000 AXPZ20 KNHC 181523 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC SAT JUN 18 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1330 UTC. ...SPECIAL FEATURES... A BROAD AREA OF LOW PRESSURE LIES S OF THE GULF OF TEHUANTEPEC. IT IS CURRENTLY ANALYZED AS A 1007 MB SURFACE LOW NEAR 13N95W. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION LIES WITHIN 270 NM NW SEMICIRCLE OF THE LOW WITH SCATTERED MODERATE CONVECTION ELSEWHERE WITHIN 270 NM NE QUADRANT. IN THE NE QUADRANT OF THE LOW...SHIP ZCDB4 REPORTED 24 KT E SE WINDS AND 8 FT SEAS NEAR 14N94W AT 1200 UTC. MODEL GUIDANCE CONTINUES TO SUGGEST GRADUAL DEVELOPMENT OF THIS SURFACE LOW OVER THE NEXT DAY OR TWO AS IT DRIFTS NW...WITH THE POSSIBILITY OF TROPICAL CYCLONE FORMATION. SOUTHWESTERLY WINDS ARE FORECAST TO INCREASE AND FEED INTO THIS SURFACE LOW OVER THE NEXT FEW DAYS. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM 11N86W TO LOW PRES NEAR 13N95W 1007 MB TO 10N100W TO 12N113W TO 08N127W. THE ITCZ EXTENDS FROM 08N127W TO 06N140W. LOCALLY OVERCAST LOW AND MID LEVEL CLOUDS ARE NOTED OVER THE ENTIRE AREA N OF THE EQUATOR TO THE E OF 100W WITH ISOLATED MODERATE CONVECTION EMBEDDED IN THIS AREA N OF 02N TO THE COAST OF COSTA RICA AND PANAMA BETWEEN 80W AND 85W. SCATTERED MODERATE CONVECTION LIES JUST TO THE W OF THIS AREA OF CONSISTENT LOW TO MID LEVEL CLOUDINESS WITHIN 270 NM EITHER SIDE OF THE MONSOON TROUGH AXIS BETWEEN 103W AND 110W. ...DISCUSSION... W OF 110W...A BLANKET OF STRATOCUMULUS CLOUDS LIES OVER MUCH OF THE AREA N OF 15N W OF 110W. THE SUBTROPICAL HIGH DOMINATES THE REGION WITH ITS RIDGE AXIS EXTENDING FROM THE 1032 NM HIGH CENTER NEAR 36N148W THROUGH 31N135W TO 15N110W. FRESH NE TRADE WINDS ARE CONFINED TO THE AREA N OF 22N W OF 130W. AN UPPER TROUGH EXTENDS OVER THE AREA FROM SOUTHERN CALIFORNIA THROUGH 31N123W INTO AN UPPER CYCLONE AT 23N138W. THIS UPPER CYCLONE IS FORECAST TO RETROGRADE TO THE NW AS AN ANTICYCLONE NEAR 23N104W REORGANIZES FARTHER W NEAR 25N120W BY MON MORNING...SEVERING THE CYCLONE FROM THE TROUGHING OVER THE WESTERN UNITED STATES. LITTLE CHANGE IS EXPECTED IN THE POSITION OR STRENGTH OF THE SUBTROPICAL HIGH THROUGH SUN OR IN THE AREA OF TRADE WINDS. BY MON MORNING...A COLD FRONT WILL APPROACH THE SUBTROPICAL HIGH FROM THE NW AND WEAKEN IT...DIMINISHING THE TRADE WINDS. THE NW SWELL ASSOCIATED WITH THIS COLD FRONT WILL MOVE INTO THE FORECAST AREA BY MON MORNING...BRINGING SEAS TO 8 FT IN N CENTRAL WATERS. ON THE EASTERN SIDE OF THE RIDGE...THE PRES GRADIENT BETWEEN THE RIDGE AND TROUGHING OVER THE SW UNITED STATES IS SUPPORTING FRESH NW WINDS ALONG THE BAJA CALIFORNIA COAST WHICH ARE FORECAST TO CONTINUE THROUGH MON MORNING. OVER THE TROPICS...CONDITIONS ARE REASONABLY QUIET W OF 110W WITH NO SIGNIFICANT DEEP CONVECTION NOTED. AN UPPER CYCLONE CENTERED NEAR 02N133W WILL WEAKEN AND SHIFT SOUTHEASTWARD...BECOMING ENGULFED IN BROAD UPPER TROUGHING CENTERED JUST S OF THE EQUATOR BY SUN NIGHT. E OF 110W...BROAD LOW TO MID LEVEL TROUGHING DOMINATES THE AREA S OF 15N AND SUPPORTS THE SPECIAL FEATURE DESCRIBED IN THE FIRST SECTION OF THIS DISCUSSION. CONVECTION OVER THE REMAINDER OF THIS REGION IS DESCRIBED IN THE ITCZ/MONSOON TROUGH SECTION ABOVE. DIFFLUENT FLOW BETWEEN THE AFOREMENTIONED ANTICYLONE ALOFT NEAR 23N104W AND THE BROAD UPPER TROUGHING CENTERED JUST S OF THE EQUATOR PROVIDES A DIFFLUENT UPPER ENVIRONMENT THAT IS FAVORABLE FOR THE DEVELOPMENT OF DEEP CONVECTION S OF 15N. AS THE ANTICYCLONE REORGANIZES TO THE W...LOOK FOR WINDS ALOFT TO BECOME MORE UNIFORM NORTHEASTERLY AND INCREASE TO 40-60 KT PRIMARILY OVER THE AREA S OF 10N BETWEEN 90W AND 105W. THIS SHEAR SHOULD INHIBIT THE DEVELOPMENT OF DEEP CONVECTION NEAR THE MONSOON TROUGH AND TO THE SE OF THE LOW PRES IN THE SPECIAL FEATURES SECTION BY LATE SUN. $$ SCHAUER