000
AXPZ20 KNHC 281005
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC FRI AUG 28 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 
0830 UTC.

...SPECIAL FEATURES...

.BROAD LOW PRES NEAR 11N118W IS ANALYZED AT 1008 MB CONTINUES 
MOVING W NEAR 20 KT. BANDS OF TSTMS CONTINUE TO DEVELOP ACROSS 
MUCH OF THE WRN SEMICIRCLE OF THIS LOW AND HAD INCREASED 
OVERNIGHT...WHILE DEEP CONVECTION WAS MORE ISOLATED ELSEWHERE 
WITHIN 240 NM OF THE LOW. AN OVERNIGHT QUIKSCAT PASS SHOWED 
WINDS OF 20-25 KT WITHIN 360 NM NE QUADRANT...480 NM SE 
QUADRANT...AND 300 NM NW QUADRANT OF THE LOW...WITH WWIII 
GUIDANCE FORECASTING 8 TO 9 FT SEAS IN THE SE QUADRANT. 
ANTICYCLONIC SHEAR ALOFT OVER THIS SYSTEM IS HELPING TO INCREASE 
AND MAINTAIN THE CONVECTION ACROSS THE WRN HALF OF THE SYSTEM. 
SEAS SURFACE TEMPERATURES ARE MODESTLY WARM IN THE PATH OF THIS 
SYSTEM...AND IT COULD DEVELOP INTO A TROPICAL CYCLONE IN THE 
NEXT 48 HOURS AS IT MOVES W TO WNW.   

.LOW PRES NEAR 14N98W ANALYZED AT 1008 MB ALONG A TROPICAL WAVE 
WAS MOVING W NEAR 15 KT. A LOW TO MID LEVEL CYCLONIC CIRCULATION 
HAS BEEN EVIDENT WITH THIS WAVE FOR THE PAST SEVERAL 
DAYS...SINCE MOVING ACROSS THE SW CARIBBEAN. BANDS OF TSTMS 
CONTINUE TO FLARE ACROSS MUCH OF THE NRN SEMICIRCLE OVERNIGHT... 
AND TRAILS THE LOW OFF TO THE E. AN UPPER LEVEL HIGH OVER MEXICO 
TO THE NE IS PRODUCING DIFFLUENT FLOW ALOFT ACROSS THIS 
SYSTEM...WHICH IS FAVORABLE FOR CONTINUED TSTM DEVELOPMENT. 20 
TO POSSIBLY 25 KT WINDS PERSIST ACROSS THE NRN SEMICIRCLE BASED 
ON PARTIAL SCATTEROMETER PASSES OVERNIGHT. SEA SURFACE 
TEMPERATURES ARE VERY WARM IN THE PATH OF THIS SYSTEM...AND IT  
COULD DEVELOP INTO A TROPICAL CYCLONE IN THE NEXT 48 HOURS AS IT 
MOVES WNW TO NW. HOWEVER...ITS CLOSE PROXIMITY TO LAND MAY 
INHIBIT SIGNIFICANT DEVELOPMENT...BUT COULD BRING HEAVY RAINS TO 
PORTIONS OF COASTAL MEXICO.   

...TROPICAL WAVES...

A TROPICAL WAVE WAS ANALYZED N OF 06N ALONG 81/82W MOVING W AT 
15 KT. THIS WAVE WAS JUST A SMALL PORTION OF THE WAVE THAT HAS 
DEVELOPED INTO TROPICAL STORM DANNY IN THE ATLANTIC...AND IS 
BERING TRACKED BY CONTINUITY. ABUNDANT TROPICAL MOISTURE... 
LIKELY ASSOCIATED WITH THE S AMERICAN MONSOON CIRCULATION...HAS 
MOVED W FROM COLOMBIA DURING THE PAST 24 HOURS AND IS ASSUMED TO 
BE ASSOCIATED WITH THIS WAVE. THIS WEAK PERTURBATION WILL 
CONTINUE TO MOVE W AND ENHANCE LOW LEVEL CONVERGENCE ACROSS 
COSTA RICA AND NICARAGUA TODAY.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS WAS ANALYZED FROM 09N83W 
TO 11.5N97W TO 11N115W TO 08N123W TO 12.5N134W TO 13N140W. 
SCATTERED MODERATE CONVECTION WAS OCCURRING WITHIN 120 NM OF 
AXIS E OF 86W. SCATTERED TO NUMEROUS MODERATE WITH ISOLATED 
STRONG CONVECTION WITHIN 120 NM LINE 05.5N86W TO 07N97W. 
ISOLATED TO SCATTERED MODERATE ELSEWHERE WITHIN 240 NM OF AXIS W 
OF 100W. 

...DISCUSSION...

AN UPPER ANTICYCLONE NEAR 19.5N124W HAS A RIDGE SW TO NEAR 
13N138W AND A RIDGE E TO NEAR 20N113W. A SECOND ANTICYCLONE IS 
NEAR 30N120W WITH A SHARP RIDGE S TO 17N118W. UPPER MOISTURE IS 
TRAPPED UNDER THE RIDGE ALONG 120W TO THE N OF 15N...BUT SEEMS 
TO BE EVAPORATING. AN UPPER TROUGH HAS NEARLY STALLED OVER THE 
NW PORTION OF THE AREA ROUGHLY ALONG 33N135W TO 27N137W...AND IS 
ACCOMPANIED BY UPPER MOISTURE W OF ITS AXIS. SOME DEBRIS 
MOISTURE FROM FORMER TROPICAL DEPRESSION IGNACIO HAS MOVED N TO 
NEAR 32N131W.  OTHERWISE THE UPPER LEVELS AREA DRY N OF 17N W OF 
122W.

AN UPPER ANTICYCLONE IS NEAR 18N96W WITH ITS ENVELOPE OF 
ANTICYCLONIC FLOW EXTENDING S OVER THE TROPICAL PACIFIC BETWEEN 
90W AND 110W...AND IS ENHANCING CONVECTION ALONG THE LOW PRES 
AND TROPICAL WAVE ALONG 97W...BOTH PREVIOUSLY MENTIONED. THE 
ASSOCIATED MOISTURE REMAINS N OF 05N.

ELSEWHERE AT THE SURFACE...A 1014 MB HIGH IS NEAR 24N121W.

$$
STRIPLING