Major Cold Spell Likely For Our Area! How Long Will This Last???
With the seasons changing on Wednesday and many looking forward to spring-like weather, I am not giving the best news to our warm weather lovers. The next 7 - 10 days will not just be cold but very cold for this time of the year. Why so cold?
What Is Causing This Cold?
Many are familiar with the El Niño, but not as many have heard of the NAO (North Atlantic Oscillation). Since we have a nearly nuetral El Niño this year, the NAO becomes a very important feature in the northern hemisphere. When the NAO goes highly negative, it creates a very intense blocking pattern in the northern Atlantic and this ultimately leads to a very cold eastern US. When the NAO is positive, we see warmer than normal temperatures in the eastern US. The NAO is not just going to go negative, but it will be the most negative since Superstorm Sandy late last year. Notice the hugely negative numbers in the late part of this month.
This highly negative NAO creates a highly complex "modified omega" block over the north Atlantic. I say modified because it is not textbook by any means, but clearly a version of an omega block. Notice the shape of the jetstream resembles the greek letter Omega... Ω.
With this low pressure consistently over the northeast US area, we will see persistent northernly winds in our area and very cold temperatures. What you see is a cascade effect. The negative NAO causes a blocking pattern in the north Atlantic, then that catches a storm and parks the low over the northeastern US, this causes a persistent northernly flow which ultimately leads to well below normal temperatures. This is a lock and you can see CPC's forecast for the next 6 - 10 days has a 90% chance of our temperatures being below normal!!!
How Cold Are We Talking???
As we look at temperatures over the next 7 days, I want to show you what is called temperature anomolies. This allows us to look at how temperatures compare to the normals. What you will notice is this pattern exactly resembles what we expect in a highly negative NAO.
GFS Temperature Anomolies By Thursday Morning
Notice the GFS is showing temperatures that are nearly 20 degrees below normal on Thursday morning.
GFS Temperature Anomolies By Friday Evening
Notice the GFS still shows temperatures that are about 5 to 8 degrees below normal on Friday.
GFS Temperature Anomolies By Sunday Morning
Notice the GFS shows its only day with temperatures above normal over the next 7 days. This is the day we have to watch because the GFS shows potential for strong storms while the EURO shows the potential for some wintery weather.
GFS Temperature Anomolies By Monday Evening
Notice the GFS takes back to around 12 degrees below normal by Monday.
GFS Temperature Anomolies By Next Wednesday Morning
Notice the GFS shows temperature nearly 20 degrees below normal again by next Wednesday morning.
My Thoughts On The Cold Spell
The data is very clear and below normal temperatures will dominate the first week of spring. Pattern changes normally last for 10 - 14 days, so I think it is highly likely that at least the next 10 days will be below normal and not just by a little, but by a TON! Take a look at the averages versus my forecast highs over the next 7 days.
My forecast highs average 14 degrees below our normal high of about 60 degrees! WOW! Get ready for winter like cold!
I know there are a lot of questions regarding the weekend storm. I will address that in my blog later this evening.
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