000
AXPZ20 KNHC 180334
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC THU JUN 18 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.

...SPECIAL FEATURE...

A 1008 MB LOW PRES CENTER WAS EVIDENT IN VISIBLE SATELLITE IMAGERY 
NEAR 16N108W...OR ABOUT 260 MILES SW OF MANZANILLO MEXICO...MOVING 
WNW AT 9 KT. CONVECTION HAS PERSISTED AROUND THE PERIPHERY OF THIS 
ELONGATED MONSOON CIRCULATION. HOWEVER...IN THE PAST COUPLE OF HOURS 
ISOLATED MODERATE CONVECTION HAS DEVELOPED WITHIN 45 NM OF THE LOW 
LEVEL CIRCULATION CENTER...MAINLY NE...WHERE WIND SHEAR IS VERY 
LIGHT AND UPPER DIVERGENCE HAS IMPROVED. THIS SYSTEM REMAINS 
ELONGATED... WITH A TROUGH CONNECTING THIS CENTER TO A SECOND LOW TO 
MID LEVEL CYCLONIC CIRCULATION CENTER NOTED NEAR 10.5N113W. MORNING  
SCATTEROMETER DATA SHOWED MODERATE TO FRESH S TO SW WINDS SOUTH OF 
THIS FEATURE...ENHANCING LOW LEVEL CONVERGENCE AND ENHANCING 
CONVECTION ALL ALONG THE S SIDE OF THIS CONNECTING TROUGH. LIGHT TO 
MODERATE N TO NE WINDS AND DRY LOW LEVEL AIR REMAIN NW OF THE LOW. 
THIS SYSTEM HAS THE POTENTIAL TO BECOME A TROPICAL DEPRESSION DURING 
THE NEXT DAY OR TWO AS IT MOVES WEST-NORTHWESTWARD AND THEN BEGINS 
TO MOVE MORE NORTHWEST. THERE IS A HIGH CHANCE...GREATER THAN 50 
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 
48 HOURS.

...ITCZ...

AXIS IS CENTERED ALONG 05N76W 05N85W 9N100W 11N110W TO LOW NEAR 
10.5N114W...THEN CONTINUES TO 8N118W 7N124W 9N130W 7N140W. SCATTERED
MODERATE TO STRONG CONVECTION WITHIN 120 NM N OF AXIS E OF 85W 
EXTENDING INTO THE GULF OF PANAMA. SCATTERED MODERATE CONVECTION 
WITHIN 90 NM S OF AXIS BETWEEN 86W AND 101W. SCATTERED MODERATE 
ISOLATED STRONG CONVECTION WAS WITHIN 180 NM EITHER SIDE OF AXIS 
BETWEEN 103W AND 118W. SCATTERED MODERATE CONVECTION WAS WITHIN 120 
NM EITHER SIDE OF AXIS W OF 126W. SCATTERED MODERATE CONVECTION WAS 
OVER GULF OF TEHUANTEPEC N OF 12N BETWEEN 91W AND 95W.

...DISCUSSION...

A REX BLOCK PATTERN DOMINATES THE DISCUSSION AREA W OF 125W WITH AN 
UPPER RIDGE IS CENTERED N OF 31N135W...N OF AN UPPER LOW CENTERED 
NEAR 15N137W. NORTHERLY FLOW ON THE EAST SIDE OF THE UPPER RIDGE IS 
AMPLIFYING A MID TO UPPER LEVEL TROUGH EXTENDING FROM NORTHERN BAJA 
TO 20N125W. STRONG JET ENERGY N OF THE AREA FLATTENS THE UPPER RIDGE 
AND CUTS OFF THE UPPER LOW OVER NORTHERN BAJA BY THU. THE IMPACT AT 
THE SURFACE OF ALL THIS IS THAT THE SURFACE RIDGE WILL PERSIST FROM 
A 1026 MB SURFACE HIGH NE OF HAWAII TO THE BAJA COAST. EARLIER 
SCATTEROMETER DATA SHOWED A SWATH OF FRESH TRADES PERSISTING S OF 
THE RIDGE FROM ROUGHLY 10N TO 20N. THE SURFACE HIGH WILL SHIFT 
NORTHWARD THROUGH FRI...ALLOWING THE SWATH OF TRADE WINDS TO SHIFT 
NORTH ACCORDINGLY. A SMALL AREA OF MODERATE TO FRESH NORTHERLY WINDS 
WAS INDICATED ON A 04Z ASCAT PASS BETWEEN THE PERIPHERY OF THE RIDGE 
AXIS AND THE CENTRAL BAJA COAST. THIS AREA WILL PERSIST OFF AND ON 
THROUGH THE NEXT COUPLE OF DAYS WITH THE SURFACE RIDGE PERSISTING.

$$
STRIPLING/AGUIRRE