First, lets talk a little bit about setting the stage for winter, and what is happening right now that gives us increasing confidence in a better winter than we've had in a long while.
Since the 80's there has been a decline in the Arctic Sea Ice, and 2012 held the record for the lowest minimum level (occurs in September), with about 2.3 million square kilometers. Things were not looking good. But things are different this year and the ice levels have rebounded at an incredible rate. Our lowest minimum level in 2013 was 3.6 million square kilometers, or almost a 64% increase over last year. What is even more encouraging is the current rate of increase. For the last three weeks or so, the sea ice increases have been averaging more than 100,000 square kilometers PER DAY to the ice fields. I wanted to quote a meteorologist on one of the weather forums I visit:
"I do expect a brief slowdown in the gains after the Laptev Sea finishes freezing; there's probably close to 100k still to be frozen in the Laptev, and that should happen in the next two nights with -16C to -20C 850s over the region with the polar vortex sitting right on top of the Eurasian Arctic.
At that point, ridging temporarily builds into the Atlantic side (the main area where we are still well below climatological ice extent), the Beaufort remains mild as ice continues to struggle to reach the Alaskan coast, and then cold air retreats to the North Pole. Thus Day 3 through Day 5 may see some smaller increases, perhaps on the order of 30k-40k.
However, I'm predicting another period of massive gains from Day 6-10. The temporary retreat of the polar vortex to the North Pole has some positive effects (though it temporarily slows ice growth) as it allows for truly bitterly cold air to develop in the Arctic Basin. By Day 7, 850s in the still unfrozen area around Svalbard get as cold as -28C; a 980mb low pressure is sitting over the Laptev Sea funneling extremely cold north winds into the vulnerable Atlantic side, where we lost a ton of ice this summer. Given that Day 6-Day 9 feature 850s from -20C to -28C in the high latitudes of the Atlantic side, including some parts of the 880k square kilometer Kara Sea, where ice remains unfrozen, it's inevitable we'll see some impressive gains.
Towards the end of the forecast period, the cold begins spreading out to areas where the ice is seriously struggling (lower latitudes of Beaufort Sea near AK coastline), northern sections of Baffin Bay and the Canadian Archipelago, and Foxe Basin/Hudson Bay. None of these areas have appreciable ice, and some are well below climo, like the AK North Slope, but this should change if the Euro verifies."
Check out this interactive page that depicts the current ice levels. I also have a ton of charts and maps that cover Arctic Ice, including a couple of new pages and images. Click here to view them all. Also, on my site, you'll find them under "Models", "Snow Data".
We are currently well ahead of all but a year or two in the 2000's, and if the gains hold out as expected, we will pass those two years also. And while the gains are significant, there is also another significant by-product of the extra ice and snow cover. As cold air develops this winter and moves south, if it moves over snow and ice, the temperature doesn't moderate as much, and that means when it arrives in Georgia, it will be colder than it would have been without the snow and ice cover. Of course last winter was non-existent for the most part, but I'm expecting this winter to be considerably colder, and maybe as cold as 2009-2010.
But it takes more than a frozen Arctic to really give us a decent winter here, and what we're looking for is "blocking". There are a couple of teleconnection indices called the AO or Arctic Oscillation, and the NAO or North Atlantic Oscillation. Both indices can have a positive or negative variation, and for us, the more negative they both go, the colder we get. A negative NAO occurs when we get a strong high pressure area near Greenland. The negative phase of the AO occurs when a similar ridge of high pressure sets up off of the west coast of the US. NASA climatologist Dr. James E. Hansen explains the mechanism by which the AO affects weather at points so distant from the Arctic:
"The degree to which Arctic air penetrates into middle latitudes is related to the AO index, which is defined by surface atmospheric pressure patterns. When the AO index is positive, surface pressure is low in the polar region. This helps the middle latitude jet stream to blow strongly and consistently from west to east, thus keeping cold Arctic air locked in the polar region. When the AO index is negative, there tends to be high pressure in the polar region, weaker zonal winds, and greater movement of frigid polar air into middle latitudes."
When you combine a -AO and -NAO, the only place the cold air can go, is south.The movement from west to east has been blocked on both the east and west ends and the Arctic air is forced south. Note that we are current in a negative phase for both indices and one reason for the cooler temperatures we're experiencing right now, and the much colder air that will arrive toward the end of next week. You can view the current AO and NAO indexes by clicking here.
And all of that, brings us back to how I started this post!
