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marine weather discussion
NWS ocean prediction center Washington DC
835 PM EST Thu 20 Nov 2008
.Forecast discussion: major features/winds/seas/significant
.Weather for North Atlantic ocean W of 50w from 30n to 50n.
A weak sfc low se of Georges Bank is racing off to the E whl
pulling a weak trailing cold front se into the cntrl/srn nt2
wtrs attm. In the immed wake of the low Max winds are up to 20
or 25 kt attm acrs the nt1 and nrn nt2 wtrs which are in line
with the 18z NAM/GFS. Max seas are likely up to 10-12 ft acrs
the NE most nt2 wtrs which are being handled fine by the 18z wna
wavewatch iii attm.
Over the short term...the 18z NAM/GFS rmn consistent with their
prev respective runs and in rnsbly good agrmt that low pres wl
form on the front over the srn nt2 wtrs late tonite...then track
NE and intensify Fri thru Sat...with the 18z NAM being slightly
slower (by abt 3hrs on avg) than the 18z GFS. The 18z gefs
ensemble members indicate that the 18z GFS may be slightly too
fast also. Therefore for now plan on using a blended 18z NAM/GFS
and 12z ECMWF fcst track for this system. Tho they differ
trackwise the latest mdls all fcst smlr gradients invof this
dvlpg low. Per the 18z NAM/GFS wl cont to fcst gales dvlpg Fri
into Fri nite thrut the nt2 wtrs as prevly fcstd. For the nt1
wtrs...with the usually conservative 12z UKMET/ECMWF fcstg 30 kt
bl winds to dvlp...and noting the 18z NAM BUFKIT soundings...wl
add the Gulf of Maine and the S of new engld wtrs to the prevly
fcst gale wrngs for Fri nite into Sat nite. Otherwise no other
major chngs are planned to the prev ofshr fcst package rgrdg
this system.
In the long range...wl favor a blended 18z GFS/12z ECMWF
solution for the triple point sfc low dvlpg invof srn new engld
early Tue then tracking slowly N later Tue whl pulling a mod
strong cold front ofshr...which is smlr to the latest HPC medium
range guidance. For now wl cont with the prevly fcst wrngs for
this system with just minor tweaks to the ascd conds.
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Previous discussion...
Update: am going to follow the 12z GFS mdl and introduce gales
for the nt1 and nrn nt2 wtrs for late Mon into Tue...since the
GFS has vry gud support from ECMWF/Gem/UKMET solns and also from
the aftn HPC Med rng fcstr guidance.
A series of trofs will move se across the ofshr wtrs this aftn
into early Fri. A low will dvlp over the se ofshr wtrs Fri
aftn...move NE and intensify late Fri...pass NE of the nt2 wtrs
Fri nite while contg to intensify Fri nite...then pass N over
the glf of St lwrc Sat. A cold fnt will dvlp across the cntrl
and srn nt2 wtrs Fri aftn...then pass E of the area late Fri.
Rdg will bld E over the srn nt2 wtrs Fri nite...spread over the
cntrl nt2 wtrs Sat...bld across the nrn nt2 wtrs sun...then pass
E over the nt2 area on Mon. A trpl point low is expctd to dvlp
near Cape Cod late Mon...then deepen and lift N into Quebec on
Tue. A warm fnt will lift NE across the nt1 wtrs on Mon. Another
cold fnt will move E over the ofshr wtrs late Mon and Tue.
About whether to go for gales over the nt2 wtrs S of Cape Fear
for late Fri into Fri nite prd...NAM and GFS say marg gales here
in stg caa over the Gulf Stream with support from other Med rng
mdls...so will incrs the Max winds here from 30 kt to 35 kt for
Fri and Fri nite.
06z GFS has vry gud support from ECMWF/NOGAPS/UKMET mdls...and
also from latest HPC Med rng fcstr guidance...so will cont to
favor the GFS with no signif changes planned to the current fcst
trend.
06z wna version of wavewatch iii mdl looks vry similar to the
00z run...and still looks a ltl slow to bld up the seas over the
nt2 wtrs with a dvlpg low and cold fnt during the Fri into Sat
timeframe.
.Warnings/forecast confidence...Preliminary. Any changes will be
coordinated through AWIPS 12 planet chat or by telephone:
.Nt1 New England waters...
.Gulf of Maine...gale Sat and Sat nite...MDT confdc...then again
Tue...MDT confdc.
.Georges Bank...Gale Fri nite thru Sat nite...MDT to hi confdc.
Gale Tue...MDT confdc.
.S of New England...Gale Fri nite into Sat nite...MDT
confdc...then again Tue...MDT confdc.
.Nt2 mid Atlc waters...
.Hudson to balt cnyn...gale Fri nite into Sat...MDT confdc.
.Balt cnyn to Hague line...Gale Fri into Sat nite...MDT to hi
confdc. Gale Tue...MDT confdc.
.Balt cnyn to Hatteras cnyn...Gale Fri into Sat...MDT to hi
confdc. Gale...Tue...MDT confdc.
.Hatteras cnyn to Cape Fear...Gale Fri into Fri nite...MDT to hi
confdc.
.Cape Fear to 31n...Gale Fri into Fri nite...MDT confdc.
.Forecaster vukits/Scovil. Ocean forecast branch.
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