION ASCAT PASS FROM LAST NIGHT AS WELL AS IN THE ASCTB PASS FROM 0312 UTC ALSO FROM LAST NIGHT. BOTH THE GFS AND NAM 10 METER MODEL GUIDANCE SUGGESTS THAT THESE WINDS ARE EXPECTED TO REMAIN AT GALE FORCE TO DAYBREAK FRI OR SHORTLY AFTERWARDS AS THE CULPRIT RIDGE WEAKENS. THE WINDS WILL BUILD SEAS UP TO AROUND 12 FT BY LATE TONIGHT IN THE GULF BEFORE SUBSIDING TO AROUND 11 FT FRI MORNING...AND TO 8 FT FRI AFTERNOON AS THE WINDS DIMINISH TO 20 TO 25 KT. THE WINDS ARE FORECAST TO BRIEFLY DIMINISH TO 15-20 KT EARLY FRI NIGHT...BEFORE PICKING UP TO 20-25 KT LATE FRI NIGHT...AND INTO SAT WITH SEAS STAYING TO AROUND 8 FT. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE ITCZ AXIS EXTENDS FROM 06N89W TO 05N100W TO 05N110W TO 04N120W TO 05N140W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM N OF THE ITCZ BETWEEN 103W-105W. ...DISCUSSION... E OF 120W... A MID/UPPER CUT-OFF LOW LIFTING NEWD IS SEEN OVER CENTRAL MEXICO NEAR 23N103W. IT IS EMBEDDED WITHIN A SHARP LONGWAVE TROUGH THAT EXTENDS FROM THE MID-WEST SECTION OF THE U.S. SW TO THE LOW...AND CONTINUES SSW TO 07N104W. WATER VAPOR IMAGERY SHOWS VERY DRY AND STABLE AIR WRAPPING AROUND THE WESTERN AND SOUTHERN SIDES OF THE TROUGH. THIS IS SUPPRESSING DEEP CONVECTION FROM DEVELOPING IN THE TROPICAL REGION OF THE AREA. THE ONLY CONVECTIVE OBSERVED IS THAT OF SCATTERED TSTMS THAT RECENTLY FLARED UP WITHIN 120 NM N OF THE ITCZ BETWEEN 103W-105W AS STATED ABOVE. THIS ACTIVITY IS RELATED TO A WEAK LOW-LEVEL TROUGH FROM 05N TO 11N NEAR 104W. THE CLOSE PROXIMITY OF THIS TROUGH TO THE AFOREMENTIONED LONGWAVE TROUGH...AND ALONG WITH INCREASING LOW-LEVEL MOISTURE IN WEAK LOW-LEVEL CONFLUENCE FOUND NEAR THE ITCZ IS ENOUGH TO HELP SET OFF THE ABOVE DESCRIBED CONVECTION. MOISTURE GUIDANCE FIELDS FORECAST THE LOW-LEVEL TROUGH AND ASSOCIATED MOISTURE TO TRACK WESTWARD TO NEAR 110W BY LATE TONIGHT...TO NEAR 116W FRI NIGHT AND TO NEAR 124W SAT. THE TROUGH MAY BECOME MORE SURFACE BASED DURING THIS TIME. WEAK LOW- LEVEL CONFLUENCE HAS HELP KICK OFF ISOLATED SMALL TSTM CLUSTERS ALONG THE EASTERN PART OF THE ITCZ. A NARROW CONVERGENCE ZONE E OF THE ITCZ IS PRODUCING SIMILAR SMALL ISOLATED TSTM CLUSTERS WITHIN 30 NM OF A LINE FROM 06N82W TO 05N87W TO 03N92W. SIMILAR ACTIVITY IS ALONG...AND WITHIN 60 NM OF THE COAST OF COLOMBIA FROM 03N-06N DUE TO A SEMI-PERMANENT COASTAL TROUGH THERE. IN ADDITION TO THE GULF OF TEHUANTEPEC...NE GAP WINDS OF 25-30 KT THROUGH THE GULF OF PAPAGAYO HAVE STARTED UP AGAIN. LIBERIA (MRLB) IN NORTHERN COSTA RICA BEGAN TO REPORT NE WINDS OF 30-35 KT WED EVENING. NE 20-25 KT WINDS EXTEND WSW FROM THE GULF WITHIN 30 NM OF EITHER SIDE OF A LINE FROM 11N86W TO 10N89W. THE 25-30 KT WINDS ARE FORECAST TO DIMINISH TO 20-25 KT BY EARLY THIS AFTERNOON WITH THE 20-25 KT DIMINISHING BRIEFLY TO 20 KT AT THAT TIME WITH SEAS TO 9 FT IN NE SWELL. HOWEVER...BY LATE TONIGHT THE NE 25-30 KT WINDS ARE FORECAST TO BLOW THROUGH THE GULF WITH NE 20-25 KT DOWNWIND FROM THERE TO NEAR 09.5N AND N TO 12N ELSEWHERE E OF 90W. SEAS ARE EXPECTED TO BUILD 8-10 FT LATE LAST NIGHT. BY EARLY FRI AFTERNOON...WINDS