Friday, April 30, 2010

Less Interesting event

Nice forecast by SPC today. I was concerned that the threat was marginalized by the wording of their outlook this morning. The concerns of the day were going to be the timing of CI and the strength of the cap in the warm sector, and the position of boundaries. There wasnt much mentioned about the tornado threat other than isolated threat. That is true, of course. The reasoning of limited moisture and also that storms would weaken after dark were incorrect.

There was little mention of hodograph shape or the evolution of hodographs. This was surprising to me and seemed to be quite important. The hodograph evolution I saw was that of little curvature near the front but big curvature away from the front. Worse was the evolution from curved to straightline hodographs. The 21 and 00 UTC soundings from OAX and TOP pseudo-confirmed the hi-res model hodographs I saw (NCAR WRF 3km convection from their 18-24 hour forecast from 29 April 00 UTC Run). I am not using a direct comparison mind you ... more like temporal neighborhood similarity.

That is the forecast reasoning depended was sullied by rather typical information and model data were discounted. Bias is models is always problem. When do you trust them and when don't you. In highly dynamic environments it is easy for them to be correct. When they go astray is usually in organizing the convection or missing the initial convective mode. The linear nature to todays convection was fully captured by the model even if the forecasters did not anticipate this initial mixed mode.

I say mixed mode because I am sure there were a few supercells, but they were lined up on the front. The scale of such linear organization along a boundary might be predicted well as opposed to smaller scale isolated cells. This is the big test of these models. What CI events do they capture well AND how well do they predict the evolution? Current techniques exist to test for this and I believe them to be regime dependent. Just dont ask which regimes yet. That awaits further research. I will update when I get the model hodographs downloaded and compare to the soundings.