Severe ingredients for Friday night

jetstreammuggysevereindexThe Storm Prediction Center’s “day three outlook”  ominously suggested a severe weather outbreak for much of Eastern Iowa and Northern Illinois for Friday.

However, I’m not sold on this just yet. Let’s look at a few factors that come into play for this event. First, the jetstream. Models are showing a speed-max over the K.C. area Friday evening. Storms usually form out ahead of the jetstream, which puts us in a favorable spot.

Dewpoints are another factor in determining severe development. Models are all in line in bringing copious amounts of Gulf moisture up here. Getting dewpoints in the 60s will be quite a feat considering our current dewpoint is 28°. We’ll see where we stand on Thursday.

Finally, our exclusive Severe Index model is putting most of the strong/severe stuff downstate on Friday evening which brings me to another thing: This is coming through during the evening/overnight. While overnight severe events are more common in the summertime, this time of year we really lack a lot of instability during the night…and the models are already showing puny amounts of CAPE (convective potential energy), the stuff you need to get storms to form. Right now it appears that straight-line wind will be the main threat with a very low threat of hail and tornadoes.

I am going to side with our FutureTrack model right now as it seems the most convective energy will be lagging in South-Central Illinois. Crazy things have happened and will continue to monitor the latest model guidance tonight and tomorrow. -ES


Posted under severe weather

This post was written by qni_it on April 28, 2010

2 Comments so far

  1. tony April 28, 2010 5:48 PM

    Where would the dewpoint need to be tomorrow eric to make it a decent shot of severe weather on friday?

  2. WI Weather Buff April 28, 2010 8:09 PM

    So… I’m not a weather scientist, I’m just a lay observer (and also a somewhat wry observer of weather models nowadays).

    My lay person observation is that the models seem not to do their best with storms that follow tracks like this one. (??? am I totally nuts here, or has anyone else noticed this?)

    The models seem to want to put the tracks too far north of where the storm system actually winds up going, and send the storm further east earlier than it actually gets there — when the jet stream is hitting California where this one is now – or at least that’s the way it seems to my amateur observer’s eye.

    So my vote is with Eric and if I were going to place a bet on this one (sorry, not this month, too much month left at the end of the money…) I would bet that it will track slower and farther south than what the models have it, i.e, maybe not even cross our path until Saturday morning.

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