2020 Mid-Atlantic Severe Weather - General Thread

[PSWired]

On 4/13/2020 at 5:34 PM, Winter Wizard said:

Ended up getting hit with an initial round of convection here in Annapolis before the main squall line went through.

Part one actually had some pea-sized hail along with torrential downpours. Second one also had torrential downpours, but contained stronger winds. No reports of damage here, but friends in Rockville reported several downed trees in their neighborhood. 

We had a few smaller (<50') trees down here in Bay Ridge (Annapolis) near the waterfront. Highest gust at my house, which is somewhat protected by surrounding trees, was 39mph at 11:15 AM. 

http://chesapeakecam.com/1w-weather/NOAA/NOAA-2020-04.txt

[Kmlwx]

2 hours ago, Eskimo Joe said:

Couple of thoughts about this past event.  These are my own casual observations, feel free to add/subtract/disagree.

1.) Severe weather events are messy here 9.9 times out of 10.  We usually bust on the low side of things.  No matter how animated the meso models are leading up to an event, always remain skeptical and rely on the nowcasting stuff the morning of to determine where everything is lining up.

2.) The warm front will struggle to push north of I-66 the night before the event.  It seems that no matter what happens, warm fronts tend to settle out between I-66 and the Potomac and not make much progress until around late morning or lunch.  The longer northward progression is delayed, the lower the chances of a middle to high end event.

3.) Big dynamics with okay instability beats great instability over meh dynamics.  The February event and this past event on April 13th show that it doesn't take much surface based instability to get things going if upstairs is rocking.  

4.) Sub 1000mb lows just to our NW don't go quietly into the night (Credit: @Rainshadow).  The June, 2013 event, the Feb 2020 event and the April 13th event reinforce my thoughts on #3.

I agree with this like 90% of the time - and definitely for tornadoes I agree for sure. If you're looking downburst winds and large hail - I would argue that huge CAPE values and maybe a little to be desired on the shear/dynamics side of things could potentially serve you better...more pulsey and isolated for sure, though. But yes - I would take your combo over the opposite more often than not. 

[yoda]

Confirmed EF1 tornado in Carroll county on Monday

https://nwschat.weather.gov/p.php?pid=202004152000-KLWX-NOUS41-PNSLWX&fbclid=IwAR1v0GiDT6Plc6TB1CFU8BtJI8JlGNWufJewk9olrBhScRSUFTQ2zCCov7U

NOUS41 KLWX 152000
PNSLWX
DCZ001-MDZ003>006-011-013-014-016>018-501>508-VAZ025>031-036>040-
050>057-501>508-WVZ050>053-055-501>506-160800-

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
400 PM EDT WED APR 15 2020

...EF1 TORNADO CONFIRMED NEAR FRIZZELLBURG IN CARROLL COUNTY MARYLAND...

LOCATION: NEAR FRIZZELLBURG IN CARROLL COUNTY, MARYLAND
DATE: MONDAY, APRIL 13TH, 2020
ESTIMATED TIME: 1:47 PM TO 1:48 PM EDT
MAXIMUM EF-SCALE RATING: EF1
ESTIMATED MAXIMUM WIND SPEED: 90 MPH
MAXIMUM PATH WIDTH: 75 YARDS
PATH LENGTH: 0.4 MILES
BEGINNING LAT/LON: 39.6087 N / 77.0850 W
ENDING LAT/LON: 39.6103 N / 77.0782 W
* FATALITIES: 0
* INJURIES: 0

...SUMMARY...
A BRIEF EF1 TORNADO TOUCHED DOWN IN THE 2000 BLOCK OF LEEWARD
DRIVE BETWEEN WESTMINSTER AND TANEYTOWN IN RURAL CARROLL COUNTY, 
MARYLAND DURING THE EARLY AFTERNOON HOURS OF MONDAY, APRIL 13TH, 
2020.

