000
AXPZ20 KNHC 010358
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC FRI MAY 01 2009

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0315 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG...678W 5N84W 8N90W 6N102W 6N110W 
6N122W 8N130W 6N140W. SCATTERED STRONG CONVECTION IS WITHIN
60 NM OF THE AXIS BETWEEN 118W-121W. SCATTERED MODERATE 
CONVECTION IS WITHIN 120 NM S OF THE AXIS BETWEEN 108W-111W.

...DISCUSSION...

AS IN PREVIOUS DAYS...HIGHLY AMPLIFIED FEATURES DENOTE THE AREA.
HE FIRST IS A BROAD RIDGING AT ALL LEVELS OVER THE CENTRAL 
PORTION OF THE AREA WITH A MEAN MID/UPPER AXIS EXTENDING 
THROUGH 32N118W S TO 23N118W TO 19N120W TO A NEARLY STATIONARY 
WELL ANCHORED ANTICYCLONE NEAR 9N120W. A WEAK LOW TO MID LEVEL 
TROUGH IN THE VICINITY OF THE ITCZ EXTENDS FROM 8N138W TO 2N136W.
UPPER LEVEL DIFFLUENCE BETWEEN THE TROUGH AND THE ANTICYCLONE 
OVER THE SURFACE TROUGH DESCRIBED BELOW HAD RESULTED IN ENHANCED 
CONVECTION NEAR THE ITCZ BETWEEN 122W-129W. CONVECTION SHOULD
INCREASE AGAIN BEFORE THE TROUGH LOSES ITS IDENTITY OVER THE 
NEXT 24 HRS AS THE DEEP LAYER TROUGH DESCRIBED BELOW TAKES 
PRECEDENCE.

ANOTHER RIDGE EXTENDS FROM THE ANTICYCLONE NE TO 17N116W TO 
ACROSS BAJA CALIFORNIA AND NW MEXICO. A NEARLY STATIONARY 
MID/UPPER LEVEL TROUGH IS OVER THE FAR ERN PORTION OF THE AREA 
EXTENDING FROM SE MEXICO SW TO A SMALL CUT-OFF UPPER LEVEL LOW 
NEAR 13N97W. BROKEN MID AND UPPER LEVEL CLOUDS ARE BEING 
CHANNELED NEWD ACROSS CENTRAL AMERICA E OF THE TROUGH WITH 
SCATTERED SHOWERS AND TSTMS OVER CENTRAL AMERICA AND WIDELY
SCATTERED SHOWERS AND ISOLATED TSTMS OVER THE E PACIFIC WATERS
N OF THE ITCZ E OF 92W UNDER AN ASSOCIATED JET STREAM BRANCH 
THAT EXTENDS FROM 8N91W NNE TO ACROSS HONDURAS AND INTO THE WRN 
CARIBBEAN SEA. THE SHOWER AND TSTM ACTIVITY WILL CONTINUE 
THROUGH AT LEAST THE NEXT 48 HRS AS THE LOW AND TROUGH REMAIN 
ABOUT STATIONARY.

THE RIDGE IS FORECAST TO DAMPEN OUT SOME AS IT GETS NUDGED EWD 
TO OVER THE WRN U.S. WITHIN THE NEXT 2 DAYS BY A RATHER SHARP 
DEEP LAYER TROUGH PRESENTLY ALONG 136W/137W. A VERY WELL 
PRONOUNCED NRN STREAM JET STREAM BRANCH WITH MAXIMUM WINDS OF 
60-90 KT SHARPLY DIVES SWD INTO THE BACK SIDE OF THE TROUGH THEN 
ENTERS THE REGION AT 13N140W...AND CONTINUES NE TO 25N130W TO
ACROSS SRN CALIFORNIA. THE TROUGH BEGIN TO SHEAR OUT FRI INTO 
SAT OVER ACROSS THE ERN AND CENTRAL SECTIONS OF THE AREA. ITS 
SURFACE REFLECTION IS OBSERVED AS A COLD FRONT THAT IS CURRENTLY
JUST NW OF THE AREA. A FRONTAL TROUGH FROM 32N135W TO 27NW138W
WILL MERGE INTO A COLD FRONT PRESENTLY JUST NW OF THE AREA LATE
TONIGHT.

AT THE PRESENT TIME...DEEP LAYER MOISTURE CONSISTING OF BROKEN 
MULTILAYERED CLOUDS WITH SCATTERED SHOWERS AND ISOLATED TSTMS IS 
ADVECTING NEWD INTO THE FAR NW WATERS MAINLY AS A RESULT OF THE 
ABOVE JET STREAM ROUNDING THE BASE OF THE TROUGH BRINGING 
ADDITIONAL MOISTURE FROM THE DEEP TROPICAL PACIFIC NEWD INTO THE 
WRN PART OF THE AREA.

BROAD/MID UPPER LEVEL RIDGING COVERING THE WRN CARIBBEAN SEA 
ALSO EXTENDS W ACROSS CENTRAL AMERICA TO THE E OF THE MID/UPPER 
LEVEL TROUGH OVER THE ERN PORTION OF THE AREA.

AT THE SURFACE...HIGH PRES OF 1026 MB IS NEAR 30N125W WITH 
A RIDGE SE TO 24N118W TO 18N110W. AS THE TROUGH W OF THE AREA 
ADVANCES EWD THROUGH THE NEXT 48 HRS...THE RIDGE WILL ALSO SLIDE 
E WHILE LOW PRES DEEPENS OVER THE PLAINS INTO NRN MEXICO. THIS 
WILL ALLOW FOR THE PRES GRADIENT TO INCREASE OVER THE NE PART OF 
THE AREA INCREASING NW WINDS ALONG THE BAJA CALIFORNIA COAST TO 
THE RANGE OF 20-25 KT IN 24 HRS...THEN DIMINISHING SLIGHTLY IN 
48 HRS AND INCREASING ONCE AGAIN AFTER THAT.

S-SW WINDS OF 20 KT WITHIN 180 NM E OF THE FRONTAL TROUGH N OF
28N WILL BECOME S-SW AND INCREASE TO 20-25 KT LATE TONIGHT AS
IT MERGES WITH A COLD FRONT ALSO ASSOCIATED WITH THE SAME UPPER
TROUGH MOVING INTO THE NW WATERS REACHING FROM 30N137W TO 
27N140W LATE. SW OF 20-25 KT WILL OCCUR N OF 28N WITHIN 300 NM E 
OF FRONT IN 24 HRS...THEN DIMINISH TO LESS THAN 20 KT IN 48 HRS 
AS THE FRONT DISSIPATES OVER THE FAR NE PART.

A WEAK TROUGH MOVING WNW 15 KT EXTENDS FROM 4N132W TO 10N131W.
THIS FEATURE ALONG WITH THE WEAK LOW AND MID LEVEL TROUGH TO ITS 
W HAD EARLIER INCREASED ITCZ CONVECTION...BUT THE CONVECTION
HAS RECENTLY WEAKENED.

$$
AGUIRRE