Sunday 25 April 2010

USA severe storms

After a very quiet start to the severe weather season in the USA, due to the cold winter and frequent cold frontal incursions into the Gulf of Mexico, severe thunderstorms have been widespread across portions of the Plains and south over the last few days.

Yesterday (Sat) in particular was very nasty, as a deep, moist and unstable airmass spread north from the Gulf into the Mississippi Delta region and surrounding area. A potent upper trough and approaching cold front provided the lift for numerous severe thunderstorms including tornadic supercells. One particularly nasty supercell moved across all of Mississippi, and produced a long-track, strong (possibly violent) tornado. Sadly, at least 10 people have been reported as being killed.

The storms were moving fast (50-60mph) and so are quickly upon communities, despite excellent warnings from the NWS.

The risk has shifted further east today, and over the next couple of days, the weather will calm down stateside. However, later in the coming week, another major upper trough looks like moving in from the Pacific, and looks likely to set the stage for a multi-day severe weather event across the central and southern USA.