nrgjeff

Rare and exciting when the Atmosphere actually looks like the textbook. Neat stuff!

Storm Prediction Center introduces 15% for Saturday. Yeah after about 4-5 waves tugging on Gulf Moisture, it could indeed be far enough north. Best dynamics may go over Midwest, but enough southern stream energy lingers over Dixie if the moisture is here. Looking ahead deeper into March, ECMWF weeklies (verbatim) tee up severe weather. Trough returns to the West with SER. We'll see..

Duds are not too discouraging this early in the season. Same week in March and I'm going off, lol! That said, I will be ready for day-of decisions if I'm not hammered at work. Next weekend would be convenient.

I have a feeling 2019 will be an active year. Atmosphere often tips its hand early. See if we can get a few more early days. Plains may end up being the most active, so I'm not mongering for Dixie. Storm track has been quite active. Low press likes to track over the Ozarks this winter. Shift that north later in spring for Central Plains action. Mid-South portion of Dixie could be seasonably active early while lows are still going through the Ozarks.

Looks like two boundaries, both in their CWA. Synoptic is north of MEM. Another sits south of MEM. Could be a fun afternoon. Still I agree with their reasons limiting the event. Probably just isolated gusty winds. Heavy rain is the other consideration.

Arkansas remains the prime areas IMHO. Obviously it is not chasable so I'm relaxing here in Chatty. Shear will be there. Instability depends on convective evolution. Few CAMs have cyclical supercells in western Arkansas, marching across the state. Others, like the NAM, have too much other stuff in the Delta. The latter solution cuts off the cells up on the boundary intersections in western Ark. Arctic air is another factor. If that air is right up on the boundaries, cancel supercells. What a mess. Must be February!

An ongoing severe wx thread is buried somewhere. Feel free to bump it. One can also start an event thread should the need arise. On the winter side, if that West trough settles in a little more Central and forecast it could get interesting. Otherwise, yeah track severe.

Sounds good to me. I'd rather travel to the Plains than try to chase Dixie. Euro monthlies have a chaser friendly look to May. BN heights Southwest and AN heights Great Lakes. Give me more of that southwest flow. QPF also hints dry line fires west of I-35 which is the prime chase terrain. Yes please! As for ENSO, one could infer the TNI is trying to set up right between Nino 1+2 and 4. However it's evolving from weak El Nino. Bullish TNI is usually from La Nina transition. We'll see though. PDO is also trying for a slightly better look.

Forget the litter box.. For southeast Tennessee, this winter is when the cat misses with the turd and sprays pee all over the room.

Fortunately I can't see either of them. 2012 was blowtorch all winter, not valid this year. 1988 was the first really infamous SER drought, quite unlikely this year. Chiefs got to the AFCC (see my prior post). Time for renewed optimism in severe wx too! UPDATE: Yeah action west of I-35 would be great. See below.

Welcome everyone to Severe Weather! In contrast to snow, I find severe wx easier to enjoy from afar. Snow you kind of have to be there. Severe can be tracked by watching radar and following chasers on Twitter or TWC. Scanner Radio is a good app to follow EM radio traffic. Now, here is how I forecast severe. Extended: I keep it simple. Look for instability and wind shear. Need temps and dews at appropriate levels (70+/60+). CAPE forecasts are available, but I like to look at temps/dews myself. Wind shear I want strong winds at 500/200 mb, preferably from the west/southwest, not really straight south. I need a strong LLJ at 850 mb, preferably south, not west. Need veering with height. Within 5 days: Starting looking at more levels in detail. Everything above plus 700 mb and 925 mb. Through all levels need to avoid veer-back-veer. Check forecast soundings. Look for a pretty hodograph forecast (long gentle hook or sickle* shape, no silly kinks). Also temperature profiles on the soundings. Might check 850/700 mb temps, esp 3-4 days out. Thickness can also shed light on cap, no cap, just right cap. 925 mb hints at lowest level wind shear. Looking for cold front, warm front, dry line placement. Do instability, wind shear and surface triggers line up? Within 2 days: Fine tune forecast. All of the above plus timing issues. Timing is everything. Also look for any rain interactions. Fine line between morning rain bullish outflow boundaries, and midday rain stabilizing things. Models offer more helicity and energy-helicity forecasts this time period. Still I check for wind shear myself by drilling down all the upper level charts. Same day I follow visible satellite trends and surface chart. * No hammers though. We're not commies! This post may be amended for a few days if I think of more stuff. Hopefully real-life will jog my memory, lol!

Regrettably the Euro has managed to kill the juxtaposition of instability and shear. One of many reasons I'd like to forget any 12Z runs ever happened. Oh well!

12Z Euro lights up Dixie Alley in less than a week. However it is just one run. If the advancing front is slow enough out of the Midwest, two waves are forecast in three days. Such a solution would give more time for moisture return ahead of the second one.

Hopefully the ECMWF finds some thunderstorms in the 6-10 day. I'm ready for severe wx season. Reality is a trough hanging out west for multiple days allows moisture return into Dixie. Bring out a shortwave, and boom! Once I take down the Christmas tree, severe wx season can start anytime.

