nrgjeff

For all my whining in the weather threads, both Tennessee and Kansas won this weekend. Football season always presents new possibilities!

The only hope for winter is a ton of aerosols. Oceans can't absorb any more heat; therefore, charts are red all over. SSTs, surface temps, Arctic source regions are all red. Even SSW is defanged with a mild source region. Maybe after several years of low solar and/or major aerosol injection. Always possible I'm just being negative though. At least Tennessee and Kansas both won their football games, and the Chiefs whipped the Raiders out there! Hanged out with climo scientists a NWAS19, but I think here is where I hand it off to the Climate Change Forum.

Chattanooga hit 100 degrees (dews 72+) before the thunderstorms Tuesday. Normally dews dip into the 60s at 100 deg, but not this time. Glad that's over. Saw Nashville storm anvils but those cells did not make it into Chatty. Lightning and thunder started slowly since it was new development for Chatty. By evening the light and thunder show improved.

Oceans appear to have trouble absorbing and sinking heat. Looks like another mild winter. That's a lot for the solar min overcome. Even with massive blocking, warm Arctic / weak source region = meh.

The SST forecast looks too cold globally. Been a long time since that much BN SST were observed. Verbatim that SST forecast correlates with the 500 mb forecast; but, I don't believe either one. I could see slight BN SST tropical Pac. However I don't believe the IO or mid-latitude projections. North Pac has a shot at verifying though. With Nina that's variable, and many headaches forecasting week by week in winter.

Then SPC drops that 'watch not expected' mesoscale discussion. Went about like tropical depression 3. Monday was kind of a choke day on those two fronts, pun intended at the mid-latitudes. However post-frontal paradise, mild temps and low humidity. will verify nicely!

Today Monday July 22, National Weather Service is hitting flooding hard along and north of the I-40 and I-81 corridors. Good call considering all of Today Monday July 22, National Weather Service is hitting flooding hard along and north of the I-40 and I-81 corridors. Good call considering Observation posts from @John1122 up that way. Ground won't hold anything before flooding quickly. Locally 2 inches of rain could fall quickly, with isolated 3 inch bursts. Hope we can all avoid flash flooding. Might be worth sharing NWS posts on regular social media too. It will still be hit or miss. Hopefully more miss.

Should be a Friday night gem. Hope it rolls down I-24 all the way to Chattanooga. Enhanced is probably the right call. We lack the ingredients for Moderate. No 500 mb short-wave or height falls helps avoid the D-word. In fact 500 mb is neutral to slightly rising. Still we have all kinds of WAA at 700/850 mb from the southwest to feed the beast. How about those MEM surface obs? Yeah the scientific word for that is gross, lol! It's evidence of great instability. However it's capped until the MCS arrives. Another MCS is forecast Saturday, but I'm thinking this first one will be the best. Pure undisturbed airmass is ready to rumble.

North Chattanooga and especially Hixson got it this morning (Thursday). Not bad for a sunrise special. Friday and Saturday more MCSs may move through Tennessee and our Regional forum. Reservoir of impressive instability looks to camp out in the region along and south of outflow boundaries. WAA is forecast at 850/700 mb which would help maintain convection. Don't see any robust 500 mb waves so it should not get too crazy. In fact 500 mb heights are neutral or slightly rising both days. Still it is the season for southeast propagating MCSs.

Wed. June 19: Northern half of the MD has a watch out. Since the MD has more forecast information than the watch, and covers areas that could see storms later, I'll post the MD. Mesoscale Discussion 1134 Mesoscale Discussion 1134 NWS Storm Prediction Center Norman OK 1235 PM CDT Wed Jun 19 2019 Areas affected...Parts of southeast Missouri...northeast Arkansas...western Tennessee and Kentucky...and adjacent portions of southern Indiana Concerning...Severe potential...Watch possible Valid 191735Z - 191930Z Probability of Watch Issuance...60 percent SUMMARY...A further increase in thunderstorm intensity and organization appears possible through 3-5 PM CDT. This may be accompanied by an increase in severe weather potential which could require a watch within the next couple of hours. DISCUSSION...An ongoing increase in thunderstorm development appears to be associated with a secondary band of large-scale ascent pivoting from the Ozark Plateau into the lower Ohio Valley, within the leading edge of larger-scale low-amplitude mid/upper troughing. As this is occurring, inhibition for seasonably moist boundary layer parcels continues to weaken in response to insolation, with mixed-layer CAPE approaching 2000 J/kg. At the same time, westerly deep-layer ambient mean fields and vertical shear are also beginning to increase, as a 40-50 kt 500 mb speed maximum gradually propagates eastward from the south central Plains. Into mid to late afternoon, the environment across western into central (middle) Kentucky and Tennessee, and surrounding portions of the lower Ohio Valley, may become conducive to increasingly organized convection. It is possible that this may include a few supercell structures, then perhaps one or two upscale growing clusters of storms accompanied primarily by a risk for potentially damaging wind gusts. ..Kerr/Guyer.. 06/19/2019

