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2022 General Thunderstorm Discussion


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Slight risk today - our typical cool season threat - limited instability/strong shear/winds

  ...Southern Appalachians through northern Mid Atlantic coast...
   Modest pre-frontal low-level moistening and, perhaps more notably,
   relatively warm layers aloft are generally forecast to limit warm
   sector boundary-layer destabilization today through tonight. 
   However, given at least weak conditional instability, mid-level
   forcing for ascent along/ahead of the eastward advancing cold front
   will probably be sufficient to maintain or support new developing
   lines of fairly vigorous convection, particularly across the
   Cumberland Plateau and Allegheny Mountains vicinity into the
   northern Mid Atlantic coast by this evening.  Coinciding with one
   belt of 50-70+ kt south-southwesterly flow in the 850-700 mb layer
   propagating to the west of the Allegheny Mountains, and another
   developing to the lee of the Blue Ridge into the northern Mid
   Atlantic coast by this evening, this convection will contribute to
   the downward transfer of this momentum toward the surface.  It seems
   probable that this will contribute to at least scattered, if not
   more widespread, damaging wind gusts.

day1otlk_1200.gif

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1 hour ago, Chubbs said:

Slight risk today - our typical cool season threat - limited instability/strong shear/winds


  ...Southern Appalachians through northern Mid Atlantic coast...
   Modest pre-frontal low-level moistening and, perhaps more notably,
   relatively warm layers aloft are generally forecast to limit warm
   sector boundary-layer destabilization today through tonight. 
   However, given at least weak conditional instability, mid-level
   forcing for ascent along/ahead of the eastward advancing cold front
   will probably be sufficient to maintain or support new developing
   lines of fairly vigorous convection, particularly across the
   Cumberland Plateau and Allegheny Mountains vicinity into the
   northern Mid Atlantic coast by this evening.  Coinciding with one
   belt of 50-70+ kt south-southwesterly flow in the 850-700 mb layer
   propagating to the west of the Allegheny Mountains, and another
   developing to the lee of the Blue Ridge into the northern Mid
   Atlantic coast by this evening, this convection will contribute to
   the downward transfer of this momentum toward the surface.  It seems
   probable that this will contribute to at least scattered, if not
   more widespread, damaging wind gusts.

day1otlk_1200.gif

Yeah the 850/500 total totals looked rather yawnable yesterday. No denying the winds.

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Funny that last year's general thunderstorm thread was started on almost exactly the same day, March 6th. Nothing like highs near 80 and evening thunderstorms to make it feel like spring (and for figs to start growing)

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  • 2 weeks later...

Day 2 SPC outlook - tstm/marginal/slight. Spot checking NAM3k, severe parameter's tomorrow are in the ballpark of a typical local event in parts of area.

 

 

day2otlk_0600.gif

floop-nam4km-2022031806.crossover.us_ma.gif

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Can’t imagine this year could be anything like last year… 2021 taught me not to be so cynical as to keep underestimating the potential around here… Yet at the same time, laws of probability say this year can’t possibly repeat last year… (Well, that’s not technically true, statistically each year’s probability is independent, but we revert to the mean which is VERY low probability…) Anyway, love that first crack of spring thunder but never expect much around here… Right now looking forward to my annual Plains storm chasing trip - been doing it since 1996, only missed three years - for the first time with my son this year, which makes it extra special… Then when that’s over, I’ll be more dependent upon Philadelphia area table scraps… 

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 Snippet from SPC - supercells with tornadoes/hail possible.

 The most favorable environment for severe thunderstorms is forecast
   to develop across eastern Pennsylvania and northwest New Jersey late
   this afternoon. Forecast soundings at 23Z from north of Philadelphia
   to near Trenton have supercell wind profiles, with 0-6 km shear near
   80 knots and gradually veering winds with height below 850 mb. As a
   result, 0-3 km storm relative helicity is forecast to be near 300
   m2/s2. This should be favorable for tornadoes with supercells that
   interact with the western edge of the low-level jet late this
   afternoon and early this evening. Although supercells will be
   relatively low-topped, the strong deep-layer shear combined with
   steep lapse rates in the mid-levels should also be favorable for
   isolated large hail. Wind damage will also be possible with the
   stronger cells.

day1otlk_1200.gif

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1 hour ago, Chubbs said:

 Snippet from SPC - supercells with tornadoes/hail possible.



