Monday, March 17, 2014

March 26-30 Potentially Significant Storm System

The potential for a potentially significant storm system over the March 26-30 period remains alive.

Tropical Tidbits
The image above shows 500mb geopotential height anomalies from the latest run of the GFS model over the Western Pacific, valid for March 20th. As this image shows, we see strong negative height anomalies present over Japan on March 20th, indicative of a rather strong storm over the area. There is a rule, well explained by Joe Renken, that states a weather phenomenon in East Asia will be reciprocated in the United States 6-10 days later. This means that if there is a storm system in Japan on a certain day, we can expect a storm in the US 6-10 days after that. The same goes for high pressure and warm weather. So, if we take this March 20th storm and move it ahead 6-10 days, we find a potential storm system around the March 26th through 30th period.

In an earlier post, I had addressed the idea of two strong storms in this timeframe. Model guidance has dropped the idea of two storms on March 20th in Japan, and appears to be going with one storm instead.

Tropical Tidbits
If we look at the long range GFS jet stream forecast for March 26th, the beginning of this four day timeframe where a storm is expected, we see a few things. The primary thing we want to discuss is the active subtropical jet stream. If you recall, there are two jet streams which have the most effect on our weather (there are three jet streams in total): the Pacific jet stream, which comes from the Pacific and is a primary driver of weather pattern, and the subtropical jet stream, usually located in the South US, with less influence but high-impact effects at times. In this case, I'm concerned because an active subtropical jet stream combined with this potentially strong storm system may create a severe weather situation. There are a lot of variables that need to come together for this to happen, but we've at least established the idea of a strong storm system hitting the US in this timeframe. This is indeed something to watch out for.