AGAIN PULSE DOWNWARD TO MOSTLY 20 KT WITH A FEW 25 KT SPEEDS. WINDS AGAIN INCREASE TO 20-25 KT LATE FRI NIGHT WITH SEAS TO 8 FT. LOOKING AHEAD...GLOBAL MODELS CARRY THE MID/UPPER LOW OVER MEXICO NEWD THROUGH FRI WHILE LOSING ITS DEFINITION. THE MODELS THEN DEPICT A STRONGER MID/UPPER LEVEL LOW THAT CUT-OFFS OVER THE SOUTHERN GULF OF CALIFORNIA ON SAT...AND MEANDERS IN THAT AREA THROUGH SUN. ITS POSSIBLE THAT DEEP LAYERED SOUTHERLY FLOW COUPLED WITH INCREASING PRECIPITABLE WATER VALUES OF 2 INCHES OR MORE COULD SET THE STAGE FOR POTENTIALLY HEAVY RAINFALL LATE IN THE WEEKEND ALONG THE COAST OF MEXICO FROM MANZANILLO TO PUERTO ANGEL. W OF 120W... BROAD MID/UPPER RIDGING SHIFTING EASTWARD WITH TIME IS SEEN HERE WITH ITS MEAN AXIS STRETCHING FROM NEAR 10N141W NEWD TO 26N131W TO NNE WELL N OF THE AREA AT 32N131W. A VERY WELL PRONOUNCED SUBTROPICAL JET STREAM BRANCH ORIGINATING FROM THE DEEP CENTRAL TROPICAL PACIFIC EXTENDS NEWD TO THE RIDGE CREST. OVERCAST MID/UPPER LEVEL CLOUDS ARE BEING ADVECTED NEWD IN MODERATE TO STRONG SW FLOW TO THE SE OF THE JET STREAM BRANCH. THESE CLOUDS HAVE SPREAD OVER THE NW PORTION TO THE NW OF A LINE FROM 32N129W TO 22N140W...BUT THIN OUT BETWEEN 130W-120W. MODERATE SUBSIDENCE ALOFT IS KEEPING THE ATMOSPHERE RATHER DRY AND STABLE TO THE SE OF THE MID/HIGH CLOUDS. AT THE SURFACE...1024 MB HIGH PRES CENTERED N OF THE AREA AT 32N126W EXTENDS A RIDGE SEWD TO 28N122W TO NEAR 21N114W. HIGH PRES COVERS THE AREA N OF 20N W OF 114W. THE PRES GRADIENT ON THE SOUTHERN PERIPHERY OF THE RIDGE IS ALLOWING FOR ONLY MODEST TRADE WIND FLOW ACROSS THE DEEP TROPICS AS WAS SEEN IN THE ASCAT PASS FROM 0542 UTC. THE PATTERN THROUGH THE REMAINDER OF THE WEEK WILL BE DOMINATED BY A SHARP UPPER TROUGH AMPLIFYING FROM THE NE PACIFIC THOUGH HAWAII...SUPPORTING THE APPROACH OF A COLD FRONT TOWARD THE NW CORNER OF THE DISCUSSION AREA BY LATE FRI NIGHT. FOR SEVERAL CONSECUTIVE RUNS...THE GFS MODEL INDICATES SOMEWHAT STRONGER SOUTHERLY FLOW IN THE FAR NW CORNER OF THE AREA AHEAD OF WEAK LOW PRES FORMING ALONG THE FRONT...HOWEVER OTHER GLOBAL MODELS ARE MUCH WEAKER WITH THESE WINDS. THE PREVIOUS COLD FRONT THAT APPROACH THE FAR NW CORNER WAS PRECEDED BY SLY WINDS OF 20-25 KT SOME OF WHICH MOVED INTO THAT PART OF THE AREA. FEEL THAT THERE IS A GOOD POSSIBILITY THE SAME WILL HAPPEN. WILL ONLY HIGHLIGHT S WINDS OF 20-25 KT IN THE FAR NW CORNER OF THE AREA FOR A SHORT PERIOD LATE TONIGHT...THEN LOWER THEM TO 20 KT OR LESS. FEEL THAT THERE IS A GOOD POSSIBILITY THE SAME WILL HAPPEN. WAVEWATCH GUIDANCE REMAINS IN GOOD AGREEMENT INDICATING LONG PERIOD NW SWELL WITH HEIGHTS TO AT LEAST 9 FT ENTERING THE AREA FRI AS THE FRONT NEARS THE AREA. THE FRONT IS EXPECTED TO LOSE MUCH OF ITS UPPER SUPPORT AS IT CROSSES THE NW PART SAT WITH THE EXPECTATION THAT IT WILL BE ON THE WEAK SIDE. FARTHER SOUTH...ALTHOUGH TRADE WIND FLOW IS RELATIVELY MINIMAL...MIXED NW AND SE SWELLS CONTINUES TO PROMOTE COMBINED SEAS AROUND 8 FT FROM 11N TO 14N W OF 127W AS NOTED IN ALTIMETER SATELLITE PASSES FROM LAST NIGHT. THIS SWELL WILL SUBSIDE BELOW 8 FT BY 42 HOURS. $$ AGUIRRE