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forkyfork

sunday severe threat 8/2

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dewpoints this high with a warm front involved tend to produce significant events in this area

namconus_Td2m_neus_27.png

 

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i'd like to congratulate everyone experiencing their 20th heat advisory or excessive heat warning of the summer, you can trade in your punchcard for a free large soup at any participating Panera Bread.

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...Northeast...

   Weak mid-level disturbance will eject across the lower Great Lakes
   ahead of the main upper trough positioned farther west over the MS
   Valley. This lead feature should encourage a weak surface low to
   track from southern ON into southwest QC by mid evening. Any
   appreciable mid-level height falls will remain north of the
   international border, along with the primary large-scale mass
   response.

   Early in the day1 period, deep convection will likely be ongoing
   within a corridor of low-level warm advection, along the nose of a
   pronounced LLJ. This LLJ will shift north across upstate NY into
   southern ON/QC during the afternoon hours as a surface warm front
   advances north of the border. At this time it appears the primary
   focus for sustained, organized deep convection will be noted
   immediately ahead of the surface low. Latest model guidance suggests
   strong boundary-layer heating will occur ahead of the surface low
   across western NY where temperatures should warm rapidly through the
   mid 80s. Renewed surface-based convection should evolve in the lee
   of Lake Ontario then track northeast. If the surface warm front were
   to be delayed advancing north into QC, low-level shear would be
   improved markedly across northern NY which would prove more
   supportive for supercells and tornadoes. Additionally, there is also
   some concern for strong convection along the trailing warm front
   that extends southeast across the Hudson Valley. While
   boundary-layer warming may not be as strong/focused as farther
   north, sustained warm advection and high PW-airmass should result in
   scattered strong convection. Forecast wind profiles favor some
   supercell threat, though clustering is also possible. Damaging winds
   should be the primary concern. 

   Farther south, a belt of seasonally strong mid-level flow will
   extend from the base of the trough over the southern Appalachians
   into the northern Middle Atlantic. While neutral/weak height rises
   are expected across this region, boundary-layer heating and
   orographic influences should encourage at least isolated
   thunderstorms. While poor lapse rates will limit convective updraft
   strength with this activity, modest cloud-layer flow should allow
   for some organization, along with a threat for localized wind
   damage.

day1otlk_1200.gif

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From OKX AFD:

Potential for strong to severe thunderstorms along the cold front
late this afternoon into the evening shows. Areas not impacted by
the showers earlier in the day could be primed for vigorous
convection with the boundary. Elevated CAPE values persist between
1500-2000 J/kg providing enough instability for strong thunderstorms
and DCAPE values between 500-1000 J/kg hint at strong downdraft
gusts. Moreover, the 0-6km shear values around 30-40kts increases
the possibility for severe storms. The primary threats remain heavy
rain and damaging winds though 0-3 km helicity values 150-200
m^2/s^2 between 21-03Z shows that directional shear will exist
within the warm sector of the low. Overall a tornadic threat can not
be ruled out particularly over the Lower Hudson Valley. SPC has
included much of our northwestern counties within a Slight Risk of
severe weather where the severe threat is most likely.

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From SPC:

Mesoscale Discussion 1376
< Previous MD
MD 1376 graphic
   Mesoscale Discussion 1376
   NWS Storm Prediction Center Norman OK
   0553 AM CDT Sun Aug 02 2020

   Areas affected...eastern Pennsylvania...northern New
   Jersey...southern New York

   Concerning...Severe potential...Watch unlikely 

   Valid 021053Z - 021330Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Locally severe wind gusts are possible over northeast
   Pennsylvania into northern New Jersey this morning. A brief tornado
   is possible if the storm cluster continues to intensify.

   DISCUSSION...Storms over eastern PA have gradually intensified over
   the past hour, acquiring broad rotation as they translate
   east/northeast along the lifting warm front. Surface analysis shows
   72 to 74 F dewpoints which is contributing to around 1000 J/kg
   SBCAPE.
   Area VWPs and objective analysis show 0-1 SRH between 100-150 m2/s2,
   which is typically sufficient for a low-end tornado risk.

   Damaging wind gusts appear possible with this isolated storm
   cluster. Should the system continue to get better organized, further
   tightening of the circulation may occur, with a brief tornado
   possible. However, this would appear most likely later today when
   heating occurs and boundary layer lapse rates become more favorable.

 

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2 minutes ago, weathermedic said:

Tornado warning to our southwest in Berks and Lehigh Counties of se PA. Sign of things to come around here later?

I am in Bethlehem Twp. PA, waiting on that Tornado warned cell just to my SW.  Getting nonstop thunder at the moment.  It is going to be a very interesting day...

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Good thread start: I forgot...just buried it in the 3 day due to Flooding.  Below from the 709A/ tropical post. 

Please follow NHC, SPC, WPC, and local office discussion statements/watches/warnings.  Plenty coming for our forum area. Whether they'll be significant for more than half our region, I don't know,  but some spots will probably be bruised with SVR-Power outages, FF-brief detours.

