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Central/Western Summer Medium/Long Range Discussions


Srain

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Finally, many of the tropical forcing analogs and years thrown around in this thread peaked in June as far as tornado numbers. Some of the years had multiple tornado outbreaks from the Northern Plains into the Ohio Valley (like I said last week, the southern Plains aren't done yet either). Given the pattern expected this June, the tropical forcing and analogs, I think I'm having trouble finding a reason not to forecast an active pattern here.

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Finally, many of the tropical forcing analogs and years thrown around in this thread peaked in June as far as tornado numbers. Some of the years had multiple tornado outbreaks from the Northern Plains into the Ohio Valley (like I said last week, the southern Plains aren't done yet either). Given the pattern expected this June, the tropical forcing and analogs, I think I'm having trouble finding a reason not to forecast an active pattern here.

 

Any thoughts on how far north the threats will extend? Interested in how things will play out here in Southern Manitoba. Based on the long range GFS/Euro, there would be some threat for elevated convection up this way next week already.

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Some of these leeside cyclogenesis episodes (particularly among the 12z GFS ensemble members) look pretty crazy for this time of year (or any time for that matter), it's not often that you see the 996 hPa contour cover such large areas.

 

Then again, when you get such a strong Pacific Jet dumping into the West like this, it's not overly surprising to see impressive solutions being generated.

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Some of these leeside cyclogenesis episodes (particularly among the 12z GFS ensemble members) look pretty crazy for this time of year (or any time for that matter), it's not often that you see the 996 hPa contour cover such large areas.

 

Then again, when you get such a strong Pacific Jet dumping into the West like this, it's not overly surprising to see impressive solutions being generated.

Late May and early June 1917 had a pattern very similar to the upcoming one...with a strong Pacific jet forcing multiple lee cyclones to develop in rapid succession.

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Late May and early June 1917 had a pattern very similar to the upcoming one...with a strong Pacific jet forcing multiple lee cyclones to develop in rapid succession.

 

Well the results speak for themselves that year, that was one of the most impressive tornado outbreak sequences on record.

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We brought tornadoes back. ;)

You sure did, as well as a much more active forecast pattern.  I do remember one met saying that everything has been pushed back a month this year seasonally, so maybe we are just now entering late April instead of May.  That Pacific jet on the models looks awesome.

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Snippet from HPC on the upcoming pattern...

 

THE GLOBAL NUMERICAL MODELS CONTINUE TO SHOW HIGH-LATITUDE  BLOCKING FROM THE NORTHEAST PACIFIC TO THE NORTH ATLANTIC THROUGH  THE MEDIUM RANGE. AN OMEGA-ISH FLOW CONFIGURATION IS EXPECTED TO  DOMINATE NORTH AMERICA INTO EARLY DAY 5--WITH UPPER LOWS NEAR  VANCOUVER ISLAND AND ASTRIDE THE SAINT LAWRENCE RIVER. BY LATE DAY  6, AN UNSEASONABLY STRONG JET IS PROGGED TO PLUNGE INTO THE  PACIFIC NORTHWEST COAST ALONG 40N, WHICH WILL INDUCE LARGE HEIGHT  RISES OVER MUCH OF THE EASTERN UNITED STATES THEREAFTER. THE  ENSEMBLE MEANS FROM THE GFS AND BOTH THE CANADIAN AND EUROPEAN  CENTRES AGREE ON THIS THEME, WITH THE DETERMINISTIC MODELS  OFFERING "NOISY"--IE UNRELIABLE--DEPICTIONS OF THE PATTERN CHANGE.  THE EUROPEAN CENTRE ENSEMBLE MEAN FORMED THE BACKBONE OF THE  MANUAL FRONTS AND PRESSURES DAYS 3-7, WITH ITS STABILITY OVER THE  PAST SEVERAL MODEL CYCLES THE MAJOR FACTOR IN ITS PREFERENCE OVER  THE OTHER GUIDANCE.
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Anybody want to comment on slight risk outlooks on tomorrow, Friday, and Saturday? Obviously the Texas Panhandle should be a prime spot for tomorrow. I see hodographs turning about 180deg. from easterly to westerly at the Panhandle tomorrow.  I think the SPC will at least put out a 15% hail/wind outlook for Friday in Kansas, and Kansas/Nebraska on Saturday. The NAM is showing helicity values of over 300 m2/s2 on all three of these days.

