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Area forecast discussion 
National Weather Service Taunton Massachusetts 
146 PM EDT Sat Sep 6 2008 


Synopsis... 
a Tropical Storm Warning continues for portions of southeast New England. 
This system will bring heavy rainfall...some flooding and the 
potential for a period of strong winds to portions of the coastal 
plain tonight. Warm...dry weather will follow for most of Sunday and 
Monday. An approaching cold front Tuesday may bring a period of 
scattered showers/thunderstorms followed by dry seasonable weather 
Wednesday and Thursday. 


&& 


Near term /until 6 PM this evening/... 
scattered and /mainly/ light showers expected for most of this 
afternoon across the area. At noon today the leading edge of the 
rains directly associated with Hanna had worked to the western CT 
state line...but will likely take a few hours to work its way 
eastward into lower CT River Valley. Likely/categorical probability of precipitation begin 
there around 4 PM...progressing to northeast Massachusetts around 6 to 7 PM. 


Low cloud cover is expected to persist this afternoon across the 
majority of the area. 


&& 


Short term /6 PM this evening through 6 am Sunday/... 
***the tropical storm watch has been upgraded to a ts warning for the 
Rhode Island and Massachusetts coastal regions including the islands*** 


The track continues to point toward Rhode Island/southeast mass east of the 
Boston-Providence corridor with passage of the storm center around 
09z early Sunday morning. Heavy downpours should continue through 
much of the night as the storm approaches. Precipitable water values 
are forecast to rebound to 2.5 inches so expect heavy downpours over 
several hours. This points to heavy rain/flooding being one problem. 


The storm center itself is expected to maintain a core wind of 45 
knots gusting to 55 knots as it passes. Tropical storms reaching our 
latitude normally have the strong winds to the eastern side of the 
storm. This would point to tropical storm force winds along much of 
our South Coast and possibly a little way north through the Outer 
Cape and the Cape Cod Bay coast. With the open water to the east...we 
could see some ts winds farther north. BUFKIT soundings from the GFS 
show 50 knot winds less than 1000 feet off the deck. Meanwhile...the 
core will be close to interior southeast New England...especially southeast 
mass and northern Rhode Island. 


With all this in mind...the tropical storm watch for coastal areas 
will be upgraded to a warning. Also...the tropical storm wind watch 
will be upgraded to a warning and expanded to include southeast 
Middlesex /near Boston/ and southern Worcester County. Most of the 
wind associated with these headlines will take place between 
midnight and 8 am Sunday. 


We probably will not see wind gusts exceed 30 or 40 miles per hour to the 
northwest of the track. However...the heavy rain and best 
probability of flooding will exist to the northwest of the track. 
Models in pretty good agreement that a total of 3 to 6 inches of 
rain will fall across portions of this region. Therefore...flood 
watches have been issued and please see our hydrology section. The 
main threat will be for urban flooding...especially since this 
amount of rain may fall in a very short period of time. In 
addition...isolated thunderstorms will be possible with this system. 


The other thing we are going to have to watch for is the potential 
for isolated weak tornadoes. Tropical systems sometimes produce 
them on their northern and eastern sections of the storm where shear 
values become quite high. Based on our current track...the risk for 
this would be on the coastal plain. 


&& 


Long term /Sunday through Friday/... 
Sunday...most of the effects from Hanna will be finished by Sunday 
morning. Strong winds...especially across the coastal waters and 
the immediate coast will continue through the morning and then 
gradually diminish through the afternoon. In addition...there may 
be a few lingering showers...especially across the northeastern 
portions of southern New England through middle morning. As Hanna or 
her remnants move off to the northeast...high pressure will build in 
behind. Could turn out to be quite a nice day...with highs around 
80 and skies clearing through the day. 


Monday and Tuesday...high pressure remains in control until an upper 
level trough and accompanying low pressure system pull a cold front 
through southern New England on Tuesday. Scattered showers and 
thunderstorms will likely accompany the front as it moves through. 
High temperatures will be slightly above normal. 


Wednesday and Thursday...high pressure builds back into the area 
behind the front. Dry...more autumn-like weather is expected...with 
high temperatures slightly below normal. 


Friday...another cold front approaches from the west. This far 
out...timing is definitely a question. 


Overall made few major changes to the grids beyond Tuesday. Mainly 
blended the current forecast with mosguide where possible to focus 
on the nearer term. 


