000 AXPZ20 KNHC 170944 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC MON JAN 17 2011 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0930 UTC. ...ITCZ... THE INTERTROPICAL CONVERGENCE ZONE AXIS IS CENTERED ALONG 7N79W 6N88W 5N100W 8N115W 6N123W 8N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 180 NM N OF THE AXIS BETWEEN 132W-136W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM N OF THE AXIS BETWEEN 127W-130W. ...DISCUSSION... OVER THE EASTERN PORTION OF THE AREA...A SHORTWAVE TROUGH PUSHING QUICKLY SWD EXTENDS FROM FAR SE TEXAS SOUTHWESTWARD TO ACROSS CENTRAL MEXICO AND TO NEAR 21N114W. VERY LITTLE IN THE WAY OF ANY MOISTURE IS ASSOCIATED WITH THIS TROUGH AS MODERATE SUBSIDENCE AND RESULTANT DRY AIR PREVAILS OVER THIS PORTION OF THE AREA N OF 20N E OF 120W. MODERATE TO STRONG UPPER FLOW EXISTS S OF THE TROUGH TO 9N...AND IS TRANSPORTING SCATTERED CIRRUS CLOUDS ENE TO ACROSS SOUTHEASTERN MEXICO. TO THE W OF OF THE TROUGH THE AREA REMAINS ENVELOPED UNDER BROAD SCALE UPPER RIDGING RESPONDING TO DEEP LAYER TROUGHING W OF THE REGION APPROACHING THE HAWAIIAN ISLANDS. WATER VAPOR IMAGERY SHOWS THE RIDGE CREST EXPANDING TO WELL N OF THE REGION. DIFFLUENT FLOW ALOFT E OF THIS TROUGH IS PROVIDING A FAVORABLE UPPER LEVEL ENVIRONMENT TO SUPPORT ITCZ CONVECTION BETWEEN 132W AND 137W AS IT SERVED AS A GOOD OUTLET FOR ABUNDANT UPPER LEVEL MOISTURE DERIVED FROM THE CONVECTION TO ADVECT NWD IN SLY FLOW E OF THE TROUGH. THE MOISTURE REACHES N TO NEAR 27N BEFORE IT SHARPLY TURNS EASTWARD TO 120W BEFORE ERODING IN A RATHER DRY AND STABLE ATMOSPHERIC ENVIRONMENT IN THE MODERATE SUBSIDENCE REGION. AT THE SURFACE...A 1027 MB HIGH IS CENTERED N OF THE AREA NEAR 36N130W. A RIDGE EXTENDS FROM THE HIGH SE TO 32N128W TO 25N122W ...AND TO NEAR 18N114W. A TIGHT PRES GRADIENT ON THE SOUTHERN PERIPHERY OF THE RIDGE DUE TO THE PRES DIFFERENCE BETWEEN IT AND LOWER PRESSURES ASSOCIATED WITH THE ITCZ CONTINUES TO INDUCE NE TO E 20 KT TRADE WINDS FROM 10N TO 19N W OF 130W. LARGE NW SWELLS DERIVED FROM A SERIES OF LOW PRES SYSTEMS WELL TO THE NW OF THE REGION WILL KEEP THE SEA STATE UP TO A MAX OF AROUND 10 FT DURING THE NEXT 24-48 HOURS. AS THE HIGH MOVES SOME TO THE NW OVER THE NEXT 48 HOURS...THE AREA OF TRADES WILL THEN DECREASE FROM E TO W. A TIGHT PRES GRADIENT TO THE NE OF THE RIDGE OVER THE NE PORTION OF THE AREA IS ALLOWING FOR N TO NE 20 TO 25 KT WINDS TO EXIST N OF 26N BETWEEN 122W AND 134W. SEAS THERE ARE UP TO 9 FT...BUT ARE FORECAST TO BUILD TO 11 FT IN 24 HOURS AS A SET OF NW SWELLS MIGRATES SEWD INTO THE AREA UNDER TIGHT PINCHED FLOW BETWEEN THE HIGH N OF THE AREA AND THE CALIFORNIA COASTAL TROUGH. THESE SWELLS WILL THEN ALLOW SEAS TO MAX OUT UP TO 13 FT MON NIGHT. ALSO BY MON NIGHT...NWW3 MODEL GUIDANCE FORECASTS A VERY IMPRESSIVE LARGE SET OF LONG PERIOD NW SWELLS WITH PERIOD OF 15-18 SEC TO APPROACH 140W N OF 19N WITH SEAS TO POSSIBLY AS HIGH AS 14 FT BEFORE BEGINNING TO SUBSIDE TO AROUND 11 FT BY TUE NIGHT. THE BROAD SCALE RIDGING ACROSS THE REGION WILL BEGIN TO BREAK DOWN ON TUE AS A CUT-OFF LOW EVOLVES FROM THE DEEP LAYER TROUGH THAT IS CURRENTLY W OF THE REGION. THE LOW THEN DROPS S ACROSS THE HAWAIIAN ISLANDS AND ON TO THE SW WED...WHILE A DEEPENING SHORTWAVE TROUGH ADVANCES SEWD ACROSS THE WESTERN U.S. WITH THE RIDGING SLIDING WESTWARD. THIS WILL ALLOW FOR TRADES OVER THE WESTERN PORTION OF THE AREA TO DIMINISH EVEN FURTHER. THE RIDGE WILL STILL BE PROMINENT ENOUGH TO HOLD BACK FRONTAL SYSTEMS FROM ENTERING THE REGION AS UPPER LEVEL ATMOSPHERIC INSTABILITY STAYS WELL TO THE N OF REGION ROUNDING THE CREST OF THE UPPER RIDGE. $$ AGUIRRE