000
AXPZ20 KNHC 252207
TWDEP 

TROPICAL WEATHER DISCUSSION                                    
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
2205 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 
 
MONSOON TROUGH AXIS EXTENDS FROM COLOMBIA NEAR 08N75W TO 03N79W 
TO 07N88W...WHERE IT TRANSITIONS TO ITCZ...CONTINUING ON TO 
06N101W TO 10N110W TO 08.5N125W TO BEYOND 06N140W. SCATTERED 
MODERATE ISOLATED STRONG CONVECTION NOTED FROM 02N TO 06N 
BETWEEN 79W AND 85W. SCATTERED TO NUMEROUS MODERATE TO STRONG 
CONVECTION NOTED FROM 02N TO 10N BETWEEN 98W AND 106W. SCATTERED 
TO LOCALLY NUMEROUS MODERATE TO STRONG CONVECTION NOTED WITHIN 
180 NM S AND 240 NM N OF ITCZ BETWEEN 106W AND 126W. SCATTERED 
MODERATE ISOLATED STRONG CONVECTION NOTED WITHIN 120 NM N OF 
ITCZ BETWEEN 131W AND 138W. 
       
...DISCUSSION... 

RELATIVELY QUIET MARINE CONDITIONS ARE STILL OBSERVED ACROSS THE 
FORECAST AREA THIS AFTERNOON. HIGH PRES BUILDING ACROSS THE SE 
U.S. BEHIND A LATE SEASON GULF OF MEXICO COLD FRONT HAS INDUCED 
A LATE SEASON GULF OF TEHUANTEPEC GAP WIND EVENT. A 1624 UTC 
ASCAT PASS REVEALED NORTHERLY WINDS OF 20-25 KT HAS SPILLED 
THROUGH THE CHIVELA PASS AND THROUGH THE GULF...REACHING TO 
15N..WHERE SEAS ARE LIKELY APPROACHING 7 TO 8 FT. WINDS THERE 
ARE EXPECTED TO INCREASE TO 20-30 KT LATE THIS EVENING INTO FRI 
MORNING WITH SEAS BUILDING TO 10-11 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 NEAR THE ITCZ BETWEEN 98W AND 112W 
TODAY...ON THE EAST SIDE OF A UPPER LEVEL TROUGH ALONG 115W S OF 
17N. ABUNDANT TROPICAL MOISTURE CONTINUES TO CONVERGE E OF THIS 
TROUGH...WITH SEVERAL LOW TO MID LEVEL PERTURBATION NOTED ALONG 
THE ITCZ MOVING W...ONE ALONG 102W AND A SECOND ALONG 110W. 
SCATTERED TO NUMEROUS DEEP CONVECTION DESCRIBED ABOVE WAS 
OCCURRING NEAR BOTH OF THESE LOW LEVEL FEATURES...WITH 
CONVECTION BEING SUSTAINED UNDERNEATH AN UPPER LEVEL RIDGE. 
THESE LOW LEVEL WAVES ARE EXPECTED TO MOVES SLOWLY WWD OVER THE 
NEXT FEW DAYS...WHILE THE PERSISTENT UPPER RIDGING WILL MAINTAIN 
FAVORABLE CONDITIONS FOR ACTIVE CONVECTION TO CONTINUE ACROSS 
THIS ZONE. 

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...BY A DEEP LAYERED CUT OFF LOW THAT 
HAS MOVED INLAND ACROSS SOUTHERN CALIFORNIA TODAY. AN ASSOCIATED 
BROAD AND WEAK 1016 MB SURFACE LOW IS CURRENTLY LOCATED NEAR 
35N126W...WITH VERY WEAK AND VARIABLE WIND FLOW EXTENDING S AND 
SE TO 20N AND 117W. 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...BROAD AND COMPLEX TROUGHING DOMINATES MOST OF THE AREA W 
OF 115W THIS AFTERNOON...WITH AN UPPER RIDGE MENTIONED ABOVE... 
EXTENDING FROM AN ANTICYCLONE NEAR 08N102W NORTHWARD TO THE GULF 
OF TEHUANTEPEC AND THEN ACROSS CENTRAL AMERICA AND W GULF OF 
MEXICO. THIS RIDGE HAS AMPLIFIED IN THE PAST 24 HOURS IN PART 
DUE TO THE BURSTS OF PERSISTENT DEEP CONVECTION MENTIONED ABOVE. 
UPPER RIDGING ACROSS THE ITCZ IS FORECAST TO CONTINUE BETWEEN 
95W AND 125W DURING THE NEXT FEW DAYS AND PROVIDE FAVORABLE 
VENTILATION FOR DEEP CONVECTION. 

$$
STRIPLING