A LINE OF SEVERE THUNDERSTORMS TRACKED ACROSS NORTHERN MARYLAND  
AND SOUTHERN PENNSYLVANIA ROUGHLY BETWEEN NOON AND 3:00 PM EDT. 
THE TORNADO DEVELOPED ON THE NORTH END OF A SMALL SURGE IN THE 
LINE OVER NORTHWESTERN CARROLL COUNTY. DIRECTLY UNDER THIS RADAR 
SIGNATURE WAS A PATH OF CONCENTRATED AND CONVERGENT TREE DAMAGE 
SPANNING NO WIDER THAN 75 YARDS AND LESS THAN HALF A MILE IN 
LENGTH. A RESIDENT IN THE PATH OF THE TORNADO WITNESSED A FUNNEL 
CLOUD APPROACHING IMMEDIATELY BEFORE THE DAMAGE OCCURRED.

DAMAGE WAS FIRST EVIDENT ON THE GROUND ON THE PROPERTY OF A RESIDENCE
ON THE WEST SIDE OF LEEWARD DRIVE (ABOUT A QUARTER TO HALF MILE 
SOUTH OF MD-832 OLD TANEYTOWN ROAD). MANY LARGE AND HEALTHY 
SOFTWOOD (PINE) TREES WERE SNAPPED, AND SEVERAL SMALL TREES WERE 
PUSHED OVER. THE TREES FELL TOWARDS EACH OTHER IN A CONVERGENT 
MANNER INDICATING A ROTATING VORTEX IN CONTACT WITH THE GROUND. A 
HOUSE ON THE PROPERTY SUSTAINED SUBSTANTIAL DAMAGE, PARTICULARLY 
TO THE GARAGE -- BOTH BAY DOORS WERE PUSHED INWARDS AND THE GARAGE
ITSELF WAS SHIFTED SLIGHTLY FROM THE FOUNDATION. MULTIPLE 
SHINGLES AND PIECES OF THE ROOF WERE BLOWN OFF OF THE HOME. A 
LARGE RECREATIONAL VEHICLE AT THE RESIDENCE WAS PUSHED OVER AND 
APPEARS TO HAVE BEEN LOFTED BRIEFLY (FOR A FEW FEET) GIVEN THE 
FACT IT WAS SIDEWAYS AND FACING THE OPPOSITE DIRECTION FROM ITS 
INITIAL POSITION.

THE TORNADO CROSSED LEEWARD DRIVE, TOPPLING SEVERAL MORE TREES AND
CAUSING SHINGLE AND SIDING DAMAGE AT A SECOND RESIDENCE. NO FURTHER
DAMAGE WAS EVIDENT BY THE TIME THE PATH REACHED MD-832 OLD TANEYTOWN
ROAD.

THE DAMAGE TO THE HOMES (SHINGLE AND SIDING REMOVAL, GARAGE
DISPLACEMENT) AND TREES (HEALTHY SOFTWOOD TREES SNAPPED) AS WELL 
AS THE DISPLACEMENT OF THE LARGE RECREATIONAL VEHICLE, COUPLED 
WITH THE MAGNITUDE OF VELOCITY AND HEIGHT OF DEBRIS SIGNATURES ON 
RADAR ARE CONSISTENT WITH A TORNADO RATED EF1 WITH PEAK WINDS OF 
ABOUT 90 MPH.

THE NATIONAL WEATHER SERVICE THANKS CARROLL COUNTY'S OFFICE OF 
EMERGENCY MANAGEMENT AND AREA RESIDENTS FOR THEIR REPORTS AND 
ASSISTANCE IN CONFIRMING THIS TORNADO.

EF SCALE: THE ENHANCED FUJITA SCALE CLASSIFIES TORNADOES INTO THE
FOLLOWING CATEGORIES:

EF0.........65 TO 85 MPH
EF1.........86 TO 110 MPH
EF2.........111 TO 135 MPH
EF3.........136 TO 165 MPH
EF4.........166 TO 200 MPH
EF5.........>200 MPH

* THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO
CHANGE PENDING FINAL REVIEW OF THE EVENT AND PUBLICATION IN NWS
STORM DATA.

$$

CS/DHOF

[Eskimo Joe]

The Carroll County tornado makes it the 2nd tornado in that watch box and verifies the watch box.  IMO, while the SPC SWODY2 & SWODY1 have been pretty iffy in the Mid Atlantic of late, their watch boxes have gotten really good.

