Greetings all. Kent Ehrhardt here in the 4 Warn Storm Center. Since late last week Steve Templeton and I have had our eyes on an unusual upper level low pressure system. Unusual because this time of year we don't normally see these types of weather systems. Based on the consistency of the models from run to run we were anticipating a fairly wet pattern over the weekend. Not a wash-out, but it appeared rain was likely. But beginning early yesterday the models did an about face. Now the low was being forecast to dip to the south much farther to our west and high pressure would build over us. This would be a completely different scenario. Instead of a wet weekend now we are looking at cool mornings, sunny skies and only moderate humidity. Quite a change from last year at this time (see Matt Chamber's entry previous to this one).
Are wholesale changes like this unusual in the models? Unusual yes, but certainly not unheard of. What never fails to impress me is how these numerical weather prediction models pick up on weather systems as far as a week ahead of time. In most cases these disturbances haven't even begun to take shape yet. This weekend's low is a perfect example. The earlier versions of the model were off on the timing and path. But once the low started to form most of the models immediately responded by correcting the timing and path.
Many times when you've had a consistent pattern being produced by a model and suddenly it makes a significant change in the course of just one run we are hesitent to take the bait. That's why Steve and I were gathered around the monitor Thursday afternoon just before 5:00. We were moments away from the start of the newscast but a new model was rendering and we wanted to see the results before we went to air with our forecast. Had the result indicated that the previous run was an anomoly we were prepared to stick with our old forecast. But the new run continued the trend from the earlier run so we went with it.
There's a saying in our business"live by the models - die by the models" meaning if you only use the models to formulate your forecasts then when the models are wrong...so are you. At News 4 we use a number of models including our own Super Predictor. But we also keep a very close eye on SkyTracker Doppler Radar, satellite imagery, surface and upper air oberservations when we formulate our forecasts.
Now let's just hope we're right! Have a great weekend.