ANOTHER TRIP AROUND THE SUN
Happy Thanksgiving everyone. Hard to believe another year, another trip around the sun, has passed us by. Since it is a day of thanks, I do want to express my sincere gratitude to all of you who find it worthwhile to spend some of your valuable time on the site. TSwails is entering its 12th year of existence, and if you are coming here, you and I obviously share a similar passion for weather and the quest to understand it, a road I travel daily. So, on this day of Thanksgiving, please know you are welcome at the table of weather anytime. When I break bread today, you will be in my thoughts and honored as family. Here's to you!
THE BIG PICTURE
Today we are entering phase 5 of the MJO (Madden Julien Oscillation). By measuring outgoing radiation from clouds and convection in the tropical Pacific including the Indian Ocean and the western Pacific, the MJO determines where disturbed weather is located in one of eight specific regions below.
In the simplest of terms, research has determined that convection in a specific phase correlates to the temperatures and precipitation we experience from mid-latitude cyclones here in the United States, especially in winter. The convection moves west to east across the Indian Ocean and west Pacific in an eastward cycle. Modeling has been formulated that can to some degree track the intensity and speed of these convective waves. We view it in what's known as a phase diagram.
Below, you can see the latest phase diagram of the EURO. Starting November 28th. You can watch the MJO's daily advance into phase 5 and eventually phase 6 December 26th.
Nationally, phase 5 which we are entering now is a mild phase west and a cold phase east. The 500mb jets cuts across the Midwest from the NW (hence the term NW flow). That means as a whole, the Midwest remains on the western periphery of a cold air mass centered over the eastern U.S. Below is the 500mb height anomaly for a phase 5 neutral ENSO (no El Niño or La Niña) in December.
The takeaway is that the MJO is shown to be in phase 5 through December 10th. The teleconnections for such a pattern would as a whole suggest near to below normal temperatures locally and minimal precipitation, with Gulf moisture suppressed. That idea is well-supported by weather guidance the next 10 days. The GFS indicates 10-day average temperature departures that look like this, ending December 7th.
These are the 10 day average precipitation departures for the same period. Much of the country is shown with below normal precip.
Following the MJO cycle deeper into December, tropical convection in the Indian Ocean moves east, and the cycle shifts from phase 5 to 6 during the period December 10th to the 26th. Track it on the phase diagram below.
Teleconnections for phase 6 typically have a strong tendency to flip the pattern, with a trough replacing the ridge over the west and a ridge evolving instead of a trough over the east. Basically, it's a complete reversal of what we are experiencing now. See the 500mb anomaly of a neutral ENSO phase 6 in December.
The end result of such a 500mb structure is limited access to cold air and well above normal temperatures. Precipitation tends to increase some as the door is opened to increased moisture. This is the MJO phase 6 correlation for temperatures and precipitation in December.
I mentioned this trend showing up a few days ago, and nothing has changed to indicate it won't. For a guy like me who enjoys winter snowstorms and forecasting them, this is painful to look at, especially if you like a white Christmas.
Look at the cold in the pattern today.
Now look at the 7-day average temperature departures December 16th-23rd. If that's not a classic phase 6 look, I don't know what is. Some places in central Canada are 35 degrees above normal. Alaska and Greenland are cold, but much of Canada is enjoying a winter heat wave. The cold that typically predominates in Canada is gone! That about makes me cry.
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You never say never in the weather game, but I really dislike phase 6 in December, and I am going to be very surprised if we do not see a mild run-up up to Christmas from mid-December on. Without cold air, snow chances dwindle as well. Man, I hope I'm wrong! The only way we get out of the mess is if somehow modeling is wrong, and we avoid phase 6 or our stay is brief, confined to 5 days or less.
Meantime, the colder air we've been promising for days is making inroads. We have ourselves a cold pattern ahead, but aside from some flurries, I don't see much for white gold through December 6th. We are in a set-up for about 7 days when some minor clippers can enter the mix. These are capable of producing quick, light hitting bursts of snow. However, they tend to be narrow and getting in the way of one is tough. If nothing else, I'm hoping that later in the next week we at least get brushed by one before we enter the death phase associated with phase 6. The GFS does show a snow system around December 7th, but I am not optimistic it will come to fruition.
All right, time to move on. Have a safe and splendid Thanksgiving. Roll weather...TS
