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November 2011

December 2011 temperature forecast – Final

The forecast is based off of weak signals provided by the La NiƱa, -PDO, -PNA, +AO and +NAO.

December is probably going to be messy temperature-wise, so confidence in the forecast is low. It has been a very frustrating forecast.

This is in STARK contrast to my forecast from mid-October:

(forecast anomalies based on the 1981-2010 normals)

So why the big difference? Blocking… or rather the lack thereof. A lot of forecasts called for the return of a -AO/-NAO blocking pattern in the Atlantic, which would pull cold air down from Canada into the U.S. This blocking was supposed to be set up by above normal October Siberian snowfall and stratospheric warming (with some persistence thrown in as well), but neither of these ended up occurring, resulting in a progressive +AO/+NAO pattern. This allows the Pacific to have more of an influence on the forecast as well, which with a -PDO and -PNA pattern puts a trough out in the western U.S. and ridging over the eastern U.S.

The big question for December is “how stable is the pattern?” and the answer is “not very.” Because of the uncertainty in the forecast, a lot of the CONUS is near normal (+/- 1F anomalies), with cooler temperatures in the western U.S. to reflect the -PDO/-PNA pattern and aboves along the East Coast to reflect the +AO/+NAO pattern.

Snow flakes in the Mid-Atlantic tomorrow?

Some snow flakes could mix in with the rain tomorrow in the Mid-Atlantic as colder temperatures push into the region. No accumulation is expected for most, but some of the higher elevations in the Appalachians could see a little accumulation.

Surface temperatures are likely going to be too warm for any sort of accumulation in the lower elevations… with most areas in the upper 30s or lower 40s. The freezing level is forecast to be somewhere in the 925-950 mb range, which gives the snow enough time to reach the surface before melting.

Snowfall rates are expected to be fairly light if/when the changeover does occur, which is more evidence that the chance of accumulation in the lower elevations is slim.

EDIT:

Here’s a sounding of the 12z GFS forecast for 1pm tomorrow… the 12z NAM has a lower freezing level than the GFS.


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Image courtesy of Twisterdata.com

New page – Weather Links

I decided to spend some time collecting my favorite weather links on one page so that other can see what I use and maybe use it themselves. I just put on my main ones that I use just about every day on there, and I plan on adding more in the future as I dig through all of my old bookmarks.

Weather Links

The link will be permanently affixed to the top navigation section. Enjoy!

Foggy sunrise in Maryland

It has been quite foggy the last couple of mornings in the DC/MD region. I snapped a shot of the sun rising through the fog this morning in Gaithersburg, MD:

The fall colors give it a nice added touch. Gaithersburg is a little past peak with the leaves, and I expect I’ll see a lot of leaves on the ground tomorrow as the cold front kicks up some wind in its wake today.

Hurricane Irene Video

I finally got around to going through all of my Hurricane Irene footage and I put six minutes of it together in a nice summary video:

The video’s description:

Chronological video clips of Hurricane Irene from 26-27 August 2011.

Locations filmed in order (all in NC): Rt. 70, Atlantic Beach, Morehead City, Beaufort, Rt. 70 (again), Rt. 17, Rt. 64 and Columbia.

Video start time is approx. 5:30pm on the 26th and runs through about 1:30pm on the 27th. Tornado damage at the end of the video was along Rt. 64 just 1-2 miles east of the center of Columbia.

I chased with Jason Foster. This was my 1st hurricane chase, and it was Jason’s 8th.

Oct. 29 snow pictures

Just posting some re-touched snow pictures from the October 29 storm. All of these were posted to my Twitter account, which you should follow to get daily thoughts and updates!

These were all shot on my Droid X, as I have yet to invest in a DSLR camera (which I plan on doing before the next chase season).

The first shot was just after daybreak, as some surprise early event sleet and snow gave us a nice base layer to build on when the back end of the system hit during the afternoon (which is when the other pictures were taken). Location is Germantown, MD.