[mappy]

2 hours ago, Eskimo Joe said:

The Carroll County tornado makes it the 2nd tornado in that watch box and verifies the watch box.  IMO, while the SPC SWODY2 & SWODY1 have been pretty iffy in the Mid Atlantic of late, their watch boxes have gotten really good.

SPC did great imo, with the risk areas too. 
 

103 confirmed tornadoes so far from Sunday/Monday 

[yoda]

https://mobile.twitter.com/Cyclonebiskit/status/1250882075999080448

[mappy]

1 minute ago, yoda said:

https://mobile.twitter.com/Cyclonebiskit/status/1250882075999080448

He’s a god send. He’s part of the team who puts all the survey data up on wiki. 

[mappy]

updated our 2020 summary page today

 

[Eskimo Joe]

 

[Kmlwx]

12z Euro with a bowling ball at H5 post 200hrs

[Eskimo Joe]

57 minutes ago, Kmlwx said:

12z Euro with a bowling ball at H5 post 200hrs

It's pretty!

[George BM]

This shows that we at least have a non-zero severe chance through the end of April.

[mappy]

yeah the rest of the month looks pretty active, especially Deep South. Not good following last weekend. Which, my map is already outdated. 8 more added since I made it lol

[Kmlwx]

1 hour ago, Eskimo Joe said:

It's pretty!

Going to be all about timing and the usual stuff! 

[Eskimo Joe]

Just now, Kmlwx said:

Going to be all about timing and the usual stuff! 

/mid atlantic

[Kmlwx]

Just now, Eskimo Joe said:

/mid atlantic

I should have said - at least at this stage - it's going to be all about whether it's even there or not...

[Eskimo Joe]

9 hours ago, Kmlwx said:

I should have said - at least at this stage - it's going to be all about whether it's even there or not...

I'd like to the see the euro pull the low just a tad NW a bit.  But that's a healthy signal for another event worth watching.

[CAPE]

On 4/13/2020 at 3:53 PM, C.A.P.E. said:

Was a pretty ordinary storm with heavy rain and some gusty winds here. If there was rotation it was just NE of me. If you look closely you can see a turkey buzzard gliding out in front.

 

A bit dated but I just saw this. The shot I took above is looking towards Baltimore corner, where it touched down. My thought at the time was most likely a rain shaft, but that was probably the location of the tornado as well.

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
300 PM EDT TUE APR 14 2020

...NWS DAMAGE SURVEY FOR 04/13/20 TORNADO EVENT...

.HENDERSON MD TORNADO...

START LOCATION...BALTIMORE CORNER IN CAROLINE COUNTY MD
END LOCATION...HENDERSON IN CAROLINE COUNTY MD
DATE...APR 13 2020
ESTIMATED TIME...327 PM EDT
MAXIMUM EF-SCALE RATING...EF-0
ESTIMATED MAXIMUM WIND SPEED...80 MPH
MAXIMUM PATH WIDTH...30 YARDS
PATH LENGTH...4.9 MILES
BEGINNING LAT/LON...39.0642/-75.8548
ENDING LAT/LON...39.0649/-75.7644
* FATALITIES...NONE
* INJURIES...NONE

...SUMMARY...
A WEAK EF-0 TORNADO TOUCHED DOWN JUST NORTH OF BALTIMORE CORNER IN 
CAROLINE COUNTY MD AT APPROXIMATELY 327 PM ON APRIL 13, THEN MOVED
IN AN EAST TO NORTHEAST DIRECTION FOR ABOUT 4.9 MILES BEFORE LIFTING 
JUST SOUTH OF HENDERSON MD. NO INJURIES WERE REPORTED, BUT NUMEROUS 
TREES ALONG OR NEAR THE PATH WERE EITHER SNAPPED OR UPROOTED IN A 
SPORADIC PATTERN. THE MAXIMUM WIND GUSTS WERE ESTIMATED TO BE 80 MPH
AT THE PEAK OF THE STORM.

[George BM]

Don't completely sleep on this Tuesday either. There could be some low-topped convection with limited CAPE along and just ahead of the cold front. Steep low-level lapse rates and fairly fast-flow aloft could translate to some of the convection having strong wind gusts.

