Wednesday, March 11, 2015

Colder, Stormier Weather Returns for Late March

Model guidance is indicating we're likely to see another stormy and cool period to end March.

Tropical Tidbits
The image above shows 500mb geopotential height anomalies over the West Pacific and eastern Asia. In this chart, oranges depict ridging aloft, a signal for warmer and generally quiet weather. Similarly blues depict toughing/storminess, and thus brings about cooler weather. In the graphic above, we see a persistent trough sitting over Japan and the Koreas, as signified by the plethora of blues. This is actually a mess of storm systems and cool weather combined.

When we apply the Typhoon Rule, which states weather phenomena occurring in Japan is reciprocated here in the US about 6-10 days later, we should expect a generally stormy and cool pattern around March 18-24 or so. This includes a stormy end to spring break for those who vacation next week, and a similarly cool/wet pattern for those who begin their vacations the week after next.

Tropical Tidbits
Models are already honing in on that colder weather. The above graphic again shows 500mb geopotential height anomalies, but this time over the United States and valid on March 18th. Here, we see prevalent ridging over the western half of the country, leading to pleasant conditions in the Rockies and Plains. However, a deep upper level low is forecast to traverse the Northeast and southern Canada, as the deep blues show. This means cold weather, possibly bringing about snowfall in the process for some.

To summarize:

- A generally stormy and cool pattern is expected for the second-to-last week or so of March, primarily around March 18-24.