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000
agnt40 kwnm 100126
mimatn
marine weather discussion
nws ocean prediction center washington dc
820 pm est tue 9 feb 2010
. forecast discussion: major features/winds/seas/significant
. weather for north atlantic ocean w of 50w from 30n to 50n.
update:
18z nam/gfs and 12z ecwmf/gem/ukmet are all in gud agreemnt with
the dvlpg hurcn force low movg off the mid atlc cst
tonite ... then tracking e over the nrn nt2 wtrs wed into thu.
only diff noted is that nam/gfs are carrying two cntrs with this
systm ... while the other mdls only hv one cntr.
main fcst problem involves a dvlpg srn stream low expctd to move
ne across the bahamas fri nite ... then cont ne over the bermuda
area on sat into sat nite. 12z gem has same timing as 18z
gfs ... but is considered to be an outlyer soln attm because it is
much deeper and stgr than any of the med rng mdls. 18z gfs is
slower and wkr than 12z ecmwf and 12z ukmet solns ... so will be
favoring a 12z ecmwf/ukmet blend for fri nite thru sun. othw the
18z gfs looks vry representative and will be favored for tonite
thru fri.
seas ... 18z wavewatch iii mdl sea hts look reasonable ... excpt are
underdone by a few ft over the srn nt2 wtrs on sat ... given the
way the srn stream low is being handled by the 18z gfs.
extratropical storm surge guidance ... 18z etss mdl indicates max
pos surge in 3. 0 to 3. 5 ft rng over long island sound wed
ngt ... and another pos surge in 2. 0 to 2. 5 ft rng near nantucket
late wed ngt into thu. with the med rng mdls likely too slow to
deepen the dvlpg hurcn force low ... blv a deeper low and stgr e
to ne flow will dvlp than shown in the gfs ... so the surge values
cld be higher than the etss mdl guidance.
prev discussion:
1012 mb coastal low near hilton head sc will be main wx player
this forecast period ... and will rapidly intensify into a
significant marine cyclone with hurcn force winds over next
couple days. 12z gfs/nam remained a tad weaker than 12z
ukmet/canadian with this sfc low. am continuing to favor a
solution stronger than gfs indicating with 12z gefs means and
00z ecmwf ensmbl mean fairly close to respective op runs with
cntrl pres. current offshr warnings appear mostly on
target ... and not planning on significant changes to opc fcst
continuity. do have hier fcst confdc with hurcn force winds wed
into thu over nern cnyns especially with typically underdone 12z
ecmwf/ukmet sfc winds both advertising expansive area of 50 kt
invof glf stream. 12z wavewatch iii was quite consistent with
its previous run in indicating max sig wv hgts 28 to 32 ft ern
portions balt cnyn to cape fear. will continue to bump up these
values by 20 to 25 percent mainly for wed ngt/thu given hier
fcst winds than those shown by gfs 10m winds.
models are in decent agreement that strong upper closed low shud
weaken as it moves ne toward cape race newfoundland ... and will
retrograde w glf of st lawrence/new brunswick. with mdt to
strong nw flow over nt1/nrn nt2 continuing into the weekend.
meanwhile global models bring yet another srn stream shrtwv thru
nrn glf of mexico fri ... and sfc low across fl peninsula. not
buying into the over amplified canadian. gfs is srn outlier with
a srn most track. 12z ukmet/ecmwf are in good agreement with
timing/track of sfc feature ... and favoring this solution with a
compromised ctnrl pres. however given forecast uncertainty will
hold off on adding any gales to srn nt2 waters. then with cold
front approaching coast sun ... gfs offers compromised timing
between ecmwf/ukmet and will again hold winds to 25 or 30 kt.
extratropical storm surge guidance ... 12z etss model shows max
surge 3 to 3. 5 ft long island sound wed ngt ... also 2 - 2. 5 ft near
nantucket wed ngt into thu. with models namely gfs normally not
able to deepen such cyclones as rapidly as what
verifies ... expect a deeper low and stronger e to ne winds than
shown by gfs. consequently expect surge values hier than this
model guidance.
. warnings/forecast confidence ... warnings are preliminary and are
subject to change. any changes will be coordinated through awips
12 planet chat or by telephone.
. nt1 new england waters
. gulf of maine ... gale wed into thu ... hi confdc.
. georges bank ... storm wed night into thu ... hi confdc.
. s of new england ... storm wed into wed night ... mdt confd.
. nt2 mid atlc waters
. hudson to balt cnyn ... storm wed into wed night ... mdt confdc.
. balt cnyn to hague line ... hurcn force wed night into thu ... mdt
confdc.
. balt cnyn to hatteras cnyn ... hurcn force wed into wed
night ... mdt confdc.
. hatteras cnyn to cape fear ... storm wed into wed night ... mdt
confdc.
. cape fear to 31n ... storm tngt into wed ... low confdc.
. forecaster scovil/clark. ocean forecast branch.