2014 Mid-Atlantic Severe Discussion Thread

[usedtobe]

Tor in Charles Co... Couplet looked like it went right by Wes' house...

It went right over me but with no wind.  Last night I got wind and there were a couple of trees blown down in the hood, one got a deck. 

[usedtobe]

No way that thing is producing. 

I thought the same thing and didn't even run to my basement.  The couplet went right over my house and it produced nothing but some rain.  It was much windier last night.

[Ian]

We don't. We get strong storms that rain on us, have some lightning and a little but of wind, and perhaps the occasional tornado, but we don't really get severe storms.

We don't usually get widespread high end severe but in recent years we seem to have less thunderstorm days than we used to and less full blown squall lines etc. Maybe it's part imagination but the last two warm seasons in particular have been pretty tame storm wise. Partly we keep getting locked into unfavorable patterns for it and have been playing with marine/northeast air much of this season. Thought maybe increased sfc moisture would help but our hot days have been mainly dominated by high pressure and then we get into NW flow that's too clean when we need more wnw usually.

[Ian]

I thought the same thing and didn't even run to my basement.  The couplet went right over my house and it produced nothing but some rain.  It was much windier last night.

A scan or two looked semi legit but it looked more like cell mergers briefly showing something more than anything that was going to be an issue, tho who knows maybe it did something there briefly. By the time it was warned it didn't look very threatening. I guess there was a report of a funnel but spotters are much better at reporting snow than features of thunderstorms unless there's a tornado doing damage in front of them.

[WxUSAF]

We don't usually get widespread high end severe but in recent years we seem to have less thunderstorm days than we used to and less full blown squall lines etc. Maybe it's part imagination but the last two warm seasons in particular have been pretty tame storm wise. Partly we keep getting locked into unfavorable patterns for it and have been playing with marine/northeast air much of this season. Thought maybe increased sfc moisture would help but our hot days have been mainly dominated by high pressure and then we get into NW flow that's too clean when we need more wnw usually.

I'll echo your comment about squall lines.  Growing up around here, all I remember of thunderstorms was big squall lines that crossed the area from W-E.  Since I moved back almost 5 years ago, seems like we've only had a handful like that.  Just going off memory, so I'm not trusting myself totally, but the longer we go without squall lines the more apparent it becomes.  Maybe there's fewer strong cold fronts coming in summer now vs. 20 years ago?  

[mattie g]

I'll echo your comment about squall lines. Growing up around here, all I remember of thunderstorms was big squall lines that crossed the area from W-E. Since I moved back almost 5 years ago, seems like we've only had a handful like that. Just going off memory, so I'm not trusting myself totally, but the longer we go without squall lines the more apparent it becomes. Maybe there's fewer strong cold fronts coming in summer now vs. 20 years ago?

I've made a comment on here before that echoes this sentiment. Growing up in South Jersey, I remember getting plenty of good squall lines that came in from the W or NW. Those were much more prevalent than discrete cells or jumbles of cells blowing up on a hot and humid day.

[WxUSAF]

I've made a comment on here before that echoes this sentiment. Growing up in South Jersey, I remember getting plenty of good squall lines that came in from the W or NW. Those were much more prevalent than discrete cells or jumbles of cells blowing up on a hot and humid day.

So...you could say you echo my echo?  I hear that!

[Bob Chill]

So...you could say you echo my echo? I hear that!

I remember that as well. Especially in the 80's. I think the minority were front related. Just hot humid afternoon lines of storms. I spent a ton of time on the bay in the 80's. Many memories of big squall lines. They have that distinct look of really dark clouds on the leading edge and then orange and/or green right behind it. You always knew good winds were on the way when you saw that sky. IMO- we don't see that sky as much as we used to.

[chris87]

the human brain is usually pretty terrible at creating unbiased samples of past events, however, it is very good at selective sampling and creating trends that don't exist [*conjecture here as I don't really have data to back up in this case*]

[Kmlwx]

I think a lot of us have made these comments before. In the 90s I distinctly remember sitting in front of TWC on stormy days watching a big long squall line move in and quickly push across the area (how could I forget the crappy radar on the local forecast?!). Also hard to forget that signature squaking from warnings coming up on TWC. 
 

Definitely seems as though we've gone over to more of a discrete cell or smaller line segment sort of regime. 

[WxUSAF]

the human brain is usually pretty terrible at creating unbiased samples of past events, however, it is very good at selective sampling and creating trends that don't exist [*conjecture here as I don't really have data to back up in this case*]

Oh, I know this very well, which is why I'm hesitant to put much confidence in this idea.  But the fact that other people have noticed it suggests it might not be total bunk.  Either way, we haven't had very many squall lines over the last 4-5 years.  Not sure if there's a way to figure out how many "squall lines" we had in the past since that's just a subjective definition in most interpretations.  

[chris87]

Oh, I know this very well, which is why I'm hesitant to put much confidence in this idea.  But the fact that other people have noticed it suggests it might not be total bunk.  Either way, we haven't had very many squall lines over the last 4-5 years.  Not sure if there's a way to figure out how many "squall lines" we had in the past since that's just a subjective definition in most interpretations.  

 

yeah it is -- generally if you go back through the last 30 or so years, reanalysis shows warm-season CAPE has generally increased here and I'd generally expect that deep level shear has decreased so you could project that we entering a period where we'd favor multi-cell convection vs. more organized convection -- so while i tend not to buy in to qualitative trends from memory there is at least a potential physically based theory to support the claims here.

