Topic: 2008 US tornado season discussion

[nzstorm]

I like the live weather cams.  I was looking at David Drummonds' a couple of days back and interesting to get the live view of a wall cloud.   

[nzstorm]

April is looking quite active.  Look at those digging long waves in the modelling.  I'm not sure about tomorrows set up though, maybe SW Oklahoma after dark.  Reed Timmer was on NZ National radio this afternoon live from Oklahoma and he said tomorrow was looking like a good tornado day for Oklahoma. He was talking about tornado chasing and his chase tour company.  Interesting guy.

[Harley Pearman]

Hello

I have been reading reports of a tornado hit on the city of Little Rock (Arkansas). A twister went through parts of the city's northern suburbs and planes were flipped at an airport (4/4/08). Not sure of its strength.

Last week, an Oklahoma City suburb in the city's northern suburbs was affected by an EF1 tornado causing some damage to homes but damage was not severe.

The interesting thing is, this is the third large urban centre / city in the United States that has suffered a tornado strike in the past four weeks which proves that tornadoes do hit large urban centres.

Another twister from the same storm system went through Benton in Arkansas inflicting significant damage on a mobile home park as well.


Harley Pearman

[Macca]

Hi all,

I usually get bored with our weather at this time of year and start forecasting in the US so here goes...

Looks like one of those marginal slight lack of moisture days coming up in the US although the cool upper level temps should assist instability somewhat.  My target is Magnum in SW Oklahoma- at least for initiation, with somewhere like Snyder, OK probably being my bet for tornado time.  This should put the virtual chaser (me) somewhere close to tail end charlie.  RUC is seemingly pushing a bit of a dryline bluge here and its further S than most are targetting as I think the moisture will be better down in SW Oklahoma than up along I-40.  Cap (which isn't that bad I don't think) should break at around 4pm and with shear like it is, storms should rapidly begin to rotate (25-30knts at 850mb from the SE to ESE and 40-50knts from the W at 500mb with the nose of a 100knt jet at 250mb kicking into SW Oklahoma late in the daylight hours).  My concern is that there may not be enough speed in the lower levels to get the job done with these storms but they should be at least very photogenic isolated supercells with a chance of a tornado or two close to dark as the LCL lowers and the LLJ picks up.  SPC only going for slight risk at the moment which is fair enough I think.

Macca

[Macca]

Not the worst forecast in the world given there was still another run of data to come out before an exact target would have to be determined.  Storm initiated 50km due S of Magnum and produced at least one brief multi vortex tornado 50km due S of Snyder (just over the Red River WNW of Wichita Falls).  2.75 inch hail was also reported although warnings were out for larger than baseball sized hail. 

Chasing the Red River region is tough as there are only limited opportunities to cross into Texas (or Oklahoma depending on which way one is coming from).  A few chasers waited up north in west central Oklahoma thinking that the Texas storm was not going to be the only one but alas…it was (well…it was last time I checked…in any case it would’ve been the only daylight show).  Hard to say what call I would’ve made but I’ve been burnt before by not heading S to a developing/developed storm so my gut tells me I would’ve probably pushed for a southward move. 

Happy enough with my forecast for now.  Looks like I might get another shot at it later this week too with more SVR weather forecast.

Macca

[nzstorm]

 By all accounts that was quite a nice supercell.  Look forward to your forecasting this season Macca, was interesting following it last year in the US.  Yes, I would have gone after the developing storm to the south.

[Macca]

Ok...as suspected, it looks like another round of severe weather on Thurdsay (just happens to be my birthday) for the US.  The last MAJOR outbreak they had on that day was back in 1979...the infamous red river outbreak which saw Witchita Falls and Vernon both take direct hits from F4 tornadoes.  57 lives were lost that day...lets not hope for a repeat.  Some good info here... http://www.srh.noaa.gov/oun/wxevents/19790410/

There is a moderate risk out already from the SPC which is no surprise given the set up.  A strong shortwave upper trough is forecast to dig into eastern New Mexico and the western Tx panhandle resulting in rapid moisture return to much of Texas and into southern Oklahoma during the evening/night hours as it rides the LLJ.  A surface low is expected to develop in the southern parts of the Tx panhandle with dryline extending southwards and warm front extending off to the ENE across northern Tx and into southern Oklahoma. 

