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Undertakerson
Rank: F5 Superstorm
56 years old
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Blue Mtn, N of Hbg, PA
Born May-22-1960
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Viewing Topic: Invest 97L
Local Time: Sep 26 2016, 08:12 PM
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Undertakerson

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20 Sep 2016
Place marker for discussion of this weekend's cool down/cold shot. Some interior sub regions to see their first frost(?) come Saturday/Sunday in the "wee hours".

A few GFS maps, just for illustrative purpose (IOW not an actual forecast, just an indicator)

Saturday starts the daytime cool down - these values are not that much below (but are slightly) we'd expect this time of year. But note that there are no "reds" above a line delineated by I-80.

Attached Image


Saturday night, we get pretty chilly even down here in CTP - certainly looks like those "exposed" regions that, typically get early frost - would see so in this scenario

Attached Image


Sunday looks like a really chilly day all around

Attached Image


Then Sunday night, the bottom comes loose from the barrel.

Attached Image


This cold shot appears to be interrupted for a day or so, but then could go back to "just as cold" on the 29th. I did not extend the thread dates to include those days, but I might IF the guidance shows a return (if for no other reason than convenience sake)

There is a typhoon that is recurving off the coast of Japan - so this does have some TR/EAR support. It looks like a "flat" recurve though, so I wonder if that is cause and effect to the transience of this shot(?)


Attached Image
5 Sep 2016
Just creating a space to place your thoughts and observations.

Here we go (again) in the Mid Atl region - this time, could be 5 days (or more) of 90+ temps. Humidity may be lower at first, but will also increase late week (9-7 and onward)

Looks as if Thursday is the apex of the values.

QUOTE
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
130 AM EDT MON SEP 05 2016

VALID 12Z THU SEP 08 2016 - 12Z MON SEP 12 2016

...RECORD HIGH TEMPERATURES POSSIBLE IN THE EAST LATER THIS WEEK...


...OVERVIEW AND GUIDANCE ASSESSMENT/PREFERENCES...

BROAD TROUGHING IS EXPECTED TO REMAIN IN PLACE OVER THE CONUS
DURING THE MEDIUM RANGE PERIOD (THU-MON) AS UPSTREAM RIDGING SOUTH
OF THE GULF OF ALASKA WOBBLES IN PLACE. ENSEMBLES REMAIN IN GOOD
AGREEMENT OVERALL THOUGH THEY CONTINUE TO SHIFT THEIR THINKING ON
EMBEDDED SYSTEM TIMING/TRACK/DEPTH. A MULTI-MODEL/ENSEMBLE BLEND
(18Z GFS/GEFS AND 12Z ECMWF/ECENS MEAN) SUFFICES FOR THE THU-SUN
PERIOD AS ONE SHORTWAVE AMPLIFIES INTO THE GREAT LAKES BY SATURDAY
BEFORE LIFTING NORTHEASTWARD SUNDAY. BY THEN, THE MODELS DIVERGE
(ESPECIALLY THE GFS) IN THE WEST. THE ENSEMBLES PREFER TO DIG THE
TROUGH INTO THE DIVIDE WHEREAS RECENT GFS RUNS WERE MUCH MORE
PROGRESSIVE. PREFERENCE BY NEXT MONDAY IS ENTIRELY WITH THE
ENSEMBLES (18Z GEFS AND 12Z ECMWF ENSEMBLE MEAN) THOUGH THE
DETERMINISTIC 12Z ECMWF WAS IN THAT SLOWER CAMP AS WELL.

TO THE SOUTH, THE NATIONAL HURRICANE CENTER TAKES A WEAKENING
TROPICAL STORM NEWTON INTO SOUTHERN ARIZONA BY EARLY THURSDAY AND
THEN INTO THE SW FLOW THEREAFTER. IN THE EAST, POST-TROPICAL
CYCLONE HERMINE SHOULD BE WELL ON ITS WAY OUT OF THE AREA BY
THURSDAY. AS ALWAYS, PLEASE CONSULT THE NHC FOR THE LATEST
INFORMATION.