Not sure if anyone has observed what happened in se PA overnight. Near Reading and now approaching Allentown PA, widespread 2-4" rainfall... won't be surprised at 5".  Not too much guidance was hinting at that but the WAA is the driver and will continue to be a player in todays weather.

Today: RGEM/HRDPS best fit to what is going on now and what sort of expect in the future. SVR/FFW (1-3 issuance of each) anticipated between 8A-1P central/NNJ, se NYS arriving NYC near Noon.  The risk probably shuts off for 3 hours early this afternoon in nw NJ/se NYC, but shifts across CT/LI this afternoon, especially CT.  Meanwhile, am concerned NAM/HRRR are so paltry on redevelopment in e PA/w NJ 4-8P with weak front approaching from the west, into high CAPE air of near 3000J (HI near 100 in PHL) and pretty strong winds fields aloft for this time of year.  IT IS POSSIBLE very little will redevelop late today, but I think unlikely. Had to take into account all dry modeling, but think sct SVR develop e PA 4P-6P, cross NJ/se NYS/CT 6P-11P.  NYC/LI am less certain but risk.   No promises on afternoon-evening and am less confident than yesterday, due to modeling, and so have to rely on pattern recognition.  Rainfall under a few strong storms: 1" in 30 minutes but these are very narrow paths.  Apparently biggest threat for heavy rainfall is between now and 1PM in NJ/NYC, se NYS.  One additional note: Wind fields are quite strong and supercells not out of the question with a TOR possible somewhere in the forum. 

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Heavy rain and continuous thunder ongoing here.  Lightning is CTC.  You folks in western NJ need to watch out for this activity.

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19 minutes ago, wdrag said:

 

Not sure if anyone has observed what happened in se PA overnight. Near Reading and now approaching Allentown PA, widespread 2-4" rainfall... won't be surprised at 5".  Not too much guidance was hinting at that but the WAA is the driver and will continue to be a player in todays weather.

 

Yeah, it was a pretty extreme heavy rainfall event for that area.

https://www.cocorahs.org/ViewData/ViewDailyPrecipReport.aspx?DailyPrecipReportID=9ce9b22d-6f90-40ff-a740-1aa6d432dd31

Station Number: PA-BR-31  Station Name: Reading 2.3 NW
Observation Date 8/2/2020 7:00 AM
Submitted 8/02/2020 7:13 AM
Total Precip Amount  5.49 in.
Notes T-storms started about 3:15 a.m. on and off rain continued until 5 when it became heavy
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16 minutes ago, bluewave said:

Yeah, it was a pretty extreme heavy rainfall event for that area.

https://www.cocorahs.org/ViewData/ViewDailyPrecipReport.aspx?DailyPrecipReportID=9ce9b22d-6f90-40ff-a740-1aa6d432dd31

Station Number: PA-BR-31  Station Name: Reading 2.3 NW
Observation Date 8/2/2020 7:00 AM
Submitted 8/02/2020 7:13 AM
Total Precip Amount  5.49 in.
Notes T-storms started about 3:15 a.m. on and off rain continued until 5 when it became heavy

Storm weakened as it passed Allentown.  It’s done here with patches of blue sky overhead.  0.45” with this round.

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5 hours ago, Tatamy said:

Storm weakened as it passed Allentown.  It’s done here with patches of blue sky overhead.  0.45” with this round.

It looks like the airport established a new all-time daily rainfall record.

https://www.wrh.noaa.gov/mesowest/timeseries.php?sid=KRDG&num=48

Date

(EDT)
Temp

(F)
Dew
Point
(F)
Relative
Humidity
(%)
Wind
Direction
Wind
Speed
(MPH)
 
Visibility

(miles)
Weather
 
Clouds
 
Station
Pressure
(inches)
Sea Level
Pressure
(mb)
Altimeter
Setting
(inches)
1 Hour
Precip
(inches)
3 Hour
Precip
(inches)
6 Hour
Precip
(inches)
24 Hour
Precip
(inches)
6 Hr
Max
(F)
6 Hr
Min
(F)
24 Hr
Max
(F)
24 Hr
Min
(F)
02 Aug 7:54 am 75 73 94 SSE 3    10.00   OVC012 29.50 1011.7 29.87 0.02   5.65 5.70
Maximum 1-Day Total Precipitation 
for READING REGIONAL AIRPORT, PA
Click column heading to sort ascending, click again to sort descending.
Rank
Value
Ending Date
1 5.64 2005-10-08
2 5.15 2010-09-30
3 4.78 1999-09-16
4 3.36 2004-09-18
5 3.23 2005-07-17

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1 hour ago, wdrag said:

Adding in other multiple 5+, one 6" near Kutztown. DIX and OKX radars vastly udnerestimati\ng...axis excellent but amounts are well above their values. 828A/2

 

Screen Shot 2020-08-02 at 8.21.50 AM.png

Going to be a very interesting 3 day period upcoming here in eastern PA with the expected rainfall from Isaias.  Good model agreement on an axis of heavy rainfall totals across eastern PA and NJ with totals of 2-4”+ just with the tropical storm.

