chrisbray
EF4
Given its likely the last weekend of the season, I am eyeing Sat/Sun for a possible trip. A decent signal for something to occur on saturday, although who know exactly what at this point. Sunday has a lot more uncertainty.
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2018 severe wx/chase season discussion
- Thread starter Warren Faidley
- Start date
Billy Ahlers
EF0
Hello all!! New here. Figured I throw in my two cents worth... For me its been a rather successful chase season. Catching both the Landspout tornadoes 5/28 near Anton Co and the tornado on 6/19 in prospect park Co. There have been numerous out and out busts too. This was a bad snow year in our mountains due to the jet stream being too far north. My experience on years like this, is that severe weather isn't as frequent in NE Colorado. I have been amazed at how little lightning has been associated with any of my chases all year. Even the two tornado days had little to no lightning. I assume we are not getting the instability we usually have. I am guessing and its really just that...most of our storm systems have been hugely outflow dominant so the missing ingredient has been that strong updraft. Capping and low level cloud cover has hurt too. Am I even close ? As to why so little lightning? Not getting the friction due to lack of height?
I’ll probably be proven wrong by those who do deeper analysis of severe setups, but my anecdotal thoughts follow. There have been a handful of nice tornadoes and landspouts in CO and WY this year, so I’m not complaining by any stretch
However, if you look at the four primary ingredients required for a severe thunderstorm: instability, moisture, lift, and wind shear; and speaking mainly for the Palmer Divide, I’ve noticed a lack of well-defined boundaries this season. During years past I recall east west boundaries, such as stationary fronts lining up along the Palmer Divide, which would allow for differential heating along the boundary and/or low level convergence to provide additional lift. It seems this year the boundaries (cold fronts tied to upper level short waves) have been located to the north in WY and the dryline to the east along the CO/KS border a majority of the time. There have been a few setups with a lee side trough as well, but some of the aforementioned setups have been wrecked by persistent stratus decks that inhibit surface heating. It seems fewer outflow boundaries from previous evening’s (MCS activity) have also been lacking, such as the one that produced Simla.
In any event I was able to witness the landspout-fest out by Flagler on 5/28, so I’m satisfied with the season. I also took a few baseballs for my trouble on the southern cell on 6/19, so that was a rather new experience for me. In 13 seasons I have tried my best to avoid gorilla hail and have been able to do so, but not that day. I was caught out by a 15 minute old radar scan that slipped my attention. Having a partner really helps in those scenarios, but I have to go solo if my wife isn’t on vacation. We’ll hopefully have a couple of July setups left with the DCVZ, so I’m hoping to bag one more landspout for the books.
However, if you look at the four primary ingredients required for a severe thunderstorm: instability, moisture, lift, and wind shear; and speaking mainly for the Palmer Divide, I’ve noticed a lack of well-defined boundaries this season. During years past I recall east west boundaries, such as stationary fronts lining up along the Palmer Divide, which would allow for differential heating along the boundary and/or low level convergence to provide additional lift. It seems this year the boundaries (cold fronts tied to upper level short waves) have been located to the north in WY and the dryline to the east along the CO/KS border a majority of the time. There have been a few setups with a lee side trough as well, but some of the aforementioned setups have been wrecked by persistent stratus decks that inhibit surface heating. It seems fewer outflow boundaries from previous evening’s (MCS activity) have also been lacking, such as the one that produced Simla.
In any event I was able to witness the landspout-fest out by Flagler on 5/28, so I’m satisfied with the season. I also took a few baseballs for my trouble on the southern cell on 6/19, so that was a rather new experience for me. In 13 seasons I have tried my best to avoid gorilla hail and have been able to do so, but not that day. I was caught out by a 15 minute old radar scan that slipped my attention. Having a partner really helps in those scenarios, but I have to go solo if my wife isn’t on vacation. We’ll hopefully have a couple of July setups left with the DCVZ, so I’m hoping to bag one more landspout for the books.