...WEATHER HIGHLIGHTS/THREATS...

LEAD FRONT INITIALLY NEAR THE GREAT LAKES THURSDAY WILL SUPPORT A
WARM SW FLOW INTO THE EAST THROUGH SATURDAY. RECORD HIGH
TEMPERATURES WILL BE POSSIBLE IN SOME LOCATIONS
. ACTUAL VALUES
WILL BE INTO THE 90S AS FAR NORTH AS NY AND SOUTHERN NEW ENGLAND

UNTIL THE FRONTAL BOUNDARY APPROACHES FROM THE NW. PRECIPITATION
WILL FOCUS ALONG AND AHEAD OF THIS BOUNDARY FROM THE CENTRAL
PLAINS NORTHEASTWARD TO THE MIDWEST AND EASTERN GREAT LAKES.
THOUGH IT WILL PUSH SOUTH OF THE MID-ATLANTIC ON SUNDAY, THE
MAJORITY OF ITS FORCING WILL LIFT INTO CANADA. MODEST COOLING WILL
BRING BACK TEMPERATURES TO NEAR OR A FEW DEGREES ABOVE AVERAGE.

A TROPICAL WAVE MOVING THROUGH THE CARIBBEAN WILL NEED TO BE
MONITORED AS ANOTHER POTENTIAL HEAVY RAIN THREAT FOR THE GULF, IF
IT MOVES THAT FAR NORTH. ENSEMBLES SHOW A LOT OF SPREAD BY LATER
THIS WEEK IN ITS TRACK, THOUGH THE MAJORITY KEEP IT SOUTH ALONG
25N.


FRACASSO
19 Aug 2016
Since no one opened one yet, I guess I'll do the honors once again.

Some have been mentioning this threat in the previously dated thread. I mentioned that I think this looks like one of the best set ups we've had in a while and posted this image.

Attached Image


QUOTE
The blue arrows and circles show the conspiracy of "players" - incoming jet streak at the base of a long wave trough, secondary cyclogenesis at the Delmarva, very moist air mass awaiting a potent temperature shift. All add up to the best set up we've seen lately for severe conditions.


So - what do the pros have to say??

SPC says no severe "forecast" - but then at the end of the disco, alludes to a possible upgrade in future outlook updates.

QUOTE
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0135 AM CDT FRI AUG 19 2016

VALID 211200Z - 221200Z

...NO SVR TSTM AREAS FORECAST...

...SUMMARY...
ISOLATED STRONG WIND GUSTS AND HEAVY RAIN ARE POSSIBLE ON SUNDAY
ACROSS PARTS OF THE NORTHEASTERN STATES.

...SYNOPSIS...
AN UPPER TROUGH WILL MOVE NEWD ACROSS THE GREAT LAKES AND NERN
STATES ON SUNDAY...WITH LEADING MID/UPPER LEVEL SPEED MAX EJECTING
NEWD INTO QUEBEC SUNDAY NIGHT. A SFC LOW IS EXPECTED TO MOVE NNEWD
OVER WRN QUEBEC WITH COLD FRONT EXTENDING SWD ACROSS NY/PA DURING
THE DAY. A MOIST AIR MASS WILL EXIST AHEAD OF THIS FRONT WITH MID TO
UPPER 60S F DEWPOINTS AND SCATTERED STORMS THROUGH THE PERIOD.
BEHIND THE TROUGH...HIGH PRESSURE WILL AFFECT MUCH OF THE PLAINS
INTO THE MS VALLEY WITH STABLE CONDITIONS.

