State of the Chase Season 2021

Jeff House

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Jun 1, 2008
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Yeah one cannot really sugar coat the rest of April. Weeklies do break down the super blocking and displaced Hudson Bay low in May. No particularly interesting pattern is shown, but it's better; plus, it's still 4 weeks out.

Three weeks ago a big West trough was advertised. Instead we get this debacle with the Hudson By low dropping south. Three weeks ago had some -NAO risk, but the forecast +ANBA busted. The -ABNA with blocking is game over at least for a couple weeks. Interesting we had a mid-April cool snap last year too.

That said I'm still optimistic about May. Weeklies are ensembles of 50 members; so, I would not expect anything classic to show up 4-6 weeks out. In fact I'd rather see it 2-3 weeks out than weeks 4-6. Last year a good May pattern showed 3-4 weeks out; then, got destroyed by small scale closed lows.

I have no reason to forecast that again this year in May. Despite fading La Nina SSTs, if the atmospheric imprint holds it's less conducive to closed lows. However if this MJO mess continues and/or on more westerly winds down there, that could squash any Nina echo.

I feel for my Plains friends (real-life and on here) April; but, there's no reason to worry about May. If March is pre-season, April and May regular season, and June post-season for those willing to travel, it's early.

Yes @Jason N this year might decay a little faster than those you note. If the imprint can just hold on to May. Oh to tag/mention someone, just start with first name and wait for the drop-down a couple seconds. Space between names loses it. I usually tag if I'm a few posts later or several days later. I saw your reply well. Good stuff!
 

Jeff House

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Yes I refer to all Weeklies (average blend) if I do not specify. On the very broadest themes, all three generally agree. Dreadful the rest of April, yields open doors right around May 1 forward. All three is the ECMWF CFS and the GFS also has a weekly product - which will eventually replace the CFS I believe. Don't laugh it's actually a decent weekly product, given that all weekly products are taken with a grain of salt.

ECMWF is slowest to come around for May; however, it's had issues with the week 3 pattern getting stuck for weeks 4-6 for a couple years now. Anecdotal, from an energy/temperature perspective, and not statistically verified. CFS/GFS weekly both have a better pattern in May. It's not classic deep blue Rockies trough. However it shows energy coming through the West with QPF in the Plains. It's a start!

MJO remains an absolute debacle. Convection is in unfavorable areas. JTWC actually has an Invest east of the Philippines which is such an awful area (for our chasing) driven partly by an unfavorable westerly wind burst. My hope is that even if it does not develop, it'll use up some of that energy. Gonna need a reset from the Indian Ocean to Martine Continent for chasing.

At least the American weekly products show a bi-modal MJO. If we can get Maritime Continent to dominate it'll be fine. Time will tell. However the season is early; plus, MJO and weekly forecasts are statistically worthless past week 3. Continue Tee Up May mode.
 

Warren Faidley

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May 7, 2006
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I'm still going with Accux-WX and their PhD's prediction of a great chase season. Seriously, I'm not liking the RH distribution or upper air patterns for the near future, especially given they are beginning to look like last year, to some degree. Lots of zonal and NW flow over the Central Plains if you follow the NCEP Ensembles. Not ready to write off May or early June as it's too far out and eastern CO is always a wild card. Might be another great hurricane season, so all is not lost.
 
Aug 9, 2012
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The next couple weeks look about as boring as anything I've seen for storm chasing. Pretty glad I got on the bandwagon early this year on March 13th in Texas...starting to wonder if we will even get local setups here this April (aside from some low end severe storms we had on Wednesday which featured a July-like mushy shelf cloud).

Today featured more heavy rainfall, northerly winds gusting over 40 mph, and highs in the 40s with wind chills in the 30s (more typical of early March than April here). Hopefully May can come in clutch with a series of 2013/2016 style setups to make up for this miserable pattern we are in.
 

Jeff House

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Yes the flaky Mays of late have driven me to actually chase Dixie Alley. Note that I live in Dixie; so, it's just local outings. When I lived in the Plains I never even gave Dixie Alley a chasing thought (just thoughts and prayers). I'm not sure what I'd do regarding Dixie if I still lived in the Plains.

That said we certainly welcome and appreciate Plains chasers swinging through, spending money, and perhaps we might even meet up - if we see each other through the trees. Plus side, the South still has very little chaser convergence.

