Oct 28th 2009

Severe threat possible ahead of developing severe squall line! This line is just starting to gain momentum. Threat could intiate an on going severe weather threat that may be on going through thursday! The severe potential tonight still remains out ahead of this developing line with any discrete cells that can form. Tornadoes are possible with any of these discrete cells but a qlcs or quasi linear convective system still has the potential at forming a tornado with the large shear in place.

Tomorrow looks even more potent as the system moves east. With an ongoing line expected the same story will apply. Discrete cells ahead of the line rooted in the boundry layer are going to have ample shear to develop low level rotation! This is an on going threat as low deepens and continues to pull in moisture along the gulf! Friday the models begin to diverge a little! But overall picture is pretty clear! Below is an image of the 850 millabar winds. Showing a very fast low level jet up around sixty knots (around 70 mph) thats a WOW! So any updrafts that do get going could just be sheared apart. But if any vigorous convection can get going and sustain itself on the partially moist LLJ! Look out!

Another thing to note is the partially backed but strong low level flow, which is leading to largely curved hodographs! Hodographs that denote definite tornado potential enviroments. Low level advection should not be an issue with a large deepening low, despite models. The main problem the models seem to suggest, is the upper level temps are just to warm. If this changes we could have a large outbreak of severe weather on our hands friday. If not the severe potential is going is going to be quite limited.

Radar image around 9:27pm is of a squall line forming in western TX. This could be ongoing through tomorrow!

July 8th 2009 Severe weather potential

Large trough and associated upper level low moves in over the upper northwest. At the surface a 999mb low is moving east through the northern plains. With an occluded front/surface trough extending north to another low center in Canada. Backing winds at surface look to converge with south westerly winds behind front later this afternoon. This should act to initiate storms, with forecasted dew points in the upper 60s and lower 70s ample moisture should be in place over ND and SD!

500mb RUC forecast for 20z showing the trough and associated jet streak. Low level jet should increase late afternoon to around 30 kts increasing low level shear. This coupled with steep mid level lapse rates and surface temps reaching the upper 70s lower 80s CAPE values should reach 2000 j/kg.

Hodograph for 23z southwestern ND. Note the turning and relatively decent speeds at lower levels. Should be an interesting enviroment for any storms in this area. Tornadic supercells are going to be very likely today!

2009 an analysis

Looking through the past couple events 2009 seems to be lacking something in the tornado market. What it is isnt exactly clear! Most explosive events with what seemed to be adequate shear have failed to produce with one or two exceptions. What it seems to boil down to is a lack of significant surface features. and when there seems to be adequate moisture the winds are lacking. The past two events that should have held high tornado potential specifically June 7th and June 5th which did yield a tornado before the cells were rooted on a cold/stationary front. June 7th seemed to yield the same results. With cells going up then moving into unfavorable air. Which is highly unlikely for a triple point event. Cells normally go up then move into the warm sector. With these events they seemed to take paths that lead them in the other direction. The lack of surface winds on the 7th really made a difference. It seemed the instability was obviously good but the cells on the 7th lacked good low level rotation. And maybe even in the lowest 1km.

It seems that 2009 is going to continue to be a frustrating year. Where most other years seemed to get better later on. Its interesting to study such cases in detail which I have yet to do. But its always a nice contrast from a learning perspective.

Chasing June 5th 2009 Live!!

Absoluteinstability.net will be teaming up with 4849 productions for the chase today and tomorrow! 4849 productions will have a live feed going for the chase through severe studios. So you'll be able to watch a chase live in the high plains today and tomorrow just follow the link below.

http://www.severestudios.com/cgi-bin/player.pl?username=walt.vanrheen

Possible tornadoes IL, MO, OK 5/13/09

Intense upper level low now over Ontario, Canada is quickly moving east with associated trough. Jet max with core winds at 90 to 100 knots within this trough now over MN will lift northeast. With intense system aloft surface cyclone will remain very deep at 988mb. Cold front trails southwestard and connects up with another low over KS, OK, TX panhandle area. 850 mb jet will be nosing into MO, and IL around 14z bringing along very moist and warm air mass. 850 jet is forecast to strenghtin to around 50 knots and with 500mb speeds approaching 40 to 45 knots shear will insane. Main forcing will be cold front later, but with likely convergence and complex surface features a few cells will go up ahead and quickly develop rotation.

