Arctic cold poised to dive south!

HOUSTON - Cue Margaret Whiting and Johnny Mercer: "Baby, it's cold outside!" 

Okay -- maybe it's not cold yet but long range model indications are it could certainly turn that way by the end of next week.

More importantly, what does all this mean for Houston? Well, it's way too early to know at this time. However, according to this tweet from Eric Berger (@SpaceCityWx), temperatures may not get out of the 40s for daytime highs if and only if, the models continue to trend cold over the next few days.

 

 

When dealing with prognostications this far out, it's important to remember not to get bogged down with the specifics but rather the overall synoptic (large-scale) pattern across the continent.

Take a look at this 06z model run from Monday:

Just looking at that map, it just looks cold. The bright pink, purples and blues represent temperatures sharply below normal making for downright cold conditions, even during the afternoons. The pinks and blues show temperature departures well below normal by as much as 10 to 20 degrees.

In the model runs since Monday, the intensity of the cold has ebbed and flowed a bit with the greatest temperature departures now occurring east and northeast of here heading into the second week of December and not as cold here. That's not to say it couldn't shift around again because it could. 

Again, this isn't the time to get bogged down with specifics of "how cold is it going to get?" Your answer to that is, "I don't know yet."  The overall pattern certainly favors a cold December though.

What's one of the clues? We monitor different oscillations around the globe including the PNA (Pacific North American), NAO (North American Oscillation) and the AO (arctic oscillation). The one with the biggest implications for the U.S., and thus Texas, is the Arctic Oscillation. 

When the AO turns negative, in this case deeply negative, as seen in the model projections above (the downward facing red lines), that signals a favorable pattern for cold outbreaks across the United States amongst many other atmospheric implications.

As seen in the below tweet from meteorologist Michael Ventrice, meteorologist at The Weather Channel, the pattern in the 10 to 15 day is ringing alarm bells for a big cold outbreak by the middle of December, evidence by the big purple spot (cold) at the bottom of the picture sitting over the United States.

 

Now add in the volcanic eruption in Bali that could have far-reaching effects on the global climate. According to meteorologist Brooks Garner, "it's interesting that not only are the models illustrating a much colder pattern but now that question has to be asked, "what happens when you add tons of sulfur-dioxide mixed with water vapor in the atmosphere? The answer, a cooling effect as the insolation (incoming solar radiation) from the Sun is blocked.""

According to the Washington Post, the cooling affect on the planet could last for upwards of three years, perhaps longer given a larger than predicted eruption from Mount Agung. 

"In the short term, ash particles would cause regional cooling, as the layer of dust prevents some sunlight from reaching the ground. In the long term, sulfur-dioxide would mix water droplets in the atmosphere, spread across the globe and reflect sunlight for up to three years. Average global temperatures could decrease significantly."

While this eruption may not play too big a part in  this outbreak, succeeding outbreaks could be interesting regarding severity and duration.

Again, regarding the upcoming cold event, it's impossible to know just how much cold air could be headed our way, if any at all. It could in theory, spill into the country but go east instead of due south. It remains to be seen.

In Houston, our first average freeze is right around December 4th. Since 2012, we've seen our first freezes a bit later than that but not by much.

If the current pattern holds, at the very least, it's going to get cold. Just not sure how cold yet. Then again I may write to you tomorrow and say in short, "Nevermind! High of 80 next week!" I don't want that and I don't suspect that's in the offering, but in theory could happen.

And just an FYI for everybody who's thinking it, NO, there's no snow in the forecast. 

 

© 2017 KHOU-TV


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