CLASSIC GFS LOOK FOR COLD AND STORMY...
Don't know how it will turn out but the GFS and its ensembles are trying to tell us something about another shot of cold air to start December. If you saw last nights post, I focused on the mixed messages regarding this trend in the available teleconnections. You can read the full post HERE but the conclusion I came to was this: When you see discrepancies in models like this (no mojo on the MJO) you know the pattern is in flux and it's a good idea to be cautious in the long term. I still think the EPO is going to drive the pattern this winter so as long as that is neutral to positive, I don't see the harsh cold getting back into the pattern for any extended period of time until after Thanksgiving.
OK, so what's the message (or trend) I've picked up on today. It's that the pattern is still in flux but I'm seeing signs on several models that the EPO (eastern Pacific oscillation) is set to go back into negative territory in early December. That is a cold signal. Below the GFS ensemble EPO forecast through December 6th.
Additionally, the MJO (Madden Julien Oscillation) associated with the GFS is also in sync. It rolls through phase 2 for about 7 days (that's a known mild phase this time of year), and then cuts back into 7, 8, and 1 (cold phases) about the time the EPO shows its crash. This type of progression would enable the negative phase of the EPO to develop. I very much like the consistency within the ensemble.
To give you an idea what the MJO depicts, phase 2 on the MJO this late in the month would be a blend of it's November/December temperature correlations which look like this.This is the short term trend.
When we get to phases 7, 8, and 1 which looks to be where we are heading, it's a complete reversal. Take a look at these temperature correlations in the month of December. The long term trend.
Another factor which has come into play is the GFS based AO (Arctic Oscillation) is also projected to go negative about the same time as the EPO.
The negative AO in conjunction with the EPO and MJO leads to a pattern that looks like this over North America. Essentially the Midwest gets cold.
Now the straw that could break the camels back! When the AO goes negative, it's a sign that the westerlies are weakening. Without their shearing effect it makes it easier for cold air masses to leave their source region (which is the Arctic) and dig into the U.S.
We also know that we're in a solar minimum (for sun spots) and that can open the door for what we call stratospheric warmings. That's something you look for to get the polar vortex dislodged and relocated over the northern U.S. Now here's the kicker, and this could be really big with major implications. When the AO goes negative it allows the heights to rise over the polar regions.That is forecast to happen on the GEFS in early Dec. This is at 10mb the highest reaches of our atmosphere. The heights are greatest near the pole.
When the heights go up, that forces the cold air that's normally there to be forced or displaced south. These are the 10mb temperature anomalies and you can see that relative to average, it's warmer in Siberia and the North Pole than it is over Florida and the entire United States!
To be clear, if the GEFS is right a stratospheric warming is underway and we could be in for some really frosty weather in some part of early December.
Not only that, the 500mb pattern (jet stream) is projected to look like this. That huge ridge poking into Alaska (in red) is the manifestation of the negative EPO and that looks COLD! Not only that, the jet is in a position where the pattern could be stormy and snowy.
Now I'm basing a lot on the GEFS, but so far it has handled the cold this season better than the EURO. Not only that, the ensembles are a far better tool than the operational runs because its based on the average of multiple members, not just one run. Aside from that, I just pointed out how the stars are aligned for this to happen. All the teleconnections are there. The only issue is (AND THIS IS A BIG ONE) would be if the model is flawed and it moves away from this solution. That possibility still exists and you can bet I'll be watching that trend like a hawk in coming days. I'm really impressed with how much has changed over the past 24 hours!.
The last thing I will mention is a potential storm about Tuesday of Thanksgiving week. The EURO shears it out and has little if any surface reflection. Nothing to worry about. The GFS however sees it differently and actually produces some snow across the NW half of my area. Both models have gone rogue several times the past 48 hours so my faith in any one solution is less than desired. However, the way the pattern is set up I could see the GFS and its stormier solution come to fruition. The track is going to be critical as to who gets snow (if anybody) and its too far away to bank on a single model. I'm going to let this simmer and just let you know something could be cooking. Sorry about the lack of commitment but the variance is just too big at this point in the game.
If you liked this summary, you would no doubt enjoy weather school which I will be presiding over January 25th. We'll get into all this stuff and have a gay old time as the Flintstones say. Space is limited and we are about half way to capacity so get off the fence and sign up. Here's all the details!
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The seminar will be held January 25th and will last from noon until 5:00pm. We have limited seating and the cost is $ 99 dollars per person. A catered lunch will be provided. Again..not a lot of seats so reservations with a pre-payment are required. Sorry, no refunds. If there’s enough interest, a second session will be added in early February. To register or get additional information send an email to email@example.com
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WEATHER SCHOOL AGENDA:
WELCOME AND INTRODUCTION
Purpose: To help weather enthusiasts understand the basics of forecasting and apply the knowledge and techniques learned to construct personal forecasts.
Session 1: DATA ACQUISITION
The essential on-line sites for models, observations, satellite and radar images, and general weather data.
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Determining your objective goals. Short term, intermediate, or long-term. Understanding the process of analysis and its relationship to forecasting.
Model options and choices. What to use and when!
The GFS, EURO, NAM 3k, NAM 12K, Canadian, HRRR, MJO, ensembles, teleconnections, etc.
Locating, learning, and knowing what’s essential to make a reliable forecast.
The art and science of model interpretation: Using and understanding model output. Its called guidance for a reason!
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Wind and pressure
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A simulation of the basic process using model output.
BREAK: A 25-30 minute recess to enjoy a catered lunch…
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Thunderstorms, tornadoes, derechoes, and squall lines.
Soundings. What are they and why should I care?
Instability (CAPE) vs (CIN) Critical interaction involving moisture, heating, and forcing.
Uncovering the ingredients of a severe weather set-up.
TVS signatures. What to look for on radar.
Role of SPC vs NWS, and your local TV station regarding the warning process.
Simulated model driven forecast of a severe weather event/tornado outbreak
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How to forecast the rain snow line.
How to forecast snow totals from QPF
Determining totals from snow ratios.
What to look for at the surface and at upper levels (500 and 850mb)
Model bias and determining the storm track
Simulated model driven forecast of a significant Midwest winter storm
QUESTION AND ANSWER SESSION
An open period for attendees to ask questions regarding relevant topics or issues discussed during the day.
Some final words of inspiration from the events headliners
Once again, to reserve a spot or ask questions send an email to firstname.lastname@example.org See you when the bell rings! T. Swails
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