000
AXPZ20 KNHC 291540
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
1605 UTC MON JUL 29 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...           
MONSOON TROUGH AXIS EXTENDS FROM 08N78W TO 10N100W TO LOW PRES 
10N108W TO 11N120W TO 08N131W. ITCZ AXIS CONTINUES FROM 08N131W 
TO 08N140W. CLUSTERS OF MODERATE TO STRONG CONVECTION N OF 04N E 
OF 83W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED 
FROM 08N TO 11N BETWEEN 100W AND 105W AND FROM 11N TO 14N 
BETWEEN 108W AND 119W. SCATTERED MODERATE CONVECTION IS WITHIN 
120 NM S OF TROUGH BETWEEN 117W AND 120W.

...DISCUSSION...                                               
ALOFT...AN UPPER TROUGH EXTENDS SW FROM CENTRAL CALIFORNIA INTO 
THE DISCUSSION AREA FROM 30N124W THROUGH AN UPPER CYCLONE AT 
18N124W...WITH THE TROUGH CONTINUING S LOSING IDENTITY OVER THE 
DEEP TROPICS NEAR 07N125W. AN ASSOCIATED SURFACE TROUGH WILL DIP 
INTO THE AREA FROM 31N121W TO 27N122W THIS EVENING...AND IS 
FORECAST TO WEAKEN LATER ON TUE AS HIGH PRES BUILDS SE ACROSS 
THE N WATERS. A MAIN UPPER LEVEL TROUGH CROSSES THE NW CORNER OF 
THE FORECAST REGION. A LARGE UPPER ANTICYCLONE REMAINS QUASI 
STATIONARY OVER NORTHERN MEXICO AND WESTERN TEXAS NEAR 30N104W 
WITH THE ANTICYCLONIC FLOW EXTENDING S OVER THE DISCUSSION AREA 
TO THE N OF 19N AND E OF 118W. AN UPPER LEVEL LOW IS SPINNING 
NEAR 17N105W. NORTHERLY WIND FLOW ALOFT DOMINATES MOST OF THE 
AREA E OF 100W. UPPER DIFFLUENCE IS HELPING TO THE INDUCE THE 
CONVECTION ACCOMPANIED BY FREQUENT LIGHTNING LOCATED N OF 04N E 
OF 83W...INCLUDING THE GULF OF PANAMA.

HIGH PRES LOCATED WELL N OF AREA EXTENDS A RIDGE ACROSS THE N 
WATERS MAINLY N OF 15NW OF 115W. GENTLE TO MODERATE WINDS ARE 
NOTED PER SCATTEROMETER DATA UNDER THE INFLUENCE OF THIS RIDGE. 
THE TRADE WINDS ARE EXPECTED TO INCREASE TO 20 KT WITH BUILDING 
SEAS TO 8 FT IN ABOUT 48 HOURS AS A NEW HIGH PRES CENTER 
DEVELOPS FARTHER SOUTH NEAR 39N138W.

STRONG WINDS ALONG THE COAST OF NORTHERN CALIFORNIA BETWEEN 
TROUGHING OVER INTERIOR CALIFORNIA AND THE SUBTROPICAL RIDGE 
CONTINUES TO GENERATE SEAS UP TO 8 FT REACHING S TO 31N/30N. 
THESE SEAS WILL SUBSIDE TO LESS THAN 8 FT TONIGHT. 

COMPUTER MODELS CONTINUE TO SUGGEST THE DEVELOPMENT OF A SERIES 
OF CYCLONIC SWIRLS ALONG THE MONSOON TROUGH OVER THE NEXT FEW 
DAYS WITH THE GFS THE MOST AGGRESSIVE. CURRENTLY...AN EMBEDDED 
1009 MB SURFACE LOW IS NEAR 10N108W. THIS LOW IS PRODUCING 
DISORGANIZED SHOWER AND THUNDERSTORM ACTIVITY. ENVIRONMENTAL 
CONDITIONS COULD FAVOR SLOW DEVELOPMENT OF THIS SYSTEM OVER THE 
NEXT SEVERAL DAYS AS IT MOVES TO THE WEST OR W-NW AT ABOUT 10 
KT. CURRENTLY...THIS SYSTEM HAS A LOW CHANCE OF BECOMING A 
TROPICAL CYCLONE DURING THE NEXT 48 HOURS. FOR NOW...EXPECT 
WINDS OF 20-25 KT AND SEAS OF 8-10 FT IN ASSOCIATION WITH THIS 
LOW...PARTICULARLY OVER ITS EASTERN SEMICIRCLE. A PAIR OF 
CYCLONIC SWIRLS ARE ALSO NOTED NEAR 10N99W AND 10N119W. BASED ON 
THE MEDIUM RANGE FORECAST...THE ONE NEAR 99W IS EXPECTED TO MOVE 
WESTWARD AS A TROUGH OVER THE NEXT SEVERAL DAYS. 

CROSS EQUATORIAL SOUTHERLY SWELLS WITH PERIODS IN THE 19-21 
SECOND RANGE ARE AFFECTING MOST THE COASTS OF MEXICO AND CENTRAL 
AMERICA LIKELY PRODUCING ROUGH SURF CONDITIONS AND DANGEROUS RIP 
CURRENTS TO THOSE COASTS. THESE SWELLS ARE EXPECTED TO MIX WITH 
THE WAVES FORMING OVER THE E SEMICIRCLE OF THE SURFACE LOW. 
LOOKING AHEAD...ADDITIONAL PULSES OF LONG PERIOD CROSS 
EQUATORIAL SW SWELL WILL PROPAGATE ACROSS THE SOUTH WATERS 
MAINLY BETWEEN 105W AND 135W WED AND THU REACHING PARTS OF THE 
COASTS OF MEXICO AND CENTRAL AMERICA BY FRI. 

$$ 
GR