weatherwiz

10 hours ago, It's Always Sunny said:

Yeah not so sure about the criteria. I've always used 240 miles as my benchmark. Another thing I noticed was dew points were only in the 50's with this serial derecho I wonder if that classifies it as a low dew point derecho. Does anyone know the threshold on that?

8 hours ago, ct_yankee said:

According to this paper: https://www.spc.noaa.gov/publications/corfidi/ldd_2006.pdf  it's below 50 and/or pwat<.5:

   "More rarely, high-wind-producing MCSs occur in en-vironments of very limited moisture, with surface dew-points at or below 50°F (10°C) and/or precipitable wa-ter less than 0.5 in. (1.25 cm). Systems forming in suchenvironments, herein referred to as low-dewpoint dere-chos (LDDs), have been observed throughout much ofthe year and over much of the United States from theGreat Basin to the East Coast. "

Personally I would guess that this event might be classified as a hybrid serial/low-dewpoint derecho. If that is a thing.

 

ahhh great point...I didn't even consider about low-dewpoint derecho. But I also do believe the distance criteria is probably standard throughout...although given how this went to the coast I would say this met criteria. 

looks like there was a confirmed tornado in NY yesterday 

Forecast models are in agreement in very steep mid-level lapse rates associated with a plume of EML air will traverse the region on Saturday. During the afternoon yet another vigorous shortwave trough is set to eject into northern New England. This will be associated with yet another potent mid-level and low-level jet with a max passing right through northern/central New England. At the surface, temperatures should push well into the 60's to lower 70's across northern New England with mid-to-upper 70's across southern New England. There are some uncertainties regarding moisture return, however, dewpoints may push into the 50's or even lower 60's. This, combined with the very steep mid-level lapse rates should contribute to more than enough CAPE to fuel convective development. Strong heating should also promote very steep low-level lapse rates.

Given the above, the potential exists on Saturday for one or multiple squall lines to propagate through NY and northern/central New England. Given the signals for widespread damaging winds, a serial derecho is possible. There is also the potential for brief tornadoes with any initial discrete cells or embedded within the squall line. 

2 minutes ago, CoastalWx said:

    

I am a bit boggled though. I mean looking at mesoanalysis in the morning it was advertising as much as 150+ 3km CAPE advancing ahead of the front with 2-6km lapse rates nearing 8 C/KM and DCAPE values were 400-500 J...who knows...maybe they just focus on their HREF products and whatever probs they spit out lol

Just now, CoastalWx said:

I've seen them hoist watches though when the line gets going. I guess I'm surprised they did not. 

The last product I recall looking at from them was an MCD out in NY that said "a few severe gusts possible" 

8 minutes ago, radarman said:

Was pretty clear by the late upgrade to slight risk that the SPC was playing wait and see, given the modest instability (esp. from their perspectives).  And the line was absolutely racing forward by that point, with the WFO already busy and about to hoist SVRs with a high wind warning already in place.  Granted, in E MA a late watch may have helped I think... At some point though the cat is out of the bag.

they did go to slight? Jeez a little late to the game. When I hopped on the computer at 6 AM and started looking I thought it was pretty obvious it was going to be a decent day...now I didn't expect it to be THAT crazy but I was shocked there wasn't an upgrade to slight. 

36 minutes ago, CoastalWx said:

How could the SPC not even have watches out when this got going in NY state. They are useless with northeast severe. I never even look to see what they have, you can figure it out on your own. They had a marginal risk in the morning and then upgraded last minute. I can't totally fault them for that, but I don't understand why no watches. 

It would be interesting to know if;

1) the SPC wanted watches but local offices said no 

2) Local offices wanted a watch but SPC said no 

3) Both sides said no

11 minutes ago, weatherwiz said:

going to fire up a thread in a little bit but Saturday looks pretty potent if enough CAPE can be generated. In fact, could be more intense than yesterday

should add though the threat this time may be slightly north 

going to fire up a thread in a little bit but Saturday looks pretty potent if enough CAPE can be generated. In fact, could be more intense than yesterday

2 minutes ago, forkyfork said:

low dewpoint derecho 

low dews were a huge help too in this

4 minutes ago, It's Always Sunny said:

So does this lose its chances of being tagged a derecho b/c it went OTS before it hit 240 miles?

I always forget but I am not sure if the distance requirement is the same for the classification of each type (serial, progressive, and hybrid). I think the criteria may be a bit more loose for serial derechos. 

2 minutes ago, radarman said:

Can't think of too many lines that produced severe gusts from ALB to BOS

May be able to argue serial derecho here

Pretty impressive overlap of 3km CAPE/3km lapse rates. Couple that with a LLJ max moving overhead with a vigorous s/w moving through...viola!

Kinda surprised BDL reported 64 mph. Didn’t really seem like it. I guess though there might have been a very brief burst. Have to watch video and see if I can spot it 

Would estimate 45-50 for gusts at BDL. 

Just saw a CG!!!

Lightning!!!!

As mine gets further removed from radar it will “look like” it’s weakening 

Just now, radarman said:

64kt BAF damn

NW @ 2113Z KBAF 072115Z 29036G64KT 2 1/2SM R20/3500VP6000FT -TSRA SQ SCT042 SCT090 14/08 A2957 RMK AO2 PK WND 32064/2113 WSHFT 2058 LTG DSNT NE AND W RAB13 TSB11 PRESRR TS N MOV E P0007 T01440083

WOW

Gust front/shelf becoming visible!!!!

Damn...70-80 mph only a few thousand feet off the ground. About to get rocked at BDL!!

At BDL...let’s go! 

That is a very healthy looking line. Actually a bit more lightning than I even anticipated but there is quite a bit of llvl CAPE associated with it too