Yes a real short-wave is forecast midweek. Today (Monday) the Marginal held with modest flow aloft. Looks like little more flow is forecast Wednesday. NWP is mixed on how much turning. At least some bows and perhaps good shelfies should be on-deck for Wednesday.

I put my chips on 3-4 chase days next week. However I don't see any big outbreaks. It is typical June chasing, but could be quality chasing. First half of the week starts with the Upper Midwest. Tuesday the ECWMF shows a true system in chasable terrain of the Northern Plains. Wednesday goes into the MN/WI forest, but maybe something can get going down in Iowa. End of next week moderate flow is forecast to remain in the Plains (almost unseasonable NE/northern KS). LLJ is forecast to respond. Might get a couple days out of that if cap is not thermonuclear. Placement is uncertain attm. So I propose we have two pairs of possible chase days. Take out one for terrain and/or bust. Nets 3 chase days?

Alex, I'll take outflow boundary for $400. Actually Knoxville does look at bit stable. Chattanooga might at least get a good Marginal thunderstorm later. Modest flow is aloft at SPC notes. LLJ may be a little veered off. 850 mb is forecast to veer off. 925 mb is trying but still SSW, and the surface will be from the SSE. Moisture might be the main question. Did I just write that in June? Honestly, much as I like storms, I love low humidity in summer. Every day with low humidity is one less of (root canal without Novocaine) misery.

ECMWF still points to a little more activity starting on Friday, and through the end of the model run. ECMWF Para/Beta (2nd deterministic) looks even a little better. The latter keeps westerly flow instead of that northerly junk end of EC Op. Both have modest LLJ response most days starting Friday. Moisture quality is slow to return, but by Friday is enough for central/high Plains. Moisture gradually improves each day, esp on the EC Para. Given what happened Saturday, Colorado and Goodland, chasers may be able to seek meso-scale events again. Good luck to those June-ing!

Crap I missed it! Friday featured a notable LLJ over the area with modest WSW flow at 500 mb. I'm not surprised to see reports of a small tornado and landspout. However I'm quickly losing interest in severe. I have fallen hard in love with the East trough on-deck, and associated 50s dewpoints.

Thursday we got a Slight going in Mississippi. That's more Deep South than our Tennessee Valley region so I will opine here. Surface low in Louisiana will track through southern/central Mississippi toward the Mississippi/Alabama border by 00Z. This little guy is what ginned up in southeast Texas after the Gulf disturbance came onshore. It should provide good low level shear and backed surface winds. At the same time a mid-latitude upper low sweeps in, with WSW winds aloft. That is key, vs unidirectional. Questionable ingredient is instability. LLJ prog is most robust MS/AL border toward 00Z. Friday the small surface low ejects off into the Carolinas, but the LLJ is forecast to veer off and/or weaken. Upper to mid-level wind remains WSW but weaker than on Thursday. Different short-wave timing (still 36+ hr out) could change things upstairs. Tis the season to watch those Carolina west-east boundaries, and one is forecast on Friday. In fact the sfc low is forecast to ride it.

Looking at my first post this thread, I was one cynical MF last winter. Ironic we actually chased on that high risk day. It was a mess though. Our best day was two days later, documenting a couple northeast OK tornadoes in somewhat less awful terrain. By late winter I had turned more optimistic. The west trough would not quit. It was there in December and back with a vengeance in Feb. Kept going for Dixie in March. Even as late April calmed down one would not be surprised if the west trough returned in May. Oh I'd say it returned - right at peak climo!

Atmosphere is so strange in recent years. TNI was ass-backwards for severe in late May; yet, outbreak city.

May 30: If that cell on the Upper Plateau does anything I'm going to slam my head through a computer monitor. We've all seen how inflow is better at elevation. However everything is sooo veered off today. Crazy cell has weak rotation at 12:45 Central Time. Deep breaths. I already saw amazing stuff in the Plains last week...

