Day 117: Four Troughs

Posted by pmarsh on 27 Apr 2010 | 0 comments

Last week was fairly quiet until a large, slow-moving trough moved through the United States.  It was this trough that brought the severe weather to much of the southern United States last Thursday through Sunday (Thursday’s Post, Friday’s Post, & Saturday’s Post).  In the wake of this trough, several more are in the process of moving through the United States, continuing the unsettled weather pattern.

The first trough is currently located in New England and is responsible for bring snow (yes, that’s correct) to portions of northern Vermont and New Hampshire.

The second trough is currently located in the southeast United States.  It brought isolated severe thunderstorms to portions of of the Carolinas.  (Brad Panovich WCNC kept busy this afternoon dealing with these!).  In the wake of this second trough unseasonably cold air has filtered in, allowing for widespread frost and freeze advisories and warnings for the Midwest and Great Lakes region.

The third trough is currently located in northern Mexico and is slowly moving east at this latitude (roughly that of the US-Mexico border.  This trough isn’t a big rain maker or anything, but the wind flow around it will wreak havoc in the transport of moisture northward into the central plains.  This trough is what is helping to limit the severe threat somewhat on Thursday and Friday.  Without it, the chances of severe weather would be much higher.

The fourth trough is another large, slowly moving trough that will cross the United States.  The entire yellow circle can be though of as the main trough with the red circle being the most concentrated area.  (In fact, the red circle would be what most meteorologists would incorrectly [or more precisely, lazily] refer to as a “piece of energy”.  It’s actually a smaller shortwave trough rotating through a larger trough.)  As this large trough moves slowly east it will be begin to draw moisture northward into the central plains.  At this point it appears that severe weather is possible but a major severe weather outbreak is not imminent.  As the trough moves into the eastern United States, widespread heavy rains appear possible and flash flooding will become a concern over areas of the southeast.

It’s going to be a busy end to the week…and this is before considering all I have to do before VORTEX II starts on Saturday.