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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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On Fb as the WxWiinii
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Joined: 12-February 10
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Last Seen: Today, 09:55 AM
Posting in topic: Tropical Depression 9
Local Time: Aug 30 2016, 10:56 AM
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Undertakerson

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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.
24 Jul 2016
http://mp1.met.psu.edu/~fxg1/NAMSFC4_12z/rloop.html

Opening a place to discuss tomorrow's potential. 4K NAM (12z today) has shown an increased signal for convection.

There appears to be a dual wave threat though - one in the a.m. and one later in the afternoon. The afternoon threat would depend, largely, on how the a.m. threat leaves the atmosphere.

Attached Image


This will update in about an hour.
19 Jul 2016
This one appears to be for real folks.

I'll start with good ol' Vojo on the extended desk.

QUOTE
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
152 AM EDT TUE JUL 19 2016

VALID 12Z FRI JUL 22 2016 - 12Z TUE JUL 26 2016

THE MEDIUM RANGE SURFACE AND 500MB PACKAGE UTILIZED A BLEND OF THE
18/12Z ECENS/CANADIAN MEANS --- BOTH OF WHICH MAINTAIN A STRONGER
MID-LATITUDE RIDGE ACROSS THE LOWER 48 (VS THE 18/12Z GEFS)
THROUGH DAY 7. FOR NATIONAL TEMPS/POPS --- THE 18/12Z ECENS/NAEFS
MEANS WERE USED THROUGH DAY 7 --- AND THE DETERMINISTIC ECMWF
UNTIL 24/12Z.

SOME OF THE 18/12Z DETERMINISTIC GUIDANCE WAS HELPFUL---THOUGH THE
SAME ISSUES ACROSS CANADA, ALASKA AND THE NORTHEAST PACIFIC MAKE
ANY CHOICE SUSCEPTIBLE TO ERROR BEYOND DAY 4 (24/00Z) ACROSS THE
NORTHERN TIER STATES (FROM THE DAKOTAS TO MAINE).

WHAT LOOKED LIKE AN EASY FORECAST PATTERN FOUR DAYS AGO--- STILL
LOOKS EASY. BUT THE DETERMINISTIC GUIDANCE WANTS TO PHASE A SERIES
OF EAST PACIFIC SYSTEMS WITH ARCTIC FLOW. AND THE RESULTING
SOLUTIONS DOWNSTREAM FOR THE LOWER 48 SEEM 'OVERDONE' WITH THE
'WEAKENING' OF THIS SUBSTANTIAL MID-LEVEL RIDGE AXIS ALONG 38N
LATITUDE. HERE AGAIN...THE 'OVERDONE' SEEMS TO BE A DIRECT RESULT
OF CONVECTION AND THEIR 'EFFECTIVE' FRONTAL PROGRESSIONS ALONG THE
NORTHERN PERIPHERY OF THE RIDGE AXIS. DIFFICULT TO USE MUCH IN THE
WAY OF DETERMINISTIC GUIDANCE BEYOND DAY 4 IN THE MEDIUM RANGE---
WHEN THE OUTCOME IS CONVECTIVELY-INDUCED AND BOUNCING FROM AREA TO
AREA ACROSS SOUTHERN CANADA.

THE PRIMARY CONCERN (FOR THE LOWER 48) IS CONVECTIVE COMPLEX
STRENGTH/TIMING AND THEIR DOWNSTREAM PROPAGATION. ALTHOUGH 500MB
HEIGHTS DO NOT FALL APPRECIABLY EAST OF THE DIVIDE...THE LOW-LEVEL
MIXING AND ORGANIZED OUTFLOW WILL LIKELY PRODUCE SOME TEMPERATURE
CHALLENGES ALONG AND EITHER SIDE OF THE OHIO AND MISSOURI VALLEYS
TO THE WESTERN SLOPES OF THE APPALACHIANS. WHAT RAIN-COOLED AIR
CAN SPILL OVER THE MOUNTAINS AND ONTO THE ATLANTIC COASTAL PLAINS
--- WILL MAKE ALL THE DIFFERENCE (EITHER HIGHS IN THE UPPER
80S/LOWER 90S OR CLOUD FREE AND AROUND 100F NEXT WEEKEND BETWEEN
LONG ISLAND AND THE EASTERN SHORE OF MARYLAND --- WESTWARD TO THE
I-95 CORRIDOR.

ABOUT THE ONLY 'CERTAINTY' SEEMS TO BE ACROSS THE UPPER GREAT
LAKES, ST LAWRENCE VALLEY AND NORTHERN NEW ENGLAND---WHERE 'TRUE'
COLD ADVECTION AND THE MODIFIED-ARCTIC AIR HAS A DECENT CHANCE TO
SPREAD SOUTHEASTWARD. THERE IS SOME 'HINT' THAT AN MCS-LIKE SYSTEM
WILL DEVELOP IN NORTHERN ONTARIO/WESTERN QUEBEC --- THEN ROLL
ACROSS NEW ENGLAND. A RARE CASE WHEN THE MEDIUM RANGE HAS TO
ACTUALLY LOOK FOR SOMETHING EMERGING 'OUTSIDE' THE USUAL SOURCE
REGION(S).

NOT ONLY IS THIS A QUESTION MARK ACROSS THE EASTERN THIRD OF THE
CONTINENT.
..BUT ALSO FOR WESTERN CANADA, THE ALASKA PANHANDLE AND
NORTHWEST COAST OF THE LOWER 48. SHOULD THE NORTHEAST PACIFIC FLOW
FAIL TO INCORPORATE SOME/ANY SUBTROPICAL MOISTURE...THEN THE
WESTERN PORTION OF THIS BUILDING RIDGE WILL BEGIN TO MOVE UP THE
WEST COAST. RIGHT NOW...THE MEANS KEEP ENOUGH ENERGY MOVING
THROUGH THE GULF OF ALASKA AND BRITISH COLUMBIA TO KEEP THE RIDGE
'FLAT' --- ALBEIT A 582DM TO 588DM 'FLAT' HEIGHT CONTOUR ALONG THE
CALIFORNIA/OREGON BORDER --- AND 'DRY' WITH NO SHOT OF A
MONSOON-LIKE SURGE INTO INTERIOR CALIFORNIA AND WESTERN NEVADA. I
SUSPECT THIS PORTION OF THE RIDGE HAS MORE 'SURPRISES' IN STORE
--- WITH MORE 'MID-LEVEL' CONVECTION THAN THE 18/12Z GUIDANCE IS
LEADING ON WITH.

VOJTESAK


Attached Image


AFD CTP
QUOTE
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Increasing heat/humidity begins Thursday, as sfc high passes off
the Mid Atl coast and return sw flow develops
. Bulk of med range
guidance keeps Central Pa dry Thursday. However, there is building
confidence in a round of convection Friday assoc with passage of
shortwave. Behind this feature, both 00Z ECENS and NAEFS indicate
anomalous upper lvl ridging building into Pa over the weekend,
which should bring hot wx and suppress convection
. Next chance of
widespread shra/tsra appears likely to come early next week, as
another shortwave and assoc cold front works se from the Grt Lks.

ECENS/NAEFS mean 8h temps are near 20C Friday through Monday,
indicating the potential of several days in a row with highs at or
above 90F in the valleys
.

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