Posted by: splillo | March 5, 2012

The heat is on

The weather is not calming down anytime soon. Following two major storm systems that affected the nation in the last week, the Northeast is covered in a fresh layer of snow and ice, and the Ohio Valley down through the Southeast is cleaning up after a major tornado outbreak. I won't go into many details; The news coverage has been excellent for this outbreak. It would appear that 2012 is taking over where 2011 left off. Hopefully this is not a sign of things to come this spring. Below I have included a map of all the severe reports from March 2nd (Source).

Here's an aerial shot of damage in Marysville, IN (Source).

The first half of this week should be calm and dry for this ravaged area, helping with the clean-up efforts. However, by Thursday, another significant system will be swinging through. There shouldn't be any major severe weather associated with this storm though; only some showers and thunderstorms with the frontal passage. Ahead of this storm, temperatures will sky-rocket. A large area of high pressure over the western Atlantic will pump warm temperatures northward. Much of the Northeast will reach into the 50's and 60's on Thursday.

Cooler temperatures will drop into the region behind the front on Saturday. However, this will be short-lived, and by Sunday we'll be back up around 50. The truth is that we're entering a very warm pattern next week. A trough over the Gulf of Alaska will translate to a large ridge downstream east of the Rockies. The image on the right shows a day-10 500mb height anomaly ensemble-mean forecast valid 00z March 15 ... wait, don't stop reading! For our purposes, red = warm. There's lots of red over eastern North America.

The jet stream will be displaced very far north into Canada, flooding the region with warm air. At first glance, it doesn't look like we'll be breaking any records, but this should be a prolonged period of temperatures consistently in the 60's ... closer to that of late April / early May standards!!

Just to cover all my bases, this doesn't preclude any stormy rainy days. In a pattern like this with the jet stream so far north, cutoff lows become more common. Picture a trough ejecting eastward from the Gulf of Alaska into the western U.S. The trough wants to dig southward, but the jet stream resists. What then happens is that the storm digs outside of the jet. Normally disturbances follow the jet stream from west to east across the nation, giving us that general rhythm of storms about once every three days. When a storm cuts off from the jet, there's no longer any force to move it forward. It's like a car pulling into the breakdown lane on a highway. These cutoff lows can linger for many days.

In this pattern, it's possible to get a cutoff situated in the Ohio Valley that would pump Atlantic moisture into New England, producing days of heavy rain. Just another potential to consider in this developing regime. The weather is never simple.