Saturday, February 7, 2015

February 22-27 Potential Winter Storm

Model guidance has been hinting at a rather strong winter storm impacting the United States around a February 22-27 period.

Tropical Tidbits
Click images to enlarge
The above image shows the GFS forecast of 500mb geopotential height values (colored shadings) and mean sea level pressure contours over the West Pacific, valid on February 16th. In this image, which is from the GFS model run on the morning of February 4th, we see a very strong low pressure system crossing Japan and moving away from the country as it does so, with a minimum central pressure here of 987 millibars. This is a very strong system, but one might argue that can be expected from long range guidance, which can/does tend to over-amplify storms in long-range forecasts.

Since that forecast was made, at least 5 other GFS runs came in with very similar solutions, meaning this could be a valid storm potential. You'll notice that the timeframe isn't exactly the same on each graphic, but the storm impacting Japan between February 16-17 is generally agreed upon.

Tropical Tidbits

Tropical Tidbits

Tropical Tidbits

Tropical Tidbits

Tropical Tidbits
While this model remains inconsistent as far as showing this storm run-after-run, the general concept of a storm in this timeframe is still present (for now).

When we apply the Typhoon Rule, which states weather phenomena occurring in Japan is reciprocated in the United States 6-10 days later, we can extrapolate the storm in this February 16-17 timeframe to get a rough estimate of a February 22-27 correlation here in the US, padding in a couple days for uncertainty. But we may also be able to figure out where it tracks.

The above image shows sea level pressure anomalies on the morning of January 24th, 2011. On this day, we saw a storm system cross Japan and rapidly strengthen as it began to exit the eastern coast of this country. Just for kicks, let's apply the Typhoon Rule here. If we do so, we likely saw a storm system impact the country between January 30th and February 3rd, 2011.
Some of you might remember that as the Groundhog Day Blizzard of 2011, which dropped close to 24" of snow in Chicago, IL, as well as incredible ice accumulations in the cold sector of this storm. When we compare the projected track of our mid-February storm in the GFS images above, we see that some (not all) forecasts have the upcoming low taking a similar track as the eventual-Groundhog Blizzard did. That's not to say I'm expecting another massive blizzard. I'm just trying to show where this storm could end up tracking, and that could be through the Midwest yet again.

Tropical Tidbits
There's also the chance we see this storm go through the East US and impact that area primarily. The reasoning behind this is the expected ridge-out-west and trough-out-east pattern which will likely deliver more than one round of accumulating snow to the East (more on this can be found in yesterday's post). The image above shows the GFS ensemble outlook at the very end of its run, depicting 500-mb geopotential height anomalies for February 22, 2015. We see a gradual departure of the trough in the East into Greenland, though the ridge in the West is still persisting. Personally, I'd bet more on the trough staying put purely out of persistence forecasting, but that's why you take model guidance with your own opinion. If this forecast did work out, however, the storm could impact the Central US and East US, whereas the trough staying put would result in an impact likely for the East.

If we factor in tropical forcing, we get yet another different picture. When the timeframe for this storm rolls around, enhanced tropical convection is forecasted (not shown here) to be placed in an area around and just east of the 90ยช East longitude line, which places us in Phases 4 or 5 of the Madden-Julian Oscillation (MJO). The above graphic shows precipitation anomalies on the left two columns; we'll ignore the colorful columns on the right for now. When we look at precipitation anomalies during Phase 4 and 5 in a January-February-March period, we tend to see the Central US into the Northeast getting in on storm activity. This could mean the storm in late February, if it happens to begin with, will hit both the Central US and East US, but anything beyond that is purely guessing.

To summarize:

- There are indications a strong storm could hit Japan in the middle of February.
- This could result in a strong storm in the United States between February 22 and February 27.
- It is not known who will/could be affected by this system yet.
- As the post thoroughly showed, significant uncertainty surrounds this event.