Bracing for an Arctic Blast

Saturday, November 8th 2014, 9:51 pm

By: News On 6

Are you ready for winter? We've seen some cool spells this season, but nothing like what is coming our way in the next week. It will warm up after this big cool down closer to seasonable levels again, but this Arctic air will likely be parked over the eastern two-thirds of the U.S. for a good two weeks or so. If high temperatures in the 30s and the chance of a wintry mix this early is hard to believe, you might find the trigger for this even more perplexing.

                This past week, a major typhoon named Nuri in the eastern Pacific was hurtling northward towards Japan. It lost its tropical characteristics as it passed by the Japanese islands, but re-strengthened as one of the deepest low pressure systems ever recorded over the Bering Sea, not far from the Aleutian Islands. (The first image is a surface map from Friday of the storm off shore of Alaska) A storm of this strength can alter the flow of the jet stream, which is exactly what is now doing. Essentially that powerful of a system is causing the jet stream to buckle northward in advance of that system, pushing warmer air poleward. The frigid air at the Arctic then has to go somewhere so the jet stream reacts by buckling equatorward downstream. It just so happens that the dip in the jet stream will be right over the eastern U.S., acting to pull that Arctic air over much of the United States. This creates a blocking pattern, thus, keeping the cold air locked in place over us for quite a while. So when that frigid air slaps you in the face later this week, you can blame Typhoon Nuri for causing this pattern. Isn't weather fascinating??

                For those reading this before Monday evening, here's the good news: you still have some nice, warm weather left to enjoy. Warm air will surge back into Oklahoma ahead of that Arctic cold front racing south with the push of the jet stream. Temperatures may top 70° both Sunday and Monday! Fire danger is even a concern given the strength of the wind and now-dormant vegetation. The cold front will arrive Monday night with a biting north wind and our temperatures will cower below 50° for the rest of the week. The second map shows the incredible temperature gradient just above the surface in a computer model for Tuesday evening. The final map shows the near certainty of much colder than normal weather occurring here through the next ten days.

                Outside of a few showers with the passage of the front, dry weather will continue. Despite the dry pattern through midweek, clouds will be tough to shake, especially after Wednesday. The clouds plus a reinforcing shot of cold air Wednesday will bring high temperatures down to nearly 25° below normal! By Thursday, those highs may not reach 40°. Just in time for next weekend, another wave of energy nearby may be enough to spawn precipitation over our area. While the cold air through next weekend is a virtual guarantee, the prospects for a wintry mix are far less certain.

                Where our computer models differ is where precipitation may occur and what the vertical temperature profile will be, which determines the precipitation type. It's too early to say whether we'll see flurries flying, a round of sleet, plain rain, all of the above or none of the above. The take away is to stay tuned to our forecasts as next weekend could very well be our first dose of wintry weather. We see measurable snow in Tulsa about 1 out of every 4 Novembers, but the majority of those instances happen in the final two week of the month. Needless to say, any winter occurrence next weekend would be highly unusual. For now, precipitation amounts look light, but the toll could be greater since many leaves are still on our trees.

                Speaking of leaves, our peak fall foliage is occurring now across our state. Before the cold winds rush in and strip some of the beautiful colors, be sure to enjoy this great taste of fall before Old Man Winter pays us an early visit. For all the updates on this Arctic intrusion, be sure to follow me on Twitter: @GroganontheGO and on my Facebook page!