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2021 Mid-Atlantic Severe Weather - General Discussion


Kmlwx
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34 minutes ago, Kmlwx said:

Can't be mad at this map....

Key takeaway:

Craven SigSvr Parameter

The simple product of 100mb MLCAPE and 0-6km magnitude of the vector difference (m/s; often referred to as "deep layer shear") accounts for the compensation between instability and shear magnitude. Using a database of about 60,000 soundings, the majority of significant severe events (2+ inch hail, 65+ knot winds, F2+ tornadoes) occur when the product exceeds 20,000 m3/s3.

The index is formulated as follows:

C = (MLCAPE J kg-1) * (SHR6 m s-1)

For example, a 0-6-km shear of 20 m s-1 (40 knots) and CAPE of 3000 J kg-1 results in a Craven SigSvr index of 60,000. Units are scaled to the nearest 1000 on the web plot.

Reference:
Craven, J. P., and H. E. Brooks, 2004: Baseline climatology of sounding derived parameters associated with deeep moist convection. Natl. Wea. Digest, 28, 13-24.

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Severe T'storm Watch for western portions of the area. It seems to be less frequently as of the past few years for them to segment the area in events like this. Perhaps a more strongly worded watch for us later if the trends continue towards a decent severe event? The probs on the watches so far have bene pretty low. 

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One thing I'm not sure I like seeing so close to the metro areas - is GAI's dewpoint has dropped to 57. Even CGS is down to 59. The immediate DC stations like DCA, ADW etc are still in the 60s, though. My (potentially not the greatest) sensor here in Colesville has gone from the mid-upper 60s down to 61.7 for the dew. We'll ideally need to advect some of the higher dewpoint air back in for my liking. I don't think we are going to get it done with 50s dews. That potentially could be why some of the CAM runs have shown the activity really getting going only once east of I-95. Could be a little razor thin margin for those in places like MoCo and western half of Howard. 

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3 minutes ago, Kmlwx said:

This map tells a pretty interesting story. You can tell where the lower dewpoint air has gotten to. Looks like right around I-95 may be the dividing line. Will have to hope I'm on the right side of that line to see some action. 

 

      good analysis.    Several CAMs now show things coming together as the system approaches the I-95 corridor, so that scenario is plausible.   I think that dews will rebound a bit this evening as mixing wanes, and the HRRR shows this.

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30 minutes ago, Kmlwx said:

One thing I'm not sure I like seeing so close to the metro areas - is GAI's dewpoint has dropped to 57. Even CGS is down to 59. The immediate DC stations like DCA, ADW etc are still in the 60s, though. My (potentially not the greatest) sensor here in Colesville has gone from the mid-upper 60s down to 61.7 for the dew. We'll ideally need to advect some of the higher dewpoint air back in for my liking. I don't think we are going to get it done with 50s dews. That potentially could be why some of the CAM runs have shown the activity really getting going only once east of I-95. Could be a little razor thin margin for those in places like MoCo and western half of Howard. 

I see a DP on my Weather station of 66 now.. That feels a bit high as it feels pretty nice outside. Will have to see. I feel another meso is coming soon for the MD/NoVa area. BTW - I know feelings mean nothing when it comes to weather.. just seems like that is the next area that could be impacted in some way.

 

 

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4 minutes ago, high risk said:

      good analysis.    Several CAMs now show things coming together as the system approaches the I-95 corridor, so that scenario is plausible.   I think that dews will rebound a bit this evening as mixing wanes, and the HRRR shows this.

Yeah - it seemed like the HRRR and some of the other CAMs wanted to push a little tongue of instability and better moisture up right to around DC proper - or even a bit north. Seems like where that gets to or sets up will determine. I still overall like where I am in eastern MoCo, but if I was in Poolesville or even Gaithersburg, I'm not sure I'd feel super warm and fuzzy about a higher severe threat tonight. Meanwhile, if I was in Annapolis I'd feel really nice. 

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