&& 


Aviation /18z Saturday through Thursday/... 
rest of today and tonight....MVFR/IFR conditions will linger the 
remainder of this afternoon. Another area of heavy rain will move in 
tonight bringing IFR/LIFR conditions. Southeast winds at fmh...hya 
and ack will increase to 35 knots with gusts 45 to 50 knots between 
03z and 10z. Brief gusts to 35 or 40 knots possible at kpvd and kbos 
during that timeframe. The center will pass across interior southeast 
mass around 09z...then winds will shift to northwest approaching 12z. 


Sunday...tempo MVFR ceilings 015-030 hundred feet eastern terminals with a 
few lingering showers possible until 15z. Otherwise VFR conditions 
with winds diminishing by afternoon. 


Outlook...Sunday night through Thursday 


Sunday night and Monday...VFR. 


Tuesday...mainly VFR...then MVFR in showers and thunderstorms as a 
front moves through southern New England. 


Wednesday and Thursday...VFR. 


&& 


Marine... 
today...southerly swell in advance of Tropical Storm Hanna will 
build seas through today. South winds will remain 10-15 knots much 
of the day...then increase toward evening as ts Hanna approaches. 


Tonight...Tropical Storm Hanna looks to track across coastal Rhode Island and 
southeast Massachusetts. This will bring tropical storm conditions to 
the waters with 50 knot gusts and seas over 10 feet from midnight to 
6 am. 


Outlook...Sunday through Wednesday... 


Sunday...winds and seas will start the period with gale or near gale 
force wind gusts especially across the northeastern coastal waters. 
Winds will gradually diminish through the day. However...seas 
between 5 and 10 feet in the eastern coastal waters and 8 to 12 feet 
in the southern coastal waters will continue. Seas will gradually 
decrease late Sunday evening. 


Monday...winds will have decreased below small craft criteria by the 
end of the day with seas remaining around 5 feet across the outer 
coastal waters through the afternoon. 


Tuesday...small craft criteria likely as upper level trough and cold 
front move through the waters. 


Wednesday and Thursday...winds and waves will remain below small 
craft criteria. 


&& 


Hydrology... 
first rain band from late last night/early this morning brought heavy 
rains primarily to southeast Massachusetts and Rhode Island. In that 
area rainfall totals ranged from 2 to 3.5 inches. 


There will be a quiet period for a few hours this afternoon with some which 
scattered showers and thunderstorms. The second and more substantial rain 
period will start late this afternoon/early this evening as ts Hanna 
approaches up the coast. Heavy downpours from around 5 PM through 5 
am will bring potential 3 to 6 inch rainfall with locally heavier 
amounts possible. 


We will continue the Flash Flood Watch. For the majority of the 
area...flood guidance is 3 inches in 1 hour...4.5 inches in 3 hours. 
Urban centers will not necessarily need this much rain to cause 
flooding. 


During this time of year...rivers tend to run at lower levels...they 
can take in a good deal of rain. But given amount of rain forecast 
minor flooding could occur on some of the larger tributaries. 


&& 


Tides/coastal flooding... 
GFS mrpsse is only showing a half to 1 foot storm surge across the 
South Coast late Sunday night. However...feel it could be 
significantly underdone since BUFKIT is showing the potential for 50 
to 60 miles per hour wind gusts in the warm sector. Astronomical tides are not 
that high...but still see the potential for a 3 foot storm surge. 
This may result in some minor coastal flooding along the South Coast 
at the time of high tide. We are not expecting any coastal flooding 
on the eastern Massachusetts coast. 


The times of high tide are as follows... 
Boston 516 am Sunday 
Nantucket 633 am Sunday 
Newport 127 am Sunday 
Providence 140am Sunday 


&& 


Box watches/warnings/advisories... 
CT...Flash Flood Watch through Sunday morning for ctz002>004. 
Tropical Storm Wind Warning until 8 am EDT Sunday for 
ctz002>004. 
Massachusetts...Flash Flood Watch through Sunday morning for maz002>024-026. 
Tropical Storm Warning for maz007-015-016-019>024. 
Tropical Storm Wind Warning until 8 am EDT Sunday for maz005- 
006-012>014-017-018. 
New Hampshire...Flash Flood Watch through Sunday morning for nhz011-012-015. 
Rhode Island...Flash Flood Watch through Sunday morning for riz001>008. 
Tropical Storm Warning for riz002-004>008. 
Tropical Storm Wind Warning until 8 am EDT Sunday for riz001- 
003. 
Marine...Tropical Storm Warning for anz230>237-250-254-255. 
&& 


$$ 
Synopsis...rlg 
near term...nmb 
short term...wtb/nmb 
long term...rlg 
aviation...wtb/Strauss/rlg 
marine...wtb/rlg 
hydrology... 
tides/coastal flooding... 

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