000
AXPZ20 KNHC 091048
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU APR 09 2009

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0915 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE LIES ALONG A LINE FROM 10N85W 
TO 03N95W TO 02N109W TO 02N125W TO 03N140W. NO SIGNIFICANT 
CONVECTION IS NOTED.

...DISCUSSION...

A BROAD AREA OF TRADE WINDS IS BEING ENHANCED ON THE SOUTHERN 
PERIPHERY OF A BROAD SURFACE RIDGE OVER THE NW QUARTER OF THE 
DISCUSSION AREA. NE WINDS TO 20 KT ARE PRESENT FROM 04N TO 21N W 
OF 120W BASED ON THE QUIKSCAT PASS AROUND 09/0300 UTC. COMPUTER 
MODEL GUIDANCE INDICATES THESE WINDS CONTINUING IN APPROXIMATELY 
THE SAME LOCATION DURING THE NEXT FEW DAYS AS THE SURFACE RIDGE 
TRANSLATES EASTWARD N OF THE DISCUSSION AREA. SATELLITE IMAGERY 
AND SCATTEROMETER DATA INDICATE THREE INVERTED TROUGHS LOCALLY 
ENHANCING THESE WINDS...THE WESTERN TROUGH EXTENDING FROM 
12N129W TO 07N129W...THE CENTRAL TROUGH EXTENDING FROM 10N120W 
TO 02N119W...AND THE EASTERN TROUGH EXTENDING FROM 13N112W TO 
06N112W. THE EASTERNMOST OF THESE TROUGHS IS BEST DEFINED...AND 
ENHANCED BOUNDARY LAYER MOISTURE CONVERGENCE NEAR THIS TROUGH IS 
SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS FROM 10N TO 13N 
BETWEEN 110W AND 113W. ALSO...SURFACE PRESSURE FALLS OVER MEXICO 
DURING THE NEXT FEW DAYS...COMBINED WITH LOCAL TOPOGRAPHICAL 
EFFECTS...WILL LOCALLY ENHANCE NORTHWESTERLY WINDS NEAR THE 
COAST OF BAJA CALIFORNIA S OF 27N AND NEAR THE COAST OF MEXICO 
FROM 17N TO 20N. WINDS WILL LOCALLY REACH 20 KT IN THESE 
AREAS...AS RECENT ASCAT AND QUIKSCAT PASSES INDICATE. AS FOR 
WAVE HEIGHTS...SEAS OF 8 TO 11 FT IN GENERALLY MIXED SW AND NW 
SWELL WILL IMPACT MUCH OF THE DISCUSSION AREA DURING THE NEXT 
FEW DAYS...RESULTING FROM PREVIOUS STORM COMPLEXES OUTSIDE OF 
THE DISCUSSION AREA ALONG WITH THE RECENT GULF OF TEHUANTEPEC 
GAP WIND EVENT.

IN THE UPPER LEVELS...THE AXIS OF THE SUBTROPICAL JET STREAM 
STRETCHES ALONG A LINE FROM 22N140W TO 24N120W TO SOUTHERN BAJA 
CALIFORNIA. THIS JET IS ADVECTING ABUNDANT MID TO UPPER LEVEL 
MOISTURE EASTWARD ACROSS THE DISCUSSION AREA. SE OF THIS 
JET...ATMOSPHERIC STABILITY AND DEEP LAYERED DRY AIR IN THE 
VICINITY OF AN UPPER RIDGE OVER THE SE PORTION OF THE DISCUSSION 
AREA IS SUPPORTING FAIR WEATHER CONDITIONS THERE.

LOOKING FURTHER AHEAD...A SHORTWAVE TROUGH CURRENTLY OVER THE NE 
PACIFIC WILL DIVE SOUTHWARD WHILE DEEPENING...AS A VIGOROUS 
MID/UPPER-LEVEL JET FORCES IT TO DIG SOUTHWARD. COMPUTER MODEL 
GUIDANCE IS IN GOOD AGREEMENT THAT AN ASSOCIATED DISSIPATING 
SURFACE COLD FRONT WILL APPROACH THE NORTHEASTERN WATERS BY 
FRIDAY...WITH STRONG WINDS ON EITHER SIDE OF THE FRONT. GUIDANCE 
ALSO INDICATES THAT A SURFACE LOW WILL DEVELOP NEAR THE 
CALIFORNIA COAST BEFORE REDEVELOPING INLAND LATE FRIDAY. THIS 
WILL SERVE TO STRENGTHEN THE SURFACE PRESSURE GRADIENT NEAR THE 
FRONT...WITH THE THREAT FOR W TO NW WINDS UP TO 30 KT W OF THE 
REMNANT SURFACE TROUGH. WAVEWATCH GUIDANCE INDICATES SEAS 
BUILDING TO 16 FT BY LATE FRIDAY IN THE WAKE OF THE FRONT.

GAP WINDS...
THE STRONG GAP WIND EVENT IN THE GULF OF TEHUANTEPEC HAS ENDED 
AS THE SURFACE PRESSURE GRADIENT ACROSS THE ISTHMUS OF 
TEHUANTEPEC HAS WEAKENED. WINDS IN THIS AREA HAVE LIKELY FALLEN 
BELOW 20 KT BASED ON THE LATEST COMPUTER MODEL GUIDANCE.

INCREASED TRADE WINDS OVER THE CARIBBEAN REGION ARE FORECAST TO 
EXTEND INTO THE GULF OF PAPAGAYO AND PANAMA DURING THE NEXT FEW 
DAYS...WHEN SURFACE WINDS ARE EXPECTED TO OCCASIONALLY REACH 20 
KT. 

$$
COHEN