Thursday, May 2, 2024

Warm and Unsettled Through Next Week, Rain Chances Low Overall

FORECAST:

Friday (High 81, Low 65): Partly to mostly cloudy with scattered showers and thunderstorms possible throughout the day. Rain showers will become more numerous at night. 

Saturday (High 80, Low 62): Partly to mostly cloudy with scattered showers and thunderstorms still possible. May the Fourth be with you . . . 

Sunday (High 83, Low 62): Partly cloudy. Widely scattered showers and thunderstorms are possible. 

EXTENDED OUTLOOK:

Monday (High 84, Low 63): Partly cloudy with a 30% chance of showers/thunderstorms. 

Tuesday (High 85, Low 63): Partly cloudy with a 20% chance of showers/thunderstorms. 

Wednesday (High 86, Low 65): Partly cloudy with a 20% chance of showers/thunderstorms.

Thursday (High 87, Low 66): Partly cloudy with a 30% chance of showers/thunderstorms.

READING TEA LEAVES:

Friday May 10th (High 85, Low 66): Partly to mostly cloudy with a 40% chance of showers/thunderstorms. 

Saturday May 11th (High 82, Low 64): Partly cloudy with a 20% chance of showers/thunderstorms.

Sunday May 12th (High 80, Low 58): Mostly sunny. 

PRONÓSTICO:

Viernes (Máxima 81, Mínima 65): Parcialmente a mayormente nublado con posibles lluvias y tormentas eléctricas dispersas durante el día. Las lluvias serán más numerosas por la noche.

Sábado (Máxima 80, Mínima 62): Parcialmente a mayormente nublado. Aún son posibles lluvias y tormentas dispersas.

Cinco de Mayo (Máxima 83, Mínima 62): Parcialmente nublado. Es posible que se produzcan lluvias y tormentas eléctricas ampliamente dispersas.

PERSPECTIVA EXTENDIDA:

Lunes (Máxima 84, Mínima 63): Parcialmente nublado con un 30 % de probabilidad de lluvias/tormentas eléctricas.

Martes (Máxima 85, Mínima 63): Parcialmente nublado con un 20 % de probabilidad de lluvias/tormentas eléctricas.

Miércoles (Máxima 86, Mínima 65): Parcialmente nublado con un 20 % de probabilidad de lluvias/tormentas eléctricas.

Jueves (Máxima 87, Mínima 66): Parcialmente nublado con un 30% de probabilidad de lluvias/tormentas eléctricas.

LEYENDO LAS HOJAS DE TÉ:

Viernes 10 de Mayo (Máxima 85, Mínima 66): Parcialmente a mayormente nublado con un 40% de probabilidad de lluvias/tormentas eléctricas.

Sábado 11 de Mayo (Máxima 82, Mínima 64): Parcialmente nublado con un 20 % de probabilidad de lluvias/tormentas eléctricas.

Domingo 12 de Mayo (Máxima 80, Mínima 58): Mayormente soleado.

NOTES:

They've had numerous rounds of severe weather in the Midwest and Plains lately. The National Weather Service in Omaha has put together the best page on it I've seen so far

Some of the stuff in the Plains got pretty weird

Tomorrow is the anniversary of a historic tornado outbreak, but not for the Southeast, for our neighbors out in the Plains. They remember May 3, 1999 well. 

DISCUSSION:







It was a mostly sunny day in the Tennessee Valley, though clouds have been increasing as we get into the evening hours. We've had a breeze at times, and winds have been variable, but generally out of the South/Southeast. The High in Cullman was 84 with a Low of 55. Jasper saw a High of 88 with a Low of 55. And Haleyville's observations are missing for much of today, but the highest temperature for the day we do have on record is 81, and the Low appears to have been 56 this morning. Huntsville had a High of 87 and Low of 62. And I just have to say, it is starting to feel like summer, even if it's about a month early. Since when did the seasons obey the calendar anyway? Nashville is another site that has several hours missing from the observations today, but it looks like a High of about 84 and Low of about 63. Kind of hard to tell with some hours of the day missing, but we'll make do with what we've got. 

The main weather story around here is going to be that ridge of high pressure giving way to several shortwave troughs out ahead of the cold front that has been terrorizing the Plains. 



The GFS shows a pretty good dump of rain from this shortwave tomorrow. 


The NAM is a little more conservative. So that's business as usual. I'm going to cap the rain chances off at 40% tomorrow, which means scattered rain across the map, about a 4 out of 10 chance of any one spot getting a shower or thunderstorm. We could see scattered showers tonight too. As far as the rain chances going above 50% into the "likely" category, think that holds off until tomorrow night. Tonight's Low should be near 65, tomorrow's High about 80 or so. 



