000 AXPZ20 KNHC 212157 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC SUN AUG 21 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2145 UTC. ...ITCZ/MONSOON TROUGH... MONSOON TROUGH EXTENDS FROM 9N84W NW TO 1008 MB LOW AT 15N95W TO 16N103W TO 1009 MB LOW 12N109W AND TO 12N115W. IT THEN RESUMES FROM 15N125W TO BEYOND THE AREA AT 10N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION EXISTS FROM 10N TO 15N BETWEEN 94W AND 100W. ...DISCUSSION... W OF 120W... AN ELONGATED UPPER LEVEL LOW IS N OF THE AREA NEAR 34N127W. A TROUGH EXTENDS FROM THE LOW SW TO NEAR 24N136W. A HIGHLY AMPLIFIED UPPER RIDGE IS TO THE NW OF THE LOW. ANOTHER UPPER LOW IS W OF THE AREA NEAR 33N147W. THE UPPER LOW NEAR 34N127W IS FORECAST TO DROP NEAR 30N128W BY MON EVENING WHILE BECOMING CUT-OFF FROM THE NORTHERN STREAM JET STREAM BRANCH. ELSEWHERE AN UPPER LEVEL ANTICYCLONE IS ANCHORED NEAR 19N141W WITH A RIDGE EASTWARD TO 125W. A NARROW UPPER TROUGH IS ALONG 123W WITH A POSSIBLE SMALL UPPER LEVEL LOW FORMING NEAR 24N122W. AT THE SURFACE...THE REMNANT LOW OF FORMER TROPICAL DEPRESSION GREG IS UNDER THIS TROUGH AT THE POSITION OF 20N 124W 1008 MB MOVING W AT 8 KT...WITH MAXIMUM WINDS OF 30 KT GUSTS TO 40 KT. IT IS MARKED BY A LARGE SWIRL OF LOW AND MID LEVEL CLOUDS WITH SCATTERED SHOWERS WITHIN 240 NM IN THE W SEMICIRCLE AND WITHIN 120 NM IN THE E SEMICIRCLE OF THE THE CENTER. THE LOW IS FORECAST TO WEAKEN FURTHER THROUGH THE NEXT 48 HOURS AS IT REACHES NEAR 19N128W. SATELLITE WATER VAPOR IMAGERY SHOWS MODERATE SUBSIDENCE COVERING MUCH OF THIS PORTION OF THE AREA INCLUDING THE UPPER ATMOSPHERE OVER THE WEST SIDE OF THE REMNANT LOW OF GREG. THIS IS ALLOWING FOR THE ATMOSPHERE TO REMAIN RATHER DRY AND STABLE INHIBITING DEEP CONVECTION FROM FORMING ALONG AND NEAR THE MONSOON TROUGH. UPPER LEVEL MOISTURE IS STREAMING SWD INTO THE AREA BETWEEN THE UPPER LOW NEAR 32N128W AND THE UPPER RIDGE TO ITS NW. ELSEWHERE AT THE SURFACE...A WEAK 1022 MB HIGH IS N OF THE AREA AT 35N137W WITH A RIDGE SE TO 28N119W. WEAK HIGH PRES COVERS THE AREA GENERALLY TO THE N OF 24N. E OF 120W...A LARGE AND NEARLY STATIONARY ANTICYCLONE ANCHORED OVER NRN TEXAS EXTENDS A RIDGE SW TO ACROSS CENTRAL BAJA CALIFORNIA...AND TO NEAR 24N120W. A SMALL UPPER LEVEL LOW IS OVER CENTRAL MEXICO AT 24N105W. THE UPPER FLOW IS SQUEEZED IN BETWEEN BOTH OF THESE FEATURES...AND IS ADVECTING UPPER LEVEL DEBRIS MOISTURE...IN THE FORM OF SCATTERED TO BROKEN HIGH CLOUDS ...WESTWARD TO SRN BAJA CALIFORNIA. THE FLOW PATTERN TO SW OF THE UPPER LEVEL LOW OVER MEXICO IS RATHER DIFFLUENT BETWEEN 104W-115W. AT THE SURFACE...A WEAK 1009 MB LOW ON THE MONSOON TROUGH IS MOVING SLOWLY WNW NEAR 12N109W. THE UPPER LEVEL ELY FLOW THROUGHOUT THIS AREA IS SHEARING SCATTERED STRONG CONVECTION THAT IS OCCURRING WITHIN 180 NM IN THE NW QUADRANT OF THE LOW. THE LOW IS FORECAST TO REACH NEAR 13N110W IN ABOUT 24 HOURS...AND TO NEAR 13N111W IN 48 HOURS. UPPER LEVEL ELY SHEAR WILL PERSIST DURING THIS TIME. SW 20 KT WINDS WILL CONTINUE TO FEED INTO THE MONSOON TROUGH IN THE VICINITY OF THE LOW FROM ABOUT 8N TO 13N BETWEEN 104W-111W OVER THE NEXT 48 HOURS WITH SEAS TO 9 FT. SATELLITE WATER VAPOR IMAGERY SHOWS ABUNDANT UPPER LEVEL MOISTURE STREAMING WESTWARD IN THE UPPER LEVEL ELY FLOW ACROSS THIS PORTION OF THE AREA... ALTHOUGH VISIBLE IMAGERY SHOWS BROAD AND DISORGANIZED CLOUDINESS AND CONVECTION AS DESCRIBED ABOVE TO THE S OF THE MONSOON TROUGH BETWEEN 92W-100W AND UPSTREAM OF THE 1009 MB LOW AT 12N109W. ALSO WITH RESPECT TO MARINE ISSUES...LONG PERIOD CROSS-EQUATORIAL SWELLS RESULTING IN SEAS TO 9 FT WILL BE CONFINED TO S OF 9N BETWEEN 98W-116W. ACCORDING TO WAVEWATCH MODEL GUIDANCE THESE SWELLS SHOULD LAST THROUGH THE NEXT 48 HOURS. $$ AGUIRRE