Weather Explained: Arctic Oscillation (AO)

Arctic Oscillation Positive/Negative phases.
Positive Phase on the left, Negative Phase on the right.

The Arctic Oscillation is an oscillating index based in the Arctic Circle region.
When the Arctic Oscillation is in a positive phase, a vortex in the upper regions of the Northern Hemisphere is strong and locks in cold air to keep it up north. This keeps the cold air up north as stated, and does not let the US get colder air.

When the Arctic Oscillation is in a negative phase, the vortex weakens, and the cold air locked in releases itself to more southerly regions of the North Hemisphere, typically affecting North America.

The AO can be a key player in winters when determining cold weather, and is an index that should be watched closely.

Weather Explained: Aleutian Low

The Aleutian Low is a semi-permanent low pressure system that sets up over the Aleutian Islands, Alaska. Below is an example of the Aleutian Low.

The Aleutian Low is most intense during the winter months, and can send energy towards North America that can eventually affect the US.

We are not publishing too much information on the Aleutian Low because we do not have enough information on it at this time.

Weather Explained: LRC

What is the LRC?

The LRC (Lezak's Recurring Cycle) is a pattern eagerly followed by many meteorologists and can be a key instrument in determining a winter forecast. Here are the guidelines:

-Pattern sets up between October 1 and November 10.
-Between this time, a certain atmospheric feature occurs that will reoccur over the winter, spring and into summer over a 40-60 day cycle.
-Pattern is never the exact same each year.

So, as an example, let's say a huge rainstorm came through the Ohio Valley on October 17th. Then, on November 30, another huge rainstorm came through the Ohio Valley. This may be considered a part of the LRC, if atmospheric conditions (similar strength, effects on atmosphere) agree with the October 17th storm.

Weather Explained: What does it mean when I see '12z' on a weather map?

Because there are so many different time zones in the world, it gets hard to track models- much more if some are made in different continents. For this reason, weather models are run on Greenwich time, which is the time equivalent of the world's clock, if you will.

Whenever you see 'z' next to a time (example: 12z, 18z, 0z, 6z) it means Noon, 6PM, midnight, 6 am, respectively, all in Greenwich time.

So let's say you live in Missouri. You saw a map with a forecast for rain in your area at 12z. You can subtract 5 hours or 6 hours (depending on daylight savings time) to get your local time in Missouri for when the rain will fall. If you subtract 5 from 12, you get 7 AM. The rain would fall at 7 AM in Missouri.