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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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