Fairly significant warm air advection in the lower levels should limit the southward extent of development somewhat with the most likely outcome being storms forming on the triple point where the dryline and warm front intersect.  This area is typically highlighted by a dryline bulge. (however other storms are likely to develop along the dryline (not far S thou due to capping)).   GFS and WRF are slightly varying at the moment as to where this triple point/bulge will be come Thursday with GFS pushing it slightly further N and W than the WRF.  The position of this will move around a bit over the next 36 hours but true to form in prior years and as was evidenced today, sitting just NE of the bulge is a pretty good starting point. 

Shear is fairly nice with a 30knt LLJ (increasing to 40-45knts around dusk/after dark) with 50-60knt 500mb flow aloft (increasing to 65-70knts around dusk/after dark) and a 100+knt jet up the top at 200mb (increasing to 110-120knts around dusk/after dark).  When storms do develop (late), they should again rapidly become supercellular and shouldn't take long to become tornado warned (an hour from initiation which at this stage I would say would be around 4pm).  Storms will have a better chance of tornado'ing later in the day as the LLJ increases and the LCL lowers as a result of both more moisture coming in and also cooling of the lower layers. 

At this stage, I'd put myself at Aspermont, Tx but that said, its still 36hrs away so I'll refine tomorrow night if I get a chance. 

Macca

[Macca]

Ok...time for an update.  Haven't yet looked at SPC's outlook but I'm suspecting they may move the risk area further S than initially anticipated.  If I was in Aspermont, Tx now I'd be wanting to drive S rather soon.  The latest RUC model (which extends out to 21z - with 0z being the prime time) shows distinct failure of moisture return up into the texas panhandle tomorrow.  That said, it is still quite a complex set up tomorrow even if a few small things change, it could become potent rapidly.  It looks like widespread convection will pop up with the strong forcing from the upper trough which is set to dig in and this widespread convection could kill off the chances of an outbreak across northern texas into the south eastern parts of the panhandle.  That's why I'm playing the southern option....too little moisture return further N and too greater chance of being cluttered. 

My initial thoughts are to play just S of I-20 maybe somewhere around Ballinger (half way between Abiline and San Antonio).  I think initiation will be early (by US standards) with the strong upper level forcing and the relatively weak cap.  Elevated storms are currently in progress across much of the southern panhandle...i'm wondering if these will push out an outflow boundary that will intersect the dryline and create a focus for some more interesting storms.  I'd want to be in Ballinger early (midday) so that a jog westwards could be made should it become evident during the morning that the action is going to be a little further W (although the better shear is further E) or a jog further S could be made if it looks like the outflow is pushing further S.  Storms should've have too much of a problem getting some legs and booting it eastwards thou with a rapidly strengthening mid-level (500mb) jet of 50knts in the afternoon, increasing to 60+knts in the evening. 

SPC is all over the tornado threat with a fairly large hatched (F2-F5) area with 10% probability and a smaller area of 15% probability of tornadoes.  I think this might be a little overcooked....hrm...perhaps not.  Just saw that the LLJ increases from 25-30knts over the target area (Ballinger) mid arvo up to 50knts by dusk (thou current analysis shows solid 40knts over much of central Tx atm).  No shortage of energy with CAPEs up to or above 3000j/kg and LI's of -6 to -8C. 

Current analysis shows the warm front holding back a heap of juice with mid 60's DP's ready to boot nort eastwards towards the target area over the next 8 hours.  If that boundary doesn't move over the next 4 hours, I'd be wanting to boot even further S as that may end up being the play of the day.

So lets say Ballinger for now but like I said, if that warm front hasn't retreated N any by midday, I'd be looking to hit the road and get down nearer to I-10. Maybe Ozona.  (bit of a dryline buldge heading for this area...interesting).

Macca

 

[lollie3]

I am hoping either next year to be able to go over for the season and chase if not next year definately the year after

[Mike]

Your reports are so informative Macca.  There's so much information that even a novice like myself can understand exactly what you're experiencing and what you are relaying re the conditions, top stuff!  Good luck with some tornado activity, by the sounds of all the set ups is there a likelihood of perhaps an outbreak of sorts?

[Macca]

Hi Mike,

I'm not actually over there.  Just forecasting and virtual chasing.  But its great for during our off season here in Australia.

Macca

[Mike]

I see, just goes to show I'm not paying attention!  If our forum was a summer weather discussion arena it would be going nuts all year in all states, fortunately brilliant sunshine does nothing for storm chasers!

