November 25-29 Potentially Significant Winter Storm

The storm system around the November 25-29/Thanksgiving timeframe continues to look like a significant storm system.

OPC

On the morning of November 8th, we saw the remnants of Typhoon Nuri reach peak strength via Ocean Prediction Center observation. As the chart shows here, the massive storm bottomed out at 924 millibars. This means the storm, located at about 170E and 55N, didn't break the record for strongest extratropical cyclone on record, but it certainly came close.

NWS

The graphic above, produced by the National Weather Service in Alaska, shows the observed mean sea level pressure of the storm at that 924mb reading, while the NWS office measured it at 930mb on the chart on the left, where strongest extratropical cyclones in the North Pacific are depicted. For multiple reasons, including the possibility that past storms may have been stronger than that 924mb reading, this storm was not declared the strongest on record in the North Pacific. Despite this, it's quite clear this storm was a historically-strong one, relative to storms in the last 60 or so years.

NOAA

Purely for comparison purposes, the team at KOPN Weather identified a strong storm in the Bering Sea on April 7th, 2011, bottoming out at 936mb, that was about 10 degrees W of where this very strong storm was observed yesterday in the Bering Sea. If you recall what happened about 2-3 weeks after the date of April 7th, we saw a certain tornado outbreak strike the South US, devastating thousands across the country, and causing millions on millions of dollars of damage. If we look at where the resultant storm ended up in mid-late April, utilizing the Bering Sea Rule, we find the storm situated in the Ohio Valley.

WPC

Now, keeping in mind that this sort of correlation is a tough one to use at best, not to mention all the caveats associated with long range forecasting, we could theoretically juxtapose the remnants of Typhoon Nuri and this storm in the Bering Sea on April 7th to get an idea of where the consequential storm in the US may end up. Recalling that the storm in 2011 in the Bering Sea was at about 180 degrees longitude, and almost the exact same latitude as the one observed in the last day or two, we find the remnants of Nuri placed about 10 degrees west of that 2011 storm. If we take the location of that storm system in late April (pictured above) and move it west, like the remnants of Nuri were west of that 2011 Bering Sea storm, we end up with a map like this:

WPC

Continuing this correlation, just to see what would happen, we notice that the remnants of Typhoon Nuri are moving eastward (a bit northeast in the process) in the Bering Sea right now, slowly at that. If this storm somehow does end up in that potential location outlined above, and if enough cold air is available (this will be discussed later), a significant winter weather event may strike the Central Plains, Midwest, Great Lakes, and Ohio Valley. Similarly, if the correlation works out, a severe weather event may strike the South US. Again, many caveats are associated with this method, and this should not be taken as "gospel", or at face value.

Tropical Tidbits

The above image shows temperature anomalies at the 850 millibar level (about 5,000 feet off the ground) over North America, as forecasted by the ECMWF ensembles ten days from today. In this image, we see a large swath of warmer than normal temperatures in the Bering Sea, with colder than normal conditions encompassing much of the United States and southern Canada. This looks to be a persistent pattern in coming days and weeks, as a large block of high pressure looks to set up shop directly over the Arctic, providing for a very cold period for North America. Extrapolating this to Thanksgiving, enough cold air should be in place for at least a modest threat of a significant snow event. Again, bear in mind long range caveats, but such a prognosis is favored right now.

To summarize:

- A potentially significant storm system still looks to evolve in the United States around Thanksgiving.
- Severe weather will be a possibility, namely in the South US.
- Significant snow will be a possibility, predominantly in the Central Plains, Midwest, Ohio Valley, and Great Lakes (for now).
- Thanksgiving travel may be severely hampered by this storm, if it does come to fruition as currently projected.

Andrew