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Good morning!

For the most part, the rain should be over (but it's still raining here at the house even though it's not showing up on radar) and today we'll start to dry out some. The morning map (300 mb isobars/dewpoints) shows very dry dewpoints out west and very moist dewpoints over parts of the east. While we have dried out in the upper levels of the atmosphere, the surface layers are still pretty moist, and they won't start to dry out until tomorrow. 

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In the long term, an overall negative NAO pattern seems to be on tap through the end of the week which will open up the eastern US to a few intrusions of colder air from our neighbors to the north. A large lobe of high PV air associated with the Arctic tropopause and also with a large associated 500 mb trough is forecast to settle in over the eastern US. A few shortwaves and TPVs which rotate through the trough will be responsible for a few surface based lows that will stay well away from the CWA, but aid in bringing through several cold fronts.

By Tuesday night, a cold front should be mostly through the CWA bringing a welcome temporary airmass change with less moisture and cooler overnight temperatures. By Wednesday into Thursday, some surface based moisture return will occur ahead of another frontal system moving into the area by Friday morning. Models do indicate the possibility of some showers over the far SE corner of the CWA Thursday in central GA, so do have small PoP's for that time period. Some moisture and forcing ahead of the front my bring some showers across north GA on Thursday night, so have small chance PoP's then as well.

Expect max temperatures to still remain in the upper 70's and 80's as the first front passes by Tuesday. This airmass has already been heavily modified and will mostly just clear the moisture out temporarily. Better frontal passage occurs Friday, where fall like weather should be on tap for the entire area once the front passes by. High temperatures are forecast to be in the 60's and 70's through the weekend with some 50's in the elevated terrain. Lows Friday night could dip into the upper 30's in some portions of north GA, so the higher elevations may need to be watched for any potential freeze (but certainly too early for any certainty on that). Another system and cold front may be moving through after all this by mid next week, but some model divergence on timing and strength, and that is a bit beyond our extended at this time.

 

Negative NAO. That is one piece we've been missing for the last 3-4 winters it seems like. For those that don't know, the NAO stands for "North Atlantic Oscillation" and is an important teleconnection for us during the winter. In the image below, you can see the impacts of a "-NAO".  The NAO along with the EPO can be a major influence during the winter, with the NAO on the eastern side of the continent and the EPO on the west side. When both of those go negative, cold air spills into the "bowl" in between both blocking ridges and we have winter! Over the last several winters the NAO has not cooperated with us and when cold shows up, it gets shunted off to the east very quickly since there is nothing to "block" or lock the cold in.. 

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Here's a look at the NAO forecast from the Euro ensemble. It's already in a negative state and the forecast keeps it that way through the 25th of the month. 

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So let's look at the EPO or Eastern Pacific Oscillation. Nice..., we see it going negative around the same time period, just a shorter duration.

ecmwf-ensemble-nhem-avg-epo-box-2460800.thumb.png.313b55da2b878f016378412caafdd1ce.png

 

And these are the winter time impacts from a -EPO

epo_neg.thumb.png.dc77d5d78c0eb62e13380aabb31a5056.png

 

But let's go one step further. We can have both -NAO and -EPO and still no cold. Why you ask? (You did ask didn't you???) The last really important piece is the Arctic Oscillation, and once again, we want to see it in a negative state. A -AO indicates blocking over the pole. When high pressure builds over the Arctic, it forces the cold air away from the pole, and if we have a -EPO and -NAO, that cold air is forced south into the lower 48 states and gets locked in by the blocking, and that can create extended cold outbreaks. This is the Euro AO forecast. Notice a negative pattern that last through the end of the month.

ecmwf-ensemble-nhem-avg-ao-box-2460800.thumb.png.4a8b4cd91d54d646df1ea078a794caa6.png

 

This is an example of the impacts from a -AO pattern.

ao_neg.thumb.png.0ba76b0b57d6fd2ba120f2eeb1da2362.png

 

The upcoming pattern change will be heavily influenced by these three teleconnections. As we move toward winter these will start to take on very prominent roles in how our winter weather evolves, so we will be paying special attention as we get closer in time.

So what does that really mean for our upcoming weather? This is the GFS temperature anomalies for the next several weeks. The first big push of cooler air happens beginning Friday. gfs-deterministic-conus-t2m_f_anom-1602460800-1602460800-1603843200-80.thumb.gif.c257a7b9a3a4f31cb66f53265af908fe.gif

 

This shows the potential upcoming temperatures for Blairsville, Athens, Cobb, and Dalton.

gfs-operational-KDZJ-daily_tmin_tmax-2460800.thumb.png.4d39002ac505ad236742e73aae5593a1.pnggfs-operational-KDNN-daily_tmin_tmax-2460800.thumb.png.2d078353de44c1882d19e99102fd1a07.png

 

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Not a bad weather week ahead with mostly sunny skies, but I'm really looking forward to the fall weather that will be here starting Friday!

I finally got a good time lapse yesterday, so here it is!

 

Hope everyone has a great Monday!

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gfs-operational-KAHN-daily_tmin_tmax-2460800.png

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