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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

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