000 AXPZ20 KNHC 170952 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC TUE MAY 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 0945 UTC. ..MONSOON TROUGH AND ITCZ AND OTHER TROPICAL CONVECTION... A MONSOON TROUGH EXTENDS FROM CENTRAL AMERICA AT 09N85W TO THE ITCZ AXIS NEAR 05N118W WHICH CONTINUES W TO 04N140W. AN EMBEDDED TROUGH WITH CYCLONIC CIRCULATION IS NOTED ALONG 103 TO 104W...WITH SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS NOTED WITHIN THE AREA FROM 04N TO 10N BETWEEN 88W AND 110W...BUT IS CURRENTLY DECREASING IN INTENSITY. MODERATE CONVECTION IS NOTED WITHIN 90 NM OF 05N118W. SCATTERED MODERATE TO STRONG CONVECTION IS NOTED OVER AND WITHIN 90 NM OF THE COAST CENTRAL AMERICA FROM 87W TO 96W. LIGHTING DATA VERIFIES ADDITIONAL THUNDERSTORMS OVER THE WATERS ELSEWHERE N OF 10N BETWEEN 94W AND 99W...WITH THE ACTIVITY INCREASING IN BOTH INTENSITY AND COVERAGE DURING THE PAST COUPLE OF HOURS. ...DISCUSSION... AN UPPER LEVEL TROUGH EXTENDS SW FROM CALIFORNIA INTO THE DISCUSSION AREA FROM 32N121W TO 25N130W...THEN CONTINUES SW INTO AN UPPER CYCLONE CUTTING OFF NEAR 21N135W...WITH AN UPPER TROUGH STILL CONTINUING S TO A BASE AT 05N138W. UPPER LEVEL MOISTURE PRECEDES THE TROUGH...BUT IS CURRENTLY EVAPORATING AS IT CROSSES THE SOUTHERN BAJA CALIFORNIA PENINSULA. A NARROW BAND OF VERY DRY AIR EXTENDS FROM CENTRAL NEW MEXICO TO ACROSS SOUTHERN ARIZONA TO NEAR 25N140W...WITH THIS DRY AIR MERGING WITH DRY AIR SURROUNDING THE UPPER CYCLONE...GENERALLY IN THE AREA FROM 18N TO 27N BETWEEN 127W AND 142W. IMMEDIATELY TO NW OF THE NARROW BAND OF DRY UPPER AIR IS DENSE UPPER MOISTURE ROTATING E THROUGH THE UPPER TROUGH...CURRENTLY CROSSING THE NORTHERN BAJA CALIFORNIA PENINSULA. AN UPPER RIDGE CONTINUES TO EXTEND E ACROSS THE DEEP TROPICS S OF 09N TO THE W OF 133W. THE NORTHERLY UPPER FLOW IS ACCOMPANIED BY DRY AIR AND IS SUPPRESSING CONVECTION ALONG THE ITCZ W OF 131W. AN UPPER ANTICYCLONE IS ESTIMATED AT 10N97W WITH AN UPPER RIDGE EXTENDING SW TO A SHARP CREST AT 07N125W...AND AN UPPER RIDGE EXTENDING E TO A ILL DEFINED CREST AT 05N83W. AN UPPER RIDGE ALSO EXTENDS N TO A CREST AT 33N111W. AN UPPER CYCLONE IS NOTED NEAR 05S111W. CONVECTION IS ENHANCED ALONG THE ITCZ BETWEEN 100W AND 130W WITH SOME OF THE DEBRIS MOISTURE PULLING S ACROSS THE EQUATOR BETWEEN 113W AND 130W IN RESPONSE TO THE UPPER CYCLONE. SOME OF THE DEBRIS MOISTURE IS ALSO ADVECTED NE IN RESPONSE TO THE UPPER RIDGE...BUT FOR THE MOST PART EVAPORATES OVER CENTRAL AMERICA S OF 20N. CLUSTERS OF THUNDERSTORMS DEVELOPED FOR THE THIRD DAY OVER SOUTHEASTERN OLD MEXICO AND GUATEMALA...WITH THE REMNANTS NOW MOVING S TO ALONG THE COAST OF CENTRAL AMERICA AS PREVIOUSLY MENTIONED. DEBRIS MOISTURE IS NOTED OVER THE DEEP TROPICS S OF 11N E OF 113W...WITH SOME MOISTURE SPREADING S ACROSS THE EQUATOR EVENTUALLY EVAPORATING ALONG 02S...AND SOME OF THE MOISTURE ALSO SPREADS NE ACROSS THE CARIBBEAN IN RESPONSE TO A PERSISTENT UPPER TROUGH OVER THE W CARIBBEAN. AT THE LOW LEVELS A BROAD SURFACE RIDGE EXTENDS ALONG 27N140W TO NEAR 17N110W. THE RIDGE HAS BEEN BLOCKING COLD FRONTS TO OVER THE EXTREME N PORTION. HOWEVER THE ASSOCIATED NORTHERLY SWELLS CONTINUE TO PROPAGATE S OVER THE SUBTROPICAL WATERS E OF 130W MERGING WITH WIND GENERATED NW SWELL ALONG THE W COAST OF BAJA CALIFORNIA PENINSULA...WITH COMBINED SEAS HEIGHTS TO 10 FT OVER THE PACIFIC WATERS N OF 20N BETWEEN 125W AND 108W. SOME SWELL REFRACTION POSSIBLE INTO THE SOUTHERN GULF OF CALIFORNIA. SOUTHERLY SWELL WILL ARRIVE ALONG 20N TODAY AND REACH ALONG 30N TONIGHT. NE TRADES TO THE SW OF THE RIDGE...GENERALLY S OF 17N W OF 115W ARE MOSTLY AT 15 KT...BUT NE SWELL IS CROSSING WITH SOUTHERLY CROSS EQUATORIAL SWELL RESULTING IN COMBINED SEAS OF 8 TO 11 FT. THE NE TRADES WILL INCREASE SOME ON WED AS THE CROSS SWELL SITUATION EXPANDS E TO THE PACIFIC WATERS FROM 05N TO 20N W OF 108W. BY THEN...THE SOUTHERLY SWELLS AT 17 TO 21 SECONDS WILL COVER ALL WATERS S OF 20N WITH RESULTANT SEAS OF 8 TO 10 FT...EXCEPT 4 TO 7 FT SEAS IN THE WATERS NE OF THE GALAPAGOS ISLANDS TO THE COAST OF CENTRAL AMERICA BETWEEN 83W TO 87W. GULF OF CALIFORNIA...A COLD FRONT WILL SWEEP ACROSS THE NORTHERN WATERS WED NIGHT ACCOMPANIED BY A 20 TO 25 KT SW TO NW WIND SHIFT. $$ NELSON