Sunday, April 26, 2009

Morning temperatures ... in April?


In the eastern half of the nation, temperatures this morning were closer to those of July norms. At 10am, much of southern New England was already in the 70's, with 80's showing up in Virginia, Delmarva, and southern New Jersey. The other feature that can be seen on the temperature maps this morning is a gradient present across the central plains and extending across the Great Lakes regions into New England. This is associated with a vast frontal boundary that has been the trigger for consecutive days of severe thunderstorms in the Midwest. The gradient in the northeast is a result of a backdoor frontal boundary that is being pushed south by high pressure in southeast Canada. This is despite a continually strengthening mid level ridge over the east that will reach 582dm this afternoon. The cold air is shallow enough however that it can slide south relatively unimpeeded. As the front moves through, we will see an increase in clouds, however the day should remain dry.

With the front to our south, will we see colder temperatures? Yes, relatively speaking. Highs will reach the upper 70's today and low 80's tomorrow. Cooler than yesterday, but still 15 to 20 degrees above normal!


Shortwave energy will approach the region from the west on Tuesday, and this will act to push the boundary back north. Expect highs to once again punch into the 80's, with 90 degree readings likely in the normally warmer areas of the region.

Tuesday night, the final front comes through from the west, driving back the ridging, and bringing temperatures back to near normal on Wednesday. It is still uncertain how much of an event will come with the frontal passage. It may be just scattered showers or it's still possible that there could be some strong thunderstorms passing through.

Next wave moves through on Saturday, with rising temperatures on Friday, followed by showers overnight and on Saturday. As an interesting piece of information. The 582dm H5 height contour over the region today, will be down in Miami, FL on Saturday.

To a degree, 2m temperatures over the last couple weeks have followed MJO composites fairly closely, as may be expected with such a strong wave recently. The wave will be entering octant 7 of phase space in the next few days which features rising temps in the southwest, and a weak southeast ridge, while the Great Lakes and Northeast cool off notable (as is anticipated). By phase 1, which should be reached around day 10, a trough builds back into the west, with southeast ridging regaining control.

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