000 AXPZ20 KNHC 191603 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC SUN APR 19 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1500 UTC. ...ITCZ... THE INTERTROPICAL CONVERGENCE ZONE AXIS LIES ALONG A LINE FROM 04.5N77W TO 03N81W TO 05N85W TO 07N96W TO 05.5N120W TO 04N140W. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION WAS WITHIN 150 NM EITHER SIDE OF AXIS BETWEEN 115W AND 138W. ISOLATED MODERATE CONVECTION WAS WITHIN 90 NM N OF AXIS BETWEEN 102W AND 110W. SCATTERED MODERATE CONVECTION WAS WITHIN 120 NM S OF AXIS BETWEEN 85W AND 94W. ...DISCUSSION... W OF 100W...THE LARGE SCALE UPPER PATTERN CONTINUES TO BECOME MORE AMPLIFIED AS A SHARP LONG WAVE TROUGH EXTENDING FROM THE GULF OF ALASKA TO NW PORTIONS OF THE HAWAIIAN ISLAND CHAIN CONTINUES TO DIG SE. UPPER RIDGING CONTINUES TO BUILD TO THE E...OR AHEAD OF THIS TROUGH...FROM 25N144W TILTED NE TO 40N131W. MEANWHILE...A SHORT WAVE TROUGH HAS CUTOFF AND EVOLVED INTO A MID-UPPER LOW SE OF THE UPPER RIDGE NEAR 27N129W. THIS HAS COMBINED WITH A BROAD UPSTREAM TROUGH ACROSS CENTRAL N AM TO EFFECT A REX BLOCK ACROSS THE REGION...WITH STRONG UPPER WLYS UNDERCUTTING THIS PATTERN ACROSS THE TROPICS...FROM 170W TO 110W. THE TREND THE PAST COUPLE OF DAYS HAS BEEN THAT THE SURFACE HIGH PRES ASSOCIATED WITH THE UPPER RIDGE WAS SHIFTING NORTH WITH THE BUILDING RIDGE. THIS SURFACE RIDGE HAS BEEN WEAKENING AS WELL WITH THE MID/UPPER SHORT WAVE CUTTING OFF. THE RESULT HAS BEEN DIMINISHING SURFACE WINDS ON THE PERIPHERY OF THE SURFACE HIGH. AN OVERNIGHT QUIKSCAT PASS INDICATED THAT NORTHERLY WINDS ALONG THE BAJA COAST AND IN THE GULF OF CALIFORNIA HAD DIMINISHED TO LESS THAN 20 KT...AND THE AREA OF 20 KT TRADE WINDS S OF THE SURFACE HIGH HAD SHRUNK. A 50 TO 70 KT UPPER JET ON THE SOUTHERN SIDE OF THE CUT OFF SHORTWAVE IS EVIDENT BETWEEN 10N TO 20N W OF 120W. UPPER DIVERGENCE RELATED TO THE JET WILL ENHANCE POCKETS OF ITCZ CONVECTION W OF 120W THROUGH TUESDAY. LOOKING AHEAD THROUGH MID WEEK...THE GFS AND ECMWF ARE IN GENERAL AGREEMENT SHOWING THE CUT OFF SHORT WAVE OPENING UP AND LIFTING NORTH AHEAD OF THE LONG WAVE TROUGH...ITSELF CUTTING OFF NE OF HAWAII. THIS WILL INDUCE A WEAK SURFACE HIGH PRES CENTER TO FORM NEAR 25N135W BY TUESDAY...WHICH MAINTAINS A BAND OF TRADE WINDS FURTHER SOUTH. MEANWHILE...AS N TO NE SWELL DECAYS THROUGH MONDAY...A NEW ROUND OF LONG PERIOD SW SWELL WILL PUSH THROUGH THE AREA S OF 20N THROUGH WED. E OF 105W...THE MAIN ISSUE THROUGH THE NEXT 48 HOURS WILL BE 20 KT GAP WIND FLOW THROUGH THE GULFS OF PAPAGAYO AND PANAMA. LATEST DATA SHOW LESS THAN 20 KT FLOW IN PAPAGAYO...BUT THIS IS LIKELY TO INCREASE DUE TO DRAINAGE LATER THIS MORNING. A 03Z ASCAT PASS SHOWED 20 KT NORTHERLY FLOW THROUGH THE GULF OF PANAMA. THE CARIBBEAN TRADE WIND FLOW IS TRENDING DOWNWARD...AND THESE WINDS WILL FOLLOW SUIT INTO MONDAY. MEANWHILE A COLD FRONT WILL PUSH INTO THE SOUTHERN GULF OF MEXICO...PROMOTING STRONG FUNNELING WINDS INTO THE GULF OF TEHUANTEPEC BY LATE MONDAY. LATEST GLOBAL MODEL GUIDANCE NOW INDICATING A TEHUANTEPEC GALE EVENT DEVELOPING DURING THE NEXT 24 HOURS AND PEAKING AT 36-48 HOURS NEAR 40 KT. THE MAIN ISSUE FROM MONDAY THROUGH LATE TUESDAY WILL BE THE POSSIBILITY OF THESE GALE FORCE WINDS COINCIDING WITH THE ARRIVAL OF SW SWELL UP TO 6 FT...AND INITIAL WAVE PERIODS TO 20 KT NEAR THE MEXICAN AND CENTRAL AMERICAN COASTS. THIS WILL PROVIDE THE POTENTIAL FOR CONFUSED SEAS IN THE FAN LIKE PLUME OF WINDS FUNNELING OUT OF THE GULF OF TEHUANTEPEC...AND STEEP SHOALING SWELL NEAR THE COAST. $$ STRIPLING