...NY...ERN PA...WRN NEW ENGLAND...
PREDICTABILITY ISSUES WILL CONTINUE INTO SUNDAY AS AN UPPER TROUGH
AFFECTS THE NERN STATES. THE SLOWER/DEEPER NAM SOLUTION APPEARS TO
BE AN OUTLIER WITH THE GFS/ECMWF SOLUTIONS PREFERRED
. SUBSTANTIAL
MOISTURE WILL EXIST AHEAD OF THE ADVANCING COLD FRONT WITH UP TO 40
KT SLY 850 MB FLOW ACROSS THE WARM SECTOR. DESPITE THE MOIST AIR
MASS...TEMPERATURES ALOFT WILL BE WARM AS THE COOLING ALOFT LAGS
BEHIND THE SFC FRONT. THIS IN TURN WILL RESULT IN WEAK INSTABILITY.
STILL...SUFFICIENT LIFT NEAR THE EWD-ADVANCING FRONT WILL RESULT IN
STORMS ONGOING IN THE MORNING AND PERSISTING
THROUGH THE PERIOD.
HEAVY RAIN AND LOCALLY STRONG WIND GUSTS SHOULD BE THE MAIN THREATS.
REF WPC QPF FORECAST. WIDESPREAD NATURE OF THE RAIN AND CLOUDINESS
MAY MITIGATE THE OVERALL SEVERE THREAT. GIVEN THIS...AND ONGOING
PREDICTABILITY ISSUES...WILL DEFER POSSIBLE MARGINAL RISK TO LATER
OUTLOOKS.

..JEWELL.. 08/19/2016


AFDCTP
QUOTE
SYNOPSIS...
A seasonably warm and mainly dry weather pattern will continue
this weekend. The risk for thunderstorms will start to increase
on Saturday,
with the most likely period for rain on Sunday


QUOTE
The risk for isolated to widely scattered diurnal convection will
increase on Saturday due to an uptick in moisture/instability on
the backside of the departing surface high. All model and ensemble
guidance show max POPs on Sunday as a cold front moves through PA.
There could be locally heavy rainfall along the advancing cold
front with PWs climbing to 1.5-2.0 inches. Some models show a
secondary wave forming near the DC area which may slow ewd frontal
progression and increase potential for locally heavy rainfall.
This wave may also contribute to an increased severe thunderstorm
risk with model data showing sufficient CAPE and deep-layer shear
.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
The extended range guidance is in good agreement with bringing a
cold front through the region during the day Sunday.

Deterministic GFS generates CAPE on the order of 1000-1500J while
the ECMWF/SREF/GEFS are all less unstable ahead of the cold
front. GFS/ECMWF do show 0-6km wind shear values in the 30-40kt
range ahead of the front, so if we can manage more
heating/instability than is currently indicated some of the
storms could become locally strong and gusty
. At this point we are
not outlooked by SPC.


CTP may be updating their wording, now that SPC has put out their outlook.

Looking at the overnight modeling, I'd have to say, they are not all that impressive looking with their reflectivity depictions - and the soundings appear to be sub-severe for many.

So I may have misread the signal I thought I was seeing - may have not picked up on the fact that the temperature aloft is lagging the actual front. There are still a couple days for this to become clearer and verify which "camp" is correct.
5 Aug 2016
Been watching a mid level disturbance, on the models, in the D7-10 time period. The Euro in particular (GFS has a similar look but with subtle timing differences than the Euro).

Anywho, this disturbance hangs out near the N GOM and waits to entrain with, what looks to be a separate, mid latitude shortwave bundle. The two combine to send slugs of moisture towards the region.

Here's D 7 and 10 of the Euro


Attached Image



Attached Image


Verbatim, this should result in a couple rounds of rain, perhaps starting out as thunder storms on the 11th - followed by a larger slug of moisture plume (check the 850 mb chart) to provide an areal rain event, more stratiform in nature.

I hope I don't jinx this very decent looking set up for relieving type rains to break the relative dryness to drought conditions.
26 Jul 2016
I've mentioned this threat on some of the other recent threads. I know a few others have been watching with interest as well.

This event should, at least, dent the HW and the drought conditions.