 

Saturday: 00z NAM has this for Grand Island NE: 82/66, 45-50 knots of 0-6km shear, 3000 J/kg of CAPE, 400 m2/s2 of helicity.

 

I would think some chasers would want to watch this and think about heading up to this area.

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Anybody want to comment on slight risk outlooks on tomorrow, Friday, and Saturday? Obviously the Texas Panhandle should be a prime spot for tomorrow. I see hodographs turning about 180deg. from easterly to westerly at the Panhandle tomorrow. I think the SPC will at least put out a 15% hail/wind outlook for Friday in Kansas, and Kansas/Nebraska on Saturday. The NAM is showing helicity values of over 300 m2/s2 on all three of these days.

I would expect slights on all three days with the main caveats being moisture return further north and potential capping. But the high plains doesn't need much moisture of course. We are in Amarillo tonight. Tomorrow looks pretty good as long as things fire right. Hodos look great on Fri in E CO and W NE... Hadnt looked at KS with the height rises. Was thinking Sat might be SD but maybe NE.
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The 00z NAM busts out a QPF feedback east of Lubbock tomorrow. I'd target over there, but watch for extremely slow-moving storms, as they may not move too much from the point of initiation. I've seen some extremely slow cyclic supercells (and of course slow squall lines) in the TX panhandle a number of times. If you drive to eastern Colorado, look for convective initiation a little more west than the models say.  Initiation in eastern Colorado always seems to gravitate to the Palmer Divide.  The GFS has dew points of something like 39 degrees for E Colorado on Friday, though.

 

Edit:

 

easterly winds seem to be strong for this time of night for the western Plains (including at my place.)

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GFS gets ~60 dews just inside the CO border at least on 18z. Sharp contrast over a short distance but verbatim should be enough where cells try to fire.. Probably more a NW KS or SW NE play as is.

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We are in Saint Louis now, making the all night trek to the Amarillo area. The 00z NAM looked pretty good. I like the location of the initial convection, as it helps to keep temperatures cool in that location, thereby increasing the frontogenesis when the sunny areas warm up. This should help to break the cap, and the shear; instability, and ML Lapse rates should produce a few gorgeous structured supercells.

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Are you taking Route 66? :)

Hahaha.

We were on route 44 and just stopped at a Denny's. No time for a hotel tonight, so I brushed my teeth in the bathroom here. Lol.

Edit: just found out that 66 and 44 are collocated! For some reason a friend told me that 66 was a old historical route that doesn't exist anymore.

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Any thoughts on how far north the threats will extend? Interested in how things will play out here in Southern Manitoba. Based on the long range GFS/Euro, there would be some threat for elevated convection up this way next week already.

I agree with your last sentence. There seems to be some uncertainty with the track next week (euro seems more threatening for you). Obviously, things will get more interesting for your area with the threats deeper into early June.

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http://www.esrl.noaa.gov/psd/map/images/reanalysis/aam_total/gltaum.90day.gif

The AAM is going down (MT tanking in progress) and the jet stream has really intensified from the Asian Hadley Cell. All the water bodies from the IO into the PAC have really gone nina here, strengthening the uplift zone near 120E. The potential for a "tornado outbreak sequence" is elevated late May-early June. I'm not sure yet if we will see something like 2004; but, the players are there for multiple days of tornadoes.

We likely haven't seen the last violent tornado or tornado outbreak.

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What HM and Dsnowx53 are talking about regarding tropical forcing etc.

 

In case one does not have access to the Euro, I'll only add this good news (for chasers). It's pretty bad news for the Plains public. Euro is more of a bowling ball trough in Southwest; however, it's Memorial Day week. Hanging back it still ejects energy each day. Above Mets already noted that's not a show stopper this time of year. GFS iff a perfect prog is high-end sequence/series. I kind of hope it's wrong for the sake of the public. Euro solution still very good for storm chasers.

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May 29-31 continue to look promising on this morning's GFS as a 992 mb low meanders from Colorado through the Dakotas.

 

The GFS also reloads the pattern following the first trough's departure and the GGEM appears to be trying to do the same thing.

 

The Euro is substantially more amplified with the initial trough (meridional flow aloft), and as Jeff said, it might be the most benign solution (although obviously bringing a trough this size over the Central CONUS this time of year is going to lead to some fireworks, in all likelihood).

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Looks like we're going to have to make a decision about leaving early. The pattern looks pretty iffy after this event thru next week. Our original return date was by June 9. Which means in theory we could chase till about June 7... but not sure it's going to be worth it.

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