000 AXPZ20 KNHC 182119 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC WED MAR 18 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2100 UTC. ...ITCZ... THE ITCZ AXIS LIES ALONG A LINE FROM 03N78W TO 04N90W TO 00N112W 01N120W TO 04N130W TO 07N140W. NO SIGNIFICANT CONVECTION IS NOTED ALONG THE ITCZ. ...DISCUSSION... THE UPPER LEVEL FLOW CONTINUES TO AMPLIFY N OF THE DISCUSSION AREA AS A DEEP LOW OVER THE GULF OF ALASKA PROPAGATES SOUTHEASTWARD CARVING OUT A DEEP TROUGH N OF THE DISCUSSION AREA. THE PREVIOUSLY STATIONARY FRONT N OF THE AREA IS NOW ADVANCING SOUTHWARD...AND IS FORECAST TO ENTER THE NORTHERN WATERS BY SUNDAY. NORTHWESTERLY WINDS OF 20 TO 30 KT WILL AFFECT AREAS IN THE WAKE OF THE FRONT...WHERE WAVE HEIGHTS OVER 12 FT IN NORTHWESTERLY SWELL WILL BE PRESENT. IN THE MEANTIME...A 1027 MB SURFACE HIGH N OF THE AREA NEAR 34N132W WILL CONTINUE TO WEAKEN IN RESPONSE TO DECREASING DEEP LAYER SUBSIDENCE WITH THE AMPLIFICATION OF THE UPPER TROUGH. THE PRESSURE GRADIENT BETWEEN THE HIGH AND A 1015 MB SURFACE LOW AND SURFACE TROUGH OVER THE GULF OF CALIFORNIA CONTINUES TO DRIVE N NW TO N WINDS OF UP TO 20 KT IN A NARROW SWATH W OF THE BAJA COAST. WAVE HEIGHTS UP TO 10 FT IN NORTHWESTERLY SWELL CONTINUE IN THIS AREA...BUT CONTINUE SUBSIDING AS THEY DEPART THEIR SOURCE REGION. THE ENHANCED SURFACE PRESSURE GRADIENT AT THE SOUTHERN PERIPHERY OF THE SURFACE HIGH ALSO IS ENHANCING NE TO E TRADES ACROSS THE REGION. THE HIGH RESOLUTION QUIKSCAT PASS AROUND 18/1500 UTC SHOWED NE TO E WINDS UP TO 20 KT FROM 09N TO 18N W OF 128W...WITH WAVEWATCH GUIDANCE INDICATING SEAS TO 10 FT IN THIS AREA WITH CONTINUING NE SWELL. THE TRADES IN THIS AREA ARE EXPECTED TO PICK UP GREATLY BY SUNDAY AS A SURFACE HIGH BUILDS SOUTHWARD IN THE WAKE OF THE AFOREMENTIONED COLD FRONT. AS FOR CONVECTIVE ACTIVITY...UPPER LEVEL DIFFLUENCE N OF THE ITCZ AXIS CONTINUES IS SUPPORTING NUMEROUS MODERATE CONVECTION FROM 11N TO 14N BETWEEN 124W AND 127W AND SCATTERED MODERATE FROM 09N TO 11N W OF 138W. THE DIFFLUENCE IS EMBEDDED WITHIN AN UPPER TROUGH LOCATED S OF 17N W OF 105W. FARTHER TO THE E...DEEP LAYER DRY AIR AND STABLE ATMOSPHERIC CONDITIONS EMBEDDED WITHIN AN UPPER RIDGE ARE RESULTING IN FAIR WEATHER CONDITIONS. GAP WINDS... A PERSISTENT RIDGE OF SURFACE HIGH PRESSURE OVER MEXICO AND THE GULF OF MEXICO WILL SUPPORT A RELATIVELY STRONG SURFACE PRESSURE GRADIENT ACROSS THE ISTHMUS OF TEHUANTEPEC DURING THE NEXT FEW DAYS. CORRESPONDINGLY...THE HIGH RESOLUTION QUIKSCAT PASS AROUND 18/1200 UTC DEPICTED N WINDS OF 20 TO 25 KT FUNNELING INTO THE GULF OF TEHUANTEPEC. COMPUTER MODEL GUIDANCE INDICATES THESE WINDS WILL CONTINUE DURING THE NEXT DAY GENERALLY WITHIN 120 NM OF THE COAST. HOWEVER STRONG SURFACE HIGH PRESSURE BUILDING SOUTHWARD FROM THE CANADIAN PRAIRIES WILL STEEPEN THE PRESSURE GRADIENT ACROSS THE ISTHMUS OF TEHUANTEPEC EVEN FURTHER ON FRIDAY...WHEN WINDS WILL INCREASE ACROSS A LARGER AREA IN THE GULF OF TEHUANTEPEC...WITH N TO NE WINDS APPROACHING 30 KT. HOWEVER...THE ABSENCE OF ANY REMARKABLE SURFACE FRONTS IN THE WESTERN GULF OF MEXICO WILL PRECLUDE THE THREAT FOR GALES. SEAS WILL BUILD OVER 10 FT DOWNWIND OF THE GULF OF TEHUANTEPEC BY SATURDAY. ALSO...TRADE WINDS ACROSS THE CARIBBEAN CONTINUE WITH A PERSISTENT SURFACE LOW OVER NW COLOMBIA. THESE WINDS CONTINUE TO BLEED INTO THE GULF PAPAGAYO. GAP WINDS AROUND THE GULFS OF TEHUANTEPEC AND PAPAGAYO ARE FORECAST TO BE STRONGEST WINDS EXPECTED LATE AT NIGHT WHEN DRAINAGE FLOW OFF HIGHER TERRAIN IS MAXIMIZED IN THE PRESENCE OF DEEP LAYER DRY AIR. $$ COHEN