I agree with that assessment. In general, winds are what has been wrong this year. The placement of jet stream and resultant lack of upper level support or organized turning with height has been the missing ingredient in almost every setup, plains or otherwise. Lack of that upper level movement is also the reason for stagnant patterns that produce harmful outflow regions or stratus decks, etc. that normally would have cleared out or setup to enhance storm activity, but have ruined a lot of #2018 borderline setups during shortwave events. I've seen plenty of moisture and instability and initial weak forcing for initiation but rare that it has been timed with sufficient strong forcing or bulk shear for anything but a rainy mess time and time again this year. Bad hodographs almost every event, and the ones that produced were all reliant on localized increase in SRH, orographic forcing, perfectly placed OFB, or the rare well timed LLJ. The atmosphere has been becalmed and stagnant on more days than I can remember and I see this not just with storms season but with sunsets / sunrises frequency greatly reduced to grey mush. I never felt like I saw a storm this year explode out in clear air with good shear. I've become very selective on what I chase now and add a #2018 pessimism factor to most setups.
Still, if some thinking is correct, we may have an active monsoon which will bring increased pulse storm activity for those of us inclined to chase summer lightning. That is where I'm turning my attention.
Jeff House
Supporter
All of the above problems would be solved by a true synoptic system, which were few and far between. Rather than closed lows, one looks for shortwaves within a broad trough. Earlier in the season a phased system brings the outbreak. Just did not happen this spring. Good for the people, but it frustrates chasers.
Perhaps the PDO is the problem. It was positive. Good years in the past had a -PDO background. Like anything it's never a perfect correlation. I have eyeballed* the data and believe the PDO is more important than ENSO or even TNI. PDO has been awful the last few years. Some of the good chasing a decade ago was during the more favorable PDO phase. Ditto for the early 90s and the late 50s through 70s. The slow years in the 80s and later 90s were unfavorable PDO.\
* not a rigorous study but looks reasonable
Perhaps the PDO is the problem. It was positive. Good years in the past had a -PDO background. Like anything it's never a perfect correlation. I have eyeballed* the data and believe the PDO is more important than ENSO or even TNI. PDO has been awful the last few years. Some of the good chasing a decade ago was during the more favorable PDO phase. Ditto for the early 90s and the late 50s through 70s. The slow years in the 80s and later 90s were unfavorable PDO.\
* not a rigorous study but looks reasonable
Andy Wehrle
EF5
Agree PDO seems to have the strongest correlation to Plains/Midwest chase opportunities of any of the teleconnections. However, according to this:
https://www.ncdc.noaa.gov/teleconnections/pdo/
the PDO was slightly negative for all of spring 2018. The atmosphere had/still has bigger problems producing severe weather in the central CONUS on a significant/synoptically predictable scale.
https://www.ncdc.noaa.gov/teleconnections/pdo/
the PDO was slightly negative for all of spring 2018. The atmosphere had/still has bigger problems producing severe weather in the central CONUS on a significant/synoptically predictable scale.
Jeff House
Supporter
That NCDC site is a great resource.
Yes the PDO was slightly negative, but got to that reading in a strange way. Central Pac is clearly warmer than the area near the North American West Coast. However the latter still has AN SSTs. So while the PDO was negative the ATMO really did not respond in kind.
Yes this year the ATMO did have other big problems. SSW going into spring was awful. Then upper level lows from the Gulf came early and often.
We need some good BN SSTs off our West Coast.
All of this 2018 debacle would be so much easier to take if we had another total solar eclipse coming, lol.
Yes the PDO was slightly negative, but got to that reading in a strange way. Central Pac is clearly warmer than the area near the North American West Coast. However the latter still has AN SSTs. So while the PDO was negative the ATMO really did not respond in kind.
Yes this year the ATMO did have other big problems. SSW going into spring was awful. Then upper level lows from the Gulf came early and often.
We need some good BN SSTs off our West Coast.
All of this 2018 debacle would be so much easier to take if we had another total solar eclipse coming, lol.
No individual low-frequency climate oscillation singlehandedly explains any given event. You need to look at the sum of all the oscillations. While there may be a correlation between -PDO and quality spring chasing, there are many other factors such as ENSO, NAO, NPO etc. that will also exert a substantial influence on the ingredients needed for a good chase season.
I agree with Jeff that the problem this season was just a general lack of synoptic scale waves that came through the central US. For whatever reason they just were not being generated over the E PAC and W CONUS like they usually are. I don't know the cause of it.
I agree with Jeff that the problem this season was just a general lack of synoptic scale waves that came through the central US. For whatever reason they just were not being generated over the E PAC and W CONUS like they usually are. I don't know the cause of it.
