Thursday, October 12

NorthGeorgiaWX · October 12, 2023

Good morning!

Has everyone enjoyed the rain? 🙂 I ended up with 0.64" of rain here at the house, so I did a little better than expected. these are very early precipitation reports, but it appears the NW corner of the state was on the sort end of the stick, but as you go further south and east, the totals increase. I've see a lot of 4"+ measurements over northern Florida, along with reports of tornadoes.

We'll have one more shot of rain tomorrow morning, as moisture surges back into the area in advance of a cold front, and the front will kick off a few showers and thunderstorms out ahead. Once the front clears, we'll see those below normal temperatures moving back in for the following 6-7 day period. The=is 500 mb anomaly loop from the Euro, shows the very active pattern, as troughs parade their way across the southeast.

One pattern that is critical for us if we want to see winter weather, is the PNA, or the Pacific-North American Oscillation. I'm copying the following information from my DacuaWeather.com website, and you can go take a look at this anytime you'd like.

Quote

The Pacific–North American teleconnection pattern (PNA) is a climatological term for a large-scale weather pattern with two modes, denoted positive and negative, and which relates the atmospheric circulation pattern over the North Pacific Ocean with the one over the North American continent. The PNA is one of the most recognized, influential climate patterns in the Northern Hemisphere mid-latitudes beyond the tropics. It consists of anomalies in the geopotential height fields (typically at 700 or 500mb) observed over the western and eastern United States. It is important to note that the PNA has been found to be strongly influenced by the El Niño-Southern Oscillation (ENSO) phenomenon. The positive phase of the PNA pattern tends to be associated with Pacific warm episodes (El Niño), and the negative phase tends to be associated with Pacific cold episodes (La Niña).

The positive phase of the PNA pattern features above-average barometric pressure heights in the vicinity of Hawaii and over the inter-mountain region of North America, and below-average heights located south of the Aleutian Islands and over the southeastern United States. The PNA pattern is associated with strong fluctuations in the strength and location of the East Asian jet stream. The positive phase is associated with an enhanced East Asian jet stream and with an eastward shift in the jet exit region toward the western United States. The negative phase is associated with a westward retraction of that jet stream toward eastern Asia, blocking activity over the high latitudes of the North pacific, and a strong split-flow configuration over the central North Pacific.

The positive phase of the PNA pattern is associated with above-average temperatures over western Canada and the extreme western United States, and below-average temperatures across the south-central and southeastern US. The PNA tends to have little impact on surface temperature variability over North America during summer. The associated precipitation anomalies include above-average totals in the Gulf of Alaska extending into the Pacific Northwestern United States, and below-average totals over the upper Midwestern United States. The negative PNA phase is associated with the opposite.

Although the PNA pattern is a natural internal mode of climate variability, it is also strongly influenced by the El Niño-Southern Oscillation (ENSO) phenomenon. The positive phase of the PNA pattern tends to be associated with Pacific warm episodes (El Niño), and the negative phase tends to be associated with Pacific cold episodes (La Niña).

This probably illustrates the difference between a positive/negative PNA better than anything.

For the short term (~10 days), the PNA will stay positive.

If we step out a little further, we see the PNA sliding back down toward the negative state. Notice how the whisker bars get longer and long as we go out in time, that indicates greater and greater uncertainty in the outcome.

If we go to the end of November, we see a pretty good negative dip in the control run, and then around the end of the month, it starts to rise again. I suspect we'll see a few weeks of milder weather as we start November, and then around or after Thanksgiving we head straight into winter.

Yes, there are many other teleconnections that matter, and when we start to see systems that may bring us some winter weather, we'll focus on those. Right now the NAO, AO, and EPO are negative, so we get cool/cold and stormy weather. Keep that in mind during the winter months. I think that what we saw overnight and today, is a sign of things to come this winter. I believe that we'll have a very active southern jet stream that will have many chances to interact with the troughs that will settle over the eastern US. I feel pretty confident that we're going to have the winter that we've been missing out on for many years.

The next two weeks will remain below normal across the southeast. The next two images are from the Euro ensemble, the first image are days 0-10, and the 2nd image are days 5-15.