Wichita / Plains friends joke I moved to the new promised land. They haven't chased here, ha. Anyway my season strategy is to chase a couple Dixie setups, just in case late-season fails. However in my mind May is still the main event; and, I really look so forward to my Plains trip.

Though this mid-April cool snap echoes 2020, key differences are noted in the ENSO state. SST snap-shot might be similar, but we are coming out of (not going into) La Nina. Usually better by the TNI papers.

Also May 2020 a beautiful jet extension was spoiled by pesky closed lows. Generally those are less favored this phase of ENSO, unless we get an absolutely dreadful GLAAM hiccup. Odds simply favor a normal May, which is game-on for chasing.
 
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B Janssen

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Apr 28, 2020
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@Jeff House. I wish I could see what you see in the long term, because CFS weeklies for May look awful. Then again, I think someone mentioned that past two weeks is really hard to forecast.
 

Jason N

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Mar 2, 2021
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Jeff House(I typed your name , I saw no pop down menu 🤷‍♂️) - We've been seeing some upticks in confidence on tropical system formation over the southern IO and another area over Madagascar over the next few weeks, not sure if this means the MJO is shifting towards phase 7 100% yet, but something to watch for sure. As for the Chase piece, I am committed for end of May now(tickets bought, truck rented), so I'll just do what I have to and I'll be smiling the whole time. I am just not a fan of Dixie chases and never have been.

That said, I am in agreement with the idea that there is just still a lot of time to see how the hemispheric scale is going to effect the Synoptic. Revisit 10-14 days from now and lets see where things are.
 
Oct 10, 2004
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Though this mid-April cool snap echoes 2020, key differences are noted in the ENSO state. SST snap-shot might be similar, but we are coming out of (not going into) La Nina. Usually better by the TNI papers.
Just anecdotally, it seems like April 2020 was more active (with the Easter outbreak, Bassfield, MS etc taking place a year ago to the day) followed by more activity later in the month which involved the Southern Plains (Madill, OK) in addition to another violent day in Dixie. Then everything by and large shut down for May and even June. It almost seems like everything that happened in April in Dixie last year, happened in March this year.

April hasn't really been a consistent producer of quality chase days for a long time (if indeed it ever was), so I'm not too concerned...yet. Would be nice if the weeklies looked better going into May, but with the skill level beyond 3 weeks being what it is, I'd be more worried if they were showing a perfect pattern for chasing right now.
 

B Janssen

Enthusiast
Apr 28, 2020
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@Jeff Duda. I have very little understanding of the MJO. I know that it can affect the storm season and that certain phases are more favorable. I am curious about when the affects of the phases predicted in the images you showed will take hold if they do?

@Jeff House. What do you think about sea surface temperatures in the Gulf of Mexico. How much of a clamper on the season do you think they might be? How detrimental do you think the upcoming cold snap will be to sea surface temperatures in the western Gulf of Mexico? 1618285002619.png
 

Jeff Duda

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@Jeff Duda. I have very little understanding of the MJO. I know that it can affect the storm season and that certain phases are more favorable. I am curious about when the affects of the phases predicted in the images you showed will take hold if they do?
I don't have a full understanding of the relationship between MJO and US severe weather either. However, I understand from the literature that, at this time of year, a big swing through phases 8-1-2 will give us a big boost in severe weather activity.
 

Dutch Jolien

Enthusiast
I'm not an expert, but I read at Severe Weather Europe, that La Nina and the high temps of the gulf stream (6 to 8 degrees celcius above average) can be a great influence at the coming stormseason.



About El Nina, she was stronger than normal and the way she acted, is simular to years wich had a tornado outbreak and very active season. But what do you think about this? Could we see an above-average tornado season in the United States due to the ongoing La Nina this spring?

Below is a graph which shows annual tornado numbers in the United States from 1954 to 2014. Looking at the years, we can see that from the top 5 most active tornado years, 4 were La Nina years. At least for the spring tornado season, which is also the most active part of the year for tornadoes.
 
Oct 10, 2004
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I'm not an expert, but I read at Severe Weather Europe, that La Nina and the high temps of the gulf stream (6 to 8 degrees celcius above average) can be a great influence at the coming stormseason.



About El Nina, she was stronger than normal and the way she acted, is simular to years wich had a tornado outbreak and very active season. But what do you think about this? Could we see an above-average tornado season in the United States due to the ongoing La Nina this spring?



