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Eastern Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 162147
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC WED APR 16 2014

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 
2145 UTC. 

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

THE EPAC MONSOON TROUGH EXTENDS SW FROM THE COAST OF COSTA RICA 
AT 09N83W TO 07N92W WHERE SCATTEROMETER WINDS INDICATE A 
TRANSITION TO AN ITCZ AXIS...WHICH CONTINUES SW TO 04N111W THEN 
WIGGLES WESTWARD ALONG 04N TO BEYOND 140W. 

SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED OVER 
AND TO THE S OF THE MONSOON TROUGH WITHIN 240 NM EITHER SIDE OF 
A LINE FROM 08N82W TO 05N92W. SIMILAR CONVECTION IS NOTED ALONG 
THE ITCZ AXIS WITHIN 90 NM EITHER SIDE OF LINES FROM 06N106W TO 
03N112W AND FROM 06N127W TO 07N140W. 

...DISCUSSION...                                                

AN UPPER CYCLONE HAS MOVED E OVER THE FAR NW PORTION OF THE 
DISCUSSION AREA NEAR 33N135W WITH A TROUGH EXTENDING SW ACROSS 
THE HAWAIIAN ISLANDS. A SHORTWAVE TROUGH IS SWINGING E ACROSS 
THE WESTERN CONUS WITH THE TROUGH AXIS EXTENDING SW ACROSS 
SOUTHERN CALIFORNIA TO A BASE OVER THE BAJA CALIFORNIA PENINSULA 
AT 30N117W. BOTH OF THESE TROUGHS ARE ACCOMPANIED BY VERY DRY 
UPPER AIR.

AN UPPER LEVEL ANTICYCLONE IS QUASI-STATIONARY NEAR 09N121W WITH 
AN UPPER RIDGE EXTENDING N TO ALONG 31N BETWEEN 120-130W...BUT 
CURRENTLY BEING ERODED BY THE PREVIOUSLY MENTIONED UPPER 
TROUGHS. THE ENVELOPE OF ANTICYCLONIC FLOW DOMINATES THE 
DISCUSSION AREA N OF THE ITCZ TO THE W OF 110W. DENSE UPPER 
MOISTURE IS ADVECTED NE ALONG THE PERIPHERY OF THIS RIDGE... 
WITHIN 360 NM EITHER SIDE OF A LINE FROM 16N140W TO 26N123W TO 
OVER MEXICO AT 25N102W. UPPER DIFFLUENCE ALONG THE SW PERIPHERY 
OF THE LARGE UPPER ANTICYCLONE IS ENHANCING THE CONVECTION ALONG 
THE WESTERN PORTION OF THE ITCZ AS PREVIOUSLY MENTIONED. 

AN UPPER TROUGH IS ADVANCING E ACROSS THE SE CONUS AND CONTINUES 
SW ACROSS THE CENTRAL GULF OF MEXICO AND SOUTHERN MEXICO INTO AN 
UPPER CYCLONE OVER THE TROPICAL PACIFIC NEAR 12N102W WITH A 
TROUGH STILL CONTINUING SW TO A BASE AT 02N113W. THIS TROUGH 
SEPARATES THE BROAD ANTICYCLONIC FLOW ALREADY MENTIONED OVER THE 
NW PORTION FROM ANTICYCLONIC FLOW OVER THE DISCUSSION AREA TO 
THE S OF 17N E OF 96W. THE ASSOCIATED UPPER DIFFLUENCE E OF THE 
FAR SOUTHERN PORTION OF THE UPPER TROUGH IS SUPPORTING THE 
CONVECTION ALONG THE ITCZ AXIS BETWEEN 106-112W AS PREVIOUSLY 
DESCRIBED.

A SURFACE HIGH PRES RIDGE EXTENDS FROM 32N136W TO NEAR 20N114W. 
NE TRADES ARE ENHANCED TO 15-20 KT S OF THE RIDGE ACROSS THE 
PACIFIC WATERS FROM 06-19N BETWEEN 124-140W WITH SEAS OF 7-9 FT 
IN MIXED LONG PERIOD NW AND CROSS-EQUATORIAL SE SWELL. THIS 
AFFECTED AREA S OF THE RIDGE WILL SHRINK WESTWARD OVER THE NEXT 
FEW DAYS AS NE WINDS OF 15-20 KT FORM NE OF THE RIDGE AND SPREAD 
S INTO THE AREA N OF 28N BETWEEN 119-128W ON THU. 

NORTHERLY WINDS HAVE DIMINISHED WELL BELOW GALE STRENGTH IN AND  
DOWNSTREAM OF THE GULF OF TEHUANTEPEC. THE RESULTANT N-NE SWELL 
WILL PROPAGATE SW MIXING WITH LONG-PERIOD CROSS EQUATORIAL S 
SWELL. SEAS WILL FINALLY SUBSIDE BELOW 8 FT NEAR 06N105W LATE 
THU NIGHT. SOUTHERLY WINDS AT 5-15 KT ARE THEN EXPECTED EACH 
DAY...AND LATE NIGHT DRAINAGE FLOW OF 10-15 KT IS EXPECTED EACH 
NIGHT THROUGH THU NIGHT. THE LATEST GUIDANCE IS SUGGESTING 
NORTHERLY FLOW WILL INCREASE TO 20-25 KT ON FRI EVENING WITH A 
MINIMAL GALE AROUND SUNRISE SAT...THEN QUICKLY DIMINISHING 
THROUGHOUT THE DAY ON SAT. 

$$ 
NELSON



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Page last modified: Wednesday, 16-Apr-2014 21:47:42 UTC