000 AXPZ20 KNHC 300916 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC FRI MAR 30 2012 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0645 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE ITCZ AXIS EXTENDS FROM 06N86W TO 03N102W TO 01N125W TO 05N117W TO 02N128W TO 01N135W. SCATTERED MODERATE CONVECTION LIES WITHIN 120 NM N OF THE AXIS BETWEEN 90W AND 96W...WITHIN 90 NM N OF THE AXIS BETWEEN 100W AND 110W...AND WITHIN 240 NM N OF THE AXIS BETWEEN 128W AND 134W. ...DISCUSSION... A ZONAL UPPER JET ALONG 40N WITH WINDS IN EXCESS OF 150 KT IS KEEPING THE NORTHERN STREAM PATTERN ALOFT REASONABLY PROGRESSIVE AT THE MOMENT. A POSITIVELY TILTED UPPER TROUGH LIES OVER THE FORECAST AREA FROM THE TEXAS BIG BEND THROUGH CENTRAL BAJA CALIFORNIA TO 23N130W THEN SOUTHWESTWARD TO A STRONG UPPER LOW JUST W OF THE AREA NEAR 14N144W. THIS ANOMALOUSLY DEEP LOW IS FOUR STANDARD DEVIATIONS DEEPER THAN THE CLIMATOLOGICAL PATTERN AT BOTH 250 MB AND 500 MB. THIS LOW WILL BEGIN TO MOVE EASTWARD ON FRI AS THE SUPPORTING TROUGH IS PROPELLED EASTWARD BY THE STRONG NORTHERN STREAM JET ALOFT. THE NORTHERN STREAM PATTERN WILL BECOME MORE AMPLIFIED AS RIDGING BUILDS OVER THE SOUTHWESTERN U.S. BEHIND THE TROUGH...SLOWING DOWN AND INTENSIFYING THE NEXT TROUGH TO ENTER THE FORECAST AREA FROM THE NW ON FRI EVENING. SYNOPTIC SCALE LIFT AND DEEP LAYERED CONVERGENCE ASSOCIATED WITH THE UPPER LOW IS PRODUCING MULTI-LAYERED CLOUDINESS AND WIDELY SCATTERED SHOWERS AND TSTMS FROM 15N TO 20N W OF 130W. 90-100 KT SW WINDS ALOFT ON THE SE SIDE OF THE UPPER LOW ARE TRANSPORTING MID TO UPPER LEVEL MOISTURE...MANIFESTED PRIMARILY AS CIRRUS CLOUDS...TO THE REMAINDER OF THE AREA FROM 08N TO 18N BETWEEN 115W AND 135W. UPPER LEVEL RIDGING TO THE N IS EXPECTED TO CUT OFF THE COLD AIR ALOFT SPILLING INTO THE BACKSIDE OF THIS CYCLONE BY EARLY SATURDAY AS THE LOW CENTER CROSSES EAST OF 140W INTO THE DISCUSSION AREA. GRADUAL WEAKENING OF THE CYCLONE WILL OCCUR OVER THE WEEKEND AS IT MOVES E-NE. THIS FEATURE WILL CONTINUE TO INITIATE CONVECTION EAST OF THE TROUGH AXIS INTO THE WEEKEND...WITH THE CONVECTIVELY ACTIVE AREA SHRINKING DURING THAT TIME AS THE ATMOSPHERE BECOMES MORE STABLE NEAR THE WEAKENING LOW. AT THE LOWER LEVELS...A 1023 MB SUBTROPICAL HIGH IS CENTERED NEAR 28N131W AND EXTENDS A RIDGE AXIS TO 13N100W. N OF THE RIDGE AXIS...STRONG NORTHWESTERLY WINDS CURRENTLY OFF THE W COAST OF THE BAJA PENINSULA N OF 25N ARE EXPECTED TO GRADUALLY DIMINISH THROUGH MIDDAY FRI. THESE WINDS WERE OBSERVED BY THE 0526 UTC ASCAT PASS. SOUTH OF THE RIDGE AXIS...FRESH TO STRONG NE TRADEWINDS PREVAIL FROM 04N TO 20N W OF 120W WITH CONFUSED SEAS OF 9 TO 12 FT FOUND THERE IN A BROAD MIX OF NE...SW...AND NW SWELL. MORE FRESH TRADES LIE FROM 05N TO 15N BETWEEN 120W AND 130W AS OBSERVED BY THE 0522 UTC AND 0702 UTC ASCAT PASSES. THESE TRADEWINDS WILL CONTRACT WESTWARD A BIT ON FRI AND REBUILD SAT AS HIGH PRES BEHIND A COLD FRONT MOVING IN FROM THE NW WILL BECOME THE DOMINANT SUBTROPICAL HIGH. STRONG NW WINDS WILL ACCOMPANY THE FRONT BUT THE BIGGER STORY IS THE LARGE NW SWELL TO 20 FEET EXPECTED OVER NW WATERS SAT. LIGHT TO MODERATE WINDS OTHERWISE PREVAIL E OF 110W...WITH GAP WIND FLOW PULSING TO NEAR 20 KT DURING THE OVERNIGHT HOURS IN THE GULF OF PAPAGAYO. LITTLE CHANGE IN THIS PATTERN IS EXPECTED DURING THE NEXT 48 HOURS. LONG PERIOD SW SWELL HAS MOVED INTO THE ADJACENT COASTAL WATERS OF CENTRAL AMERICA AND WILL CONTINUE TO PRODUCE BUILDING SURF ALONG REEFS AND BEACHES. POWERFUL MODERATE SIZED SURF IS EXPECTED ALONG THE CENTRAL AMERICAN COASTS THROUGH FRIDAY...CREATING STRONG RIP CURRENTS. $$ SCHAUER/HUFFMAN