000
AXPZ20 KNHC 080946
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE OCT 08 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 15.3N 125.4W AT 0900 UTC MOVING 
WNW OR 290 DEG AT 11 KT. MAXIMUM SUSTAINED WINDS ARE 50 KT 
GUSTING TO 60 KT WITH SURFACE PRESSURE OF 999 MB. CURRENTLY 
NUMEROUS MODERATE TO STRONG CONVECTION IS NOTED WITHIN 60 NM OF 
THE CENTER EXCEPT WITHIN 120 NM OVER THE SW QUADRANT. NARDA IS 
EXPECTED TO TRACK W ALONG THE SOUTHERN PERIPHERY OF AN UPPER 
RIDGE WITH LITTLE CHANGE IN INTENSITY OVER THE NEXT 24 HOURS 
THEN GRADUALLY WEAKENING THEREAFTER. 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 W ACROSS THE AREA ALONG 08-09N 
FROM THE NW COAST OF COLOMBIA TO THE PACIFIC COAST AT THE BORDER 
OF PANAMA AND COSTA RICA...THEN WESTWARD TO 10N97W... THEN NW AN 
EMBEDDED 1009 MB SURFACE LOW AT 11N106W...THEN CONTINUES NW TO 
15N119W WHERE IT LOSES IDENTITY IN THE BROAD CYCLONIC 
CIRCULATION ASSOCIATED WITH TROPICAL CYCLONE NARDA. 
SCATTEROMETER DATA INDICATES THAT THE MONSOON TROUGH RESUMES SW 
OF TROPICAL CYCLONE NARDA NEAR 12N126W...THEN SW TO 09N131W 
WHERE THE SCATTEROMETER WINDS INDICATE A WEAK 1008 MB SURFACE 
LOW AND A TRANSITION TO AN ITCZ AXIS.

SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED WITHIN 30 
NM OF 10N87W AND SURROUNDING THE EASTERN SEGMENT OF THE MONSOON 
TROUGH FROM 06-14N BETWEEN 90-103W...AND ALONG THE WESTERN SEGMENT 
OF THE THE MONSOON TROUGH WITHIN 60 NM EITHER SIDE OF A LINE FROM 
11N130W TO 08N140W. 

FURTHER TO THE N OF THE MONSOON TROUGH...SCATTERED MODERATE 
ISOLATED STRONG CONVECTION DEVELOPED LATE MON OVER INTERIOR 
MEXICO AND HAS PROPAGATED SW OVER THE PACIFIC WATERS WITHIN 180 
NM OF THE COAST OF MEXICO FROM 97-105W AND IS ACCOMPANIED BY 
FREQUENT LIGHTNING.

...DISCUSSION...

AN UPPER TROUGH EXTENDS FROM 32N126W TO 28N140W REINFORCING A 
BROAD UPPER TROUGH CURRENTLY DOMINATING THE DISCUSSION AREA N OF 
24N AND TO THE W OF THE BAJA PENINSULA...WITH SUB-JETSTREAM 
ZONAL FLOW. AN UPPER CYCLONE CONTINUES OVER THE DEEP TROPICS 
NEAR 01N122W...WITH AN INVERTED UPPER TROUGH EXTENDING N TO 
10N121W. AN UPPER ANTICYCLONE IS NOTED NEAR 17N135W AND ANOTHER 
NEAR 19N118W RESULTING IN AN UPPER RIDGE EXTENDING E TO W ACROSS 
THE DISCUSSION AREA TO THE W OF 105W. UPPER DIFFLUENCE ALONG THE 
S PERIPHERY OF THIS RIDGE TO THE E AND W OF THE INVERTED UPPER 
TROUGH PREVIOUSLY DESCRIBED...HAS ENHANCED CONVECTION ALONG THE 
MONSOON TROUGH...AND NEAR TROPICAL CYCLONE NARDA...WITH SOME OF 
THE RESULTANT UPPER DEBRIS MOISTURE SPREADING S TOWARDS THE 
EQUATOR BETWEEN 122-132W. SOME OF THE MOISTURE IS ALSO ADVECTED 
NE...AND LATER E...AROUND THE CENTER OF THE EASTERN ANTICYCLONE 
BUT APPEARS THAT IT WILL EVAPORATE BEFORE REACHING MEXICO.

AN UPPER TROUGH MOVING THROUGH THE SE CONUS CONTINUES SW ACROSS 
THE GULF OF MEXICO TO BASE OVER THE MEXICAN PACIFIC COAST AT 
18N103W. IMMEDIATELY TO THE E OF THIS TROUGH IS AN UPPER 
ANTICYCLONE OVER THE GULF OF TEHUANTEPEC...WITH ITS ANTICYCLONIC 
ENVELOPE DOMINATING THE DISCUSSION AREA TO THE N OF 06N BETWEEN 
80-103W. WEAK DIFFLUENCE UNDER THIS RIDGE ENHANCED MOSTLY 
ISOLATED CONVECTION CONVECTION OVER CENTRAL AMERICA LATE MON. 
HOWEVER....THE UPPER LEVELS APPEAR VERY MOIST WITHIN THIS UPPER 
RIDGE.

GULF OF TEHUANTEPEC...NE 20-25 KT DRAINAGE FLOW...WITH SEAS 7-10 
FT...IS EXPECTED TO REACH NEAR 13N97W THIS MORNING THEN BEGIN TO 
DIMINISH WITH WINDS BELOW 20 KT BY WED AFTERNOON.  

GULF OF CALIFORNIA...LIGHT SOUTHERLY WINDS ARE EXPECTED TODAY 
INCREASING TO SW AT 20-25 KT ACROSS THE GULF WATERS N OF 29N 
TONIGHT AND CONTINUING THROUGH WED NIGHT WHEN SEAS MAY REACH 8 
FT ACROSS THAT AREA. A TROUGH WILL MOVE INTO THE NORTHERN GULF 
WATERS ON THU. THE ASSOCIATED LIGHT NW WINDS WILL SPREAD S 
ACROSS THE ENTIRE GULF OF CALIFORNIA BY THU EVENING. THESE NW 
WINDS WILL INCREASE TO 10-15 KT OVER THE UPCOMING WEEKEND. 

ELSEWHERE AT THE SURFACE...A RIDGE EXTENDS FROM 32N135W TO 
18N105W. N-NE WINDS AT 15-20 KT...WITH SEAS TO 9 FT IN MIXING 
LONG PERIOD N AND S SWELL...ARE CURRENTLY OBSERVED ON 
SCATTEROMETER DATA ACROSS THE AREA NW OF A LINE FROM 32N129W TO 
29N140W. THESE CONDITIONS WILL SPREAD SE ACROSS THE AREA TO THE 
NW OF A LINE FROM 32N120W TO 20N140W LATE TONIGHT. ALTHOUGH THE 
GRADIENT WILL RELAX ON WED...LONG PERIOD N SWELL WILL PROPAGATE 
S TO ALONG 25N BETWEEN 115-135W ON THU...THEN BEGIN TO SUBSIDE 
AND BELOW 8 FT BY LATE FRI.  
 
NELSON