000 AXPZ20 KNHC 201519 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC THU SEP 19 2012 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 1500 UTC. ...SPECIAL FEATURES... SURFACE LOW PRES HAS DEVELOPED ALONG THE MONSOON TROUGH NEAR 12N100W 1009 MB. THE LOW IS EXPECTED TO MOVE NW AND INTENSIFY REACHING NEAR 12N103W TONIGHT AND NEAR 12N104W ON FRI NIGHT. TROPICAL CYCLONE FORMATION IS POSSIBLE. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH 10N86W TO 1009 MB LOW PRES 12N100W TO 10N120W. ITCZ AXIS 10N120W TO 11N125W TO 06N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 150 NM S OF AXIS FROM 104W-112W AND WITHIN 90 NM S OF AXIS FROM 128W-131W. ...DISCUSSION... LONGWAVE RIDGE DOMINATES THE EASTERN N PACIFIC AND THE WESTERN U.S. WITH AN UPPER ANTICYCLONIC CIRCULATION AT 22N127W. RIDGE EXTENDS FROM THE ANTICYCLONE TO 32N120W. AN UPPER RIDGE ALSO EXTENDS FROM THE ANTICYCLONIC CIRCULATION SW TO 12N140W. SOME UPPER MOISTURE IS SPREADING NE ACROSS THE W PORTION OF THE RIDGE AXIS. A 50-65 KT JET STREAM ACROSS THE NW PORTION OF THE DISCUSSION AREA BETWEEN THE RIDGE AND A SHARP TROUGH NW OF THE AREA EXTENDS FROM 27N140W TO 32N131W. AN UPPER TROUGH EXTENDS FROM 20N121W TO 11N115W WITH ANOTHER ANTICYCLONIC CIRCULATION OFF THE SW MEXICO COAST NEAR 16N100W. WEAK UPPER DIFFLUENCE SW OF OF THE ANTICYCLONE IS SUPPORTING THE CONVECTION ALONG THE MONSOON TROUGH AND ITCZ BETWEEN 105W AND 135W AS PREVIOUSLY DESCRIBED. SURFACE TROUGH WITH AXIS FROM 22N134W TO 18N133W NE WINDS 20-25 KT ARE WITHIN 240 NM W OF THE LOW. THE PRES GRADIENT BETWEEN LOWER PRES ACROSS THE PACIFIC AND HIGH PRES IN THE GULF OF MEXICO IS RESULTING IN NLY WIND 20-25 KT THROUGH THE GULF OF TEHUANTEPEC. THESE CONDITIONS ARE EXPECTED TO PERSIST FOR THE NEXT FEW DAYS. $$ DGS