Randy Jennings
Supporter
- Joined
- May 18, 2013
- Messages
- 855
After a fairly rainy Aug so far here in DFW, a seeming uptick in tornados the last few days across the US, and actually going on a local chase on Saturday (not that great - but was much better than expected), I began to wonder if we where turning the corner on this slow season. That was wishful thinking on my part. I used the IEM Automated Data Plotter (https://mesonet.agron.iastate.edu/plotting/auto/?q=191) and pulled the data on tornado warnings across the US from 2000-now. I then figured the median monthly tornado warning count for 2000-2017 (I didn't use average because things like Hurricanes would really skew the results) and compared it to 2018 so far:
We all know this has been a slow year, but what shocked me was just how bad May 2018 really was. At least the rest (except March 2018) was close to the slope of the median. Aug 2018 isn't over yet, so my graph is a little misleading, but if it doesn't pick up 2018 is moving even further away from the median.
We all know this has been a slow year, but what shocked me was just how bad May 2018 really was. At least the rest (except March 2018) was close to the slope of the median. Aug 2018 isn't over yet, so my graph is a little misleading, but if it doesn't pick up 2018 is moving even further away from the median.
Devin Pitts
EF2
What a year this has been...
Brett Roberts
EF5
Medium range guidance points to an extended period of western CONUS troughing coming up centered on next weekend (10/6-10/7). Initial shortwaves embedded in SW flow could be worth watching late this work week (10/4-10/5) before a more amplified trough looks to take residence over the intermountain West after that. No point delving into details yet, but without any frontal intrusions expected between now and then, moisture should at least be seasonably decent over the Plains warm sector.
The beginning of October has produced several high-end Plains chase events over the past 20 years, so it's always nice to see a favorable large-scale pattern heading into this period. It's also true that your margin for error tends to be lower than May and June, especially with warmer mid-level temperatures often limiting buoyancy even when you've got respectable low-level moisture (e.g., mid 60s dews). One common failure mode I've seen during the second season is influence from tropical cyclones, and at least for now, that doesn't look to be a factor next week.
The beginning of October has produced several high-end Plains chase events over the past 20 years, so it's always nice to see a favorable large-scale pattern heading into this period. It's also true that your margin for error tends to be lower than May and June, especially with warmer mid-level temperatures often limiting buoyancy even when you've got respectable low-level moisture (e.g., mid 60s dews). One common failure mode I've seen during the second season is influence from tropical cyclones, and at least for now, that doesn't look to be a factor next week.
It certainly looks exciting to see a big huge longwave trough like that setup over the western US. Too bad it couldn't be May instead of October, though.
However, from what I've seen, the flow in the mid-upper troposphere is going to be too meridional to get a solid widespread severe weather event from it. We're just not getting the differential temperature advection needed to setup steep lapse rates to get the instability, which seems to be the only real ingredient missing from this setup. Looks more like a persistent heavy rain event lasting a few days over the Plains. WPC largely agrees with the heavy rain outlook.
Interestingly enough, many recent GFS runs want to bring yet another eastern Pacific hurricane ashore in the Baja California and up into the southwest US, which should set the stage for yet another round of heavy rain.
However, from what I've seen, the flow in the mid-upper troposphere is going to be too meridional to get a solid widespread severe weather event from it. We're just not getting the differential temperature advection needed to setup steep lapse rates to get the instability, which seems to be the only real ingredient missing from this setup. Looks more like a persistent heavy rain event lasting a few days over the Plains. WPC largely agrees with the heavy rain outlook.
Interestingly enough, many recent GFS runs want to bring yet another eastern Pacific hurricane ashore in the Baja California and up into the southwest US, which should set the stage for yet another round of heavy rain.
Randy Jennings
Supporter
- Joined
- May 18, 2013
- Messages
- 855
Thanks to Hurricanes Florence and Michael, the Sept 2018 and Oct 2018 tornado warning counts surpassed the median monthly counts for this century, but we are still on track to have the third lowest tornado warning count this century .
See my earlier post in this thread if you would like to know how I pulled this data and made the graph. Here is the raw counts:
See my earlier post in this thread if you would like to know how I pulled this data and made the graph. Here is the raw counts:
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