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Eastern Pacific Tropical Weather Discussion (Text)

000
AXPZ20 KNHC 231622
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
1605 UTC THU MAY 23 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 
1430 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

MONSOON TROUGH AXIS EXTENDS FROM COLOMBIA NEAR 06.5N74.5W TO 
13N87.5W TO LOW PRES NEAR 10.5N103W 1009 MB TO 08.5N118W...WHERE 
IT TRANSITIONS TO ITCZ...CONTINUING ON TO 09N123W TO 11.5N133W 
TO BEYOND 07N140W. SCATTERED MODERATE TO STRONG CONVECTION NOTED 
WITHIN 180 NM S OF TROUGH BETWEEN 78W AND 86W...AND WITHIN 210 
NM N AND 300 NM S OF TROUGH BETWEEN 90W AND 100W. SCATTERED TO 
LOCALLY NUMEROUS MODERATE TO STRONG CONVECTION NOTED WITHIN 90 
NM N AND 180 NM S OF TROUGH BETWEEN 102W AND 116W. SCATTERED 
MODERATE TO STRONG CONVECTION NOTED WITHIN 90 NM S AND 180 NM N 
OF ITCZ BETWEEN 129W AND 135W. 

...DISCUSSION...

A GENERALLY RIDGE-TROUGH-RIDGE UPPER LEVEL PATTERN PREVAILS 
ACROSS THE DISCUSSION AREA THIS MORNING. THE TWO RIDGES ARE S OF 
22N-24N AND SPAN BETWEEN 120W AND 144W...AND BETWEEN 70W AND 
126W RESPECTIVELY...AND CONTINUE TO VENTILATE DEEP TROPICAL 
CONVECTION ALONG AND NEAR THE MONSOON TROF AND ITCZ DESCRIBED 
ABOVE. A SHORTWAVE TROUGH HAS MOVED OVER THE WESTERN RIDGE AND 
IS MOVING E-SE AND SLOWLY DIVING INTO THE BACK SIDE OF THE 
TROUGH PREVAILING BETWEEN THE TWO RIDGES...BETWEEN 110W AND 
120W...AND HAS ERODED MODESTLY W PORTIONS OF THE EASTERN-MOST 
RIDGE. THE FORWARD PROGRESS OF THE MEAN UPPER TROUGH IS FORECAST 
TO END TONIGHT WHILE THE TROUGH SHARPENS OVER THE WEEKEND...AS 
THE TWO UPPER RIDGES AMPLIFY.

AT LOW LEVELS...EPAC SURFACE RIDGE DOMINATES THE AREA W OF 
110W...CENTERED ON A 1033 MB HIGH NEAR 41N143W...WITH RIDGE AXIS 
EXTENDING SE TO NEAR 18N112W. OVERNIGHT SCATTEROMETER PASSES 
INDICATED MINIMAL N-NW GALES CONTINUING OFF THE CENTRAL 
CALIFORNIA COAST...WITH FRESH N TO NE WINDS SPILLING S AND SW 
INTO NORTH PORTIONS OF THE DISCUSSION AREA N OF 24N. NORTHERLY 
SWELL GENERATED WITHIN THIS REGION OF WINDS CONTINUES TO 
PROPAGATE S AND SE...AND WAS PRODUCING SEAS OF 8 TO 13 FT ACROSS 
THE AREA N OF 24N...WITH HIGHEST SEAS WELL OFFSHORE OF BAJA 
CALIFORNIA NORTE. 

THE REMNANTS OF ALVIN WERE LOCATED ACROSS SW PORTIONS... 
PROPAGATING WWD AS A LARGE AMPLITUDE WAVE ALONG THE ITCZ AT 
133W. A MODEST REGION OF FRESH NE WINDS AROUND 20 KT CONTINUE N 
OF THIS WAVE AND ARE PRODUCING SEAS 8-9 FT. THIS WAVE WILL 
CONTINUE W AND EXIT THE AREA IN THE NEXT 36 HOURS. AS IT PASSES 
DIRECTLY S OF THE EPAC HIGH...WINDS MAY INCREASE SLIGHTLY TO 20-
25 KT.

E OF 110W...MODERATE MONSOONAL FLOW DOMINATES THE TROPICS AND IS 
PRODUCING CONVERGENCE OF ABUNDANT TROPICAL MOISTURE INVOF THE 
MONSOON TROUGH. SATELLITE IMAGERY THE PAST 24 HOURS HAS REVEALED 
A LOW TO MIDDLE LEVEL CYCLONIC CIRCULATION...AND SCATTERED TO 
NUMEROUS CONVECTION...NOW CURRENTLY INVOF 10N104W. A 1009 MB  
SURFACE LOW HAS DEVELOPED NEAR THERE NEAR 10.5N103W...WITH MOST 
CONVECTION NOW FLARING TO THE S AND SW OF THIS LOW. GLOBAL 
MODELS SUGGEST THERE IS SOME CHANCE FOR SLOW AND GRADUAL 
ORGANIZATION OF THIS LOW AS IT MOVES WWD DURING THE NEXT SEVERAL 
DAYS. 

FARTHER E...LOW TO MIDDLE LEVEL CYCLONIC TURNING IS ALSO NOTED 
CENTERED INVOF 08N87W. S TO SW MONSOONAL WINDS PREVAIL AT THE 
SURFACE IN THIS LOCATION...BUT AS THIS FEATURE DRIFTS W OVER THE 
WEEKEND IT IS EXPECTED TO BECOME BETTER ALIGNED WITH THE MONSOON 
TROUGH. STRENGTHENING HIGH PRES ACROSS THE SW N ATLANTIC IS 
EXPECTED TO ENHANCE THE TRADE WINDS ACROSS THE CENTRAL AND W 
CARIBBEAN BY THE EARLY PART OF THE UPCOMING WEEK...WHICH WILL 
INDUCE GAP WIND FLOW ACROSS CENTRAL AMERICA AND INTO THE EPAC. 
THIS SCENARIO WILL CREATE FAVORABLE LOW TO MIDDLE TROPOSPHERIC 
CONDITIONS FOR A WAVE TO DEVELOP AND GROW ACROSS THIS AREA AS IT 
SHIFTS WWD AND DOWNSTREAM OF THE GULFS OF PAPAGAYO AND 
TEHUANTEPEC. GLOBAL MODELS ARE PRESENTLY IN DISAGREEMENT IN THE 
STRENGTH OF DEVELOPMENT OF THIS WAVE...WITH THE GFS MODEL 
DEVELOPING A TROPICAL CYCLONE WITHIN THE NEXT 5 DAYS. THIS AREA 
IS BEING MONITORED FOR THIS POTENTIAL DURING THE UPCOMING WEEK.

LONG PERIOD CROSS HEMISPHERIC SW SWELL AT 17-19 SECONDS IS 
MOVING THROUGH THE AREA WATERS THIS MORNING AND HAVE BEGUN TO 
INCREASE ALONG THE CENTRAL AMERICAN AND MEXICAN COASTS. 
OVERNIGHT ALTIMETER PASSES INDICATED THAT WW3 MODEL GUIDANCE WAS 
GENERALLY 1.5 TO 2 FT TOO LOW IN ITS FORECAST OF THIS SWELL. 
EXPECTED SW SWELL AND ADDITIONAL PULSES TO DOMINATE THE AREA 
WATERS THROUGH THE WEEKEND...AND PRODUCING STRONG AND DANGEROUS 
SURF ACROSS THE COASTS AND REEFS OF THE AREA COASTLINES.

$$
STRIPLING