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Severe weather risk 3-28 and 3-29 2017


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28 minutes ago, Jim Martin said:

With the lack of more storms tonight, you just wonder if things could get very interesting 18 - 24 hours from now...

If the massive blob of rain/storms moving out of LA doesn't fester and linger well into to tomorrow, maybe, but I'm definitely not counting on it. Not too optimistic about tomorrow for that reason. 

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Latest runs of the HRRR are devastating for any potential tomorrow. Large convective complex currently across Louisiana festers and never really dies off much, which of course negates any moisture advection/return further north into the main threat area. Not sure it is relevant anyways. Both the 00z 3km NAM and 00z 12NAM show a pretty awful and funky wind profile tomorrow. 

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52 minutes ago, jojo762 said:

Latest runs of the HRRR are devastating for any potential tomorrow. Large convective complex currently across Louisiana festers and never really dies off much, which of course negates any moisture advection/return further north into the main threat area. Not sure it is relevant anyways. Both the 00z 3km NAM and 00z 12NAM show a pretty awful and funky wind profile tomorrow. 

I agree. The 00z 12km NAM says that for many areas of the Moderate risk region, the SRH may be medium, like 150 m2/s2. For some areas where the SRH may be higher, there's a loop in the hodograph, which is not helpful for long-lived tornadic storms.  With some 118kt winds at 300mb in the unstable region, you don't want to say the severe weather potential is low.

Sometimes, great long-lived storms (like EF4 storms) have very strong 0-8km shear, like 80 kt, above and beyond the strength of the 0-6 km shear.

GFS has less extreme wind at 300mb. Darn it, the Pivotalweather forecast soundings are kind of hit and miss, sometimes not functioning.

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Couplet question for the more experienced folks.

As radar resolution has improved it seems tornado warning have as well, it terms of accuracy. But, it seems I've seen an increasing amount of couplets, more so this year than previous years, where they do not get warned.

Is the NWS paying more attention to CC now or do they have a certain inbound/outbound velocities within the couplet they're using to determine if a it should be warned?

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I know I have seen ridiculous couplets in the plains that are not tornado warned. I can only venture to guess that different offices look for different parameters when warning or not. I would think that the offices in the plains have a much better idea of when a storm is producing vs. not as they follow more classic progressions than, for example, in my home office (LIX) where everything is rainwrapped, it is a hot mess on radar and you can have nothing one frame and an EF-2 on the ground the next. We are far more likely to see any decently strong rotation trigger a tornado warning here. They are also more likely to have conditions where people can see what is happening. I'd guess nighttime storms trigger warnings differently than ones with great visibility and 100 storm chasers on the scene.

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9 hours ago, Weatherdemon said:

Couplet question for the more experienced folks.

As radar resolution has improved it seems tornado warning have as well, it terms of accuracy. But, it seems I've seen an increasing amount of couplets, more so this year than previous years, where they do not get warned.

Is the NWS paying more attention to CC now or do they have a certain inbound/outbound velocities within the couplet they're using to determine if a it should be warned?

If it is showing up on CC that means it is already on the ground and therefore too late. A warning should ideally be out before any type of debris signature shows up on CC.

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14 hours ago, weunice said:

I know I have seen ridiculous couplets in the plains that are not tornado warned. I can only venture to guess that different offices look for different parameters when warning or not. I would think that the offices in the plains have a much better idea of when a storm is producing vs. not as they follow more classic progressions than, for example, in my home office (LIX) where everything is rainwrapped, it is a hot mess on radar and you can have nothing one frame and an EF-2 on the ground the next. We are far more likely to see any decently strong rotation trigger a tornado warning here. They are also more likely to have conditions where people can see what is happening. I'd guess nighttime storms trigger warnings differently than ones with great visibility and 100 storm chasers on the scene.

 

Thanks for the replies.

Good points.

On Cc, Yea, I understand when you see something there the tornado is causing damage but I was just throwing that out there as an extreme example of waiting to see.

 

 

 

 

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On 3/30/2017 at 8:35 AM, Weatherdemon said:

Couplet question for the more experienced folks.

As radar resolution has improved it seems tornado warning have as well, it terms of accuracy. But, it seems I've seen an increasing amount of couplets, more so this year than previous years, where they do not get warned.

Is the NWS paying more attention to CC now or do they have a certain inbound/outbound velocities within the couplet they're using to determine if a it should be warned?

It probably has to do with the expected surface conditions. If conditions don't favor surface based storms, or if the storm is elevated, or the radar beam is hitting it high and they suspect it's elevated, they won't issue a warning. On days that favor surface based storms, and the atmosphere is very unstable, they'll warn everything, at least in the Springfield CWA. 

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