More model madness as we get into Saturday, and I don't think the GFS has the best handle on this particular setup. Even it is backing away from the idea of a major washout. If we see that this weekend, it should be Friday night into Saturday morning. But the majority of the day Saturday does not look that way. 


The NAM shows a lot more clearing by early afternoon. 



And if you take a look at the ECMWF, it doesn't show a total washout day either, but does focus the rain more up in Tennessee than in Alabama counties. 

This pattern is a little more summerlike than springlike, as we are making that transition already this year. The computer models, especially the global ones, usually don't do a great job handling that type of convection. That's why you need human forecasters who know the area and how storms behave, at least a little better than the forecast models do. 

As of right now I'm going to maintain a 40% chance of rain for Saturday as well. But will review these several days of unsettled weather as a whole after going over them one at a time. Fine tune the probabilities of precipitation. 

Should see a High of 80 or so, Low of 60 or so. 



Then we'll get another wave Sunday and Sunday night. This is one of those rare times when you don't have to wait for the extended outlook to have a lot of uncertainty. From glancing over things, already I think the extended here may be a higher-confidence forecast than the next few days. I'm inclined to cut the rain chance back to 30% for Sunday during the day, but then during the evening and night bump it back to at least 40-50%. Should still have a High in the lower 80's and Low in the lower 60's. 



Then on Monday a 30% chance of rain is the most I'd feel right about keeping in the forecast, might scale it back to 20% by then. Looks like the better moisture will be up in Tennessee and Kentucky and up into the rest of the Ohio River Valley. The High may make it into the mid-80's, the Low should stay in the lower 60's. 



The rain chances become minimal by Tuesday as high pressure starts to build back over the Southeast again. Should probably keep a 20% chance in there, a lot like on a typical summer's day. High should be in the mid-80's again, Low in lower 60's. 

A lot of the forecasts I'm seeing are overdoing the rain chances though, so I may take rain chances out just to go against the grain. If this was a summer day, I might opt not to include even a 20% chance here. 



Then Wednesday a 20% chance of rain does look justified, but it is a close call. This pattern is awfully summerlike and unsettled. The rain chances are not that great on any day of this forecast period. We could actually edge into the upper 80's for the High, confident in mid-60's for the Low. 

Notice our upper-level wind flow has turned back to the Southwest there on the 500-millibar forecast map from the GFS. 



And it looks to stay unsettled even next Thursday. So will keep the 20% chance of rain in there. Probably looking at upper 80's for the High though. 



And the general idea is on the table that we could see a frontal passage this next weekend. So that would bring us an uptick in showers/thunderstorms for a day or two, then a shot of milder, drier air. So we'd see Highs near 80 again and Lows dropping to about 60 or upper 50's. The GFS and ECMWF disagree on the exact timing of the frontal passage. Imagine that. 

Since the weather does not look high-impact for this forecast period, I guess I'll throw caution to the wind and do a 10-day-outlook this time. Definitely rain chances for Friday but maybe some for Saturday too. Cut them out for Sunday which will be Mother's Day actually. I hate sappy holidays like that. 

Or maybe I'm just saying so and wondering if anyone will notice. 


Rainfall totals for this forecast period should average an inch or less. 




Some of our neighbors out west have had a mighty rocky time of it lately with severe thunderstorms, some of which have produced tornadoes, and some of those particularly damaging tornadoes. 

One interesting thing, a tornado that hit Hollister, Oklahoma had the kind of crazy radar signatures that had just about everyone on the social networks raving that it must be an F-5 taking everything in its path. And then when they surveyed things, the National Weather Service in Norman only found F-1 level damage. It passed over an unpopulated area, but I did see a structure it passed over. Looked like a house that sustained a fair amount of damage, at least to the roofing. If it was weaker than a sturdy house, it should have been destroyed even more easily. If this was really worthy of being rated an E/F-5. So I don't think it is always as simple as whether or not it hits a populated area. Radar signatures can be deceiving. And I remember a professor from UAH predicting this years ago (Tim Coleman), saying that when Doppler Radar came out, they caught a lot more tornadoes, but the false alarm rate also went way up. And he was afraid with dual-pol radar, the same thing would happen, where a lot of tornadoes would look really alarming on radar, but not always be quite as bad on the ground as they looked by what the radar beams can see. I'm paraphrasing him from memory, and I haven't seen any kind of comprehensive discussion of the Hollister storm. Maybe it is too early for one. I do wish instead of these fragmented arguments about what a storm should be rated, or if the F-scale needs yet another enhancement, I saw an occasional link to where somebody took some time and wrote a thoughtful post about, for example, the Hollister tornado. 