The next month or two will be an intersting one to look out for in the US once the season kicks into gear.  Are these storm events that you have been 'nowcasting' similar to conditions of pre-tornado alley seasons in the past whereby there's a general increase in supercell activity as the weeks go by or does their season come in waves of outbreak scenarios?

[Peter J]

Mike,

I'm also attuned to some of the virtual world (internet) when it comes to US weather, also I have a sister who lives just outside Dallas TX, and she sometimes keeps me informed on dangerous weather there. They did get a tornado to the NE of their house a couple of days ago, but it was too far away for her to see - they do get some ferocious supercell storms crossing over, but so far according to my brother-in-law they have never had a direct strike from one.

A good place to check for report updates on US weather, I found, is www.accuweather.com - they give informative discussion to storms and also have 2 meteorologists / storm chasers on their team that also give quite informative details on storms.

Worth a look if interested.

Big Pete
(ps - maybe one day I will get the chance to go and see live supercells and tornadoes over there - at least I'll have a place to stay if i need to).

[Macca]

My initial thoughts are to play just S of I-20 maybe somewhere around Ballinger (half way between Abiline and San Antonio). 

So lets say Ballinger for now but like I said, if that warm front hasn't retreated N any by midday, I'd be looking to hit the road and get down nearer to I-10. Maybe Ozona. 

Macca

Not a bad forecast again for (last) Thursday in the US.  The warm front lifted during the late morning to be located about 30mi N of Ballinger by the time storms initiated.  This was the more obvious play for the day and most chasers eventually locked onto the main show of the day which developed W of Abeline (50mi N from Ballinger).  This storm rode the warm front for several hours and cycled through various phases.  I know hindsight is lovely but I suspect I would've cruised N with the warm front as it passed over Ballinger on its way N so should've been relatively close to the storm had I been chasing.  It displayed some AWESOME echos on radar with some impressive hook echoes.  There were several tornado reports from this cell and hail up to 2.75 inches was also reported.

It looks like things will be quiet for the next week or so over there with this system forcing all the moisture way back into the southern Gulf (of Mexico) and it'll take some time to replace it.  The next system might end up being slightly moisture starved (moreso in terms of moisture quality) but give it 10-14 days and things should be well and truely back to normal ready for what is seemingly becomming a fairly standard severe weather period from 26th April through to 6th May. 

Macca

[Macca]

I wasn't going to do a forecast for tomorrow (today in the US) as I initially thought that moisture was going to be a problem but it appears this may not be the case.  The quality of the moisture isn't great but if I was there, I'd be playing with tomorrow anyway.

Low level shear is not great in my target area but the mid and upper level shear is definitely supportive of supercells.  Also, instability is decent and I reckon there is a good chance of daytime convection as the front sags southwards.  Target town...Throckmorton, Texas.  Looks to be near the intersection of the dryline and the front.  Dryline runs nearly N/S and the front kicks off to the NNE.  Not a great alignment of the boundary given the shear but I'd take it if I was chasing.  GFS hints at the intersection of the D/line and the front to sit slightly further S (closer to a town called Putnam on I-20).  If this was the case and convection initated there, with the shear, storms should move NNE initially with stronger storms moving NE and that would put them in the Breckenridge - Graham corridor which is not far from Throckmorton anyway so I'm happy enough to stick with Throck. as a target for now with some south and slight eastward jogging possible depending on position of intersection of these boundaries by mid afternoon.

Instabilty is reasonable in this area too with LI's in the -6 to -8 range and CAPE (ML) being around 1500-2000j/kg.  With 25-30knts at 850 from the S, 40knts from the SSW at 700 and 70knts at 500 from the SW, shear is pretty nice too so supercells are definitely on the cards.  DPs are just nosing into the low 60's in the models which will limit tornado potential but I can see why SPC is going for a 5% given the combination of instability and shear.  If the front aligns itself slightly more E-W than it is currently forecast, the low level winds will swing more to the SE and things could get interesting with moisture pooling in a triple point situation.  Per my target, best bet for a tube IMO is in the Throckmorton - Olney - Graham area.

Incidentally - both GFS and RUC have a subtle (yet kicky) shortwave moving into this region by mid afternoon with -16 to -18C at 500mb moving into the region.  Decent hail would be on the cards tomorrow - i'd suggest up to 3 inches with the strongest storms. 

Enough from me. 

Macca