CTP has a decent write up:

.
QUOTE
LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
In the medium to long-range period...conditions slowly revert to
near normal in temp and precip as several chunks of short wave energy
in the westerly flow aloft helps to carve out a mean 500 mb
trough axis over the Glakes and Ohio Valley region during the
Thu-Fri timeframe.

The peak in unsettled weather (with perhaps some periods of down-
right rainy conditions) occurs Thursday night and Friday as a
well-defined wave of sfc-850 mb low pressure lifts ENE out of the
Ohio Valley and heads across the I-95 Megalopolis.

Followed a blend of EC/GEFS/superblend and NBM guidance for that
particular 24-36 hour period to arrive at likely pops for rain and
scattered TSRA. Some uncertainty in timing and areal coverage of
the convection led us to undercut the NBM by 10-20 percent for
now, recognizing issues with large scale model convective
parameterization schemes (and subsequent exaggeration of the areal
coverage and broader qpf amounts) means that we`ll likely see more
concentrated areas/bands of heavy convection, compared to the
model depicted, larger cold season stratiform look to the precip
shield.

Portions of Southern and Central PA...close to the track of the
1006-1008 mb sfc low will likely see some localized heavy 1-2
inch,12-24 hour rainfl amounts by Friday afternoon...with even
the potential for some pinpoint heavier amounts from embedded
TSRA, as a tongue of 2 inch pwat air lifts north and wraps
cyclonically into sern PA and the Lower Susq Valley.


AFD NY NY
QUOTE
LONG TERM /THURSDAY THROUGH TUESDAY/...
Models are in general agreement with the H5 pattern across North
America through the long term. A cutoff low over Northern Quebec
Thu morning will be slow to move NE through Friday keeping
a broad trough across the NE quarter of the US. As the cutoff
lifts into the Maritimes heights will slowly begin to rise as a
deep anticyclone reestablishes itself over the Central US.

Somewhat of a complex scenario at the sfc during the first half of
the period.
A cold front approaches from the west as a wave of low
pressure ejects out of the mid-Mississippi valley Thu/Thu night.
12z NWP guidance have come into better agreement that this low
will impact the area on Fri into Fri night. However...there are
still differences with timing...track and strength that need to be
resolved. Have increased pops to likely on Fri since there is
better agreement amongst the guidance. Instability not very
impressive...although there could be some rumbles of thunder.
There is also the potential for locally heavy rain with PW`s
forecasted to be in excess of 2 inches. Once the wave moves by
there should be a lull on Sat although with the front remaining
close to the area have kept schc pops.


Another wave may impact the area Sat night into Sun...although the
long range models diverge at this point. Have kept low chc pops
for now...but it could end up being mostly dry if the wave doesn`t
materialize. The boundary is finally nudged southward early next
week as high pressure builds in from Canada


Mt Holly hems and haws a bit

QUOTE
LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
The front will remain fairly stationary over the Delmarva
Wednesday night into Thursday before starting to push back north
as a warm front Thursday night into Friday. This boundary will
act as a focus for weak low pressure development. These waves will
then ride along the boundary and will result in a flare-up of
showers and thunderstorms. Specific timing for this can be tricky
and subject to change, but current thinking is for Thursday night
into early Friday and then again on Saturday. Outside of these
times, expect generally diurnal driven climatological threat of
showers and thunderstorms.

After a bit of a reprieve with lower humidity levels mid-week, dew
points will increase back to 70-75 over the Philadelphia metro
area, southern New jersey and the Delmarva by Thursday and
Thursday night. This will push the heat index values into the
upper 90s, almost 100 on Thursday. After that, expect lower heat
indices for Friday and the weekend as high temperatures will be
suppressed by increased cloud cover.

It appears that the weather will remain warm, muggy and unsettled
through the start of the next week, before the frontal boundary
finally sinks far enough south to allow a marginally cooler, but
drier airmass the infiltrate the entire region.
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