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Eastern Pacific Tropical Weather Discussion (Text)

000
AXPZ20 KNHC 220948
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
1005 UTC WED MAY 22 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 
0930 UTC.

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

THE MONSOON TROUGH AXIS EXTENDS W ACROSS THE CARIBBEAN FROM 
COLOMBIA AND COSTA RICA ALONG 11N TO 11N90W...THEN TURNS NW TO 
12N96W...THEN TURNS SW TO A 1012 MB EMBEDDED LOW PRES AT 
09N116W. SCATTEROMETER WINDS INDICATE AN ITCZ AXIS FORMS JUST
TO THE W OF THE LOW PRES AND TURNS NW TO 11N130W WHERE THE 
REMNANTS OF FORMER TROPICAL CYCLONE ALVIN HAVE WEAKENED TO A
TROUGH FROM 10N132W TO 14N128W. THE ITCZ RESUMES SW OF THIS 
TROUGH AT 10N132W AND CONTINUES SW TO BEYOND 05N140W. SCATTERED
MODERATE ISOLATED STRONG CONVECTION IS NOTED WITHIN 75 NM EITHER
SIDE OF A LINE FROM 06N83W TO 11N99W AND WITHIN 45 NM EITHER SIDE
OF A LINE FROM 11N109W TO 09N118W...AND DEVELOPING WITHIN 30 NM
OF A LINE FROM 07N126W TO 13N128W. ISOLATED MODERATE TO 
OCCASIONALLY STRONG CONVECTION IS OBSERVED ELSEWHERE WITHIN 150
NM OF THE AXIS OF BOTH THE MONSOON TROUGH AND THE ITCZ. GUIDANCE
IS SUGGESTING THE EMBEDDED SURFACE LOW AT 08N116W WILL DISSIPATE
OVER THE NEXT 24 HOURS WHILE ANOTHER EMBEDDED LOW DEVELOPS ALONG
THE MONSOON TROUGH AT 10N110W. 

A TROPICAL WAVE CURRENTLY ALONG 71W IN THE CENTRAL CARIBBEAN 
WILL REACH THE SW CARIBBEAN TONIGHT AND ENHANCE THE DEVELOPMENT
OF A SURFACE LOW ALONG THE MONSOON TROUGH AXIS NEAR 10N81W. A
SECOND LOW PRESSURE CENTER IS EXPECTED TO DEVELOP LATE TODAY IN
THE PACIFIC NEAR 10N88W WITH THE LOW SHIFTING W ALONG THE 
MONSOON TROUGH ON THU. THE LOW IN THE CARIBBEAN IS EXPECTED TO 
MEANDER ON THU...AND THEN CROSS CENTRAL AMERICA INTO THE PACIFIC 
TO NEAR 10N87W LATE FRI. MODEL GUIDANCE IS SOMEWHAT IN AGREEMENT 
WITH THIS LOW FORMING AND MOVING W ALONG THE MONSOON TROUGH OVER 
THE WEEKEND. THE GFS MODEL IS MUCH MORE AGGRESSIVE THAN OTHER 
GUIDANCE...AND DEVELOPS THE LOW INTO A TROPICAL CYCLONE. I USED 
THE GFS TRACK AND POSITIONS IN MY EXTENDED GRIDS...BUT TONED 
DONE THE WINDS CONSERVATIVELY TO A 20-25 KT LOW NEAR 10N92W LATE 
SUN. MY CONFIDENCE LEVEL IS VERY LOW AT THIS TIME.

MODEL GUIDANCE SUGGESTS THE NORTHERLY DRAINAGE FLOW WILL 
INCREASE TO 20 KT IN THE GULF OF TEHUANTEPEC ON FRI NIGHT AND 
GRADUALLY INCREASE TO 20-25 KT ON SAT NIGHT...THEN PULSE THROUGH 
SUNRISE ON MON. THE STRENGTH OF THESE DRAINAGE WINDS IN THE 
FORECAST GUIDANCE IS INFLUENCED BY THE STRENGTH OF THE TROPICAL 
LOW FORECAST TO DEVELOP ALONG 10N BETWEEN 87W-92W OVER THIS 
UPCOMING WEEKEND...THUS THIS TEHUANTEPEC EVENT MAY BE OVER 
FORECAST TO SOME DEGREE.

A SURFACE RIDGE EXTENDS FROM NW TO SE FROM 32N136W TO 16N110W. 
NW WINDS ARE CURRENTLY AT 10-15 KT ALONG THE ENTIRE W SHORE OF 
THE BAJA CALIFORNIA PENINSULA WITH SEAS OF 4-5 FT. NORTHERLY 
WINDS AT 15-20 KT CONTINUE ACROSS THE N-CENTRAL PACIFIC WATERS 
FROM 27-30N BETWEEN 119W-131W WITH SEAS MAXING AT 9 FT IN THE 
ASSOCIATED N SWELL THAT CONTINUES TO MIX WITH LONG PERIOD CROSS-
EQUATORIAL SW SWELL. THE N WINDS ARE AT 20-25 KT IN THE WATERS 
FROM 30-32N BETWEEN 118-125W. THE NORTHERLY 20 KT FLOW WILL 
SPREAD S ACROSS THE WATERS N OF 24N W OF 115W TONIGHT...WITH 
SEAS BUILDING 8 TO 13 FT IN LONG PERIOD N SWELL. SEAS OF 6-8 FT 
ARE EXPECTED TO REACH ALONG THE BAJA PENINSULA TO THE N OF 28N 
AS EARLY AS SUNRISE ON THU...AND MAY REACH AS FAR S AS 25N NEAR 
BAHIA SANTA MARIA LATE THU NIGHT...MOSTLY IN REFRACTIVE SWELL. 
WIND/SEAS WILL BEGIN TO DIMINISH/SUBSIDE ON FRI WITH WINDS 15 KT 
AND SEAS 5-7 FT ACROSS THE SUBTROPICAL WATERS ON SAT.

NE TRADES CONTINUE AT 15-20 KT WITHIN 240 NM W OF THE REMNANT 
TROUGH OF ALVIN. THE TROUGH IS EXPECTED TO CONTINUE TO SHIFT W 
REACHING FROM 10N136W TO 13N132W TONIGHT AND FROM 09N140W TO 
13N135W ON THU NIGHT...THEN SHIFT W OF 140W ON FRI.

ALOFT...A TROPICAL MOISTURE PLUME...THAT PARTIALLY ORIGINATED 
FROM THE CONVECTIVE DEBRIS MOISTURE FROM FORMER TROPICAL CYCLONE 
ALVIN...CONTINUES TO STREAM ACROSS EPAC AND MEXICO WITHIN 120 NM 
OF A LINE FROM 18N113W TO 26N94W. A SECOND TROPICAL PLUME 
ORIGINATES FROM ITCZ CONVECTION BETWEEN 140W-152W AND STREAMS NE 
WITHIN 180 NM OF A LINE FROM 18N140W TO 32N110W. 

$$
NELSON