Sunday and Monday looks like plenty of CAPE. What about turning with height? What makes the composite parameter soar? Is it CAPE without good turning? Is it turning on a warm front with cloudy stable stratoform rain? Obviously the former is much more likely than the latter this case (CAPE chart previous page); however, the latter happens often early season. For legit severe we need both juxtaposed. Is turning with height forecast? Let's take a look at the Central Plains both Sunday and Monday on the ECMWF. At 250 mb winds are seasonable (modest but not dead) from the WSW. At 500 mb a short-wave passes Sunday but winds weaken Monday. Both days 500 mb is WNW. Despite AN heights, 700 mb is not too hot. 700 mb wind is also from the WNW. Sunday and Monday 850 mb is straight south (good) but modest. Surface and 925 mb are from the southeast. So, we have great turning with height from surface to 700 mb. Winds are not too strong however. Pretty sure not tornado outbreak. Actually this is what late season chasers seek. Keep it subtle. Avoid crowds. Maybe find an isolated gem. Veer back is forecast from 500 mb to 250 mb; however, that high up is not a deal killer. It's especially OK late-season vs early. I've already taken my chase trip and found what we sought last week. I think the weather pattern looks good for those out there late-season and/or still looking for their tornado; but, it is not good enough to justify another trip after seeing a two-cycle tornado event last week. Who knows? Maybe a CO/WY gem could happen in upslope flow. Best to check all constant pressure level forecast charts in the extended. Forecast soundings are worthless past 36 hours, esp if convection contaminates. Constant pressure level forecasts are OK a few days out to discern forecast turning with height (or not). At the very least, check both CAPE and Helicity forecasts separately for juxtaposition. The latter forecasts turning with height, but even it can mislead if speed overwhelms no turning. Composite parameters are not that useful. So, drilling down (or up) the constant pressure charts is best.

Chasers rejoice; the GL trough is even weaker and less important now! Friday it now appears ample moisture will be up on the dry line. Low level winds are backed a bit. Uppers are SSW to SW, and probably enough turning with height. Saturday remains TBD based on mesoscale factors. Upper winds get a little meridional in the Plains. However if an outflow gets down to Texas, winds show more turning upstairs on the ECMWF. I'm not sure whether to hope for that though. Texas tends to be messy. Sunday could be a break. Might need a rest and or reposition day. Monday through Wednesday I figure two more chase days. I doubt all 3, but who knows. Looks like another trough comes out Monday; placement is TBD between Iowa and Kansas. Tuesday or Wednesday looks like another. Models still sorting out which, and there is a slight chance all 3 days go.

Indeed SPC started with Friday (Sunday Day 4-8). Looks like they left Saturday for post-MCS meso-scale details. Friday could be more active up on the WF. I'm afraid dews are not high enough on the DL; but, anything can happen on the High Plains. More importantly, it appears we have reeled in the weeklies and ensembles into the Day 5-7 forecast. That's an accomplishment compared to the last few years. Remember the epic flip last year? A perfect pattern out weeks 3-4 turned into trash by week 2. Not this year! Complex signals add confidence to model forecasts. Pacific jet extension will set the table. Then a +AAO and -NAO combo this time of year actually helps keep a west trough and systems going through the Plains. NAO is not the same animal as back in April. +AAO helps avoid that awful GL trough no longer progged. Boundary layer moisture has improved the last few runs, not a surprise really. This weekend should be just the start of an active 7-10 day period, perhaps as long as two weeks. It's on!

Slight goes up the Mississippi Alabama line almost to Tenn. 2% strong! Just kidding. The Plains beckons in a week. Locally we do have outflow lifting through MS/AL. Thunderstorms are in progress from west Mississippi. Looks sloppy without any new development. However they are on or close to that boundary.

ECMWF comes out after the Day 2 from SPC. Evidence now supports a slight risk Saturday from North Alabama into North Georgia. NAM and Euro both have a lot of CAPE along and south of a lifting boundary. I thought the 12Z NAM was nuts showing a right mover there; other CAMs do not. Now.. Euro introduces a mesolow on the said boundary. Low level winds are veered off, and the upper levels are not robust. However it's May which is CAPE season. While the Day 2 update is still Marginal, I figure on waking up to Slight. No I'm not staying up, lol! Something to watch Saturday though.

The period from May 17/18-ish for 7-10 days looks very active in the Plains. This 500 mb chart forecast is accompanied by strengthening upper level jet stream from the WSW and LLJ response most days from the straight south. Tee. It. Up!