The AO, NAO, PNA, QBO and YOU!

Co-Written By:  Lester Rhoads and Bryan Polivka

This article will focus a little bit on that as well as the active and stormy pattern that is ongoing and will continue for the rest of March.

First, let’s look at the AO. It will continue to be negative but it drops to around -4 to -5. If this blocking continues this may push the storm track to the south and allow for the cooler weather to continue. But at the same time this may lead to a few more light snow showers for folks in Northern Ohio. If the AO rises some, then we might get into some severe weather events across the Southern portions of the Ohio Valley.

Now, we will look at the NAO. It will be mostly negative. That means a trough will persist over the eastern us. This will allow for some cooler temps but as I said above, the storm track will be south and west and this may end up giving us some more rain. It could be heavy at times and cause some flooding issues.

Looking at the latest PNA, it will continue to drop around -1 and -2 by the middle to the end of the month. We might see a ridge starting to develop across the eastern us and this might bring us back to normal or above normal late this month.   But for now, I believe that the –AO / -NAO combo, will offset the –PNA to a degree that a sustained warm pattern will not develop for the Great Lakes and Ohio Valley regions for the next few weeks.  The combination of the three things will allow for an active pattern to continue with the storm track over the Midwest and Ohio Valley regions.  Our current storm system will slow moving fronts and large temperature gradients will deliver the goods in bringing in numerous high precip. events.

Below is the 500 MB Height Anomalies from the ECMWF and GFS long range models. Both are showing a  very active pattern setting up with a –PNA, -NAO, and –AO.  As I explained above, this combination of features will bring active weather to our part of the country.

The last thing that I want to talk about is the QBO.  This was a big factor in bringing in the cold for the second half of winter and this also triggered the –AO and –NAO that started in February and is still continuing right now.  Last Fall, the QBO was strongly negative and you want a –QBO to help promote high latitude blocking.  The QBO was too negative so we had to wait until it rose.  Once that happened, we were able to get the AO and NAO to tank and as you have seen so far for March, we are still seeing those effects in the atmosphere.  Below are the QBO values from last fall through February.

September:  -26.60

October:  -24.51

November:  -18.95

December:  -10.02

January:  -6.07

February:  -1.23

Source:  http://www.esrl.noaa.gov/psd/data/correlation/qbo.data

In conclusion, get ready for mainly below average temperatures for the rest of March along with above normal precip.  We still will see a nice day or two every now and again, but if you’re looking for a 5-7 day period of dry weather and 60s and 70s for temperatures, then I’m afraid you’re going to have to wait a while.