000 AXPZ20 KNHC 070950 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC MON OCT 07 2013 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0945 UTC. ...SPECIAL FEATURE... TROPICAL STORM NARDA CENTERED AT 13.2N 120.9W AT 0900 UTC MOVING W OR 275 DEG AT 12 KT. MAXIMUM SUSTAINED WINDS ARE 40 KT GUSTING TO 50 KT WITH SURFACE PRESSURE OF 1003 MB. CURRENTLY NUMEROUS STRONG CONVECTION IS BANDED WITHIN 180 NM OVER THE W SEMICIRCLE AND WITHIN 60 NM OVER THE SE QUADRANT OF CENTER. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED OVER THE E SEMICIRCLE WITHIN 30 EITHER SIDE OF LINES FROM 16.5N115W TO 16N120W. NARDA IS EXPECTED TO TRACK W ALONG THE SOUTHERN PERIPHERY OF AN UPPER RIDGE WITH FAVORABLE UPPER LEVEL CONDITIONS...AND ACROSS WARM SEA WATERS...OVER THE NEXT FEW DAYS. THUS NARDA IS FORECAST TO INTENSIFY REACHING MINIMAL HURRICANE FORCE LATE TUE AND CONTINUE AT HURRICANE FORCE THROUGH LATE WED. THEREAFTER...THE SEA SURFACE WATERS WILL GRADUALLY BECOME COOLER AND ATMOSPHERIC CONDITIONS WILL BECOME LESS FAVORABLE AND NARDA WILL BEGIN TO WEAKEN AND TRACK MORE NORTHWESTWARD. REFER TO NARDA FORECAST ADVISORY UNDER WMO/AWIPS HEADERS WTPZ24 KNHC/MIATCMEP4 FOR ADDITIONAL DETAILS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS WNW ACROSS CENTRAL AMERICA FROM THE NW COAST OF COLOMBIA TO ACROSS THE BORDER OF PANAMA AND COSTA RICA TO 09N84W...THEN NW TO 11N90W...THEN SW TO 10N100W... THEN CONTINUING NW TO 16N115W WHERE IT LOSES IDENTITY DUE TO THE BROAD CYCLONIC CIRCULATION ASSOCIATED WITH TROPICAL CYCLONE NARDA. SCATTEROMETER DATA INDICATES THAT THE MONSOON TROUGH RESUMES SW OF TROPICAL CYCLONE NARDA NEAR 11N125W...THEN SW TO 10N130W WHERE THE SCATTEROMETER WINDS INDICATE A TRANSITION TO AN ITCZ AXIS...WHICH IN TURN CONTINUES SW TO BEYOND 07N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION DEVELOPED LATE SUN OVER INTERIOR CENTRAL AMERICA AND HAS PROPAGATED SW OVER THE PACIFIC WATERS WITHIN 150 NM OF THE COAST CENTRAL AMERICA FROM 86-98W. SIMILAR CONVECTION IS NOTED ALONG THE EASTERN SEGMENT OF THE MONSOON TROUGH WITHIN 60 NM EITHER SIDE OF A LINE FROM 11N92W TO 09N98W TO 07N110W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS ALSO NOTED ALONG THE MONSOON TROUGH ITCZ TRANSITION AREA...WITHIN 60 NM EITHER SIDE OF A LINE FROM 10N128W TO 12N134W. ...DISCUSSION... AN UPPER CYCLONE IS RACING NE NEAR 34N127W TRAILING AN UPPER TROUGH SW INTO THE DISCUSSION AREA TO A BASE NEAR 27N129W...AND INTERRUPTING THE BROAD ANTICYCLONIC UPPER FLOW THAT IS DOMINATING THE SUBTROPICAL PORTION OF THE DISCUSSION AREA. AN UPPER CYCLONE CONTINUES OVER THE DEEP TROPICS AT 02N128W...WITH AN INVERTED UPPER TROUGH EXTENDING NW TO 09N133W. THESE UPPER CYCLONES ARE SEPARATED BY ANTICYCLONIC FLOW ASSOCIATED WITH A LARGE UPPER ANTICYCLONE CENTERED NEAR 