[Ian]

the human brain is usually pretty terrible at creating unbiased samples of past events, however, it is very good at selective sampling and creating trends that don't exist [*conjecture here as I don't really have data to back up in this case*]

Some day I'll start looking at data across the area. Thanks for the good idea.

[Bob Chill]

Some day I'll start looking at data across the area. Thanks for the good idea.

It's a burning question so please have the report done by 5pm. Tnx

I agree with Chris about using pieced together memories being a terrible way to draw conclusions. It's likely much less of a fact or anecdote than we probably think. But since a number of us seem to have the similar memories, there is likely at least something to it.

[Ian]

I do think one issue which can change a season even without anything unusual happening is timing. This yr we've had a lot of stuff timed wrong.. same last year I believe. There's a big difference between putting a shortwave thru at 4pm with 3-4k CAPE and at night with decreasing instability and increasing inhibition.  

 

Though we can also get higher CAPE days that don't produce with upper level or sfc ridging as well so more CAPE is not necessarily equal to more storms.  

 

Just from my own experience here the ops to photograph storms in DC itself are at a personal low the last two years. Even 2012 to some degree other than the derecho.  

[Ian]

It's a burning question so please have the report done by 5pm. Tnx

I agree with Chris about using pieced together memories being a terrible way to draw conclusions. It's likely much less of a fact or anecdote than we probably think. But since a number of us seem to have the similar memories, there is likely at least something to it.

 

No doubt our memories are bad... you see selective memory nonstop from Nov-early June during the snowy season here.

[chris87]

Some day I'll start looking at data across the area. Thanks for the good idea.

 

it would be a good time to break out a "number of thunder days at DCA" excel plot 

[mattie g]

So...you could say you echo my echo? I hear that!

Hey...lecho my echo!

[high risk]

I do think one issue which can change a season even without anything unusual happening is timing. This yr we've had a lot of stuff timed wrong.. same last year I believe. There's a big difference between putting a shortwave thru at 4pm with 3-4k CAPE and at night with decreasing instability and increasing inhibition.  

 

 

               I'm fully on board with the concept of the past few convective seasons in DC being underwhelming, and I also agree that squall lines have not been as prevalent as I remember them being while growing up.     The comment about timing, in my mind, has some merit.    It seems like we have had a lot of setups the past few years in which a lee trough sets up across the area during the afternoon;  the lee trough events tend to favor more scattered cells or short line segments as opposed to the "big honking squall lines".    So localized areas get good storms (and they can even be significant), but the resulting cloud shield and outflow and wind shift overall reduce instability across the area.   The cold front then comes marching through in the evening with little instability to work with.

[chris87]

               I'm fully on board with the concept of the past few convective seasons in DC being underwhelming, and I also agree that squall lines have not been as prevalent as I remember them being while growing up.     The comment about timing, in my mind, has some merit.    It seems like we have had a lot of setups the past few years in which a lee trough sets up across the area during the afternoon;  the lee trough events tend to favor more scattered cells or short line segments as opposed to the "big honking squall lines".    So localized areas get good storms (and they can even be significant), but the resulting cloud shield and outflow and wind shift overall reduce instability across the area.   The cold front then comes marching through in the evening with little instability to work with.

 

you make it sound like the mountains haven't been there the whole time -- does a physical explanation come to mind that would support an upward trend in days with lee trough development?

[high risk]

you make it sound like the mountains haven't been there the whole time -- does a physical explanation come to mind that would support an upward trend in days with lee trough development?

 

        Well, I have nothing to substantiate the claim that lee trough development is more pronounced in recent years.     The sharpest, most-defined lee troughs occur here when the mid-level flow is more westerly (perpendicular to the mountains), so perhaps we're getting more synoptic setups with more zonal flow with embedded shortwaves as opposed to more amplified troughs which would lead to mid-level flow with less of a westerly component??   pure conjecture.

[Kmlwx]

I do think one issue which can change a season even without anything unusual happening is timing. This yr we've had a lot of stuff timed wrong.. same last year I believe. There's a big difference between putting a shortwave thru at 4pm with 3-4k CAPE and at night with decreasing instability and increasing inhibition.  

 

Though we can also get higher CAPE days that don't produce with upper level or sfc ridging as well so more CAPE is not necessarily equal to more storms.  

 

Just from my own experience here the ops to photograph storms in DC itself are at a personal low the last two years. Even 2012 to some degree other than the derecho.  

The derecho almost took you away from us. 

[Ian]

CAPEday is around the corner.

 

[Kmlwx]

This map is money. How? Because areas immediately north, south, east, and west have higher CAPE than DC. 

The river could be causing that I'd bet. 

[Ian]

This map is money. How? Because areas immediately north, south, east, and west have higher CAPE than DC.

I didn't even notice that really. Too much detail for so far out anyway. Wednesday seems like our favored day this yr so there's that.

[Ian]

I split today-tomorrow off. This thread is long: http://www.americanwx.com/bb/index.php/topic/44014-july-2-3-severe-weather-and-possible-pre/

[Ian]

Now we can move on to next CAPEday. 

 

[Subtropics]

Now we can move on to next CAPEday. 

 

gfsNE_con_sbcape_177.gif

Why does north always do better than us? Would we do better at severe if we combined our efforts and blew up the mountains to our west?

[WhiteoutMD]

Now we can move on to next CAPEday. 

 

gfsNE_con_sbcape_177.gif

Very funny when you think about it CAPE Wednesdays!

[Eskimo Joe]

Blue Box until 9:00 pm.

 

Link:  http://www.spc.noaa....ch/ww0389.html