Here is the house damage I was thinking about, that I saw while scrolling earlier. If this tornado had been as bad as it looked on radar, there is no way that house would have survived with only E/F-1 damage. We'll see when there has been more time to analyze the event. Maybe there was a brief period it was unusually strong, that caused those scary radar signatures. But you really have to be careful. I remember a tornado that came through West Central Alabama a few years ago, that had such a strong TDS (Tornado Debris Signature) that it was called a "violent" tornado on the air, but then ended up being rated F-2 at its strongest point.

And here's a look at the scary radar presentation from yesterday in Oklahoma. As great as these tools are, they are not infallible. This tornado might have done more damage if it had hit a more populated area, but the one house I've seen that it hit survived remarkably well for a tornado that looked that bad on radar. Who's to say that this wouldn't be another one that would have proved less than catastrophic even if it did hit a populated area? 

The reality out of this multi-day severe weather outbreak in the Plains and Midwest has been bad enough. The death toll has been lower than would be expected with such a tornado outbreak, but there was still some loss of life. 

I'm not going to jump on the hype train when I take the time to post a blog. A tornado can look like it'll make history on radar and then only do enough damage to be rated an E/F1-F2. I think that's what happened just East of Hollister. If it did reach the intensity we saw on radar, it must have been briefly, while it was out over open country. Even then though, there are damage indicators like ground scarring and debarking of trees that would give a clue to rate the tornado higher. So I'm not quite sure what went on there yet. Just something to talk about. 

And just for fun, will post the text of that survey in bold, along with the survey for the anticyclonic tornado that also happened last night in Oklahoma. As Rick Smith said, it was some stuff you don't see every day. 

.East of Hollister...


Rating:                 EF1

Estimated Peak Wind:    105 to 110 mph

Path Length /statute/:  6 miles

Path Width /maximum/:   1200 yards

Fatalities:             0

Injuries:               0


Start Date:             04/30/2024

Start Time:             09:32 PM CDT

Start Location:         2 ENE Hollister / Tillman County / OK

Start Lat/Lon:          34.36 / -98.83


End Date:               04/30/2024

End Time:               10:12 PM CDT

End Location:           5 ENE Hollister / Tillman County / OK

End Lat/Lon:            34.38 / -98.80


Survey Summary:

This tornado produced EF1 damage, although it was likely much

stronger. The tornado was first observed by a storm chaser around

932 pm. The tornado moved east through very rural areas producing

occasional power pole, tree and outbuilding damage. The tornado

turned northeast and damaged two farmsteads about 6 miles east-

northeast of Hollister. The tornado then turned west-northwest

and dissipated about two miles northeast of where it began.


.Anticyclonic Tornado Northwest of Grandfield...


Rating:                 EF1

Estimated Peak Wind:    95 to 100 mph

Path Length /statute/:  2.1 miles

Path Width /maximum/:   To be determined

Fatalities:             0

Injuries:               0


Start Date:             04/30/2024

Start Time:             10:18 PM CDT

Start Location:         2 SSE Loveland / Tillman County / OK

Start Lat/Lon:          34.27 / -98.75


End Date:               04/30/2024

End Time:               10:32 PM CDT

End Location:           2 WNW Grandfield / Tillman County / OK

End Lat/Lon:            34.25 / -98.73


Survey Summary:

Estimated path of anticyclonic tornado. Some tree damage was

observed with this tornado, and investigation continues which

may further define the path.


&&

 

A tornado 1200 yards wide is still more than a half-mile. So if this had hit more structures, maybe it would have been rated E/F2-F3. It seems like if it was stronger than that, the structures it did hit would have been destroyed or at least more heavily damaged, and that you'd see trees debarked like you typically see with the E/F4-F5 tornadoes. 

If I'm going to read all the yacking about it on Twitter/X, then I'm going to try to bring some logic to the conversation too. 

It does strike me as an odd situation, since it did hit a few structures, which only sustained enough damage to get it an F-1 rating. It was almost an (E) F-2 by the estimated wind speeds (105-100 mph). Based on those crazy radar signatures, I would expect a random house it hit to be levelled. But that is not what happened. 



It really did look awful on radar. I can see why people got really excited by it. 




They actually have another severe weather risk today/tonight, though it's mainly in Texas this time. 

And again tomorrow, Texas is the main focus, though something isolated could develop elsewhere in the Plains. 

Then on Saturday, the chances are marginal for anything severe even in Texas. 


Monday might pose another risk for organized severe weather in the Plains. 

Technically our severe weather season is not over until the end of May. But this pattern favors keeping the severe stuff to our North and West for the foreseeable future. The waters are awfully warm this year, so we'll have to watch the tropics from June to about November. Around here, I guess that beats just complaining about the heat. 

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