Major Thanksgiving Storm Likely For Midwest, Great Lakes

I am making the call for a major Thanksgiving storm system (likely with snow) to hit the Midwest, Great Lakes, and possibly the Plains and Northeast. Let's take a look at why I am now making this call.

This is a 500mb height anomaly forecast, valid a few days out. As you can see, there isn't much going on in the United States, so why am I showing you this? Well, we have to go to East Asia for that answer. If you look in the top left corner of the image, you will see a strong trough present in East Asia. It has been shown that there is a 6-10 day gap between what happens in East Asia and what happens in the East US. So, if we use this forecast (valid November 13) and apply the 6-10 day gap to it, we end up at November 22, or a day or two from Turkey Day.

We can also use the Lezak Recurring Cycle (LRC), which is, in the simplest of simple explanations, a repeating pattern that forms every fall and cycles through the winter. This pattern first forms in September-October. A strong storm system hit the Plains, Midwest and Great Lakes on October 2. If we use the expected 51 day gap between each cycle and add on a day or two to give the forecast a little wiggle room, we find this strong storm system hitting the Midwest/Great Lakes on November 21-23, which falls right on Thanksgiving!

I think it's time we turn to the models to see what they're saying. This is the morning forecast from the GFS model for Thanksgiving. This image shows precipitation over a 12 hour period, as well as MSLP lines. The pink line is the rain/snow line. Any precipitation above that line would be snow, and precip. below the line is likely to be rain. The GFS is forecasting a pretty strong storm system to be present across the Midwest/Great Lakes on the morning of Turkey Day. While the GFS has been juggling the position of this storm system, it has been forecasting a strong storm system in the general East US on Thanksgiving.

As you can see in the above forecast, there is a lot of color above the pink line. Yes, this would mean snow. However, because all I am confident in is the presence of a storm in the mentioned regions, I don't think now is the appropriate time to make calls on precipitation. However, if there is to be precipitation, it will most likely focus in on the Upper Midwest and Great Lakes.

This is likely to be the most accurate forecast for this system if we rely on the LRC, but any East US forecast with a strong storm system could verify if we use only the East Asian theory. Personally, I think it's a good idea to combine the two and use the GFS forecast above (which will definitely change in coming days).

Let's sum this all up:
•I am making a call for a storm system on Thanksgiving Day.
•This system will hit the Midwest, Great Lakes, and Northeast.
•Snow is likely, possibly heavy in some areas.
•Cold weather will follow the system.

Andrew

ENSO Update: El Nino Lurking Beneath The Waters

The ENSO state as of now remains troubled, with a large expanse of warm waters below the surface, but very little amounts of warm water are actually reaching the surface, where it matters.

The image above shows the latest observed underwater temperature anomalies. Above normal temperature waters are shown in yellows and oranges, while cooler waters appear in blues. At about the 100-200 meter zone, there is a big body of above normal water to the east of the 180 longitude line. That puts this warm body of water roughly in the Nino 3.4 - Nino 3 regions, known as the area most used for identifying the ENSO state. While this body of water may look pretty strong, observe the cool body of water just developing between 50-300 meters below the surface to the west of the 180 line. This cooling trend has just started developing, and based on an animation of underwater temperature anomalies, this cooling trend should continue. That would eat away at the warm body of water, especially in the Nino 3.4 region.

There is a second warm body of water between the surface-150 meter mark, which is more compact and appears more likely to move to the surface. However, just as the aforementioned body of water is having trouble, this second above-normal body of water is also struggling. If you see the upper-right corner of the picture, you can see a small pocket of much below-normal temperature anomalies. That is just off the coast of South America on the Equator. This pocket of cold water is also eating away at the warm waters, but I have more confidence that this body of warmth will propagate to the surface rather than sit underwater and be slowly eaten away by the cool waters, like what is happening near the 180 longitude line.

Observed sea surface temperatures as of Halloween show pretty much what I was diagnosing in the underwater section below. We can see a warm body of water on the surface to the west of the 180 longitude line, while there is a general mess of above and below normal anomalies to the east of the 180 longitude line. In other words, the areas to the east of this line are undetermined as far as the ENSO state goes.