From what I understand, the La Nina has pretty much dissipated to near neutral. MJO should be a much bigger influence on seasonal potential.
 

adlyons

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I understand Andy, but is only the presence of La nina in the winter not enough to influence the weather?
What's the meaning of MJO btw?
Subseasonal forecasting at these ranges is complicated. While La Nina tends to produce more severe weather that's not always the case. Several very quiet years have been associated with a resurgent la nina. There are other significant contributions to the overall weather pattern.

MJO stands for the Madden Julien Oscillation which is a cyclic pattern of rising and sinking motion that migrates around the tropics and mid lattitudes What is the MJO, and why do we care? | NOAA Climate.gov
 
May 1, 2011
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April 1-15 has landed "BA" but hasn't been dead quiet. About 30 tornadoes compared to about 50 for climo.

Now for the back half of April, this could get a bit tricky to forecast due to timing and confidence factors. As has been teased in the last 2 weeks, there's some tropical forcing signal, with growing confidence, that could land us some severe weather at the end of the month going into early May. And we're going to need it as long range guidance has so far suggested more ridging, horribly disorganized jet and just a few attempts here and there at some good southwest flow.

Other than the occasional "Del Rio'ing" or South Texas and gulf coast tornadoes, not much is expected until tropical forcing switches things up. So, I'm going to call the back half of April a "BA*" but with a giant asterisk. Or BA+? A-? Can we do that? At any rate, opportunities may exist at the very end of the period, and depending on the ceiling for that activity, might reverse the forecast.

Early May however could be a very different story. Depending on how long this active period persists, it could result in A or even AA conditions. I'm going to go on the aggressive end here because of the time of year, and past examples where this occurred at around the same time period in a similar background state. (1999 for one). In my experience watching these for the past few years, there seems to be delays in getting our AAM drop/GWO-MJO Orbits/Jet extensions compared to forecasts by models. Perhaps that's just me.

Second half of April Climo: ~75 Tornadoes
First half of May Climo: ~100 Tornadoes


1618418116397.png 1618418137196.png 1618418154674.png


March 1-15 Forecast: BA, Actual: A.... Notable: March 12-14 Severe Sequence / CO Blizzard [Scored 1 tornado]
March 16-31 Forecast: AA, Actual: AA....Notable: March 16-18 Severe Sequence / South High Risk. March 25th South High Risk. March 27th Arklatex/TN Tornadoes [Scored 1 tornado]
April 1-15 Forecast: BA, Actual: BA....Notable: 4-7 to 4-10 active in deep south. My friend's house in Bryon Center, MI got hit by a random EF0, Big Texas hailer
April 16-30 Forecast: BA*
May 1-15 Forecast: AA
 
Feb 22, 2015
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Yeah that signal for the MJO to begin progressing across the Indian Ocean late this month into the first half of May is growing across all guidance, including bias corrected options. The current state favors eastern troughing and a generally cool pattern in spring (which is what we're seeing), but as can be seen in that North Pacific Phase diagram plot above, there is a growing signal for a cycle through an equatorward shift and jet extension towards the end of the month, which has been a precursor to extended periods of AA activity in the past. The addition of a recurving TC in the West Pacific adds another layer to this, which may provide a boost in westerly momentum across the Pacific.

The longevity of said AA period is still TBD, but seems to me that some interesting is coming here.

On top of the tropical forcing becoming more interesting, it seems this down period will not be completely fruitless, as medium range guidance consistently indicates widespread precip across the southern/central Plains thanks to embedded shortwaves in the southern stream, not overly dissimilar to what happened yesterday evening/overnight across Oklahoma. E.g. is the 12z ECMWF accumulated QPF output at FH 120 and 240 (half the period and the full period).

1618428391039.png
1618428328409.png
 
Apr 10, 2008
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I don't put a lot of stock into these outlooks. The outlook for February was a bust, and April has been much cooler than what has been forecast. I had my yearly "the season is going to be trash" meltdown last week. This week I am much more optimistic going into May. There are continuous signs at a transition in the MJO with an 8-2-1 progression possible by the beginning of May. Still a lot of uncertainty as to how things play out, however it's not looking nearly as bleak as even a week ago. 🤞
 

Jason N

EF0
Mar 2, 2021
27
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1
South Carolina
You know , lets just say for a moment that their forecast pans out and that's the average pattern trough May. what that picture tells me is that the intersection of the temp trough from South Dakota, Ern NE, through Iowa and into Illinois intersects with the NW corner portion of their Moisture field area, it tells me that's where to look for possible good things. that's me just trying to see through the negative lol.
 
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