000
AXPZ20 KNHC 282205
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC MON MAR 28 2011

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY 
THROUGH 2145 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS IS CENTERED ALONG 6N78W
4N90W 3N105W...THEN RESUMES AT 4N118W 3N130W 3N140W. SCATTERED 
MODERATE TO STRONG CONVECTION IS WITHIN 60 NM OF THE AXIS BETWEEN
83W-85W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN
30 NM OF THE AXIS W OF 137W.

...DISCUSSION...

A FAIRLY PROGRESSIVE UPPER FLOW REMAINS IN PLACE ACROSS THE 
DISCUSSION AREA. THE TAIL END OF A DAMPENING UPPER TROUGH NOW 
OVER THE WESTERN U.S. EXTENDS SW INTO THE REGION THROUGH 32N119W 
AND EXTENDS SW TO NEAR 22N120W...S TO 14N120W...AND BENDS SE TO 
NEAR 15N117W. BROAD W TO NW FLOW INTO THE BACKSIDE OF THE TROUGH 
EXTENDS AS FAR S AS 28N AND TO 127W. S OF THE TROUGH BROAD SWLY 
FLOW COVERS JUST ABOUT THE ENTIRE AREA TO 9N AND TO THE E OF 
ANOTHER UPPER LEVEL TROUGH THAT IS TO THE S OF THE FIRST TROUGH 
ALONG 14N116W 7N113W 2N112W. TO THE W OF THIS TROUGH...THE UPPER 
FLOW IS BROADLY ANTICYCLONIC AHEAD OF A VERY SHARP UPPER LEVEL 
TROUGH IN THE VICINITY OF THE HAWAIIAN ISLANDS. A JET STREAM 
BRANCH RIDES OVER THE NORTHERN CREST OF THE ANTICYCLONIC FLOW 
ENTERING THE REGION THROUGH 24N140W. IT THEN CONTINUES SE TO 
20N125W...AND NE TO ACROSS SOUTHERN BAJA CALIFORNIA TO INLAND 
CENTRAL MEXICO. UPPER AIR DATA INDICATES MAXIMUM WINDS IN THE 
RANGE OF 60-70 KT ARE WITHIN ABOUT 480-540 NM S OF THIS JET. 
THESE WINDS ARE ADVECTING UPPER LEVEL MOISTURE IN THE FORM OF 
MOSTLY BROKEN HIGH CIRRUS CLOUDS FROM THE DEEP TROPICS OF THE 
CENTRAL PACIFIC NORTHEASTWARD TO ACROSS THE FAR EASTERN PORTION 
OF THE AREA FROM 17N-22N AND TO THE E OF THE UPPER TROUGH.

OVER THE FAR SOUTHERN PORTION OF THE AREA...A MID/UPPER LEVEL 
TROUGH IS E OF THE RIDGE ALONG 90W. A REGION OF DIFFLUENCE AHEAD 
OF THIS TROUGH IS HELPING TO ENHANCE ITCZ CONVECTION QUITE 
SIGNIFICANTLY BETWEEN 83-85W. THE TROUGH IS FORECAST TO MOVE E 
OF THE PACIFIC BASIN AND INTO THE FAR SW CARIBBEAN SEA THROUGH 
LATE TUE NIGHT WHILE WEAKENING. TO THE SW OF THIS TROUGH A 
RATHER ELONGATED UPPER LEVEL ANTICYCLONE IS CENTERED JUST W OF 
THE GALAPAGOS ISLANDS WITH A RIDGE W TO THE SECOND UPPER TROUGH 
MENTIONED ABOVE. MID/UPPER LEVEL RIDGING IS PRESENT ACROSS THE 
AREA TO THE S OF THE JET STREAM...AND BETWEEN THE TROUGH ALONG 
90W AND THE UPPER TROUGH THAT LIES ALONG 14N116W 7N113W 2N112W.
MODERATE SUBSIDENCE ALLOWING FOR GENERALLY STABLE ATMOSPHERIC 
CONDITIONS ALLOWING FOR VERY LIMITED TO NO MOISTURE TO BE SEEN 
COVERS THE AREA E OF ABOUT 101W.

AT THE SURFACE...A 1030 MB HIGH CENTER IS LOCATED JUST NW OF THE 
AREA NEAR 33N138W WITH A RIDGE SE TO 24N123W TO NEAR 18N112W.
HIGH PRES COVERS THE DISCUSSION AREA N OF 14N AND W OF 113W. 
FRESH NE TRADE WINDS ARE PRESENT S OF THE RIDGE AXIS FROM 4N TO 
20N W OF 130W...WITH A SMALLER AREA OF TRADES 16N TO 21N BETWEEN
110-130W. A WEAK TROUGH NEAR THE SECOND UPPER TROUGH IS ANALYZED 
FROM 9N111W TO 6N115W TO 2N119W. ISOLATED SHOWERS AND WEAK TSTMS
ARE WITHIN 60-75 NM OF THE TROUGH. THE TRADES ARE EXPECTED TO 
EXPAND NORTHWARD TO 26N IN 24 HOURS...AND TO 28N IN 48 HOURS
AS THE HIGH CENTER N OF THE AREA SLIDES E WHILE SLIGHTLY 
STRENGTHENING. THE SURFACE TROUGH SHOULD CONTINUE IN A GENERALLY 
WESTWARD TRACK THROUGH THE NEXT 24-48 HOURS...AND WEAKEN BETWEEN
36-48 HOUR TIME PERIOD.

THE PRES GRADIENT BETWEEN THE SUBTROPICAL RIDGE AND LOWER PRES 
OVER NORTHERN MEXICO CONTINUES TO RESULT IN INITIAL NW TO N WINDS
OF 20 KT N OF 24N E OF 124W TO THE BAJA CALIFORNIA COAST. THESE 
WINDS ARE EXPECTED TO BECOME CONFINED TO WITHIN THE AREA N OF 
27N BETWEEN 119W AND 127W IN 24 HOURS...AND TO N OF 27N BETWEEN 
120W-128W IN 48 HOURS. ANOTHER SET OF LARGE N SWELLS WITH SEAS
UP TO 12 FT IS EXPECTED TO BEGIN TO MOVE INTO THE FAR NE CORNER 
BEGINNING IN 24 HOURS.

$$
AGUIRRE