000 AXPZ20 KNHC 192143 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC THU MAR 19 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 02N78W TO 03N91W TO 00N106W 00N135W TO 01N140W. NO SIGNIFICANT CONVECTION IS NOTED ALONG THE ITCZ. ...DISCUSSION... THE UPPER LEVEL FLOW CONTINUES TO AMPLIFY N OF THE DISCUSSION AREA AS AN UPPER LEVEL JET MAXIMUM DIVES SOUTHWARD...FORCING THE UPPER TROUGH TO DIG SOUTHWARD. DEEP LOW OVER THE GULF OF ALASKA PROPAGATES SOUTHEASTWARD CARVING OUT A DEEP TROUGH N OF THE DISCUSSION AREA. A COLD FRONT N OF THE CONTINUES ADVANCING SOUTHWARD...AND IS FORECAST TO ENTER THE NORTHERN WATERS BY SUNDAY. NW TO N WINDS OF 20 TO 30 KT WILL AFFECT AREAS IN THE WAKE OF THE FRONT...WHERE WAVE HEIGHTS OVER 14 FT IN NORTHWESTERLY SWELL WILL BE PRESENT. GALES ARE EXPECTED TO REMAIN N OF THE AREA...WHERE THE STRONGER SURFACE PRESSURE GRADIENT WILL BE LOCATED. IN THE MEANTIME...A 1025 MB SURFACE HIGH N OF THE AREA NEAR 32N137W WILL DISSIPATE OVER THE NEXT DAY IN RESPONSE TO DECREASING DEEP LAYER SUBSIDENCE WITH THE AMPLIFICATION OF THE UPPER TROUGH. WAVE HEIGHTS UP TO 10 FT IN NORTHWESTERLY SWELL CONTINUE IN NORTH CENTRAL PORTIONS OF THE DISCUSSION AREA...BUT CONTINUE SUBSIDING AS THEY DEPART THEIR SOURCE REGION AND WINDS DIMINISH. THE ENHANCED SURFACE PRESSURE GRADIENT AT THE SOUTHERN PERIPHERY OF THE SURFACE HIGH ALSO IS ENHANCING NE TO E TRADES ACROSS THE REGION. THE QUIKSCAT PASS AROUND 19/1450 UTC SHOWED NE TO E WINDS UP TO 20 KT FROM 04N TO 18N W OF 125W...WITH WAVEWATCH GUIDANCE INDICATING SEAS TO 9 FT IN THIS AREA WITH CONTINUING NE SWELL. THE TRADES IN THIS AREA ARE EXPECTED TO PICK UP SUBSTANTIALLY ON 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 IS SUPPORTING SCATTERED MODERATE CONVECTION FROM 16N TO 20N BETWEEN 127W AND 134W AND SCATTERED MODERATE CONVECTION FROM 26N TO 18N BETWEEN 116W AND 119W. FARTHER TO THE E...DEEP LAYER DRY AIR AND STABLE ATMOSPHERIC CONDITIONS EMBEDDED WITHIN AN UPPER RIDGE ARE RESULTING IN FAIR WEATHER CONDITIONS S OF 16N E OF 100W. 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 ASCAT PASS AROUND 19/1620 UTC DEPICTED N TO NE WINDS OF 20 TO 25 KT FUNNELING INTO THE GULF OF TEHUANTEPEC. STRONG SURFACE HIGH PRESSURE BUILDING SOUTHEASTWARD FROM SW ONTARIO CANADA 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. COMPUTER MODEL GUIDANCE IS TRENDING UPWARD WITH THE INTENSITY OF THESE WINDS DESPITE THE ABSENCE OF ANY SUBSTANTIAL SURFACE FRONTS. IN FACT...GALE FORCE WINDS ARE EXPECTED FROM LATE TONIGHT THROUGH SATURDAY MORNING IN THE GULF OF TEHUANTEPEC...GIVEN THE STRONG PRESSURE GRADIENT SW OF A 1035 MB SURFACE HIGH OVER THE MID ATLANTIC STATES THIS WEEKEND. 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 OF PAPAGAYO. GAP WINDS AROUND THE GULFS OF TEHUANTEPEC AND PAPAGAYO ARE FORECAST TO BE STRONGEST LATE AT NIGHT WHEN DRAINAGE FLOW OFF HIGHER TERRAIN IS MAXIMIZED IN THE PRESENCE OF DEEP LAYER DRY AIR. $$ COHEN