000 AXPZ20 KNHC 191557 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC MON SEP 19 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 1515 UTC. ...ITCZ/MONSOON TROUGH... MONSOON TROUGH FROM 10N85W TO LOW PRES NEAR 12.5N93.5W 1009 MB TO 08N105W CONTINUES AT 16N108W TO LOW PRES NEAR 16N112W 1012 MB TO 09N140W. SCATTERED MODERATE TO STRONG WITHIN 90 NM EITHER SIDE OF AXIS FROM 87W TO 91W AND WITHIN 120 NM N OF AXIS FROM 91W TO 96W AND WITHIN 120 NM N OF AXIS FROM 117W TO 124W. ...DISCUSSION... ALOFT...A NARROW UPPER LEVEL RIDGE SPANNED THE AREA THIS MORNING CENTERED ON TWO ANTICYCLONES...ONE NEAR 21N113W AND EXTENDING E ACROSS CENTRAL MEXICO AND INTO THE W CENTRAL GULF OF MEXICO... AND A SECOND ANTICYCLONE NEAR 18N135W EXTENDING SW TO THE ITCZ S OF THE HAWAIIAN ISLANDS. BROAD AND WEAK TROUGHING PREVAILS TO THE N OF THIS RIDGE FROM 28N TO 40N WITH A SERIES OF WEAK SHORTWAVES MOVING SLOWLY E-NE ACROSS MID LATITUDES. A TUTT AXIS LIES IMMEDIATELY S OF THE RIDGE...EXTENDING FROM THE YUCATAN PENINSULA W-SW ACROSS S CENTRAL MEXICO TO A WEAK MID LEVEL PERTURBATION NEAR 12N115W. THE PRES GRADIENT DUE S OF THE UPPER ANTICYCLONE NEAR 21N113W WAS PRODUCING A JET SEGMENT ALOFT TO AROUND 40 KT AND AIDING IN INDUCING A ZONE OF UPPER LEVEL DIVERGENCE FROM 115W TO 130W. ANTICYCLONIC FLOW ALOFT WAS OCCURRING S OF THE TUTT ACROSS CENTRAL AMERICA AND WAS PRODUCING A BROAD ZONE OF DIRECTIONAL DIVERGENCE ALOFT FROM THE PACIFIC COASTS OF CENTRAL AMERICA EXTENDING OUT SOME 360 NM TO THE SW. THIS WAS AIDING IN MAINTAINING ACTIVE CONVECTION FROM THE OFFSHORE PACIFIC WATERS OF SE MEXICO TO THE GULF OF PANAMA. AT LOW LEVELS...A 1023 MB SURFACE HIGH WAS CENTERED NEAR 35N140W WITH MODEST RIDGING EXTENDING SE TO NEAR 22N113W. GENERALLY LIGHT TO MODERATE TRADEWINDS CONTINUE ACROSS THE AREA BASED ON OVERNIGHT SCATTEROMETER PASSES...WITH 20 KT TRADES GENERALLY W OF 140W...EXCEPT JUST TO THE N OF THE MONSOON TROUGH BETWEEN 130W AND 140W...WHERE WEAK LOW PRES IS KEEPING THE PRES GRADIENT TIGHT ENOUGH TO SUPPORT A SMALL AREA OF 20 KT WINDS. THE SURFACE HIGH PRES WILL CONTINUE TO WEAKEN THROUGH WEDNESDAY AS A DEEP LAYER TROUGH WELL NW OF THE AREA DIGS EASTWARD THROUGH THE N CENTRAL PACIFIC. THE AREA OF FRESH TRADES W OF 130W N OF THE MONSOON TROUGH WILL SLOWLY DIMINISH AS A RESULT. THE MONSOON TROUGH ACROSS THE EPAC REMAINS BROKEN INTO TWO SEGMENTS TODAY...WITH THE EASTERNMOST SEGMENT ANCHORED ON BROAD LOW PRES ACROSS COLOMBIA AND THE SW CARIBBEAN EXTENDING GENERALLY W TO 105W...AND A SECOND SEGMENT ANCHORED ON A PERSISTENT CYCLONIC CIRCULATION MEANDERING SW OF THE S TIP OF BAJA CALIFORNIA. SATELLITE IMAGERY THIS MORNING SUGGESTS SEVERAL SMALL CYCLONIC CIRCULATIONS EMBEDDED WITHIN THE W SEGMENT OF THE TROUGH...WITH THE MOST SIGNIFICANT A 1008 MB LOW PRES CENTER NEAR 10N133.5W. COMPUTER MODEL GUIDANCE INDICATE THAT THESE LOWS ALONG THE TROUGH WILL SLOWLY WEAKEN AND DRIFT W WITHIN THE TROUGH OVER THE NEXT FEW DAYS...WITH WINDS TO 20 KT POSSIBLE ON BOTH SIDES OF THE TROUGH IN THE VICINITY OF THE LOWS. WEAK RIDGING IS NOTED BETWEEN 105W AND 112W...EFFECTIVELY BREAKING THE MONSOON TROUGH. THE TROUGH CONTINUES AT 105W TO A DEVELOPING 1009 MB LOW PRES CENTER NEAR 12.5N93.5W. THE GFS AND ECMWF SHOW INCREASING WINDS AND BUILDING SEAS AS THIS LOW DEEPENS AS IT MOVES NW OVER THE NEXT SEVERAL DAYS...AND WILL INCLUDE FRESH GAP WIND FLOW THROUGH THE GULF OF TEHUANTEPEC. SCATTERED MODERATE CONVECTION IS NOTED ALONG THE MONSOON TROUGH AND OFF THE PACIFIC COAST OF CENTRAL AMERICA FROM COSTA RICA TO SOUTHERN MEXICO. $$ STRIPLING