February 1-5 Potential Winter Storm

There is increasing potential for a winter storm in the February 1-5 period.

Shown above is the 500mb anomaly forecast off the ECMWF model, valid on the morning of January 26th. If you've followed this blog for a while, you know that we can use that area of negative height anomalies over Japan to forecast a storm in the United States. As Joe Renken states, we can extrapolate a storm over East Asia out 6-10 days to arrive at the timeframe for a storm here in the United States. Going that length past January 26th gives us a storm timeframe of February 1-5. That's not the only thing we can take away from this predictor, however. Looping the ECMWF forecast tells me that the storm system will be moving essentially due east as it passes through central Japan. This tells me that we could (keyword here is could) see our February 1-5 storm system also moving on a west-to-east track, not really curving north or dropping south too much. The 12z and 18z GFS models caught on to that idea of a west-to-east storm, but had the storm hitting the US on January 31st to February 1st, which is just outside the timeframe presented here. We'll discuss the models a bit later on in this post.

Adding to the evidence of a possible storm in the early February timeframe is what we saw happen in the Bering Sea on January 18th. The image above shows contoured 500mb height anomalies over the north Pacific on January 18th. We see a storm system moving east from far northeast Russia, which is the westernmost 'X' on the image above. The next day, we saw the storm move nearly due east to the second 'X' in the image, only moving just a bit north in the process. Going back to that link I posted above, there is also something called the Bering Sea Rule, developed by Joe Renken. The Bering Sea Rule states that a storm in the Bering Sea can result in a storm over the United States 17-21 days later. If we extrapolate the January 16th date out using the 17-21 day timeframe, we arrive at a potential storm in the February 2-6 timeframe. This fits well in the February 1-5 timeframe we got from the East Asian correlation, and the nearly west-to-east movement in the Bering Sea tells us the storm in the US may be west-to-east as well, like we saw in the ECMWF forecast.

Now, model guidance is pretty iffy on the timing of this storm, and that is to be expected. The GFS model wants to bring a zonal (west to east) track storm through the US, but on the January 31-February 1 timeframe rather than the early February time periods established by the East Asian correlation and the Bering Sea Rule. The ECMWF model brings a west-to-east track storm system through the US on February 2-3, which fits right into the two time periods we established above. However, the ECMWF is much less robust on snow totals; the GFS allows significant snow in the January 31 forecast above, while the ECMWF only lays down a handful of inches from the Plains to the Great Lakes.

I think we'll end up seeing a compromise, where the GFS slows down the storm to the ECMWF's timeframe of the first days of February, but we see increased precipitation amounts like the 0z ECMWF and 12z + 18z GFS put down, rather than the weak amounts put down by the 12z ECMWF model.

Andrew