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Just missed our area too the southwest, but we're seeing 1/2-1" amounts in parts of the forum area of nw NJ this morning.  A start.  Am unsure whether more big storms develop late today (busted this morning's svr), but I think so...  so far no svr/ffw  (1130A) but CT LI might be favorable early-mid afternoon for iso SVR/FFW. 

Sun out in Wantage with 0.27" this morning - minor, normal summer showers with rolls of thunder on two separate occasions around 9A.  

Dewpoint here 78!!  Dry air crossing apps now so we'll see where the boundaries show up at 3P.  Will monitor til 120P, then out of touch for a while. 

See what we missed this morning... from the Reading Eagle!  Reading 1 day day record for any August. 

Reading Regional Airport, the primary weather service site in Berks, was under the gun for several hours before and after dawn. The official site recorded 5.7 inches of rain, a record for the date and any date in the 151 Augusts in the precipitation database.

At 9 a.m., other high measurements for Sunday included Riverview Park, 7.4 inches; Kutztown, 4.73; Newmanstown, 3.59; and Bernville, 3.53.

--

 

you saw the wx underground data. I'll post more as time allows late today.

 

 

Walt 1134A/2

 

 

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8 minutes ago, TriPol said:

Too early to call today a bust?

Very juicy out there. Soupy if you will. I think a line of severe weather will start developing just east of the PA/NJ border in the next hour!

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57 minutes ago, TriPol said:

Too early to call today a bust?

No watch issued & Mt Holly nws is on the fence if anything severe develops 

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Dry air aloft definitely coming into e PA of Hazleton.  Like the potential but may take awhile to get this going... not give ing up. If it goes, plenty of wind to draw down. 

For now last post for a few hours.  I see HI in s NJ/PHL area 98- ~105 at 1P.  Primed but need the subtle trough to activate. 120/2

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Mesoscale Discussion 1377
   NWS Storm Prediction Center Norman OK
   0100 PM CDT Sun Aug 02 2020

   Areas affected...much of New York State...central/eastern
   Pennsylvania...and northern New Jersey

   Concerning...Severe potential...Watch possible 

   Valid 021800Z - 022000Z

   Probability of Watch Issuance...60 percent

   SUMMARY...A gradual increase in convective coverage/intensity is
   expected through the afternoon.  A WW issuance will be considered
   for parts of the region.

   DISCUSSION...Radar mosaic and satellite imagery indicate a few areas
   of deepening convection from near SYR to near GFL in northern
   portions of New York State.  Another area of convection was located
   near BDL in Connecticut.  This deepening convection is likely
   attributed to a few factors, including surface
   heating/destabilization, subtle low-level confluence/convergence
   over the open warm sector, and the approach of a mid-level shortwave
   trough centered over western New York.  Instability increases with
   southward extent, with MUCAPE values as high as 3000 J/kg across
   eastern Pennsylvania and between 1000-2000 J/kg along and south of a
   warm front located from near MSS to near BAF.  The expectation is
   that convection will continue to gradually deepen in an environment
   with sufficient shear for updraft rotation, with damaging wind gusts
   and perhaps a few tornadoes possible given veering flow with height
   and appreciable low-level shear - especially near the warm front. 
   These expectations are further supported by recent CAMs, with a
   couple of corridors most likely to materialize into strong to severe
   convection - one across northern New York State and another across
   Massachusetts/Connecticut and vicinity.

   Over the course of the afternoon, one or two WWs will be considered
   for at least portions of this region pending convective trends.

C12BC5BF-D0D1-466B-8F26-DC4FBA5A3C67.gif

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URGENT - IMMEDIATE BROADCAST REQUESTED
   Tornado Watch Number 410
   NWS Storm Prediction Center Norman OK
   310 PM EDT Sun Aug 2 2020

   The NWS Storm Prediction Center has issued a

   * Tornado Watch for portions of 
     Central and western Connecticut
     Western Massachusetts
     Extreme northern New Jersey
     Eastern New York
     Extreme northeast Pennsylvania
     Western Vermont

   * Effective this Sunday afternoon and evening from 310 PM until
     1000 PM EDT.

   * Primary threats include...
     A few tornadoes possible
     Scattered damaging wind gusts to 70 mph possible
     Isolated large hail events to 1.5 inches in diameter possible

   SUMMARY...Scattered severe thunderstorms are expected across the
   watch area the remainder of this afternoon and early evening.  A few
   tornadoes will be possible along with damaging straight-line winds
   and isolated large hail.

   The tornado watch area is approximately along and 70 statute miles
   east and west of a line from 35 miles north northwest of Saranac
   Lake NY to 25 miles south of Poughkeepsie NY. For a complete
   depiction of the watch see the associated watch outline update
   (WOUS64 KWNS WOU0).

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Every recent tornado watch here has been a major bust. Hopefully this one isn’t as disappointing. 

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1 minute ago, NJwx85 said:

Every recent tornado watch here has been a major bust. Hopefully this one isn’t as disappointing. 

If ya hadn't noticed this is kind of a bad place to have a tornado. Too many trees, too many overhead utility lines and an awful lot of dumb people that would go out to watch. I dunno, maybe your town is different...

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