I will be targeting the IL MO area later today.

Below is an image of the RUC 500mb forecast!

Severe weather outbreak and bow echo.

May 9th 2009 was forecasted a few days ago to actually be a severe weather day for the red river vallery and central plains. Due to model inconsistencys and mesoscale uncertaintys a moderate risk was issued by the storm prediction center for the red river valley, then taken away the night of May 8th. Then the morning of Fri may 9th a moderate was reissued for portions of the ohio valley!? Partly due to an on going derecho and forecasted severe indices ahead of the on going system lead to a reissue of moderate risk.

Below is an incredible image of the bow echos book end vorticy/comma head. Also rooted in the upper levels it gets called an MCV or mesoscale convective vortex. This thing is extreme though an extreme case. With a gust measured at or around 100 mph its more like a hurricane! It also has an eye type feature if you look closey.

Below is the RUC analysis for 21z and it shows an area of max CAPE and 0-1km helicity values at or around 250-300, which is incredible. It should be noted however that, that area is in the appalachians. Not chase friendly country I might add. But none the less thats concernedly high and would be prime for supercells if not tornadic supercells.

Below are the same areas right around 21z and oh look, several supercells with probable tornadoes on the ground, not good! That area is in the mountains and so visibility can be obstructed, so warnings are all speculative until someone either confirms damage or a sightning takes place. It was a very dangerous situation situation today. The image below shows two main supercells in TN.

Showing the cells to the north of the previous image, several tornado warnings were issued at the time of this image.

Difficult forecasting ahead.

Models are now having trouble picking out whats going to happen at anytime in the near future. Why this is happening is unknown. One thing you can always rely on is the three ingredients as is needed by severe weather. Instability, shear, and lift. The present system is one that is not giving clear signs of evolution. The only thing that is clear is that its spring and severe weather is likely somewhere in the united states everyday, usually. Most likely spring is still trying to set in in some places leaving everything backed up like last year. Indiana has not really had a normal spring yet. With snowfall in april and temps being wild everywhere, its no surprise to see anomalous things popping out of the models lately.

Below is an GFS (500mb heights and wind) model image grab valid for 21z friday may 1st. It shows a huge hudson bay vortex that is usually associated with blocking patterns. This can be bad for chase prospects but in this case it is hard to determine.

March 23rd 2009 Possible tornadoes!

Around 988 mb low is emerging from the high plains area and forcast to move across NE during the day. With a decent warm sector south to OK and great shear profiles thoughout, a big day is likely for large hail and possibly a few tornadoes, with a chance for some long tracked violent tornadoes. However this threat is not clear cut, with moisture one of the big concerns. Such a hugh area possible its hard to really narrow down an area. I am thinking the greatest threat for daytime supercells and possible tornadoes will be up in NE around the warm front close to the low.

March 8th 2009 reports

I ended up chasing a cell at the tail end of a small line in west central IN. The storm motions, speed of the storms were to fast to really keep up with. The main tornado producer on this day was a small bow echo that went pretty much straight thur southern IL and IN. Preliminary reports indicate that this bow echo did EF-3 damage in southern IN. I am a little upset that I missed the storm and a chance to document a tornado with a bow echo type stucture. But given that area being mostly trees and hills and the fast storm speeds it would have been a dangerous pursuit. I will have a chase account up later today on my site. My info on the storms and damage can be obtained here http://www.crh.noaa.gov/news/display_cmsstory.php?wfo=ind&storyid=22735&source=0

Mean while another severe event is expected for tuesday! This event will be for mainly IL but western IN could see some severe weather!

Possible tornadoes in IL, IN

Both images are courtesy of UCAR. Below is the ruc model forecast surface MLSP and wind field. Much of the area I mentioned is in the warm sector of an approaching extra tropical cyclone. With marginal instability inplace and good upper level support plus wind shear (see 500mb map below) the threat will continue for possible tornadoes this afternoon.