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AXPZ20 KNHC 182148
TWDEP

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2345 UTC.


...SPECIAL FEATURE...

GALE WARNING FOR THE GULF OF TEHUANTEPEC...

A SURFACE LOW OVER THE NE GULF OF MEXICO WILL DRAG THE SOUTHERN END OF A COLD FRONT E THROUGH THE S-CENTRAL GULF OF MEXICO TONIGHT. NORTHERLY FLOW WILL INCREASE ACROSS THE WESTERN GULF OF MEXICO IN THE WAKE OF THIS FRONT WITH NORTHERLY 20-25 KT WINDS SURGING INTO THE GULF OF TEHUANTEPEC THIS EVENING. THE GRADIENT WILL TIGHTEN FURTHER WITH MINIMAL GALE CONDITIONS EXPECTED BY MIDNIGHT TONIGHT WITH THESE MINIMAL GALE CONDITIONS CONTINUING THROUGH SUNRISE ON SAT. WINDS WILL QUICKLY DIMINISH THROUGHOUT THE DAY ON SAT WITH ONLY N-NE 20-25 KT WINDS EXPECTED ON SAT EVENING THROUGH SUNRISE ON SUN. THE NOCTURNAL MAXIMUM DRAINAGE SHOULD ONLY MAX 15-20 KT EACH NIGHT FROM SUN NIGHT THROUGH WED NIGHT.


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

THE EPAC MONSOON TROUGH EXTENDS SW FROM THE COAST OF PANAMA AT 08N82W TO 06N90W WHERE SCATTEROMETER WINDS INDICATE A TRANSITION TO AN ITCZ AXIS...WHICH CONTINUES W TO 07N97W...THEN DIPS SW TO 05N111W...THEN WIGGLES WESTWARD TO BEYOND 06N140W.

SCATTERED MODERATE ISOLATED STRONG CONVECTION IS DECAYING ALONG THE COLOMBIAN COAST WITHIN 75 NM OF 05.5N78W. SIMILAR CONVECTION IS NOTED ALONG THE MONSOON TROUGH AND ITCZ AXIS WITHIN 150 NM EITHER SIDE OF A LINE FROM 07.5N84W TO 03N107W AND WITHIN 120 NM EITHER SIDE OF A LINE FROM 08N120W TO 04.5N132W. ISOLATED MODERATE TO STRONG CONVECTION IS ALSO NOTED ALONG THE WESTERN PORTION OF THE ITCZ WITHIN THE AREA BOUNDED BY 02-77N BETWEEN 135-140W.

A PERSISTENT MID-UPPER TROUGH NOW HAS A SURFACE REFLECTION EXTENDING FROM 14N107W TO 02N111W. ISOLATED MODERATE TO STRONG CONVECTION IS FLARING WITHIN 90 NM EITHER SIDE OF A LINE FROM 13N108W TO 03N110W TO 04N117W.


...DISCUSSION...

AN UPPER CYCLONE HAS MOVED EASTWARD ACROSS THE NORTHERN PORTION OF THE DISCUSSION AREA OVER THE PAST FEW DAYS AND IS NOW MOVING E ACROSS THE NORTHERN BAJA CALIFORNIA PENINSULA. A MID TO UPPER TROUGH EXTENDING TO THE SW HAS AMPLIFIED TO A BASE NEAR 17N127W. DENSE UPPER DEBRIS MOISTURE THAT ORIGINATED IN THE CENTRAL PACIFIC IS NOW CONCENTRATED TO THE E OF THE TROUGH AXIS AND SPREADING E ACROSS NORTHERN MEXICO WITH SIGNIFICANT MOISTURE ALSO SPREADING N ACROSS SOUTHERN CALIFORNIA...ARIZONA...NEW MEXICO AND EXTREME W TEXAS. SOME OF THIS MOISTURE WILL SPREAD E ACROSS THE WESTERN GULF OF MEXICO TONIGHT.

AN UPPER LEVEL ANTICYCLONE IS CENTERED JUST W OF THE AREA AT 08N141W WITH A RIDGE EXTENDING E ACROSS THE TROPICS TO A CREST NEAR 06N113W. UPPER DIFFLUENCE UNDER THIS RIDGE HAS ENHANCED THE INCREASE IN CONVECTION ALONG THE ITCZ TO THE W OF 115W. THE PREVIOUSLY DESCRIBED SURFACE TROUGH FROM 14N107W TO 02N111W IS UNDER AN UPPER TROUGH THAT IS QUASI-STATIONARY FROM 04-15N BETWEEN 100-112W. THIS UPPER TROUGH SEPARATES THE ANTICYCLONIC FLOW JUST DESCRIBED OVER THE WESTERN PORTION FROM ANOTHER TROPICAL ANTICYCLONE OVER THE SE PORTION ASSOCIATED WITH AN UPPER RIDGE EXTENDING W OFF THE COAST OF COLOMBIA ALONG 07N TO THE E OF 100W. THIS UPPER RIDGE IS IN PHASE WITH THE LOWER LEVER MONSOON TROUGH AND ITCZ...AND IS SUPPORTING THE INCREASE IN CONVECTION. SOME OF THE RESULTANT DEBRIS MOISTURE IS ADVECTED NE ACROSS CENTRAL AMERICA...THEN TURNS E-NE ACROSS THE CENTRAL CARIBBEAN.

A SURFACE HIGH PRESSURE RIDGE EXTENDS FROM 29N140W TO NEAR 18N105W. NE TRADES ARE ENHANCED TO 15-20 KT BETWEEN THE RIDGE AND 07N TO THE W OF 122W...WITH SEAS OF 6-8 FT IN MIXED LONG PERIOD NW AND NE SWELL WITH ADDITIONAL LONG PERIOD CROSS- EQUATORIAL SE SWELL. THIS AFFECTED AREA S OF THE RIDGE WILL PERSIST THROUGH THE WEEKEND. NW TO N 15 KT WINDS TO THE NE OF THE RIDGE WILL CONTINUE TO THE PACIFIC COAST OF THE BAJA CALIFORNIA PENINSULA WITH SEAS OF 4-5 FT. A NEW BATCH OF NW SWELL WILL ARRIVE AT 30N140W SAT NIGHT...AND CONTINUE TO PROPAGATE E REACHING THE NW COAST OF THE BAJA PENINSULA IN THE FORM COMBINED SEAS OF 6-9 FT ON MON. SEAS OF 8-9 FT IS EXPECTED ACROSS THE DISCUSSION WATERS N OF 20N BETWEEN 112W-135W ON TUE.

$$ NELSON

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