000
AXPZ20 KNHC 180222
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SUN APR 18 2010

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 
0215 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 05.5N77W TO 06.5N81W TO 05.5N89W TO 
08.5N100W TO 06N116W TO 09N132W TO 07.5N140W. ISOLATED MODERATE 
TO STRONG CONVECTION WITHIN 150 NM S OF AXIS BETWEEN 98W AND 
103W. ISOLATED MODERATE TO STRONG CONVECTION BETWEEN 210 AND 420 
NM S OF AXIS BETWEEN 115W AND 122W. SCATTERED MODERATE TO 
ISOLATED STRONG CONVECTION WITHIN 150 NM EITHER SIDE OF AXIS 
BETWEEN 123W AND 130W.  

...DISCUSSION...

A WELL DEFINED UPPER LEVEL CYCLONIC VORTEX EMBEDDED IN A HIGH 
AMPLITUDE TROUGH IS OBSERVED ON SATELLITE WATER VAPOR IMAGERY TO 
BE NEAR 29N136W. THE RESULTING SURFACE FEATURE IS A RATHER 
COMPLEX SYSTEM WITH TWO LOW CENTERS...ONE N OF THE AREA NEAR 
32N136W WITH COLD FRONT EXTENDING FROM THE LOW ACROSS THE 
FORECAST AREA FROM 30N133W TO 25N133W TO 21N138W. NEAR GALE 
FORCE WINDS ARE WITHIN 240 NM E OF THIS COLD FRONT. THE SECOND 
LOW IS OVER THE NW PART OF THE FORECAST AREA NEAR 26N138W WITH 
COLD FRONT FROM THE LOW TO 26N136W TO 25N135W TO 22N140W. NEAR 
GALE FORCE WINDS ARE WITHIN 420 NM OF THE SOUTHERN QUADRANT OF 
THE LOW. 

AN UPPER LEVEL ANTICYCLONE IS CENTERED NEAR 09N118W WITH A 
HIGHLY AMPLIFIED RIDGE EXTENDING N TO WELL BEYOND THE AREA TO 
OVER THE WESTERN U.S. AND RESULTING BROAD ANTICYCLONIC 
CIRCULATION COVERING THE AREA E OF THE UPPER TROUGH MENTIONED IN 
THE PREVIOUS PARAGRAPH TO 100W. EAST OF THIS UPPER LEVEL 
ANTICYCLONE...A HIGH AMPLITUDE TROUGH PREVAILS WITH AXIS 
EXTENDING FROM THE CENTRAL GULF OF MEXICO SWD ACROSS SE MEXICO 
AND GUATEMALA...INTO THE E PACIFIC TO 00N90W. 

ELSEWHERE AT THE SURFACE...A WEAKENING 1018 MB HIGH IS CENTERED 
NEAR 26N122W. AS A RESULT OF THE WEAKENED HIGH...THE PRESSURE 
GRADIENT BETWEEN THE HIGH AND LOWER PRESSURE OF THE ITCZ HAS 
RELAXED...AND TRADES HAVE DIMINISHED BELOW 20 KT. WITH THE 
DECREASE IN TRADES...MOISTURE CONVERGENCE INTO THE ITCZ HAS 
DECREASED. AS A RESULT...CONVECTION W OF 113W HAS DECREASED 
SIGNIFICANTLY COMPARED TO THE PAST COUPLE OF DAYS. ITCZ 
CONVECTION BETWEEN 90W AND 100W HAS ALSO DECREASED SIGNIFICANTLY 
AS THIS AREA NOW LIES UNDER SUBSIDENT AIR ON THE W SIDE OF THE 
UPPER LEVEL TROUGH AXIS MENTIONED IN THE SECOND PARAGRAPH. 

$$
AL