Weather

421 
fxca62 tjsj 061548 
afdsju 


Area forecast discussion 
National Weather Service San Juan PR 
1148 am AST Monday Oct 6 2008 


Update...the weather forecast office Doppler radar showed a very limited weather 
morning. At this moment a few showers are developing over the 
interior sections of Puerto Rico. The potential for large 
quantities of rainfall accumulations remain high as light winds 
are expected to prevail across the island through Tuesday. 


&& 


Previous discussion... /issued 548 am AST Monday Oct 6 2008/ 


Discussion...large upper level low to the NE of the local region 
this morning presently producing narrow zone of middle level 
subsidence from Hispaniola to the northern vi...with a narrow upper 
level deformation zone aloft. This will likely aid in the 
enhancement of at least one cluster of deep convection across PR this 
afternoon...similar to yesterday...as convection develops along the moisture 
discontinuity. As this low has marched west across the central 
Atlantic...a broad low level trough has developed at llvls... inducing a 
northeasterly flow to the west of the upper low. This northeasterly flow is expected to 
become light and variable today as a weak low level trough associated 
with this upper low shifts slowly west across the area. Light low level 
winds and ample morning sunshine today should allow for local 
diurnal effect to be main forcing mechanism today...and should 
favor the higher elevations of PR and the north slopes. A more southeasterly 
flow at llvls Tuesday and Wednesday is expected to bring an increase in 
tropical moisture across the area for a slight increase in 
rainfall potential and intensity. 


This upper low is forecast to drift ever so slightly west of the next 
few days and weaken or fill...leaving an upper trough lingering 
across and just to the east of the local area...and in fact the 
GFS has this upper trough to our east through next weekend. This will 
maintain modest instability aloft during most of this time. 


High pressure sliding into the west central Atlantic later in the 
week..behind a cold front...is expected to induce a return to a 
more east-northeast to Ely low level flow...and shunt tropical moisture lingering 
across the area Tuesday and Wednesday to the SW. Thus it appears 
as though the infamous local effects will continue to be the main 
weather focusing feature for most if not all of the upcoming week. 


Global models continue to be aggressive in the intensification of a 
tropical wave that has just exited Africa. Will continue to 
monitor this as oceanic conditions across the tropical Atlantic remain 
anomalously warm and favorable for significant instability across 
this region. 


Aviation...VFR conditions are expected across all taf sites before 
dawn and during the morning hours. However...patchy weather and 
isolated to scattered showers could affect some of the local taf 
sites this morning..especially the U.S.V.I. MVFR ceilings are 
expected 14z-20z over tist...with the same category at tjmz and tjbq 
where thunderstorms are expected to develop roughly 18z-22z. Cloud 
tops of 40k to 50k feet will be possible by late this afternoon over 
central interior towards northwestern Puerto Rico. 


Marine...light and varying winds...and lack of long period swell 
energy moving through the regional waters will make for tranquil 
marine conditions across the local waters. Next significant swell 
not expected until the end of the week when northerly swells generated 
behind a cold front invade the region. However...this is currently 
forecast to be of moderate size and short lived. 


&& 


Preliminary point temps/pops... 
sju 88 77 88 77 / 40 20 40 30 
stt 87 78 87 78 / 40 40 50 40 


&& 


Sju watches/warnings/advisories... 
PR...none. 
Vi...none. 
&& 


$$ 


72/10