Daily Archives: December 16, 2012

First look at Texas’ Christmas Weather; Cold and Wintry?

It’s hard to believe that we’re only nine days away from Christmas and our high temperatures here in Dallas were in the mid 70s. It feels like Spring, yet if you look at climatology, we’re supposed to be out and about with heavy jackets and long pants. Everyone is asking when is the next cold snap coming south. It looks like it will it arrive in time for Christmas. We won’t be able to answer the question of the exact weather for Christmas until we get much closer, but we are within range of being able to tell what the general weather pattern should be and what might occur around December 25.   Please keep in mind that the following data could drastically change and what results may end up being nothing like we discuss this evening. With that advisory out of the way, let’s go ahead and talk about the general weather pattern leading up to Christmas!

 

The Arctic Oscillation 

Arctic Oscillation

 

One of the tools we use to help predict the weather pattern upwards of 10 to 14 days out is the Arctic Oscillation. This index simply helps us determine whether or not the pattern will be favorable for air-mass movements out of the northern latitudes further south into the United States. When the Arctic Oscillation (AO) is positive, then the chance of having a cold airmass moving south out of Canada decreases. On the other hand, when the AO is negative, the chance for cold air moving south out of Canada increases. Having a negative AO doesn’t guarantee a cold air mass or a long-term period of below average temperatures, but it does provide us with some clues as to what could potentially unfold. As you can see, we’ve had a negative AO since late November. Even with that, we’ve had above average temperatures in Texas with cool-downs every few days. After our cold air outbreak in early December, the cold air has had to reform across the Arctic Circle into Canada. Even now, temperatures in southern Canada are not very cold for this time of year. However, those temperatures are going to cool down dramatically this week and by the weekend, a very cold air mass will exist across Alaska eastward into parts of Canada. It will simply be a matter of time before that air-mass gets pulled south by the jet-stream.

Even though we are pretty confident in a cold air-mass moving south into the United States early next week, there are many different directions that cold air could go. While one pattern would bring the cold air-mass directly into the Texas, another would shunt it further east into Tennessee leaving Texas with only a slight cool-down. It is simply too soon to tell how much we will cool down next week, but I do feel confident in saying that we will have a slight cool-down, at least. Will it be in time for Christmas? Once again, we are too far out to tell. However, let’s see what’s ahead and look at the two primary weather models and see what they are showing.

Global Forecast System: Christmas Morning

Global Forecast System: Christmas Morning

The first weather model I’m showing above is the Global Forecast System (GFS) and is the primary American weather model for the 7 to 14 day time-frame. This model is run every 6 hours and this graphic comes from the Sunday morning run. For this run of the GFS, it has a cold front pushing south to the Interstate 10 corridor by 6 AM on Christmas morning. Temperatures are falling into the upper 20s and lower 30s in the Texas Panhandle with temperatures in the 40s along and north of Interstate 20. Warm and humid conditions still exist in extreme Southeast Texas southward into the Valley (Deep South Texas). The GFS has a tendency to move these systems too quickly, and as you’ll see in the next graphic, may be pushing this cold air south too quickly.

European Weather Model: Christmas Morning

European Weather Model: Christmas Morning

The other primary weather model for the 7 to 14 day time-frame is the European Weather Model. This model runs twice a day and is also from Sunday morning’s run. The European weather model, known as the EURO, has shown increased accuracy in the longer range with cold air situations compared to the American model (GFS). Thus, I’m more inclined to believe it compared to the GFS. This model has the cold front knocking on the Panhandle’s door by Christmas morning with warm conditions across much of Texas. In fact, this run shows a risk for thunderstorms in East Texas with gusty west winds along and west of Interstate 35.

Let me remind you again, we are not looking for specific time-frames this far out. We are watching for trends in model data. While they do have timing differences, the GFS and Euro both show a cold air outbreak in the Central and Southern United States by next week. The coldest air would likely arrive just after Christmas, but that will be refined as we get closer. The main point of all this is that Christmas Day itself could be somewhat active with either a strong cold front moving through or preparing to move into the Texas shortly thereafter.

For the fun of it, lets jump ahead to Wednesday, December 26.

European Weather Model: Wednesday morning, December 26

European Weather Model: Wednesday morning, December 26

American Weather Model: Wednesday morning, December 26

American Weather Model: Wednesday morning, December 26

Again, there will be timing differences when looking at weather models this far out. However, the European and American weather models are in agreement right now that a cold air outbreak will invade Oklahoma and Texas shortly after Christmas. We don’t know how significant this cold air outbreak may be or the exact timing. With the Arctic Oscillation being negative and the cold air bottled up in Canada, this solution does have creditably.

There is NO way to accurately forecast precipitation in the long-range and if you ask us will it snow in the next two weeks, we’re going to say we don’t know. However, for the snow weenie fans, I’ll go ahead and share a graphic from the American Weather Model for December 27. This will not happen and the afternoon run of the GFS has a completely different look, but here is a little model voodoo for you. This graphic shows snow depth in inches.

gfs_snow_depth_west_71

I hope you enjoyed this detailed discussion of our thoughts about the upcoming Christmas weather. We’ll keep you updated and as we get closer we’ll refine the forecast.

Severe Weather Outlook for Southeast Texas Issued

 

The Storm Prediction Center has indicated portions of extreme Southeast Texas will have the potential to experience a few severe storms later this morning. A weak cold front will spark an area of thunderstorms later this morning. As this area of storms moves towards the coast, it will tap into the rich, unstable Gulf of Mexico air and likely intensify. Because this will be during the morning hours, the atmosphere will only be slightly unstable. This will likely keep most of the storms in line and under severe limits. However, a few storms will have the potential to become severe and produce winds over 60 MPH. All storms will be capable of producing lightning. This event should be out of Texas by early afternoon. Be sure to keep an eye to the sky as you head off to morning services!
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