000 AXPZ20 KNHC 300919 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC FRI JUL 29 2011 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0715 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS FROM 11N86W TO 1008 MB LOW PRES NEAR 10N97W TO 1009 MB LOW PRES NEAR 13N116W TO 10N140W. SCATTERED MODERATE CONVECTION LIES WITHIN 120 NM NE SEMICIRCLE...330 NM S QUADRANT AND 550 NM W QUADRANT OF LOW PRES NEAR 10N97W. SCATTERED MODERATE CONVECTION LIES WITHIN 150 NM NW QUADRANT OF LOW PRES NEAR 13N116W. ...DISCUSSION... A LOW ALOFT NEAR 27N130W IS BEING PICKED UP BY AN AMPLIFYING NORTHERN STREAM TROUGH. THE MEAN TROUGH OVER THE EASTERN NORTH PACIFIC IS EXPECTED TO SHIFT SLIGHTLY WESTWARD OVER THE NEXT FEW DAYS. AN ANTICYCLONE LIES TO THE NW OF THE LOW NEAR 30N145W. THIS ANTICYCLONE WILL MOVE LITTLE AND WILL WEAKEN AS THE NORTHERN STREAM TROUGH APPROACHES. THE SUBTROPICAL HIGH AT THE SURFACE ASSOCIATED WITH THIS ANTICYCLONE IS DISPLACED WELL TO THE N NEAR 40N150W. THE SUBTROPICAL SURFACE RIDGE HAS BEEN COMPROMISED BY THE SURFACE TROUGH FROM 30N128W TO 27N129W ASSOCIATED WITH THE DEEP LAYER TROUGHING OVER THE N CENTRAL PORTION OF THE FORECAST AREA. THE NE TRADE WINDS HAVE BEEN REDUCED TO A GENTLE TO MODERATE BREEZE OVER MUCH OF THE AREA AS A RESULT. THE EXCEPTION LIES JUST W OF THE SURFACE TROUGH OVER NW WATERS WHERE THE PRES GRADIENT IS TIGHT ENOUGH TO SUPPORT FRESH NE WINDS. NE SWELL FROM A NEAR-GALE TO GALE WIND AREA OFF THE U.S. PACIFIC NW COAST ASSOCIATED WITH THE DEEP LAYER TROUGHING HAS MOVED INTO NW WATERS AND RAISED SIGNIFICANT WAVE HEIGHTS TO 9 FT. THESE CONDITIONS WILL REMAIN MOSTLY UNCHANGED FOR THE NEXT TWO DAYS. A SECOND ANTICYCLONE ALOFT IS NEAR 19N119W. A RIDGE AXIS EXTENDS E OF THE LOW TO 17N112W. A WEAK LOW ALOFT NEAR 25N114W ACTS TO SEVER THE RIDGE THAT RESUMES NEAR 17N108W AND EXTENDS NE TO AN ANTICYCLONE OVER N CENTRAL MEXICO NEAR 27N105W. SCATTERED MODERATE CONVECTION LIES WITHIN 90 NM OF THE MEXICAN COAST BETWEEN 99W AND 105W S OF 20N AND WITHIN 120 NM OF THE MEXICAN COAST BETWEEN 90W AND 98W. THIS CONVECTION IS BEING ENHANCED BY THE DIFFLUENCE ALOFT ASSOCIATED WITH THE RIDGE AXIS. AS THE DEEP LAYER TROUGH TO THE NW SHIFTS WESTWARD AND BEGINS TO WEAKEN TODAY...THE PRES GRADIENT AT THE SURFACE OVER NE WATERS WILL WEAKEN. THIS WILL ALLOW FOR THE FRESH NW WINDS SEEN IN THE 0434 UTC ASCAT PASS OFF THE CENTRAL AND NORTHERN BAJA CALIFORNIA COAST TO DIMINISH. THE 0426 UTC ASCAT PASS SHOWED THE LARGEST AREA OF FRESH WINDS LIES FROM 03N TO 08N BETWEEN 91W AND 110W. THIS FRESH SW MONSOON FLOW IS FEEDING INTO THE AREA OF LOW PRES CENTERED NEAR 10N97W AND IS EXPECTED TO SHIFT NORTHWARD AS THE LOW DRIFTS NW OVER THE NEXT FEW DAYS. A NEW BATCH OF SW SWELL IS MAKING ITS WAY THROUGH THIS AREA OF FRESH WINDS AND LOWER PRES. THIS SWELL WILL DAMPEN TO LESS THAN 8 FT WELL BEFORE IT REACHES THE CENTRAL AMERICAN AND MEXICAN COAST LATE TODAY. THE FORECAST GUIDANCE HAS COME INTO SLIGHTLY BETTER AGREEMENT ON SOME DEVELOPMENT OF THIS LOW PRES SYSTEM AS IT SLOWLY MOVES NW. THE NE SHEAR OVER THE LOW IS EXPECTED TO DIMINISH SOME OVER THE NEXT FEW DAYS AND THE LOW WILL TRACK UNDER A DIFFLUENT AREA BETWEEN 20 KT E-NE FLOW TO ITS N AND 20-40 KT N FLOW TO ITS S. $$ SCHAUER