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.

MJO Forecast Unfavorable For Winter Weather

MJO Forecast

MJO Precip. Anomalies for Phases 3 and 4

MJO Temp. Anomalies for Phases 3 and 4

The MJO, a strong influence of weather in the winter season, is not looking favorable for the next several days for the US. The GFS and ensembles have the MJO moving into Phases 3 and 4. Phases 3 and 4 would mean the following effects for the US:

1. Warm for Much of US
2. Cool for SE in Phase 4, Cool for SW in Phase 3.
3. Dry for Midwest, Ohio Valley, Upper North US for both Phases
4. Wet in West US, Southeast in Phase 3.
5. Wet in NW, NE in Phase 4.

12z GFS Predicts Colder Weather, Potentially Snow

Today's new 12z GFS is predicting colder weather for the US in the long range (11-15 days out), falling into line with the potential for teleconnections to move into a better weather pattern more conductive for snow. The GFS has been having some trouble lately, so we will see if the GFS continues with this pattern before making an assumption about it.

Teleconnections Gearing Up for Winter Pattern Change

Forecast PNA Index.
Positive Phase is Good for Snow and Cold

Forecast AO Index.
Negative Phase is Good for Snow and Cold

Forecast NAO Index.
Negative Phase is Good for Snow and Cold

The teleconnections are looking much better than they have been looking and may be hinting that this winter pattern change is closer than we think. Above are 3 important indices that are commonly tracked and do affect the weather. We have labeled what is good for snow and cold people in each image. Click on the following links for explanations of the indices:
PNA (Pacific North American Pattern) --- NAO (North Atlantic Oscillation) --- AO (Arctic Oscillation)

PNA
The PNA has recently been in a strong negative phase, leading to unfavorable chances for snow and cold. However, in the above images, we see the majority of ensemble members are trending towards at least a weak positive phase already in progress but most likely becoming prominent just before November 30 or so. If the PNA is to go positive, chances for snow and cold would rise.

AO
The AO has been in a positive phase most recently. When it is in a positive phase, a vortex around the North Pole strengthens and literally locks in cold air, forcing it to stay up north. However, if the AO is in a negative phase, this vortex weakens and the cold air can escape south, sometimes into the US. The ensemble members forecasting for the AO indicate equal chances for repeating positive spikes or a downward trend towards negative territory. We will have to watch this closely to see what happens.

NAO
The NAO has recently also been in positive phase, not a good sign for those who like snow and cold. The ensemble members indicate there is a very substantial potential for the NAO to go negative, increasing chances for snow and cold. The AO and NAO are closely related, so if one goes negative it is possible the other will as well.