In the latest Area Forecast Discussion from the Atlanta NWS office, they had this to say:
"COLD FRONT SWEEPS SOUTH ON WEDNESDAY... WITH HIGH PRESSURE BUILDING IN FOR THE REMAINDER OF THE WEEK INTO THE WEEKEND. MODELS ARE PROGGING A MUCH COOLER AIRMASS TO SETTLE ACROSS MUCH OF GA THROUGH THE END OF THE WEEK. CURRENTLY... FRIDAY NIGHT / SATURDAY MORNING LOOKS TO BE THE COLDEST WITH MIDDLE/UPPER 30S ACROSS THE METRO AREA. HAVE GONE AHEAD AND ADDED PATCHY FROST TO THE GRIDS FOR THURSDAY MORNING... FRIDAY MORNING AND SATURDAY MORNING TO GIVE THE AG INTERESTS A HEADS UP. FROST DEVELOPMENT DEPENDS HEAVILY UPON THE SKY AND WIND FORECASTS. CURRENTLY... SKY COVER IS CLEAR WITH NEARLY CALM WINDS LEADING TO POTENTIALLY GOOD CHANCES FOR FROST. HOWEVER... CHANGES TO EITHER OF THESE PARAMETERS WILL SIGNIFICANTLY INHIBIT FROST DEVELOPMENT. AG INTEREST SHOULD CONTINUE TO MONITOR THE FORECAST FOR ANY CHANGES."
The models are showing a nice blast of cold air that will take us well below normal for a few days. What many meteorologist believe is that the setup that will bring cold air south next week, will be similar to what we can possibly expect this winter, only with much colder air to work with. We'll watch this and give you a mid-week update, but right now, if you have plants that can't handle the frost and cold temperatures, I would go ahead and make plans to bring them indoors.
The signs of the transition from fall to winter are everywhere. I have a couple of new pages that I think are awesome (of course...!) for checking out the weather in other parts of the country with a quick glance (Southern Region | Central Region). On these pages are images that each forecast office uses to highlight the weather in that location. If you hover over the thumbnails, the full size image will popup. You can mouse over the images to quickly see what's going on at that location. There are other links to the AFD's, HWO's, soundings and meteograms for that location, as well as forecast for every major location in that state. I've included a couple of links to images to give you an idea what others are experiencing elsewhere. Here's Minnesota and Michigan as examples. You can find these two pages on my main page, and under "Forecast" from the main menu.
Also, take a look at the forecast for Grandfather Mountain in North Carolina for next week. Brrrrrr.... Speaking of mountains and weather, how about the location that claims "The World's Worst Weather", Mount Washington in New Hampshire! I love checking this page out in the winter time. 4 webcams and current conditions will give you an idea of how extreme this location is. The meteorology research station on the top is manned 365 days a year. This mountain STILL hold's the record for the highest wind speed ever recorded by a human being, at 231 mph. Incredible mountain. Visit this page to find out all about it. The current last 24 hour peak wind speed is around 75 mph right now (as of Monday morning), but during the winter when the jet stream plows over the mountain, you'll see winds well over 100 mph on a routine basis.
DEEP BROAD UPPER TROUGH FINALLY FLATTENS BY SUN/MON WITH STRONG
SHORTWAVE DIGGING SOUTH INTO THE SOUTHERN ROCKIES. THIS WAVE COULD BE A POTENTIAL BIG WEATHER MAKER OVER THE SOUTHERN STATES BY NEXT WEDNESDAY BASED ON 12Z ECMWF AND GFS.
EDIT: Wednesday, 5:04am
URGENT - WEATHER MESSAGE
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
349 AM EDT WED OCT 23 2013
...FROST ADVISORY IN EFFECT FROM 2 AM TO 9 AM EDT THURSDAY...
THE NATIONAL WEATHER SERVICE IN PEACHTREE CITY HAS ISSUED A FROST
ADVISORY...WHICH IS IN EFFECT FROM 2 AM TO 9 AM EDT THURSDAY.
• LOCATIONS...MAINLY ALONG AND NORTH OF A LINE FROM LA GRANGE TO
FORSYTHE TO WARRENTON.
• TEMPERATURES...MINIMUM TEMPERATURES WILL RANGE FROM THE LOWER TO
• TIMING...THURSDAY MORNING FROM 2AM TO 9AM.
• IMPACTS...THOSE WITH SENSITIVE OUTDOOR PLANTS SHOULD MAKE
PREPARATIONS TO PROTECT VEGETATION.
A FROST ADVISORY MEANS THAT FROST IS EXPECTED. SENSITIVE OUTDOOR
PLANTS MAY BE KILLED IF LEFT UNCOVERED.
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