Derechos are long-lived convectively-driven wind storms. In the upper midwest, they typically form in northwesterly flow just poleward of very warm and moist air and then surge southward. Convection overnight on 13-14 August 2007 developed into a long-lasting complex with a bow echo that propagated from north of Minneapolis to... Read More
Wave clouds downstream of mountain ridges are a fairly common sight for regular observers of satellite data. See, for example, the parallel bands of clouds over southern Virginia in this image from the Record-setting Nor’easter in April of 2007. Such clouds develop as air is forced upward by the ridges of the... Read More
An mesoscale phenomenon that sometimes emerges out of Mesoscale Convective Systems (MCS) is the Mesoscale Convective Vortex (MCV). Intense latent heating within the rain core of an MCS can help spin up a vortex that will occasionally live on even as the MCS that spawned it withers away. The spin-up can be visualized as a potential... Read More
Because of relatively mild and snow free conditions in the first half of January, many stories appeared in the media about the lack of winter and mild temperatures. In a classic case of Beware What you Wish For, cold winter temperatures have struck back with a vengeance. Dangerously cold weather covered... Read More
