03.28.10
Spring Comes to the Plains
Warm, south winds and mostly sunny skies? Temperatures in the 70s and 80s? What is this strange weather?
It appears as if spring has finally arrived.
Take a look at the map below, from the NOAA Earth System Research Laboratory. This is a model forecast of 850mb (low-level atmosphere) temperature anomalies for 00Z on Thursday, or 7pm Central Time on Wednesday. Wednesday is probably going to be the warmest day of the week for central Oklahoma (unfortunately, for those of you on the West Coast, you will be receiving some cooler weather). Note that the 850mb temperatures in central Oklahoma are forecast to be 8-10 degrees CELSIUS above normal!
Why are we expecting such warm weather?
The models are finally showing a nice ridge of high pressure beginning to build over the eastern US early this week, with a trough of low pressure over the western US (the thin gray lines on the plot above). This pattern is great news if you want southerly surface winds advecting warm, moist air up into the Southern Plains.
The map below, also from the Earth System Research Lab, is a model forecast of 500mb (mid-level atmosphere) height anomalies for the same time as above (7pm Central Time on Wednesday). What you should take from this map is that there is higher-than-normal pressure (higher heights; i.e., the ridge)) in the eastern US and lower-than-normal pressure (lower heights; i.e., the trough) in the western US.
A potentially good piece of news for storm chasers is that the southerly winds can give us the warm temperatures and higher dewpoints that we need for strong thunderstorms to form. Moreover, the trough in the West looks like it may be sending a number of shortwave troughs our way, starting late this week. Those troughs provide the needed lift for a thunderstorm. As I’ve mentioned before, we’ve had plenty of lift and wind shear for strong thunderstorms, but an overall lack of moisture and instability–at least until next week, shortly after Easter.
Time to gear up for the storm season and batten down the hatches–it looks as if April could be a busy month.