Friday, January 9, 2015

January 17-21 Potential Winter Storm

There is potential for a disturbance in the January 17-21 timeframe.

Tropical Tidbits
The above image shows 500mb vorticity values across the Western Pacific from the (soon to be retired) GFS model, valid the morning of January 11th. Here, we see elevated vorticity values pushing east from the mainland of Asia. Of note is the shortwave evident just west of Japan, as the depression in the 500mb contour lines shows. This is the storm system we are watching.

A look at mean sea level pressure (MSLP) values for this same timeframe indicates the storm would be crossing almost squarely over the middle of Japan. Using the Typhoon Rule for timeframe, extrapolating the date of this graphic out 6-10 days, we come up with a possible storm in the US during a January 17-21 timeframe.

The above image shows teleconnection forecasts from the ESRL agency shows the Pacific North American index dropping to near-neutral levels when this storm is projected to strike. Add in the moderately-positive NAO forecast, and chances are this storm will mainly take a west-to-east track, and is unlikely to "cut" north or south in any drastic manner.

To summarize:

- A storm system may impact the US during the January 17-21 timeframe.
- Indications are this storm could affect primarily the mid-section of the country.