000
AXPZ20 KNHC 150927
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SAT MAY 15 2010

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 
0900 UTC.

...TROPICAL WAVES...

A WEAK TROPICAL WAVE IS ALONG 91W FROM 03N TO 09N MOVING W AT 
NEAR 10 KT. THIS WAVE SHOWS UP WELL IN THE TOTAL PRECIPITABLE 
WATER IMAGERY. SOME SHOWER AND TSTM ACTIVITY IS NOTED BEHIND THE 
WAVE AXIS. 

...ITCZ...

THE ITCZ AXIS IS ALONG AXIS ALONG 06N78W TO 07N103W TO 09N113W 
TO 07N130W TO 08N140W. SCATTERED MODERATE TO ISOLATED STRONG 
FROM 04N TO 08N BETWEEN 92W AND 99W. SIMILAR CONVECTION IS NOTED 
NEAR 07N79W AND ALONG THE COAST OF COLOMBIA N OF 4N. SCATTERED 
MODERATE IS WITHIN 120 NM N OF AXIS BETWEEN 121W AND 130W...AND 
WITHIN 100 NM N OF AXIS W OF 133W.

...DISCUSSION...

AN UPPER LEVEL TROUGH EXTENDS FROM NORTHERN BAJA CALIFORNIA TO 
NEAR 26N117W. AN UPPER LEVEL RIDGE IS IN PLACE W OF THE TROUGH 
WITH ANOTHER UPPER LEVEL TROUGH NOW APPROACHING THE FAR NW 
PORTION OF THE AREA. MODERATE TO STRONG UPPER LEVEL SUBSIDENCE 
AND IMPLIED DRY AIR MASS IS NOTED N OF 20N AND W OF 110W WITH A 
BAND OF MOISTURE CURRENTLY ENTERING THE FAR NW PORTION OF THE 
FORECAST REGION. 

AN UPPER ANTICYCLONE IS CENTERED NEAR 10N103W WITH A RIDGE 
EXTENDING TO THE NE OVER SE MEXICO AND NORTHERN CENTRAL AMERICA 
AND TO THE W ALONG 10N TO 140W. A JETSTREAM BRANCH WITH CORE 
WIND SPEEDS OF 70-90 KT LIES BETWEEN THE AFOREMENTIONED TROUGH 
AND THIS ANTICYCLONE ENTERING THE DISCUSSION AREA NEAR 18N140W 
AND CONTINUING TO THE E-NE AROUND THE NORTHERN PERIPHERY OF THE 
ANTICYCLONE AND INTO CENTRAL MEXICO. WATER VAPOR IMAGERY SHOWS A 
BAND OF TRANSVERSE HIGH CLOUDS ASSOCIATED WITH THIS JET. THE 
RIDGE IS HELPING TO INDUCE CONVECTION ALONG THE ITCZ. 

AT THE SURFACE...A 1025 MB HIGH PRES CENTERED NEAR 30N138W 
EXTENDS A RIDGE OVER THE FORECAST WATERS TO NEAR 17N120W. A 
WINDSAT PASS FROM AROUND 0300 UTC AND THE SUBSEQUENT 0634 UTC 
ASCAT PASS INDICATED A BROAD AREA OF FRESH TO STRONG TRADE WINDS 
OF 20 TO 25 KT ON THE SOUTHERN PERIPHERY OF THE HIGH WHICH IS 
FORECAST TO REMAIN NEARLY STATIONARY DURING THE NEXT 24 HOUR 
THEN WILL WEAKEN IN ABOUT 48 HOURS AS A COLD FRONT MOVES INTO 
THE NW PORTION OF THE AREA. 

A WEAK 1010 MB LOW PRES IS CENTERED NEAR 07.5N105W. CONVECTION 
HAS DIMINISHED OVERNIGHT DUE TO SOME UPPER LEVEL NLY SHEAR AND 
ONLY SOME CONVECTIVE ACTIVITY IS OBSERVED WITHIN 120 NM OF 
CENTER IN SE QUADRANT. MOST OF THE COMPUTER MODELS KEEP A WEAK 
SYSTEM MOVING MAINLY WWD DURING THE NEXT 48-72 HOURS. 

NE WIND WAVES AND CROSS EQUATORIAL SW SWELL DOMINATE THE 
MAJORITY OF THE FORECAST REGION. THE SEA STATE WILL BECOME MORE 
COMPLEX DURING THE NEXT 24-48 HOURS AS A SET OF LONG PERIOD SE 
SWELL BEGINS TO PROPAGATE N OF THE EQUATOR.

GAP WINDS...NE TO E WINDS AT 20 KT ARE SURGING THROUGH THE GULF 
OF PAPAGAYO DOWNWIND TO 90W. THESE WINDS ARE EXPECTED TO 
DIMINISH TO LESS THAN 20 KT IN ABOUT 24 HOURS.

OF NOTE...TODAY MARKS THE BEGINNING OF THE 2010 EASTERN NORTH 
PACIFIC HURRICANE SEASON WHICH RUNS FROM MAY 15 TO NOVEMBER 30. 
ON AVERAGE...SIXTEEN TROPICAL STORMS FORM EVERY YEAR...NINE OF 
WHICH WILL BECOME HURRICANES WITH 4 REACHING MAJOR STATUS. THE 
FIRST TROPICAL STORM THIS SEASON WILL BE NAMED AGATHA.

$$
GR