000 AXPZ20 KNHC 180942 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC TUE JAN 18 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 0915 UTC. ...ITCZ... THE INTERTROPICAL CONVERGENCE ZONE AXIS IS CENTERED ALONG 6N78W 6N97W 5N106W 9N115W 8N130W 7N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM N AND 60 NM S OF THE AXIS BETWEEN 112W-121W...AND ALSO WITHIN 120 NM N OF THE AXIS BETWEEN 121W-126W. ...DISCUSSION... OVER THE FAR NE PORTION OF THE AREA...AN UPPER LEVEL TROUGH MOVING EASTWARD EXTENDS FROM 32N126W SE TO A WEAK CYCLONIC CIRCULATION NEAR 28.5N119.5W TO 25N115W TO 21N111W. A MID/UPPER LEVEL RIDGE EXISTS TO THE E OF THE TROUGH ACROSS THE GULF OF CALIFORNIA. WATER VAPOR IMAGERY SHOWS A LARGE AREA OF MODERATE SUBSIDENCE AND RESULTANT DRY AIR PREVAILING N OF 17N E OF 120W...AND ALSO NW OF THE TROUGH. TO THE W OF THE TROUGH ...THE AREA REMAINS ENVELOPED UNDER BROAD SCALE UPPER RIDGING RESPONDING TO DEEP LAYER TROUGHING JUST PAST HAWAII. WATER VAPOR IMAGERY SHOWS THAT THE RIDGING STRETCHES WELL N AND NE OF THE REGION. AN UPPER LEVEL TROUGH IS OVER THE FAR WESTERN PORTION OF THE AREA FROM 16N138W TO 10N134W TO 8N127W. DIFFLUENT FLOW ALOFT E OF THIS TROUGH IS PROVIDING A FAVORABLE UPPER LEVEL ENVIRONMENT TO HELP SUSTAIN THE ABOVE MENTIONED ITCZ CONVECTION. SW UPPER LEVEL FLOW OVER THIS CONVECTION IS ADVECTING UPPER LEVEL MOISTURE IN THE FORM BROKEN CIRRUS CLOUDS NE TO 14N...AND EASTWARD FROM THERE TO 110W BEFORE IT THINS AND STREAMS NE TO ACROSS SOUTHEASTERN MEXICO. MODERATE TO STRONG SUBSIDENCE IS EVIDENT TO THE SE OF THIS MOISTURE WITH ONLY ISOLATED WEAK CONVECTION OCCURRING ALONG AND NEAR ITCZ. AT THE SURFACE...A HIGH CENTER LOCATED WELL N OF THE AREA EXTENDS A RIDGE SE THROUGH 32N120W TO NEAR 22N124W. 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 AND COUPLE OF WEAK TROUGHS MOVING WWD THROUGH THE ITCZ CONTINUES TO INDUCE E 20 KT TRADE WINDS FROM 11N TO 19N W OF 130W WITH SEAS OF 8 TO 12 FT IN NW SWELL. LONG PERIOD NW SWELLS GENERATED FROM A LARGE AND INTENSE STORM CENTER WELL NW OF THE REGION HAVE ENTERED THE WESTERN PORTION OF THE AREA...AND WILL ALLOW FOR MAX SEAS OF 13 FT OVER THE FAR NW SECTOR OF THE AREA THROUGH THIS AFTERNOON. WITH THE HIGH CENTER FORECAST TO MOVE TO THE SW OVER THE NEXT 48 HOURS AND A TROUGH JUST W OF THE AREA ALONG 143W MOVES SLOWLY...THE GRADIENT WILL RESPOND BY RELAXING. THIS WILL DECREASE THE AREA OF TRADES TO W OF 135W IN ABOUT 24 HOURS. A TIGHT PRES GRADIENT OVER THE NE PORTION OF THE AREA IS ALLOWING FOR N TO NE 20 WINDS TO EXIST N OF 26N BETWEEN 122W AND 132W...WITH SEAS OF 8 TO 12 FT IN N SWELL. THESE SEAS ARE FORECAST TO BUILD TO 9 TO 13 FT IN 24 HOURS AS ANOTHER SET OF NLY SWELLS PROPAGATES INTO THE AREA UNDER TIGHT PINCHED FLOW BETWEEN THE HIGH N OF THE AREA AND THE CALIFORNIA COASTAL TROUGH. THE SWELLS WILL LAST DURING THE NEXT 48 HOURS. SATELLITE IMAGERY ALONG WITH PARTIAL ASCAT DATA FROM 0600 UTC SUGGESTS THAT A WEAK CYCLONIC CIRCULATION IS EMBEDDED ALONG THE ITCZ NEAR 8N126W. TO ITS E...A COUPLE OF WEAK TROUGHS ARE ALONG 122W FROM 3N TO 9N AND ALONG 117W FROM 5N TO 11N. THESE FEATURES ALONG WITH DIVERGENT FLOW ALOFT E OF THE ABOVE STATED UPPER TROUGH ARE SIGNIFICANTLY ENHANCING ITCZ CONVECTION. THE LOW IS FORECAST TO REMAIN WEAK AS IT SLOWLY MOVES W OVER THE NEXT 48 HOURS. THE BROAD SCALE RIDGING ACROSS THE REGION WILL BEGIN RETREAT TO THE W TODAY AS A DEEPENING SHORTWAVE TROUGH ADVANCES SEWD ACROSS CALIFORNIA THROUGH WED NIGHT AND OVER THE CENTRAL U.S. THU...WHILE A CUT-OFF LOW WITHIN ABOUT 390 NM NE OF THE BIG ISLAND OF HAWAII CURRENTLY MOVING SE BEGINS TO MOVE SW. 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. $$ AGUIRRE