Baltimore, MD - Mike Masco
ABC 2 BALTIMORE
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September so far is living up to my expectations running at to around slightly below average temperature wise in Maryland , PA, DE, and NJ. So far for the month the average daytime and nighttime max has average 66 degrees which is one off the normal of 67. These numbers vary city to city but the point is; we are slightly below average to around average and should finish that way going into the first of October.
So, two questions will be answered in this post. Will temperatures stay cool going through October? And, Will it stay that way?
Now that we are losing the long days and short nights our temperatures will cool natural in response to the change in sun angle which automatically locks in the notion 90s will be scarce to nonexistent in October and 80s will be few and far between. Overnight temperatures will stay at average levels and warm nights will be confined to the first couple of weeks in October. These are the natural processes of the start to fall.
NAO's ROLE IN TEMPERATURES
Yes, NAO, three letters that shorten the term for a weather variable we watch called "NORTH ATLANTIC OSCILLATION". Simply point when it's negative we get cool/cold; when positive we stay mild/warm. It's a little more complex than that but just know it's a weather variable that is far more important than any other factor we look at in the weather world. Without that being negative there is not a shot down under we stay cool!
The trend through September has been negative and in fact VERY NEGATIVE. The late summer months had the second lowest most negative readings since the early 1950s (an era that was brutally cold!) Studies have been done saying if the NAO is predominately negative heading out of summer and into fall it will stay that way going into winter. However, there have been a few winters that haven't followed that trend INCLUDING 2011 the famous WARM winter! So as the saying goes the trend is our friend and through October I believe the NAO will stay the course and remain at or below negative bringing waves of fresh, cool Canadian air into the east. Thats not to say a few rounds of warming could take place. I say that not to cover my butt, but because the pacific ridge may collapse and bring pacific air right through the country. I do not anticipate that lasting but the first week of October could bring on some warmer than average days NOT 90 however!
The ARCTIC Oscillation is another variable that will remain negative through October and some models suggest it being VERY NEGATIVE! This usually works well with the NAO and can even enhance the effects of the blocking over Greenland as it forces cold air south. The AO involves high pressure over the North Pole with lower pressures balancing it out over the continental USA and Atlantic. Should this dominant going into the fall months and eventually winter .. WATCH OUT . We could be in for a very cold winter ahead.