000
AXPZ20 KNHC 181539
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN APR 18 2010

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1515 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 6N78W 6N91W 8N100W 8N110W 6N120W 
7N130W 7N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS 
WITHIN 30 NM OF THE AXIS BETWEEN 83W-85W. SCATTERED MODERATE 
CONVECTION IS WITHIN 60 NM OF THE AXIS BETWEEN 96W-98W...AND 
ALSO WITHIN 30 NM OF THE AXIS BETWEEN 119W-121W.

...DISCUSSION...

A CYCLONIC VORTEX MOVING E 20-25 KT NEAR 29N131W IS EMBEDDED IN 
A DEEP LAYER TROUGH THAT EXTENDS FROM THE WESTERN PORTION OF THE
U.S. INTO THE AREA THROUGH 30N128W TO THE VORTEX AND SSW TO 
16N135W...AND S TO 7N135W. THE SURFACE LOW OF 1006 MB IS 
ANALYZED NEAR 29N132W WITH AN OCCLUDED FRONT TO 28N129W...THEN 
COLD FRONT TO 23N130W TO 18N134W AND DISSIPATING STATIONARY 
FRONT TO 15N140W. DRY AIR INTRUSION FROM W OF THE AREA IS NOTED 
AS A SWATH OF MODERATE SUBSIDENCE WITHIN 150 NM SE AND S OF THE 
VORTEX.

TO THE SE OF VORTEX...THE DOMINANT LARGE SCALE FEATURE CONTINUES 
TO BE AN UPPER ANTICYCLONE NEAR 8N118W WITH A HIGHLY AMPLIFIED 
RIDGE EXTENDING NNE TO WELL BEYOND THE AREA TO ACROSS THE NW 
MEXICO AND THE SW U.S. ANOTHER RIDGE EXTENDS WSW FROM THE 
ANTICYCLONE TO 7N133W. BROAD ANTICYCLONIC CIRCULATION IS NOTED W 
OF 98W TO THE ABOVE DEEP LAYER TROUGH. A VERY PRONOUNCED 
SUBTROPICAL JET STREAM ENTERS THE REGION THROUGH 20N140W...AND 
ROUNDS THE BASE OF THE TROUGH AS IT SHOOTS NEWD TO ACROSS SRN 
CALIFORNIA. SATELLITE-DERIVED WINDS SHOW WINDS IN THE RANGE OF 
70-130 KT IN THE RIGHT ENTRANCE REGION OF THE JET. THESE VERY 
FAST WINDS IN COMBINATION WITH SW WINDS IN THE NW SEMICIRCLE OF 
THE ANTICYCLONE CONTINUE TO ADVECT AMPLE MID AND UPPER LEVEL 
MOSITURE IN THE FORM OF BROKEN TO OVERCAST CLOUDS...SOME FORMER 
DEBRIS MOISTURE FROM PRIOR ITCZ CONVECTION...NEWD TO OVER MUCH 
OF BAJA CALIFORNIA AND THE AREA JUST NE OF THE REGION INCLUDING 
SRN CALIFORNIA. THIS MOISTURE PLUME ALSO WRAPS AROUND THE 
AMPLIFIED RIDGE SEWD TO ACROSS SRN BAJA TO ALONG THE W MEXICO 
COAST AS SCATTERED HIGH CLOUDS.

A VERY LARGE LATITUDINAL UPPER TROUGH ORIGINATING FROM WELL NE 
OF THE AREA...IN THE CENTRAL U.S...EXTENDS SSE TO THE CENTRAL 
GULF OF MEXICO S TO ACROSS THE YUCATAN PENINSULA...GUATEMALA AND 
WELL INTO THE E PACIFIC TO A BASE NEAR 1N89W. VERY LITTLE IN THE
WAY OF DEEP TROPICAL MOISTURE IS ASSOCIATED WITH THE TROUGH
AS EXTENSIVE DRY AIR PREVAILS ON EITHER SIDE OF THE TROUGH TO 
AS FAR W AS 110W. A SURFACE TROUGH IS NOTED ON FIRST VIS IMAGES
TO EXTEND FROM 5N102W TO 13N99W. MINIMAL CONVECTION DUE TO
THE TROUGH AS BEEN SHEARED OFF TO THE S AND SE UNDER THE NLY
FLOW ALOFT ON THE BACK SIDE OF THE UPPER TROUGH. THIS CONVECTION
IS DESCRIBED ABOVE UNDER ITCZ. SW WINDS AHEAD OF THE TROUGH 
ARE PUSHING SOME DEBRIS MOISTURE NE ACROSS CENTRAL AMERICA...
ALTHOUGH THIS MOISTURE HAS DIMINISHED MARKEDLY OVER THE PAST
24 HRS DUE TO THE DRY AIR ALOFT PREVALENT THROUGHOUT THIS PORTION
OF THE REGION.

ELSEWHERE AT THE SURFACE...A WEAKENING 1015 MB HIGH IS ANALYZED
NEAR 22N120W. BROAD LOW PRES IS OBSERVED TO THE N OF 14N AND W OF
110W. MODELS INDICATE THAT STRONG HIGH PRES WILL BUILD E AND SE
INTO MUCH OF THE NW PORTION OF THE AREA MON AND TUE ONCE THE 
1006 MB LOW AND FRONT DISSIPATE. THE BUILDING HIGH PRES WILL 
INTENSIFY THE PRES GRADIENT ALLOWING FOR N TO NE WINDS OF 20-25 
KT TO FILTER INTO THE NRN AND CENTRAL WATERS. WAVEWATCH GUIDANCE 
HINTS AT ANOTHER EVENT OF LONG PERIOD NW SWELLS INVADING THE NW 
PORTION OF THE AREA BEGINNING ON MON WITH SEAS BUILDING UP TO 
POSSIBLY 12 OR 13 FT PARTICULARLY IN THE FAR NW CORNER.
    
OVER THE SRN WATERS...NE TRADES OF 20 KT ARE OCCURRING FROM 8N 
TO 15N W OF 134W BETWEEN 115W AND 130W WITH SEAS OF 8 FT. THESE 
TRADES ARE EXPECTED TO VARY LITTLE WITH RESPECT TO COVERAGE OVER 
THE NEXT 48 HRS...HOWEVER A NW SWELL PRODUCING SEAS OF 8-10 FT 
SHOULD PROPAGATE THROUGH MAINLY THE W SECTOR OF THE TRADES 
BEGINNING MON AFTERNOON AND INTO TUE. ELSEWHERE S OF 11N W OF 
112W WINDS ARE LESS THAN 20 KT...WITH SEAS TO 8 FT IN SW SWELL 
EXCEPT NW SWELL W OF 130W. THESE ARE SWELLS ARE FORECAST TO 
DECAY THROUGH EARLY MON AFTERNOON.

$$
AGUIRRE