[high risk]

18 minutes ago, George BM said:

Don't completely sleep on this Tuesday either. There could be some low-topped convection with limited CAPE along and just ahead of the cold front. Steep low-level lapse rates and fairly fast-flow aloft could translate to some of the convection having strong wind gusts.

         Was just coming in here to post this, but you beat me to it.      The forecast soundings look better to our northeast (in the MRGL area) due to it being colder aloft, but there might be a small amount of instability in areas along and east of the Potomac.    NAM nest actually has an interesting evolution for Tuesday afternoon.

 

 

[Vice-Regent]

2 hours ago, George BM said:

Don't completely sleep on this Tuesday either. There could be some low-topped convection with limited CAPE along and just ahead of the cold front. Steep low-level lapse rates and fairly fast-flow aloft could translate to some of the convection having strong wind gusts.

Stuff has a history of amping up as we move closer to the event. I would feel good east of the Blue Ridge.

[high risk]

Slight improvement for Tuesday in the 00z suite.    Best chances still appear to be for those further northeast, but both instability and simulated reflectivity improved a bit.    Will be tougher to get decent convection the further west you are due to downscoping.

[yoda]

Maybe a lil something?  Day 2 morning OTLK from SPC 

   ...Much of the Northeast...
   Lapse rates will steepen throughout the day in the vicinity of the
   cold front, due to surface heating as well as rapid cooling aloft.
   Low-level moisture and thus instability is expected to be minimal
   for much of the day, especially over western parts of the Marginal
   Risk area. However, forecast soundings indicate dewpoints in the 40s
   F will be sufficient to create surface-based buoyancy along the cold
   front. Therefore, shallow convection is expected along the length of
   the front. Localized wind damage may occur as 40 kt winds will exist
   just off the surface.

   In addition, storm mode may become cellular from the NYC area to DCA
   after 18Z as lift encounters a slightly more unstable air mass.
   Forecast soundings indicate a few hundred J/kg of SBCAPE will be
   possible. Furthermore, deep-layer shear, along with 200+ m2/s2 ESRH,
   may favor a single-cell storms with hail threat. Instability is the
   main mitigating factor to higher severe probabilities, but higher
   probabilities are possible should SBCAPE be greater than currently
   forecast.

[high risk]

no real change in the 12z guidance.    While they differ on coverage/intensity/timing, all CAMs have some amount of convection in our area early to mid afternoon tomorrow.     The best signals for coverage and intensity are areas well northeast of here, and the signal within our area is better on the east side of town than on the west.      Sfc-based cape isn't great, but there is some in all progs.     Soundings support some stronger wind gusts, and I agree with SPC that due to the very cold air aloft and low freezing levels, some hail is possible in any stronger, discrete cells.     The MRGL seems to cover the threat well for now.

[Eskimo Joe]

Baltimore and upper eastern shore slight risked on the SWODY2

[CAPE]

Thoughts from Mt Holly for tomorrow-

Interesting weather shaping up for Tue with a strong cold front attached to a strong H5 trough expected to swing thru the area during the afternoon. The latest SWODY2 has upgraded our CWA to a slight risk for severe with strong winds and small hail the main threats. There is plenty of cold air aloft and strong winds for tstms, but the overall moisture and instability is limited, so we`ll have to wait and see how things unfold Tue morning.

[Stormfly]

I'm in the yellow (slight)...

Mark my words we'll have wind of sort, enough for damage.

Why?  I have a fir that's cracked halfway up and I can't get a bucket truck out here before tomorrow to pull it down.

And if it falls it will go squarely through the roof of the poolhouse!  Lovely!

[Kmlwx]

The latest (10z) HRRR actually looks pretty good around, and to the east of DC in the 16-17z timeframe. 

[H2O]

4 minutes ago, Kmlwx said:

The latest (10z) HRRR actually looks pretty good around, and to the east of DC in the 16-17z timeframe. 

The morning looks like it could be more cloud free than previous threat days.  Might be a sneaky severe day.  Jinx! No Jinx!!

[Eskimo Joe]

Today has sneaky severe written all over it.  Could be a legit big hailer or two even back towards Frederick.