000
AXPZ20 KNHC 251520
TWDEP 

TROPICAL WEATHER DISCUSSION                                    
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
1605 UTC THU APR 25 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 COLOMBIA NEAR 04N77W TO 09N86W 
TO 08N90W...WHERE IT TRANSITIONS TO ITCZ TO 10N108W TO 08N125W 
TO 05N140W. SCATTERED TO NUMEROUS MODERATE TO STRONG CONVECTION 
IS NOTED FROM 03N TO 07N BETWEEN 101W AND 108W. SCATTERED 
MODERATE TO ISOLATED STRONG CONVECTION CAN BE FOUND FROM 07N TO 
15N BETWEEN 101W AND 108W. SCATTERED MODERATE CONVECTION IS  
FROM 07N TO 12N BETWEEN 112W AND 119W...AND FROM 04N TO 07N 
BETWEEN 120W AND 128W.
       
...DISCUSSION... 

RELATIVELY QUIET CONDITIONS ARE STILL OBSERVED ACROSS THE 
FORECAST AREA THIS MORNING. HIGH PRES BUILDING ACROSS THE SE 
U.S. BEHIND A LATE SEASON GULF OF MEXICO COLD FRONT IS EXPECTED 
TO INDUCE A LATE SEASON GULF OF TEHUANTEPEC GAP WIND EVENT. 
PRESENTLY...GLOBAL MODELS INDICATE NORTHERLY WINDS OF 20-25 KT 
WILL BEGIN TO SPILL THROUGH THE CHIVELA PASS BY THIS 
AFTERNOON...AND INCREASE TO 20-30 KT FROM THURSDAY EVENING INTO 
FRI MORNING WITH RAISING SEAS UP TO 11 FT. HOWEVER...WINDS MAY 
BRIEFLY REACH NEAR GALE FORCE WINDS EARLY FRI WITH THE 
ASSISTANCE OF THE NOCTURNAL DRAINAGE FLOW. SIMILARLY...THE 
NOCTURNAL DRAINAGE FLOW WILL AID FRESH WINDS ACROSS THE GULF OF 
PAPAGAYO OVER THE NEXT COUPLE OF DAYS...WITH GLOBAL MODEL 
GUIDANCE SUGGESTING INCREASING WINDS TO 20-25 KT ACROSS THE GULF 
OF PAPAGAYO EARLY FRI AND SAT MORNINGS. 

OTHERWISE...WINDS ARE EXPECTED TO REMAIN BELOW 25 KT OVER THE 
REMAINDER OF THE FORECAST WATERS THROUGH EARLY SAT. THE NE SWELL 
THAT HAS PROPAGATED INTO NE PORTIONS OF THE AREA...BUILDING SEAS 
TO 8-9 FT MAINLY N OF 29N W OF 130W WILL CONTINUE TO SUBSIDE TO 
BELOW 8 FT BY LATER TODAY. 

CONVECTION HAS INCREASED ON THE EAST SIDE OF A SURFACE TROUGH 
THAT EXTENDS FROM 15N107W TO 08N109W. THIS TROUGH IS EMBEDDED 
WITHIN THE ITCZ. UPPER LEVEL DIVERGENCE JUST SOUTH OF THE ITCZ 
IS ENHANCING THE SCATTERED TO NUMEROUS STRONGER CONVECTION 
PREVIOUSLY DESCRIBED NEAR THE ITCZ AXIS. THIS SURFACE TROUGH IS 
FORECAST TO MOVE WWD AND WILL REMAIN BETWEEN 110W AND 120W 
DURING THE NEXT 48 HOURS. A DIFFLUENT PATTERN ALOFT WILL 
CONTINUE TO SUPPORT THE SHOWER/THUNDERSTORM ACTIVITY IN THE 
VICINITY OF THE TROUGH. 

HIGH PRES REMAINS GENERALLY BLOCKED FROM THE LOCAL AREA...WHICH 
IS LIMITING THE STRENGTH OF THE LOCAL TRADE WINDS. AS A 
RESULT...A WEAK RIDGE DOMINATES THE N WATERS. THIS SUBTROPICAL 
RIDGE IS BEING DISRUPTED...OR BLOCKED BY A DEEP LAYERED CUT OFF 
LOW PERSISTING OFFSHORE OF SOUTHERN CALIFORNIA...THAT HAS 
FINALLY MOVED INLAND. THE ASSOCIATED 1013 MB SURFACE LOW IS 
CURRENTLY LOCATED NEAR 34N126W AND DRAGS A WEAK AND BENIGN 
FRONTAL TROUGH SW TO 28N130W TO 25N136W. DURING THE NEXT 48 
HOURS...THE SURFACE LOW IS EXPECTED TO WEAKEN TO A TROUGH AS THE 
SUPPORTING CUT OFF LOW CONTINUES TO MOVE AWAY FROM THE 
DISCUSSION AREA WHILE WEAKENING. AS THIS OCCURS...THE 
SUBTROPICAL RIDGE WILL BUILD IN AGAIN ACROSS THE FORECAST REGION 
BY SAT...WITH AN INCREASE IN THE TRADE WIND FLOW. MARINE 
GUIDANCE ALREADY SHOWS A BELT OF FRESH TO STRONG TRADE WINDS 
WITH BUILDING SEAS TO AROUND 9 FT AFFECTING THE WEST-CENTRAL 
WATERS BY EARLY SUN. 

ALOFT...A RIDGE/TROUGH/RIDGE PATTERN CONTINUES TO DOMINATE THE N 
WATERS. AN ANTICYCLONE HAS DEVELOPED NEAR 10N93W AND EXTENDS A 
RIDGE NORTHWARD TO THE GULF OF TEHUANTEPEC AND THEN ACROSS 
CENTRAL AMERICA AND W GULF OF MEXICO. THIS RIDGE IS HELPING TO 
INDUCE CONVECTION NEAR THE ITCZ AXIS AND THE AFOREMENTIONED 
SURFACE TROUGH...PARTICULARLY BETWEEN 100W AND 110W.   
 
$$
GR