Cheeseland is passionate about severe wx and welcome here. Note the smiley face. I was going to take down my Christmas tree MLK Day weekend. If it is still up Monday, I will also use the shutdown reasoning as a later deadline. Wetumka tornado is an unfortunate verification of the 5%. These things can happen with a dynamically forced line marginal instability. Most importantly sky will clear out in time for the lunar eclipse tonight! High clouds could come into the northwest quad of our Region but not a show stopper.

Saturday showcase includes thunderstorms. CAMs mostly line out the activity which is not a surprise. Line will be very forced with limited instability. Kinematics and wind field looks excellent. Rain and clouds should keep it a little cool though. If instability somehow verifies higher it might be worth a second look on a weekend. Otherwise the real show is the ESPN Saturday Showcase; lots and lots of good college basketball. Sunday evening should clear out in time for the lunar eclipse. Yes, back to fair weather chasing.

NAM raised snow amounts like it is playing catch up to the Euro. NAM still relatively lower amounts might be due to surface and ground temps. However right after Thanksgiving the Euro scored a big coup even inside the time frame where the NAM should prevail. Might have happened one other time, but I remember Thanksgiving more thanks to visiting KCMO. Looks like a big I-70 special from KC to STL. Everyone enjoy! And the Chiefs better win!! PS. Climate blog looks solid. More TV Mets should do that.

No high risk. 975 tornadoes. I know that's less than 2018 prelim. We lack the baroclinicity in the current climate regime. If the cold verifies in February, those lingering effects of the SSW may fade by April. Everything a month ahead of last year? Get Dixie going in April. Plains craps out again in May. If the Chiefs win a playoff game I may be more optimistic across the board.

ECMWF and CFS monthlies both show April better than May. Fits El Nino climo. So I will look early and often in Dixie. Plains may be yet another crap May. No EML in the Plains means slop. If I'm going to chase slop, Dixie is a whole lot closer!

Bye bye severe wx season.

I promised some TROWAL explanation on the Dec 8-10 storm thread. Trough of Warm air Aloft stands for TROWAL. It often happens behind an occluded front/system. One can easily find cross section diagrams of an occlusion with a web search. However these two images show what I'm looking for when forecasting. Here it is on satellite, an old storm over the Great Plains. Bring it baby! On an 850 mb chart (also 925/700) one can see WAA from the north, vs usual southeast. Average comma head is associated with the cold conveyor belt, and some split off the warm conveyor belt. Usually the better precip is off the more robust warm conveyor belt. (Conveyor belts are also an easy web search.) TROWAL feature is interesting because it can amp up the normally secondary comma head. WAA is notable into the comma head. Example below is ECMWF forecast valid Monday. Most of the snow has fallen, but the 850 mb chart shows it better at the end of the event. Note WAA from north to south. Favors I-40 north. CAA south of I-40 shuts off precip.

The question is age old in the South. True that textbook HP is fair weather. However we do need a supply of low level CAA for snow. At the same time we need WAA aloft to create the precip. It is a delicate dance anywhere. In the South it's a delicate dance on a tight rope that often results in a fall, lol! Sometimes 500 mb offers the answer. PVA just south, with surface low farther south (a good tilt) and cold air in place, usually good. PVA at latitude / overhead, risk of ice if cold air in place. PVA north, probably rain. EDIT for below: I did not realize Knoxville climo has shifted so much. Yuck!

I remain bullish, slightly cold, for winter. Current El Nino is moderate, but it's only a snapshot. Two of the last three weak/mdt El Ninos briefly spiked strong before trailing off. Those were 2002-03 and 2009-10 both cold winters. Most recent weak-mdt El Nino 2014-15 stayed below moderate; it was also a cold winter. November verified cold eastern half to 2/3 of USA. It looks similar to 2014, but that year was colder to the East Coast. This year remember the cutter systems? Snow fans of course want that to end. Anyway 2014-15 was the last snow thump in Chattanooga. I'm quite comfortable with ENSO at the moment.

Saturday afternoon events Middle Tennessee and points west might luck out if rain can get out before events start. John I hope the Christmas parade works out. I've lost interest in thunderstorms; so, I will hope for fair weather. Appears severe starts Friday in the Ozarks; even more LOL with early sunset. Saturday dynamics seem to drift north of instability; so, rain here should be fairly benign. Rain timing should be in the morning many areas, including Mid-Tenn. Might still be afternoon showers in East Tenn. GFS is slower (wetter for Mid-Tenn) but ECMWF and NAM both push out the rain in time.

ECMWF remains consistent with a chance of severe weather Friday night and Saturday from the Mid-South to the eastern Tennessee Valley. Many details need to work out from instability to short-wave timing. Looks like multiple waves, which can giveth or taketh away. I infer from the text SPC really wants to outlook Saturday, but I agree it would be hard to place the 15%. Too early to worry for those who dislike severe. Just those of us who like it, we want to track it. Honestly, at Day 6, it is not any more likely than snow in Dixie, lol! PS.. I will comment on December after the ECMWF weeklies update. Maybe I should have stayed with Carver for Dec. Did I go cold too fast?