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Eastern Pacific Tropical Weather Discussion (Text)

000
AXPZ20 KNHC 172148
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU APR 17 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. 

...SPECIAL FEATURE...

GALE WARNING FOR THE GULF OF TEHUANTEPEC...N-NE SWELL FROM 
YESTERDAYS STORM/GALE EVENT IN THE GULF OF TEHUANTEPEC WILL 
CONTINUE TO PROPAGATE SW MIXING WITH LONG-PERIOD CROSS 
EQUATORIAL S SWELL. SEAS WILL FINALLY SUBSIDE BELOW 8 FT NEAR 
07N104W LATE TONIGHT. A SURFACE LOW WILL FORM ALONG A NORTHWARD 
DRIFTING WARM FRONT OVER THE NE GULF OF MEXICO EARLY TONIGHT. AS 
THE LOW LIFTS OUT TO THE NE IT WILL MOVE THE SOUTHERN END OF THE 
FRONT E AGAIN AS A COLD FRONT WITH NORTHERLY FLOW INCREASING 
ACROSS THE WESTERN GULF OF MEXICO. NORTHERLY FLOW WILL INCREASE 
TO 20-25 KT IN THE GULF OF MEXICO ON FRI EVENING WITH A MINIMAL 
GALE CONDITIONS EXPECTED BY MIDNIGHT AND CONTINUING THROUGH 
SUNRISE ON SAT...THEN QUICKLY DIMINISHING THROUGHOUT THE DAY ON 
SAT WITH ONLY 15-20 KT N WINDS EXPECTED ON SAT EVENING. THE 
NORTHERLY DRAINAGE FLOW WILL INCREASE AGAIN TO 20-25 KT LATE SAT 
NIGHT THROUGH SUNRISE ON SUN. THE NOCTURNAL MAXIMUM SHOULD ONLY 
NE 15-20 KT EACH NIGHT FROM SUN NIGHT THROUGH THU NIGHT.

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

THE EPAC MONSOON TROUGH EXTENDS SW FROM THE COAST OF COSTA RICA 
AT 10N85W TO 06N90W WHERE SCATTEROMETER WINDS INDICATE A 
TRANSITION TO AN ITCZ AXIS...WHICH CONTINUES WSW TO 05N101W TO
05N114W TO BEYOND 03N140W.

SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED ALONG
THE MONSOON TROUGH AND THE EASTERN SEGMENT OF THE ITCZ WITHIN 
60 NM EITHER SIDE OF LINES FROM 05.5N82W TO 04.5N99W AND 
FROM 10N91W TO 05.5N95W. SIMILAR CONVECTION IS NOTED OVER AND
TO THE N OF THE ITCZ WITHIN 60 NM EITHER SIDE OF A LINE FROM 
08N103W TO 04N108W AND WITHIN 180 NM EITHER SIDE OF A LINE 
FROM 04N122W TO 06N140W.

...DISCUSSION...                                                

AN UPPER CYCLONE IS OVER THE NORTHERN PORTION OF THE DISCUSSION  
AREA AT 31N125W WITH AN UPPER TROUGH EXTENDING SW TO BEYOND 
25N140W AND ACCOMPANIED BY DRY UPPER AIR. A SHORTWAVE TROUGH IS 
SWINGING E ACROSS THE CENTRAL CONUS WITH THE TROUGH AXIS 
EXTENDING S ACROSS CENTRAL OF MEXICO TO A BASE AT 22N103W. A 
BAND OF VERY DRY UPPER AIR FOLLOW THE TROUGH AXIS ACROSS NW OLD 
MEXICO. 

AN UPPER LEVEL ANTICYCLONE IS CENTERED AT 08N129W WITH AN UPPER 
RIDGE EXTENDING N-NE BETWEEN THE TWO UPPER TROUGHS TO A SHARP 
CREST OVER THE NORTHERN GULF OF CALIFORNIA. AN UPPER RIDGE ALSO 
EXTENDS W FROM THE ANTICYCLONE ACROSS THE DEEP TROPICS TO BEYOND 
13N140W WITH UPPER DIFFLUENCE S OF THIS RIDGE ENHANCING THE 
CONVECTION ALONG THE WESTERN SEGMENT OF THE ITCZ AS PREVIOUSLY 
DESCRIBED. A RIDGE ALSO EXTENDS E-NE FROM THE ANTICYCLONE TO A 
FAIRLY SHARP CREST AT 14N109W. DRY UPPER AIR WITHIN THE 
ANTICYCLONIC ENVELOPE IS SUPPRESSING CONVECTION ACROSS THE 
TROPICS FROM 06-17N BETWEEN 107-127W...EXCEPT FOR A THIN LINE OF 
MODERATE CONVECTION FROM 02N116W TO 03N120W. DENSE UPPER 
MOISTURE IS ADVECTED E ALONG THE N PERIPHERY OF THIS UPPER 
ANTICYCLONE...WITHIN 180 NM EITHER SIDE OF A LINE FROM 16N140W 
TO 25N116W TO OVER THE GULF OF MEXICO AT 24N96W WHERE THE 
MOISTURE TURNS NE AHEAD OF THE SHORTWAVE OVER THE CENTRAL CONUS.

AN UPPER TROUGH IS DISSIPATING OVER THE TROPICAL PACIFIC FROM  
16N95W TO 03N113W. THIS TROUGH SEPARATES THE BROAD ANTICYCLONIC 
FLOW ALREADY MENTIONED OVER THE NW PORTION FROM ANTICYCLONIC 
FLOW OVER THE DISCUSSION AREA TO THE S OF 15N E OF 94W 
ASSOCIATED WITH AN UPPER ANTICYCLONE OVER THE SW CARIBBEAN NEAR 
10N80W. UPPER DIFFLUENCE ALONG THE SOUTHERN PERIPHERY OF THE 
ANTICYCLONE IS SUPPORTING THE CONVECTION ALONG THE MONSOON 
TROUGH AND THE EASTERN SEGMENT OF THE ITCZ AS PREVIOUSLY 
DESCRIBED.

A SURFACE HIGH PRES RIDGE EXTENDS FROM 31N140W TO NEAR 16N102W.  
NE TRADES ARE ENHANCED TO 15-20 KT BETWEEN THE RIDGE AND 05N TO 
THE W OF 122W...WITH SEAS OF 6-8 FT IN MIXED LONG PERIOD NW AND 
NE SWELL AND STILL MIXING WITH LONG PERIOD CROSS-EQUATORIAL SE 
SWELL. THIS AFFECTED AREA S OF THE RIDGE WILL SHRINK WESTWARD 
OVER THE NEXT FEW DAYS. NE WINDS OF 15-20 KT NE OF THE RIDGE 
WILL SPREAD SE ACROSS THE WATERS N OF 28N BETWEEN 120-130W WITH 
SEAS OF 6-9 FT IN MIXED N AND LONG PERIOD S SWELL. THE SEAS WILL 
SUBSIDE BEFORE REACHING THE PACIFIC WATERS ALONG THE BAJA 
PENINSULA WITH SEAS OF 4-7 FT EXPECTED TILL EARLY MON. GUIDANCE 
SHOWS A NEW BATCH OF NW SWELL ARRIVING AT 30N140W LATE SAT AND 
REACHING THE NW COAST OF THE BAJA PENINSULA IN THE FORM COMBINED 
SEAS OF 6-9 FT ON MON.

$$
NELSON