Severe Weather 2018

[Richardjacks]

M. Grantham at KBMX doing a good job of foreshadowing of what may be down the road...
The potential for strong to severe storms may be increasing for
Tuesday night into Wednesday morning as low amplitude shortwaves
in the northern and southern streams eject eastward across the
Plains. Currently it appears that these shortwaves will only
partially phase, but there is quite a bit of model variability
between the much more phased UKMET and the GFS. The ECMWF is
perhaps the middle ground. Significant CAPE is expected to surge
northward from the western Gulf into the Lower Mississippi Valley
ahead of the approaching front. The positive tilt nature of the
front suggests convection will not be pre-frontal and will be
generated by the front itself. The strongest instability to remain
to our west, but CAPE values around 1000 J/kg, as suggested by the
ECMWF, would support a potential for isolated damaging winds along
a line of storms. If this system becomes more phased as shown by
the UKMET, the severe weather threat would increase substantially.
A low confidence risk of severe storms will be placed in the HWO.

Dry and cooler weather should return for Thursday behind the
front, but there are signs that a much more ominous weather
pattern is brewing for Friday and especially toward the Day 10
time frame. Any system that moves across the CONUS in this low
amplitude pattern will have to be watched closely as high octane
air lurks across the Gulf of Mexico and Dixie.

 

[CheeselandSkies]

Where did this all come from? Everything I've been hearing on AmWx and on the CPC 6-10 and 8-14 day says -NAO/blocking/cold dominating the central and eastern CONUS through the first half of April.

 

[Kory]

Where did this all come from? Everything I've been hearing on AmWx and on the CPC 6-10 and 8-14 day says -NAO/blocking/cold dominating the central and eastern CONUS through the first half of April.

That is your first problem...reading AmWx. I don't see a very cold pattern on the models for the Southern tier states. It looks like we're gonna see a wavebreak with this current system that came through as it races NE into Canada and North Atlantic. It will spur a NAO block which displaces the polar vortex, but in a very west to east elongated fashion over Central Canada. There will be a very large temp gradient, but the Pacific jet looks very cooperative for bigger systems as they enter the West Coast.

The 8-14 day CPC upper air analogs feature 1974 as an analog match...several times.

 

[Richardjacks]

That is your first problem...reading AmWx. I don't see a very cold pattern on the models for the Southern tier states. It looks like we're gonna see a wavebreak with this current system that came through as it races NE into Canada and North Atlantic. It will spur a NAO block which displaces the polar vortex, but in a very west to east elongated fashion over Central Canada. There will be a very large temp gradient, but the Pacific jet looks very cooperative for bigger systems as they enter the West Coast.

This kind of pattern can produce multi-day/episode events...question is exactly where and what, but wow, there should be areas of both high shear and cape very close together.

 

[ARCC]

Tell that to both 1932 and 1974. Both of them featured a CONUS-wide large scale trough leading up to those outbreaks.

View attachment 571

View attachment 572

Point taken, but still I'd feel much better about a substantial threat if the deep layer ridging gets going of FL. The GFS definitely gets it going later on in its run.

Looking at '74, deep layer ridging was pretty strong until the system March 29-30 beat it down and then flexed back as the first(primer) trough entered into the Plains on March 31. So if we take the Euro, we need to be looking in the 288hr+ range for our threat.

 

[rolltide_130]

Here it comes on the 0z Euro..

 

[tennessee storm chaser]

Point taken, but still I'd feel much better about a substantial threat if the deep layer ridging gets going of FL. The GFS definitely gets it going later on in its run.

Looking at '74, deep layer ridging was pretty strong until the system March 29-30 beat it down and then flexed back as the first(primer) trough entered into the Plains on March 31. So if we take the Euro, we need to be looking in the 288hr+ range for our threat.

Think end run on euro clearly shows the pattern Fred and kory hint on. Think it will be after the first week April when we really got watch for Vitotale systems ...

 

[tennessee storm chaser]

Here it comes on the 0z Euro..