GOING FORWARD
I expect a warming trend on the surface, focused between the 140-100 W longitude lines as the warm body of water tries to move towards the surface. Cooling is likely just off the immediate S. American coast on the Equator, as the cold pocket I explained above could very well bump up to the surface.

Seeing as the CPC cancelled their El Nino watch (as was widely expected), and the first days of November bring about an undetermined ENSO state, I expect this unknown state to continue through the month of November, possibly in to December. This possibility for December will ride on what the big body of water I mentioned first does.

Andrew

Sandy Repeat On The Horizon?

Preword: The title 'Sandy Repeat' refers to a similar way to how Sandy formed, NOT the strength or effects.

The ECMWF model is printing out a scenario all too familiar for those who went through Superstorm Sandy. Please take a look below.

The ECMWF model is showing a tropical system moving up the waters off the East Coast about 10 days away. Storm systems on this map are defined by oranges and red- the deeper the color, the stronger the storm. As you can see, this storm looks pretty strong. But look out to the west. See that blob of oranges and reds? Yes, that is another storm system. My fear is that these two could phase (combine) into one stronger storm, the same way Superstorm Sandy formed. The reason this is a concern rather than an out to sea forecast is because the strongest vorticity values of this storm are located on the western flank, which means this likely-tropical system is being pulled west.

This is still the ECMWF model, and still for the same time frame. This map now shows 500mb geopotential height, the best level to show high and low pressure systems. High pressure systems are shown by arcing lines, and low pressure systems are shown by depressions in these lines shown above. As you can see, there is a big depression in the East in this image, showing a strong storm system. See the small black circle to the east of North Carolina? That is the same system that I showed you above offshore. Considering that there are only a couple black lines separating these two systems in the image above, I believe that the ECMWF is indicating that these two systems are phasing, just like Sandy.

Now, if this even happens (which there is no for-sure indication it will), it will probably not be as bad as Sandy. Sandy was a Category 1 hurricane just before landfall. This system looks like it would be a Category 1 hurricane at maximum- it will be weaker than Sandy. Also, the ONshore system would likely be weaker than the Arctic one that merged with Sandy, meaning that the possible new, combined system would be weaker than Superstorm Sandy.

However, keep in mind that the ECMWF kept on the right track of Sandy while other models incorrectly took it out to sea. Considering the ECMWF has been showing this Sandy-repeat system for at least two model runs, this is definitely something to watch.

I am not making a call yet, I want to see how the other models react to the ECMWF. Right now, the GFS is not in favor of this solution, so just keep an eye out. This is the wait-and-see mode, not PANIC-RIGHT-NOW mode.

Andrew

Siberia Endorsing Back-Loaded Winter Theory

Observed snow cover in Siberia during the month of October is supporting the idea of a back-loaded winter, something many winter weather lovers out there are dreading.

Something forecasters use in the fall months to help predict the upcoming winter is indeed Siberia. In October, the anomaly of snow cover over the region has been proven to correlate with observed Arctic Oscillation anomalies in the following winter. For example, if the month of October held a very below normal snow cover situation for Siberia, the Arctic Oscillation would most likely be on the positive side (warmer weather) for the winter.

If we apply that rule to the observed October 2012 snow cover, here is what I find:

-Generally warm start to winter.
-Slight improvement through Nov., Dec.
-Cooler towards January.
-Brutal cold in January-February.

Whether this happens remains to be seen, but Siberia is known to stick to its guns with this theory, so the above conclusions could very well verify.

High Impact Snowfall Event for North Plains

I am forecasting a High Impact event for the Northern Plains in the next 5 days, as a major winter weather event hits the region.

What is a High Impact event?

•Heavy precipitation
•Property and Life threatened
•Major travel disruptions

I am anticipating over a foot of snow hitting Montana into the northern part of North Dakota. This could get pretty extreme, especially for rural areas that may see their roads covered, possibly for a long period of time.

Farther to the south, amounts from a half foot to 12'' are likely, as lesser effects of this High Impact event are felt, yet still remain disruptive to travel.

Keep up to date on the latest weather conditions. Make sure you have proper provisions, possibly to use for an extended period of time if your roads are unplowed for an extended period of time.

Andrew