000
AXPZ20 KNHC 081546
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
1605 UTC WED MAY 08 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 05N77W TO 04N80W TO 08N85W TO 08N115W 
THEN AS ITCZ TO 09N125W TO BEYOND 06N140W. SCATTERED MODERATE 
CONVECTION WITHIN 120 NM N OF AXIS BETWEEN 115W AND 120W.

...DISCUSSION...

A SHORT WAVE TROUGH IN THE MID/UPPER LEVELS OF THE ATMOSPHERE 
EXTENDING FROM SOUTHERN CALIFORNIA TO 20N130W CONTINUES TO PUSH 
EASTWARD AT THE BASE OF AN UPPER LOW NEAR 38N130W. THIS FEATURE 
IS WEAKENING A SURFACE RIDGE EXTENDING E TO W ALONG ROUGHLY 25N 
AND SUPPRESSING IT TO THE SOUTH. ASCAT AND ALTIMETER DATA FROM 
THE PAST 12 HOURS INDICATES ONLY GENTLE TO MODERATE TRADES S OF 
THE WEAK RIDGE AXIS...BUT GENERATING ENOUGH LOW LEVEL 
CONVERGENCE TO SUPPORT CLUSTERS OF CONVECTION ALONG THE ITCZ. 

THU INTO FRI...THE TROUGH WILL MIGRATE E THROUGH NORTHERN BAJA 
AND NW MEXICO...MERGING WITH QUASI-STATIONARY LOW OVER THE FOUR 
CORNERS AREA. THE RIDGE WILL BUILD NEAR 30N135W IN 
RESPONSE...ACCOUNTING FOR A SLIGHT FRESHENING OF TRADE WIND FLOW 
FARTHER SOUTH INDICATED IN OPERATION MODEL OUTPUT. THE BUILDING 
RIDGE WILL ALSO ENHANCE NW TO N FLOW ALONG THE COAST OF NORTHERN 
BAJA BRIEFLY ON FRI. INTO SAT...THE RIDGE SHIFTS SLIGHTLY 
EASTWARD AHEAD OF ANOTHER IMPULSE DIGGING ACROSS THE N CENTRAL 
PACIFIC...RESULTING IN MODERATE TO FRESH SW FLOW N OF 25N W OF 
135W.

MEANWHILE...OPERATIONAL WAVE MODELS INDICATE AN AREA OF SW SWELL 
WILL PUSH ACROSS THE EQUATOR W OF 110W...MIXING WITH SHORTER 
PERIOD WAVES GENERATED BY TRADE WIND FLOW. THE MWW3 REMAINS THE 
MOST AGGRESSIVE WITH COMBINED SIGNIFICANT WAVE HEIGHTS BREACHING 
8 FT IN THE AREA OF THE MAIN TRADE WIND FLOW FROM 10N TO 15N W 
OF 130W...WHICH SEEMS PLAUSIBLE.

LOOKING AHEAD...AN INTERESTING SITUATION IS DEVELOPING IN THE 
DEEP TROPICS. THE IMPETUS IS WEAK LOW TO MID LEVEL TROUGHING 
OVER THE SW CARIBBEAN...ENHANCED IN PART BY DIVERGENT FLOW ALOFT 
ASSOCIATED WITH AN UPPER TROUGH EXTENDING FROM A CLOSED LOW OVER 
VIRGINIA SOUTHWARD THROUGH NICARAGUA. TWO OTHER FACTORS ARE IN 
PLAY. A WEAK LOW AMPLITUDE/LOW LATITUDE TROUGH OVER NORTHERN 
SOUTH AMERICA NEAR 60W WILL MERGE WITH THE GENERAL TROUGH OVER 
THE SW CARIBBEAN. NEXT A MID LATITUDE SURGE INTO THE WESTERN 
TROPICAL ATLANTIC IS ENHANCING EASTERLY LOW TO MID FLOW INTO THE 
CARIBBEAN...THUS AIDING TROUGH GROWTH. BY LATE WEEK...THE UPPER 
SUPPORT DIMINISHES AS THE UPPER TROUGH DAMPENS OUT AND SHIFTS 
EAST AHEAD OF AN UPPER ANTICYCLONE NOSING EASTWARD ACROSS THE 
EASTERN PACIFIC...LEAVING THE NASCENT LOW PRES OVER PANAMA IN 
SOMEWHAT UNFAVORABLE SUBSIDENT AND DRY NORTHERLY FLOW ALOFT. GFS 
AND ECMWF AND THEIR RESPECTIVE ENSEMBLE MEANS REMAIN IN 
REASONABLE AGREEMENT SHOWING THE UPPER ANTICYCLONE PUSHING EAST 
OVER SOUTHERN MEXICO BY SAT...AHEAD OF MID/UPPER TROUGHING 
EXTENDING FROM N CENTRAL MEXICO TO 15N115W. BY SUN...THE 
FAVORABLE COMBINATION OF DEEP LAYER EASTERLY FLOW...HIGH 
PRECIPITABLE WATER VALUES AND LATENT HEAT RELEASE WILL ALLOW LOW 
PRES MIGRATING WESTWARD ALONG 10N FROM PANAMA TO 90W TO DEEPEN. 
EXTENDED RANGE GUIDANCE SHOWS THIS LOW SHIFTING FARTHER W TO A 
FAVORABLE POSITION BETWEEN THE MID/UPPER ANTICYCLONE TO THE EAST 
AND MID/UPPER TROUGH TO THE WEST...WITH SIGNIFICANT DEEPENING. 
THIS MAY BE CONVECTIVE FEEDBACK BUT IT IS A COMMON THEME IN THE 
MODELS. STILL A LOT OF TIME TO MONITOR THIS. MEANWHILE...BOTH 
THE GFS AND ECMWF INDICATED A SYMBIOTIC SURGE IN THE TEHUANTEPEC 
AND PAPAGAYO GAPS MON INTO TUE...WITH THE GFS ADVERTISING GALES 
IN TEHUANTEPEC EARLY TUE AND THE MORE CONSERVATIVE ECMWF SHOWING 
25 TO 30 KT.
  
$$
CHRISTENSEN