AXPZ20 KNHC 180258 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC THU MAR 18 2010 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0130 UTC. ...ITCZ... THE INTERTROPICAL CONVERGENCE ZONE WAS ANALYZED FROM 03N77W TO 04N85W TO 06N105W TO 03N125W TO 03N140W. SCATTERED MODERATE CONVECTION WAS WITHIN 240 NM N OF THE ITCZ AXIS BETWEEN 82W AND 89W. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION WAS WITHIN 180 NM N AND 60 NM S OF THE AXIS W OF 22W. A TROUGH IS EMBEDDED IN THE ITCZ FROM 10N107W TO 03N109W WITH SCATTERED MODERATE CONVECTION WITHIN 60 NM W AND 180 NM E OF THE TROUGH FROM 05N TO 08N. ...DISCUSSION... N OF 20N... A DEEP LAYER RIDGE IS BUILDING NORTHWARD AHEAD OF A TROUGH W OF THE AREA THAT WILL ENTER N WATERS OVERNIGHT THU NIGHT AND SEND A COLD FRONT WITH N WINDS W OF IT AT 20 KT INTO THE FORECAST AREA. THE PRES GRADIENT BETWEEN THE SURFACE RIDGE AXIS OVER NW WATERS AND TROUGHING ON EITHER SIDE OF IT HAS ALLOWED FOR WINDS IN THE 20 TO 25 KT RANGE IN WATERS N OF 25N W OF 127W...WITH WINDS SHIFTING FROM NE TO SE ACROSS FAR W WATERS. SHIP WDC3786 NEAR 29N129W REPORTED 24 KT AND SHIP 3FQS8 NEAR 26N134W REPORTED 25 KT AT 0000 UTC. THESE WINDS WILL MOVE NE OF AREA WITH THE MID TO UPPER LEVEL TROUGH OVERNIGHT TONIGHT. MEANWHILE...20 KT SE WINDS WILL CONTINUE IN NW WATERS AHEAD OF THAT NEXT COLD FRONT AS IT APPROACHES THU. S OF 20N... BOTH THE 1928 AND 1750 UTC ASCAT PASSES SHOW STRONG NE TRADE WINDS PRIMARILY SW OF A LINE FROM 24N140W TO 05N120W TO 05N. THESE TRADE WINDS WILL DIMINISH TO 20 KT AND SHRINK SW AND AS THE RIDGE AXIS TO THE N WEAKENS AHEAD OF THE NEW FRONT MOVING INTO NW WATERS OVER NIGHT THU NIGHT. A SURFACE TROUGH IS EMBEDDED IN THE ITCZ FROM 08N136W TO 00N138W WITHIN THE AREA OF STRONG TRADE WINDS. MODERATE WITH ISOLATED STRONG CONVECTION CAN BE FOUND ON EITHER SIDE OF THIS TROUGH. THIS TROUGH LIES UNDER THE DIFFLUENT REAR RIGHT QUADRANT OF THE SOUTHWESTERLY UPPER JET ON THE SE SIDE OF AN UPPER TROUGH AXIS FROM 20N136W TO 10N140W. ANOTHER TROUGH EMBEDDED IN THE ITCZ FROM 10N107W TO 03N109W HAS SCATTERED MODERATE CONVECTION NEAR IT. IT ALSO LIES IN THE REAR RIGHT QUADRANT OF AN UPPER JET WHOSE AXIS STRETCHES FROM THE NORTHERN YUCATAN PENINSULA SW TO NEAR 12N110W. AN UPPER RIDGE AXIS LIES JUST TO THE E OF THIS LOW LEVEL TROUGH AND EXTENDS E TO THE PANAMA/COLOMBIA BOARDER. THE UPPER DIFFLUENCE ASSOCIATED WITH THIS RIDGE IS HELPING STIMULATE CONVECTION ALONG THE ITCZ BETWEEN 82W AND 89W. GAP WINDS... GALE FORCE WINDS ARE AFFECTING THE GULF OF TEHUANTEPEC AS STRONG HIGH PRES BUILDS OVER THE SW GULF OF MEXICO AND TIGHTENS THE PRESSURE GRADIENT OVER SOUTHERN MEXICO AND CENTRAL AMERICA. GALES ARE EXPECTED TO DIMINISH THU NIGHT AND WINDS WILL QUICKLY DROP BELOW 20 KT FRI AFTERNOON. TO THE S...VISIBLE SATELLITE IMAGERY JUST BEFORE SUNSET SHOWED THE BEGINNINGS OF AN ARC CLOUD FORMING SW OF THE GULF OF FONSECA. THE NUMERICAL MODELS HAD BEEN SLOW WITH THE ARRIVAL OF STRONG WINDS IN TEHUANTEPEC LAST NIGHT...AND THEY SEEM TO BE HAVING SIMILAR PROBLEMS THIS EVENING ASSUMING THIS ARC CLOUD IS THE BEGINNING OF 20 KT N WINDS IN THE GULF OF FONSECA AND THAT THE 26 KT OBSERVATION FROM SHIP ZCDG4 NEAR THE COAST OF THE GULF OF PAPAGAYO FROM 1700 UTC IS STILL REPRESENTATIVE. AS HIGH PRES OVER THE GULF OF MEXICO AND WESTERN CARIBBEAN SHIFTS E THROUGH THE DAY TOMORROW...LOOK FOR WINDS TO DIMINISH IN FONSECA BUT SPREAD DOWNSTREAM W OF 90W FROM PAPAGAYO AS THE WIND DIRECTION SHIFTS MORE EASTERLY. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ SCHAUER