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Eastern Pacific Tropical Weather Discussion (Text)

000
AXPZ20 KNHC 180231
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC FRI APR 18 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0215 UTC. 

...SPECIAL FEATURE...

GALE WARNING FOR THE GULF OF TEHUANTEPEC...N-NE SWELL FROM 
YESTERDAYS STORM/GALE EVENT IN THE GULF OF TEHUANTEPEC HAS 
PROPAGATED WELL SW OF THE AREA NEAR 10N105W AND CONTINUES TO 
MIX WITH LONG-PERIOD CROSS EQUATORIAL S SWELL. COMBINED SEAS
WILL FINALLY SUBSIDE BELOW 8 FT NEAR 07N104W LATE TONIGHT. 

A SURFACE LOW WILL FORM ALONG A NORTHWARD DRIFTING WARM FRONT 
OVER THE N-CENTRAL GULF OF MEXICO TONIGHT. AS THE LOW LIFTS OUT 
TO THE NE ACROSS FL ON FRI IT WILL DRAG THE SOUTHERN END OF THE 
FRONT E AGAIN AS A COLD FRONT WITH NORTHERLY FLOW INCREASING 
ACROSS THE WESTERN GULF OF MEXICO. NORTHERLY 20-25 KT WINDS WILL 
SURGE INTO THE GULF OF TEHUANTEPEC 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
05N113W TO BEYOND 03N140W.

SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED ALONG AND 
TO THE SE OF THE MONSOON TROUGH AND THE EASTERN SEGMENT OF THE 
ITCZ WITHIN 90 NM EITHER SIDE OF A LINE FROM 09N83W TO 05N87W TO 
06N94W TO 04N100W. SIMILAR CONVECTION IS NOTED OVER AND TO THE N 
OF THE WESTERN PORTION OF THE ITCZ WITHIN 150 NM EITHER SIDE OF 
A LINE FROM 04N120W TO 06N138W.

...DISCUSSION...                                                

AN UPPER CYCLONE IS OVER THE NORTHERN PORTION OF THE DISCUSSION  
AREA AT 31N122W WITH AN UPPER TROUGH EXTENDING SW TO BEYOND 
24N140W AND ACCOMPANIED BY DRY UPPER AIR WITHIN 180 NM OF THE 
TROUGH AXIS. A SHORTWAVE TROUGH IS SWINGING E ACROSS THE CENTRAL 
CONUS WITH THE TROUGH AXIS EXTENDING S ACROSS CENTRAL OF MEXICO 
TO A BASE AT 23N100W. A BAND OF VERY DRY UPPER AIR FOLLOWS THE 
TROUGH AXIS ACROSS NORTHERN OLD MEXICO. 

AN UPPER LEVEL ANTICYCLONE IS CENTERED AT 07N130W WITH AN UPPER 
RIDGE EXTENDING N-NE BETWEEN THE TWO UPPER TROUGHS TO A SHARP 
CREST AMPLIFYING N ACROSS THE NORTHERN GULF OF CALIFORNIA. AN 
UPPER RIDGE ALSO EXTENDS W FROM THE ANTICYCLONE ACROSS THE DEEP 
TROPICS TO BEYOND 09N140W 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 13N105W. THIN LINE OF 
MODERATE CONVECTION HAVE DEVELOPED FROM 12.5N102W TO 07N120W 
AND FROM 02N113W TO 03N118W. DENSE UPPER MOISTURE IS ADVECTED
E ALONG THE N PERIPHERY OF THIS UPPER ANTICYCLONE...WITHIN 150 
NM EITHER SIDE OF A LINE FROM 18N140W TO 25N115W TO ACROSS MEXICO
BETWEEN 18-24N...THEN TURNING NE ACROSS THE GULF OF MEXICO AHEAD 
OF THE SHORTWAVE OVER THE CENTRAL CONUS. THIS MOISTURE WILL 
CONTINUE TO FEED INTO THE CONVECTION OVER THE NORTHERN GULF OF 
MEXICO. 

AN UPPER TROUGH IS DISSIPATING OVER THE TROPICAL PACIFIC FROM  
15N92W TO 07N107W. 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 93W 
ASSOCIATED WITH AN UPPER ANTICYCLONE OVER THE SW CARIBBEAN NEAR 
12N80W. 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 WITH SOME OF THE RESULTANT DEBRIS MOISTURE ADVECTED
NE ACROSS CENTRAL AMERICA.

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 6-9 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 TO THE 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