000
AXPZ20 KNHC 021600
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC THU JUL 02 2009

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1530 UTC.

...TROPICAL WAVE...

A TROPICAL WAVE EXTENDS FROM 17N101W TO 12N103W TO 05N103W 
MOVING W 10-15 KT. THIS WAVE COINCIDES WITH A MAXIMUM IN DEEP 
LAYER MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT 
FROM CIMSS. HOWEVER...THE WAVE IS NOT PARTICULARLY WELL-DEFINED 
AS FAR AS THE LOW LEVEL WIND FIELD IS CONCERNED BASED ON THE 
QUIKSCAT PASS AROUND 02/1200 UTC...WITH GENERALLY LIGHT N TO NE 
WINDS ACROSS THE N HALF OF THE WAVE...AND CROSS EQUATORIAL 
SOUTHWESTERLY FLOW OF 10 TO 15 KT ACROSS THE S HALF OF THE WAVE. 
THE POSITION OF THE WAVE IS BASED ON CONTINUITY FROM PREVIOUS 
POSITIONS. THIS WAVE IS EMBEDDED WITHIN THE ITCZ...AND ANY DEEP 
CONVECTION NEAR THE WAVE IS LIKELY BEING DRIVEN BY LOW LEVEL 
CONVERGENCE NEAR THE ITCZ.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 09N83W TO 10N95W TO 11N105W TO 
09N120W TO 06N140W. SCATTERED MODERATE TO STRONG CONVECTION IS 
WITHIN 300 NM S OF THE AXIS E OF 92W. SCATTERED MODERATE 
CONVECTION IS N OF 04N BETWEEN 93W AND 99W. SCATTERED MODERATE 
CONVECTION IS N OF 14N BETWEEN 98W AND 103W. SCATTERED MODERATE 
CONVECTION IS FROM 07N TO 11N BETWEEN 101W AND 106W.

...DISCUSSION...

S OF 20N...
THE MAIN FORECAST CONCERN ACROSS THE TROPICS WILL BE THE 
DEVELOPMENT OF A SURFACE LOW ABOUT 420 NM SW OF GUERRERO MEXICO 
DURING THE NEXT FEW DAYS. IN THE UPPER LEVELS...A 
QUASI-STATIONARY DEEP-LAYER WARM-CORE HIGH CONTINUES BUILDING 
OVER MEXICO...SUPPORTED BY THE JUXTAPOSITION OF AN UPPER LEVEL 
HIGH AND SURFACE HIGH OVER CENTRAL MEXICO. THE PRESSURE GRADIENT 
SW OF THIS HIGH WILL INCREASE LOW/MID-LEVEL E TO SE WINDS SW OF 
MEXICO DURING THE NEXT FEW DAYS. AT THE SAME TIME...CROSS 
EQUATORIAL SOUTHERLY FLOW WILL INTERACT WITH THE INCREASING E TO 
SE FLOW...RESULTING IN AN AREA OF INCREASED LOW-LEVEL CYCLONIC 
VORTICITY WELL OFF THE MEXICAN COAST DURING THE NEXT 48 HOURS. 
ALL GLOBAL MODEL GUIDANCE SUGGESTS THE DEVELOPMENT OF A SURFACE 
LOW...WITH THE CONSENSUS POINTING TOWARD A 24-HOUR POSITION OF 
10N101W OF A 1009 MB LOW. THIS LOW COULD FORM ON A 
WESTWARD-MOVING SURFACE TROUGH CURRENTLY EMBEDDED WITHIN THE 
ITCZ EXTENDING FROM 15N95W TO 11N97W TO 07N98W. THIS TROUGH IS 
BECOMING BETTER DEFINED BASED ON THE 02/1200 UTC QUIKSCAT PASS 
AND CYCLONIC TURNING IN THE BOUNDARY LAYER CUMULUS FIELD. WINDS 
OF 20 TO 25 KT WILL DEVELOP OVER THE E SEMICIRCLE OF THE LOW BY 
48 HOURS AS THE LOW/MID-LEVEL FLOW STEERS THE LOW WESTWARD 
AROUND 10 KT. THEREAFTER...THE LOW WILL BE ACCELERATED WESTWARD 
AS IT INTERACTS WITH STRONGER STEERING FLOW SW OF THE 
AFOREMENTIONED RIDGE. THE ENHANCED WINDS IN THE E SEMICIRCLE ARE 
THE RESULT OF THE STRONGER PRESSURE GRADIENT BETWEEN THE LOW AND 
THE SURFACE RIDGE OVER MEXICO.

AT THE SAME TIME...CROSS EQUATORIAL FLOW IS BRINGING SE TO S 
WINDS TO 20 KT S OF 05N BETWEEN 92W AND 98W...WITH THIS AREA 
LIKELY EXPANDING NORTHWARD DURING THE NEXT FEW DAYS. 
ALSO...MODERATE EASTERLY LOW/MID-LEVEL FLOW S OF THE 
AFOREMENTIONED RIDGE OVER THE W CARIBBEAN WILL BLEED INTO THE 
GULF OF PAPAGAYO...WITH SURFACE WINDS BEING ACCELERATED INTO THE 
20-30 KT RANGE NEAR AND DOWNSTREAM OF THE GULF OF PAPAGAYO BY 
EARLY SATURDAY DUE TO VARIATIONS IN LOCAL TOPOGRAPHY. THESE 
WINDS WILL BE MAXIMIZED LATE AT NIGHT WHEN NOCTURNAL DRAINAGE 
FLOW IS AT ITS PEAK. STRONG SOUTHERN HEMISPHERIC STORMS ARE ALSO 
SENDING LONG-PERIOD SOUTHWESTERLY SWELL NORTHWARD...WITH WAVE 
HEIGHTS OF 8 TO 10 FT COVERING A LARGE PART OF THE AREA S OF 15N 
E OF 116W BY LATE SUNDAY...BRINGING LARGE BATTERING WAVES TO THE 
SW COAST OF MEXICO BY LATE IN THE WEEKEND.

N OF 20N...
A 1017 MB SURFACE HIGH NEAR 26N143W IS SUPPORTING A SMALL AREA 
OF NE TO E TRADE WINDS TO 20 KT FROM 08N TO 14N W OF 125W NE TO 
E WINDS TO 20 KT. THIS AREA OF TRADE WINDS WILL BECOME CONFINED 
TO LOCATIONS W OF 137W DURING THE NEXT 24 HOURS AS THE 
CORRESPONDING SURFACE RIDGE AXIS BECOMES MORE N/S-ORIENTED NW OF 
THE AREA...WITH A WEAKER SECONDARY RIDGE AXIS OVER THE N PORTION 
OF THE DISCUSSION AREA ALONG 28N W OF 120W. A STRONGER 
W/E-ORIENTED RIDGE IS NOT BE SUPPORTED AS A BROAD UPPER LEVEL 
TROUGH BECOMES SITUATED OVER THE N PORTION OF THE AREA...WITH A 
STRONGER MID-LEVEL VORTICITY MAX SWINGING THROUGH THE TROUGH 
THIS WEEKEND. THE ONLY IMPACT ON SENSIBLE WEATHER FROM THE 
VORTICITY MAX WILL BE STRENGTHENING UPSTREAM SUBSIDENCE BUILDING 
SURFACE HIGH OVER THE N DISCUSSION AREA BY LATE THIS WEEKEND.

$$
COHEN