Big time trouble brewing there...no doubt

 

[Fred Gossage]

Be careful dealing with analogs. What we're really looking at with them this far out is that the large scale pattern driving individual systems is similar to the large scale pattern in place around those dates. It will be up to individual systems to take full advantage of the background environment. HOWEVER, when you get a pattern that is driven all the way from the global scale down to be favorable, it really gets your attention. This is the type of large scale pattern that has been in place in association with some large scale very violent outbreaks here in the heart of Dixie Alley in the past.... and it's just speculation still at this point, but I have to think that one of the systems in the line will be able to fully pull it off.

 

[SilentShadow87]

I know these people are effectively making guesstimates at best and in all likelihood wild guesses, but several of these chasers are predicting a total of less than 850 tornadoes for the year with one predicting around 750, which adjusting for the undercounting of the 80s and earlier would make this by far the least active tornado year on record...Am I missing something? I think the yearly total will probably end up being lower, maybe in the 950 to 1000 range, but what is there that suggests that the final tornado count will be 100 to 150 fewer even than 2013?

https://stormtrack.org/community/th...-tornadoes-and-first-high-risk-of-2018.30037/

 

[rolltide_130]

I know these people are effectively making guesstimates at best and in all likelihood wild guesses, but several of these chasers are predicting a total of less than 850 tornadoes for the year with one predicting around 750, which adjusting for the undercounting of the 80s and earlier would make this by far the least active tornado year on record...Am I missing something? I think the yearly total will probably end up being lower, maybe in the 950 to 1000 range, but what is there that suggests that the final tornado count will be 100 to 150 fewer even than 2013?

https://stormtrack.org/community/th...-tornadoes-and-first-high-risk-of-2018.30037/

Plains chasers are often annoyingly pessimistic, especially when an event isn't in ideal territory W of I-35. With the upcoming pattern I find it hard to believe we're dealing with counts that low.

 

[SilentShadow87]

Plains chasers are often annoyingly pessimistic, especially when an event isn't in ideal territory W of I-35. With the upcoming pattern I find it hard to believe we're dealing with counts that low.

True. Plus as one chaser in the thread did point out, a decaying Nina actually seems to support a more active severe season for the far southern Plains, and several weak Nina/decaying Nina years have been fairly active overall (1971, 1975, 1984, 1996, 2001). Probably just flat out pessimism with those guys. My honest impression is that this feels like a fairly average year with what will probably turn out to be a pretty active April.

 

[Kory]

I don't know how anyone can make predictions on the year's tornado tally given hurricane season (which can produce a sizeable chunk of tornadoes) looks very uncertain at this point. Take out the more than 100 tornadoes produced by hurricanes last season, we would've fallen below normal yet again.

I feel like people are more concerned with the bravado associated with these "bold" predictions than the usefulness (in my opinion, there isn't any) of tornado prediction numbers.

 

[SilentShadow87]

Take out the more than 100 tornadoes produced by hurricanes last season, we would've fallen below normal yet again.

2017 had 1,414 tornadoes. Take out all of the hurricane-related tornadoes and there still would have been ~1,250 tornadoes.

 

[Weatherphreak]

Any update on the weekend system? I know a couple mentioned it was going to be the bigger threat this week.

 

[rolltide_130]

Any update on the weekend system? I know a couple mentioned it was going to be the bigger threat this week.

Models are doing a terrible job resolving it. It's got the higher ceiling but there's not much we can read into until the models get a grip.

 

[CheeselandSkies]

Models are doing a terrible job resolving it. It's got the higher ceiling but there's not much we can read into until the models get a grip.

You know it's bad when even Broyles can't find a reason to introduce a risk area on the Day 4-8.

 

[rolltide_130]

You know it's bad when even Broyles can't find a reason to introduce a risk area on the Day 4-8.

I don't want to beat a dead horse but these things are miles behind where they were in 2011. The attempts to make them higher res and more precise have failed miserably.

 

[tennessee storm chaser]

I don't want to beat a dead horse but these things are miles behind where they were in 2011. The attempts to make them higher res and more precise have failed miserably.

2nd week April that year. That’s when things really started to ramp up

 

[Argus]

Any update on the weekend system? I know a couple mentioned it was going to be the bigger threat this week.

This could actually be a winter wx threat for parts of the SE.