June 7, 2009

Tornadoes in Kansas!?!

Tornado chances are looking stellar for tomorrow in eastern KS if we can get initiation to the south of the warm front. The forecast hodograph shapes are just about classic; unfortunately the second lobe of this potent EML will be over the target area tomorrow afternoon featuring 700mb temps likely 1-2C degrees higher than the cap bust we had today. BUT we will have a couple things working for us tomorrow that today lacked. First of all, low-level moisture may be of much higher quality given the trajectories coming from the western Gulf instead of northeast Mexico. This richer moisture may not make it far enough north in time to have a huge positive consequence but the extended period of low-level moisture pooling we've had along the surface front should be sufficient to weaken the cap and provide high instability. Now all we need is some lift to fire this loaded gun, which brings me to:

Above, from left to right, there is the 5z IR image, the NAM 500mb vorticity map for 18z and the GFS 500mb vorticity map for 18z. What you can see is a small piece of subtropical energy that was sucked up into this swrly flow from off the coast of the Baja. This subtle upper-level disturbance is forecast to be slightly upstream of the target area near initiation time which will hopefully provide lift with the help of upper-level diffluence and more significantly the strong, negatively-tilted shortwave ejecting across the Central Plains. This little piece of energy may not have a big roll in initiating convection on the warm front or triple point, but if I were targeting further south along the dryline I would be keeping a very close eye on it.

June 5, 2009

June is the new May

Friday June 5th, 1:15 pm: This darn ridge is finally breaking down as the cut-off low is forecast to be scooped up into the polar jet and eject across the Plains this weekend. Today has a decent shot for some daytime tor's around Cheyenne, WY and southeast along the surface boundary. I'll be chasing tomorrow somewhere between Omaha, NE and Great Bend, KS. Yep, the forecast is still that hazy. If I think the cap can be breached I'll head west to the dryline; if the cap looks too strong on morning soundings I'll head northwest to the surface front and maybe west from there to the triple point. One of those days where you have to hedge your bets and not take yourself out of position for a potentially better show, but that's going to be tough given such wide range of targets.

Sunday is looking good across eastern KS where strong moisture return will result in high instability beneath a powerful jet, the problem once again will be the seasonably high 700mb temps which could cap most of the warm sector. On both days, IF the cap is breached south of the surface front, along the dryline, tornadic supercells are a definite possibility. If the cap holds south of Nebraska and Iowa on Sunday, it will mean lots of sunburns but Monday's chances will look much better.

On Monday the cold front is forecast to finally drift through eastern KS, and given three days of substantial moisture return via 50kt nocturnal LLJ's and continuous southerly surface flow, the warm sector will be primed for a big day. This is especially true if the airmass isn't worked over by an MCS, which would likely happen if the cap is breached on Sunday. The increased surface dew points will make the high 700mb temps less of a hindrance on initiation away from the undercutting cold front.

Looking over this quick forecast, I'm leaning towards rolling the dice tomorrow (Saturday) and playing the dryline given the decent tornado chances on the next two days. If it were a one day event, I would be tempted to target the warm front for its higher chances of seeing a storm but with a risk-reward tossup like this it's nice to have two other days to make up for it.

Monday June 1st, 11:42am: Leaving for St. Joseph, MO here shortly where I'll have to make an east or west decision. There will be storms all over this east-west boundary, it's just a matter of finding the best low-level shear and getting on the storms verrrrry early in the life cycle before they gust out. Probably more of a structure day but I can't rule out a tornado. Live stream and chat room will be up shortly. To view the live stream, click on the green car icon on the radar map below.

Sunday May 24th, 11:42pm: I'm driving for Tempest Tours this week and should be able to update via Twitter semi-regularly on what we see and where we are. The stream won't be up until this tour is over on Saturday but I'll upload some pics and vids if I get anything worthwhile. The weather pattern this week looks just awful for severe weather across the Plains but it is May and anything can happen. The 0z GFS run tonight has officially re-sparked my interest in this season. It shows this death-ridge breaking down over the weekend and an extended period of western US troughing (ie May's tornado conveyor belt). There is hope yet!