Topic: 2008 US tornado season discussion

[Mike]

What's your success ratio with the forecasts you've done yourself looking afar?  Have your interpretations been pretty well spot on from the information you have gathered when doing your research?  From reading the posts you have a fairly knowledgable insight for discecting the models! A great read and I'm learning much from them.

[Macca]

Hi Mike,

Of the three forecasts I have done so far this season, the best storm of the day has been within 50mi of my targets so I think I'm doing ok.  I'd like to get that number down into the 20-30mi range (have had one 20mi, one 40mi and today's was 50mi) but I guess its not too bad given that I usually miss 7 or so hours of data between when I got to sleep and when I next check in the morning...given that this is the most important part of the day when you need to refine your forecasts based on how the day is unfolding its not going too badly. 

Macca

[Macca]

Turns out that yesterday's storm was quite a bit better than I anticipated with reports of baseball hail, 1 tornado and lots of other golfball or larger hail reports coming from it.  It had great structure on radar and had very intense reflectivities several times during its life. 

A few quiet days coming up now before another decent event in a few days time.

Macca

[Mike]

Here's a neat video showing golf ball hail in Texas 17 April 2008 from a tornado warned storm....quite a bit of it also from the amount on the ground!

http://youtube.com/watch?v=uCf7gPXuZA4

Also Macca...just on your forecasting.  I was asked this today by someone in the US who is just now starting to get into chasing, although he has been educating himself for over a year to assist him.  He said this re 21/22 April 2008 days.. 'As I look at the model data (500 speeds, 850 speeds, dewpoints, SBCAPE, MLCAPE, CIN), I see things of interest as well. My problem is that I'm not really sure how everything interacts with each other to produce a severe weather potential.'

Now this is probably the $64,000 question.  From what you have been noting and deciphering, is he looking for all the right numbers?  Is there something, the one model that you look at religiously that aids your forecasting so that I can pass the info on to him to help him?  From what i can gather from him he reads all the right numbers, but has trouble working out where they all fit in and 'what' to look for in advance for severe weather potential.

Any info you can give would be appreciated!

[Macca]

Hi Mike,

Sounds like he is looking at the basic key indicators.  There are so many different things that people look at and its a matter of becoming comfortable with your own set of parameters which are used for forecasting. 

Few things with regard to 21st.  Looks like the cap is pretty strong and the moisture looks to be quite shallow (850mb relative humidity is pretty low with dry SW'ly winds pushing in from SW Tx/New Mex.).

Kenny Drake posted on stormtrack earlier today and pretty much sums up my thoughts- he said "at this stage I won't be chasing but I'll keep an eye on the next 24hrs of model runs in case things change".

Hope that helps.

Macca

[nzstorm]

Looking a bit ridgy over the southern plains atm with the upper air dynamics being shunted north a bit.  These situations are hard work for storm chasers but I wouldn't be suprised if a good severe weather day pops up this week. The dps and CAPE look OK.

[Macca]

Don't really have time to look at much else but the Mesoanalysis atm but d/line bulge (weak) is sitting over south west central OK.  A few "AWS's" are showing low 70's DPs in N TX, S OK with some high 60's around it.  This is to the E of the bulge.  850 Td's (dewpoints) also show a similar pattern. I'm concerned about the SSW (nearly SW'ly) flow at 850mb and also the lack of decent convergence at the surface.  That said, the mid level trough is nice (700mb).  It is currently sitting over the TX panhandle and will move eastward over the next 3-4 hours.  This will result in some nice destabilization and should see the cap erode.  500 temps aren't too bad given the temp/dp with -12 to -13C across much of OK.  This *may* cool by a degree or so during the rest of the day but the main upper level support is still quite a way back to the west. 

Instability is quite nice with surface-based CAPE's sitting above 4000j/kg at the moment over south central OK and LI's of -11 to -12 at the moment.  :D

At this stage, there is nothing that I can see which screams "target here" apart from the weak dryline bulge (which may sharpen up over the next few hours).  So that's my target for now.  I don't think there will be any signficant tornadoes today (brief spin ups would be a *very* slight chance) but if the cap breaks, there should be some MONSTER hail :D .  Hail parameters are up to 3 (inches) already and that will no doubt get better over the next 2-4 hours!

I'm going to sit myself (virtually) at Marlow in SW Cent Oklahoma (60mi SSW of Oklahoma City).  Its right on the dryline (bulge) there at the moment.  I might even consider a further 5mi west of there if it means there is better visibility in the dry air.  Its still a bit dubious as to whether the cap will break given the limited forcing but its worth playing with with 4000j/kg and 35-40knts at 500mb because if something does take off its going to look very very nice indeed. 

Macca

Edit:  Ok...just looked at the latest RUC run and its picked this like a dirty nose.  It has convective precip starting up at 21z (soon) with quite a bit forming over S Cent OK this afternoon (for them).  I'm pretty happy still with Marlow as a target based on this.

[Macca]

Cap broke 20mi ENE of Marlow during the late afternoon. SPC issued a tornado watch for this area.  There was possibly a brief window of opportunity for a brief tornado (in daylighthours) in the area just E of I-35 but I don't think anything was reported.

A severe thunderstorm watch was also issued for north central Oklahoma up into S Central Kansas which went up later than the southern Oklahoma stuff in slightly less instabilty.  It was a fair enough call from  SPC to only go for a severe as opposed to tornado watch in that area. 

One report of hail to the size of baseballs from the right mover of the two storms over south central Oklahoma from earlier today. The report was from near Maysville (only 35mi from Marlow).

Albeit no lead up forecast, I'm happy enough with my forecast this morning.

Macca

[David C]

Good stuff Macca.