 The most favorable environment for severe thunderstorms is forecast
   to develop across eastern Pennsylvania and northwest New Jersey late
   this afternoon. Forecast soundings at 23Z from north of Philadelphia
   to near Trenton have supercell wind profiles, with 0-6 km shear near
   80 knots and gradually veering winds with height below 850 mb. As a
   result, 0-3 km storm relative helicity is forecast to be near 300
   m2/s2. This should be favorable for tornadoes with supercells that
   interact with the western edge of the low-level jet late this
   afternoon and early this evening. Although supercells will be
   relatively low-topped, the strong deep-layer shear combined with
   steep lapse rates in the mid-levels should also be favorable for
   isolated large hail. Wind damage will also be possible with the
   stronger cells.

day1otlk_1200.gif

 

 

 

I thought today was going to be a washout, but now spotty showers and increase in severe t-storms by night fall. How things change overnight. 🙄

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5 hours ago, Chubbs said:

 Snippet from SPC - supercells with tornadoes/hail possible.



 The most favorable environment for severe thunderstorms is forecast
   to develop across eastern Pennsylvania and northwest New Jersey late
   this afternoon. Forecast soundings at 23Z from north of Philadelphia
   to near Trenton have supercell wind profiles, with 0-6 km shear near
   80 knots and gradually veering winds with height below 850 mb. As a
   result, 0-3 km storm relative helicity is forecast to be near 300
   m2/s2. This should be favorable for tornadoes with supercells that
   interact with the western edge of the low-level jet late this
   afternoon and early this evening. Although supercells will be
   relatively low-topped, the strong deep-layer shear combined with
   steep lapse rates in the mid-levels should also be favorable for
   isolated large hail. Wind damage will also be possible with the
   stronger cells.

day1otlk_1200.gif


Haven’t actually looked at any data (and probably won’t, no time today and rarely worth the effort around here, last year’s two big days notwithstanding), but the 13Z outlook language no longer seems quite as bullish.

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...North Carolina into the Lower Hudson Valley...
   A mid-level impulse will eject into the Hudson Valley during the
   afternoon and overspread the core of the low-level jet, promoting an
   intense tropospheric vertical wind profile and associated strong
   deep-layer shear. Enlarged hodographs from the Carolina Piedmont
   northward suggest storm organization with any convection that can
   intensify and become surface-based. The primary factor limiting the
   introduction of higher probabilities this outlook is scant buoyancy.
   5.5-6.5 C/km low- and mid-level lapse rates atop 55-60F surface
   dewpoints may promote SBCAPE up to 750 J/kg across North Carolina,
   to 250-500 J/kg into the Hudson Valley. Damaging gusts and a brief
   tornado may accompany any sustained, robust updrafts, hence the
   maintenance of a Category 2/Slight risk. Given 50-60 kt flow at/just
   below 500 meters AGL and the enlarged hodographs, higher
   wind/tornado probabilities may be needed in subsequent outlooks if
   it becomes evident that greater surface-based instability will be
   realized.

day1otlk_1200.gif

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HRRR is concerning. Instability (shading) and low level winds this evening plotted below (lines show speed with height above ground). Enough instability for forced convection with very strong low-level winds. Outer scale ring below is 40 knots

floop-hrrr-2022033110.sbcape_hodo.us_ma.gif

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5 minutes ago, tombo82685 said:

Parameters look solid, but I wonder with timing around 10pm for the city diminishes this a bit?

Back in the day, I'd say yeah that seems a very likely outcome. Now it just seems it does not hold all of the time.

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41 minutes ago, DebShadow23.0 said:

Back in the day, I'd say yeah that seems a very likely outcome. Now it just seems it does not hold all of the time.

Sun isn't going to do much today. Low 60s dew point will be pretty uniform across region so there isn't an obvious weakening zone before coast.

 

index.gif

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