19N116W. THIS ANTICYCLONE HAS AN UPPER RIDGE EXTENDING SE OVER THE PACIFIC COAST OF CENTRAL AMERICA TO A FAIRLY SHARP CREST OVER COSTA RICA AT 11N85W. AN UPPER RIDGE EXTENDS WSW FROM THE ANTICYCLONE ACROSS THE TROPICAL PACIFIC TO A SHARP CREST JUST W OF THE DISCUSSION AREA AT 12N146W AND IS PROVIDING THE CURRENT STEERING FOR TROPICAL CYCLONE NARDA. AN UPPER RIDGE IS ALSO AMPLIFYING N ACROSS THE BAJA CALIFORNIA PENINSULA AND NOW APPEARING TO BECOME UNSTABLE OVER SE CALIFORNIA. UPPER DIFFLUENCE ALONG THE SW PERIPHERY OF THIS RIDGE AND NE OF THE INVERTED UPPER TROUGH PREVIOUSLY DESCRIBED HAS ENHANCED CONVECTION ALONG THE MONSOON TROUGH AND TROPICAL CYCLONE NARDA WITH SOME OF THE RESULTANT UPPER DEBRIS MOISTURE SPREADING S TOWARDS THE EQUATOR BETWEEN 119-125W. SOME OF THE MOISTURE IS ALSO ADVECTED N AND LATER NE AROUND THE CENTER OF THE ANTICYCLONE AND WILL SPREAD E ACROSS CENTRAL MEXICO LATE TODAY. WEAK DIFFLUENCE ALONG THE SOUTHEASTERN RIDGE ENHANCED CONVECTION OVER CENTRAL AMERICA LATE SUN...WITH REMNANTS OF THE CONVECTION STILL DISSIPATING ALONG THE PACIFIC COAST OF CENTRAL AMERICA AS PREVIOUSLY DESCRIBED. THE ASSOCIATED UPPER DEBRIS MOISTURE IS ADVECTED SW COVERING THE DISCUSSION AREA TO THE NE OF LINE FROM 08N86W TO 10N102W. GULF OF CALIFORNIA...NW 20-25 KT WINDS...WITH SEAS 5-8 FT...ARE OCCURRING ACROSS OPEN FETCH WATERS N OF 29N...BUT EXPECTED TO DIMINISH TO 15-20 KT WITH SEAS SUBSIDING TO 4-5 FT THIS MORNING...THEN FURTHER DIMINISHING TO 5-10 KT WITH SEAS OF 1-3 FT BY THIS EVENING. THE LOW LEVEL FLOW WILL BECOME SOUTHERLY ON TUE PULSING AT 15-25 KT OVER THE NORTHERN GULF WATERS THROUGH WED NIGHT ALL AHEAD OF A TROUGH MOVING INTO THE NORTHERN GULF WATERS ON THU. LIGHT NW WINDS WILL SPREAD S ACROSS THE ENTIRE GULF OF CALIFORNIA BY THU EVENING. GULF OF TEHUANTEPEC...A COLD FRONT IS CURRENTLY MOVING INTO THE BAY OF CAMPECHE. NORTHERLY 15-25 KT DRAINAGE FLOW IS EXPECTED TO SOON BEGIN ACROSS THE GULF OF TEHUANTEPEC WATERS AND INCREASING TO 20-30 KT BY THIS EVENING WHILE EXTENDING AS FAR S AS 14N96W...WITH COMBINED SEAS BUILDING TO 7-11 FT. WINDS WILL BEGIN TO DIMINISH BELOW 20 KT AFTER SUNRISE ON WED. ELSEWHERE AT THE SURFACE...A RIDGE EXTENDS FROM 31N140W TO 18N105W WITH A WEAK TROUGH NOTED N OF THE RIDGE FROM 28N132W TO 33N127W. THIS TROUGH WILL LIFT OUT TO THE NE EARLY TODAY ALLOWING THE RIDGE TO BUILD E AGAIN ACROSS THE NORTHERN PORTION. NE 15-20 KT TRADES CONTINUE S OF THE RIDGE WITH SEAS OF 5-7 FT PRIMARILY IN MIXED LONG PERIOD NW AND CROSS EQUATORIAL SE SWELL. THE GRADIENT WILL TIGHTEN SOME ON TUE WITH SEAS BUILDING BRIEFLY TO 8 FT NEAR 29N137W. LONG PERIOD NW SWELLS...COMBINED SEAS OF 7- 10 FT...WILL PROPAGATE SE INTO THE WATERS N OF 28N BETWEEN 118W- 130W EARLY WED...REACHING AS FAR S AS 26N LATE THU BEFORE BEGINNING TO SUBSIDE. NELSON