Looks like a few decent photos being posted on storm track http://www.stormtrack.org/forum/showthread.php?p=174777#post174777

These are the large hail reports from SPC:

0130   175    1 N MAYSVILLE    GARVIN    OK   3483    9741   (OUN)
0149   175   SLAUGHTERVILLE    CLEVELAND    OK   3510   9728   (OUN)
0153   195   MAYSVILLE    GARVIN    OK   3482   9741   HAIL WAS ABOUT TWICE THE DIAMETER OF A 1 EURO COIN. REPORTED BY A METEOROLOGIST FROM MUNICH GERMANY. (OUN)
0225   75   7 SW SHAWNEE    POTTAWATOMIE    OK   3526   9700   (OUN)
0230   225   3 W PAOLI    GARVIN    OK   3483   9732   LARGE HAIL BROKE WINDSHIELDS (OUN)

These times are UTC so convert her http://hurricanes.noaa.gov/zulu-utc.html
To get a feel for time of day go here >> http://www.timeanddate.com/worldclock/sunearth.html

[Macca]

I'm going to target Snyder, Tx. There is some convection ongoing in the area in at this stage in response to a shortwave moving through but with the 40-50knt mid level jet, this should clear off and the atmosphere will recover to deliver the goods this afternoon as well. (Or ongoing convection will become surface based and go beserk).

My target...Snyder, TX (with the thought of having to drop south down to I-20 to get to the southern most side of any convection which develops). The cap is quite strong S of here so hopefully could get onto tail end charlie and BAM. Tornadoes not out of the question with hail to at least 3 inches with the best storms. Cloud is prevalent across most of TX atm with a nice storm heading for Snyder but its elevated. Still hefty thou and would provide a nice wake up call if you were there already. Cloud should clear during the day.

Macca

EDIT: Actually - the dryline is currently sitting a LONG way west. I'd be keen to keep an eye on this. Whilst it should shunt eastwards during the day, if it takes its merry time, I'd considering dropping from Snyder down to I-20 and then westwards towards Big Spring.

[Peter J]

Macca,

Looks like tornado alley area is a bit quieter this year, than previous seasons - wonder if the proposed great outbreak season seems to have been put on hold?
Keep up the updates though, coz if i ever get the chance to go chase in the US, I might need u as a guide.

Big Pete

[nzstorm]

I didn't follow todays set up but have had a quick look at tomorrow.  The numbers look big over southern Kansas and so my virtual target will be Pratt.  There are road options from that town as well.   

Pete, the Alley has looked quieter thus far compared to recent Aprils but the last 3 seasons have been funny in that they have ended early or not been that active for tornadoes after early May.  This year I am optimistic for a change in this pattern with a more active May.  But I am no expert so just being hopeful I guess.  I am heading over there early May.

[Macca]

Nailed yesterday's target well with a tornado reported 5mi E of Snyder. 

But today...

I'm going to be greedy today. Apart from the fact that I'm forecasting from LAX (working in Vancouver for 4-5 days before heading down for a chase for a few weeks), I'm going to pick two targets.  Note that you couldn't actually chase both on the same day as they are a day's drive apart and given that I would've chased central western Texas yesterday had I been there, I would've had to play the first target today (see below).

I'm going to send half of me (not literally, just virtually) to Medicine Lodge in south central Kansas to play the dryline bulge. In this area, CAPE is forecast to get up over 4000j/kg and whilst shear is nothing to write home about, it that was here, we'd be pretty damn excited. There should be some big storms in this region but quite late given the warmer air keeping a lid on things. I wouldn't expect anything in this region before 5pm (local time). With the amount of instability and shear that is good enough, brief tornadoes are definitely on the cards as is some more VERY large hail (baseballs+).

My other half (virtual) is going to play with some upslope flow over the Nebraska panhandle. I was originally going to say Sidney, Nebraska but the road network there is cr@p to say the least so I'm going to head a little further east and sit at Big Springs, Nebraska. Instability is still looking ok in this area with CAPE forecast to get up over 2000j/kg. Also up in this area, the low level shear is nicer with ENE'ly winds at 850 of 25-30knts (compared with 25knts from the S in my other target) and this is sitting under a 40-45knt mid level jet and sitting on the nose of the upper level jet. 500mb temps are forecast to be about -18C and DP's are forecast to hit the mid 50's (which is nice given the elevation of this region coupled with the cold upper temps). I expect this area to fire earlier than my other target and also turn to crap more quickly but there is probably a 2 hour window (3-5pm) when supercells and tornadoes will be possible.

Its somewhat amusing but both of my targets are JUST outside of the moderate risk area issued by SPC with Medicine Lodge being just S of the moderate risk and Big Springs, NE being just west of the moderate risk. However, I suspect the majority of this moderate risk will relate to the MCS which is likely to develop during the late evening/overnight hours. (Just read the SPC convective outlook...sounds scarily similar to what i've written...).

Macca

[nzstorm]

Southern Kansas was a good bust today, cap just too strong.  From what I saw on the visible imagery there wasn't much in the way of turkeys either so the cap wasn't tested that strongly either.    Northern target fired.

[Macca]

Yep - good ole clear sky bust in S Kansas y'day.  Sunburn for those who stuck it out and  reward for those who headed N (although reports on stormtrack seem to indicate the it went HP outflow beast on dusk and the reported tornadoes were impossible to see).

Interestingly enough, mesoanalysis late yesterday showed 850 temps increase to 23-24C over S Kansas which probably didn't help the situation at all.  From what I saw, not too many of the models (if any) had it quite this warm over the area.  I think the SW'ly flow at 850 probably pushed a little further north east than was initially thought, thus resulting in the warm air/cap. 

Tell you what - its much easier to take a clear sky bust when virtual chasing as opposed the real thing.  Lesson learned though (which is the main thing).

Macca