Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1040 am EDT Tuesday Oct 6 2015
Canadian high pressure builds towards the area through
Thursday...then slides offshore Thursday night. A low pressure
system approaches from the west late Thursday night and Friday
morning...then crosses the area Friday afternoon and night. A
coastal low develops along its associated cold front off the middle
Atlantic coast Saturday...then tracks southeast of Long Island
Saturday night. High pressure builds in from the west Sunday and
Sunday night...then slides offshore on Monday.
Near term /until 6 PM this evening/...
forecast on track with just minor adjustments to reflect latest
Cutoff upper low off the southeast coast will weaken as it tracks slowly
to the NE today. Meanwhile...a trough tracking east from the central
Canadian provinces will result in a confluent west/northwest flow aloft
across the NE.
Will continue to monitor the progression of stratocu advecting southeast
from upstate New York overnight. Uncertain just how far into the County Warning Area
they reach. It appears that progression has slowed over the last
few satellite images. Have brought some clouds in this
morning...but steered clear of the NAM which deviates from the
rest of the guidance which keeps any partly sunny sky conditions
confined to north portions of the lower Hudson Valley this morning.
Narre and sref agree with non- NAM solution.
Seabreezes will be possible at the coast late this afternoon with
temperatures maxing out in the upper 60s to lower 70s across the area.
Short term /6 PM this evening through 6 PM Wednesday/...
upper low off the middle Atlantic coast this evening will continue to
weaken as it is picked up in the northern stream flow and tracks
out to sea. Trough in Canada continues eastward with a quasi-
zonal flow aloft continuing across the NE. High clouds from the
Midwest will probably make it in tonight. Canadian surface high pressure
will build towards the area through Wednesday with dry weather and above
Long term /Wednesday night through Monday/...
west-northwest to zonal flow aloft Wednesday night-Thursday night. Noting no
shortwaves of note embedded in the flow...it should be dry during
this time frame. There should be minimal cloud cover Wednesday and
Wednesday night...then increasing mainly high and middle clouds
Thursday night with warm advection aloft.
For lows Wednesday night...with minimal cloud cover and light winds
expected...favored cooler of mav/met/ecs/NAM 2-meter
temperatures...and undercut slightly at normally colder spots. Lows
should be within a few degrees of either side of normal. A blend of
mav/met guidance...NAM 2-meter temperatures and a mix down from 875
hpa was used per BUFKIT soundings for highs on Thursday...with
values forecast to be within a couple degrees of normal. For lows on
Thursday night...a blend of mex/men/ekd/ece/ecm/wpc guidance and NAM
2-meter temperatures was used...with readings forecast to be around
5 degrees above normal.
There are differences in the models for the system forecast to
impact the area from Friday into possibly the first part of the
weekend. Based on its recent stellar performance...its historical
track record...and that it has been indicating a secondary low
developing off the middle Atlantic coast for at least 4 model cycles
now...have generally favored the European model (ecmwf) from Friday-Saturday night.
Main difference between the European model (ecmwf) and the GFS/CMC is that it is
sharper with the 700-500 hpa trough that reaches the coast Saturday.
This sharper trough enables the development of a coastal low off the
middle Atlantic coast Saturday. The European model (ecmwf) then forecasts a closed low
to develop at 700 and 500 hpa near the middle-Atlantic coast...which
would have the low linger offshore Saturday and Saturday night. Did
tweak solution somewhat to allow for possibility of more
progressive...weaker 700-500 hpa solution of the other models.
Expect showers to develop ahead of an approaching 700-500 hpa
trough and 850 hpa cold front. Also have a slight chance of
thunder...with an average of GFS and European model (ecmwf) showalter indices being
around 2...indicating some instability aloft. Have likely probability of precipitation
over western zones Friday afternoon and eastern zones Friday
evening. However...did limit probability of precipitation over northwest zones Friday night to
chance as other solutions would suggest that those areas are dry
Friday night. Also confined chance probability of precipitation Saturday/Saturday night to
the eastern 1/2 of the County Warning Area...and kept far west areas dry in some
deference to the non-European model (ecmwf) solutions in this time frame.
All models agree that deep layered ridging then builds in Sunday-
Monday...so have continued a dry forecast for this time frame.
For temperatures Friday-Monday used a blend of
mex/men/ekd/ece/ecm/wpc guidance. Did adjust upward slightly on
Friday to reflect potential impact of slower cold frontal timing in
European model (ecmwf)...and downward slightly Saturday to reflect potential
cloudier/wetter European model (ecmwf) solution. Highs Friday/lows Friday night
should be around 5 degrees above normal...and highs Saturday around
5 degrees below normal. Near normal temperatures are forecast for
now Sunday-Monday...though there are some indications Monday could
end up at least 5 degrees warmer than currently forecast.
Aviation /14z Tuesday through Saturday/...
high pressure in place with a weak trough nearby.
VFR. North-north-northwest winds under 10 knots with afternoon sea breezes shifting winds
mainly S to SW. Presence of trough brings some uncertainty with
sea breeze timing. Winds back to northwest to west wherever sea breeze does
New York metropolitan enhanced aviation weather support...
Detailed information...including hourly taf wind component forecasts
can be found at:
http:/www.Erh.NOAA.Gov/zny/n90 (lower case)
Kjfk fcster comments: sea breeze timing could be off by 1-3 hours.
Klga fcster comments: sea breeze timing could be off by 1-3 hours.
Kewr fcster comments: sea breeze possible 21z-00z.
The afternoon kewr haze potential forecast is green...which
implies slant range visibility 7sm or greater outside of cloud.
Kteb fcster comments: sea breeze possible 21z-00z.
Khpn fcster comments: sea breeze possible 21z-00z.
Kisp fcster comments: sea breeze timing could be off by 1-3 hours.
Outlook for 12z Wednesday through Saturday...
Friday-Friday night...chance MVFR or lower. A chance of showers. A
slight chance of a thunderstorm Friday afternoon.
Sat...a chance of showers along coastal and mainly eastern
terminals where MVFR or lower will be possible.
minor changes were made with this update to reflect the latest
trends in observations and guidance. The forecast appears on
A Small Craft Advisory for hazardous seas remains in effect on
the coastal ocean waters through 16z Wednesday with a southeast swell
and high seas from Joaquin slow to subside. 6-9 feet seas at the
offshore buoys are expected to fall below 5 feet by Wednesday afternoon.
For now it appears conditions should remain below small craft
thresholds on the coastal ocean waters from Wednesday night into
Friday. Small Craft Advisory conditions are then possible later Friday and Saturday.
Sub-Small Craft Advisory conditions are expected on the non-ocean waters through
Saturday...with winds generally 10 knots or less. There is the
potential though for gusts up to 20 knots Friday afternoon and
dry through Thursday night.
There is the possibility of rainfall from Friday-Saturday
night...with the possibility of at least 1/2 an inch of quantitative precipitation forecast
falling area wide during this time frame. It should then be dry
early next week.
Marine...Small Craft Advisory for hazardous seas until noon EDT
Wednesday for anz350-353-355.