Wednesday, November 16, 2011

Why is everyone saying the Midwest will have the worst winter?

I'm sure you may be wondering why everyone is thinking the Midwest is under the gun for the biggest snowfall and worst winter this year. We were too, and when we got our answer, we decided you would want to know too.

It is predicted that more moisture will be guided into the US, likely via the polar jet stream and tropical jet stream.  This additional moisture will only enhance any possible precipitation that may occur with storm systems in the US.

La Nina makes the eastern equatorial Pacific Ocean cooler than normal, thus preventing warm air from rising and overall cooling down the atmosphere. This enables a bigger potential for colder air to migrate south into the US, and for snow to occur slightly more times than rain in this occasion.

3. AMO
The AMO (Atlantic Multidecadal Oscillation) index is complicated and something we're still trying to map out. However, last year, the AMO index was in a strong positive phase. This was a helper to induce blocking, which basically stalls the atmosphere (example: a high pressure system stays in place for several days due to blocking). This year, the AMO much weaker. Therefore, blocking will not be as prevalent, meaning a more active storm track and thus more precipitation.

4. NAO
The NAO (North Atlantic Oscillation) index oscillates between positive and negative. The negative phase involves a high pressure in Greenland that lets cold air flow south. The positive phase involves the cold air bottled up in Canada and warm air moving slightly north and affecting portions of the north US. Last winter, the NAO was already negative as this point in time. This month, we have a positive NAO moving towards a negative phase. Therefore, it can be expected that blocking will also be less of a factor, combined with the AMO compared to last year.

5. AO
The AO (Arctic Oscillation) oscillates between positive and negative as well. When the AO is positive, winds circling an area in the far north hemisphere spin tighter and stronger, locking cold air in that region and not letting it go south into the US. In the negative phase, the winds are weaker, and the cold air escapes southward into the US. The AO is variates more each month, so it's a little harder to identify patterns.

Solar Activity is something that is worth watching this year. Every year the sun goes through cycles. It is currently entering cycle 24, but as it enters the new cycle, the maximum number of sunspots will be greatly reduced from normal. This loss of sunspots means cooler weather for the globe. The temperatures this winter will be affected by the sunspots, and it is important to note that temperatures will not improve due to the sunspots until more sunspots form.

Explanation of WHY Midwest will have bad winter coming this afternoon

An explanation of why the Midweat will have the worst winter will be coming out this afternoon right here, on The Weather Centre.