Tornado Warning - Atlanta, GA Metro Area

ULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
600 PM EDT MON MAR 18 2013

THE NATIONAL WEATHER SERVICE IN PEACHTREE CITY HAS ISSUED A

* TORNADO WARNING FOR...
SOUTHERN CHEROKEE COUNTY IN NORTH CENTRAL GEORGIA
NORTHERN COBB COUNTY IN NORTH CENTRAL GEORGIA
NORTHWESTERN DEKALB COUNTY IN NORTH CENTRAL GEORGIA
FORSYTH COUNTY IN NORTH CENTRAL GEORGIA
NORTHEASTERN FULTON COUNTY IN NORTH CENTRAL GEORGIA
NORTHWESTERN GWINNETT COUNTY IN NORTH CENTRAL GEORGIA
SOUTHERN BARTOW COUNTY IN NORTHWEST GEORGIA
NORTHERN PAULDING COUNTY IN NORTHWEST GEORGIA
NORTHEASTERN POLK COUNTY IN NORTHWEST GEORGIA

* UNTIL 645 PM EDT

* AT 557 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
LINE OF SEVERE THUNDERSTORMA CAPABLE OF PRODUCING A TORNADO NEAR TAYLORSVILLE...
MOVING EAST AT 60 MPH. THERE IS ANOTHER AREA OF ROTATION CAPABLE OF PRODUCING
A TORNADO SOUTHEAST OF BRASWELL.

* OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO
EMERSON...ACWORTH...KENNESAW...MARIETTA...WOODSTOCK...HOLLY
SPRINGS...CANTON...MOUNTAIN PARK...SANDY SPRINGS...BUFFINGTON...
ROSWELL...DUNWOODY...ALPHARETTA...MILTON...FREE HOME...NORCROSS...
BERKELEY LAKE...JOHNS CREEK...DULUTH...CUMMING AND SUWANEE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

HEAVY RAINFALL MAY OBSCURE THIS TORNADO. TAKE COVER NOW! IF YOU WAIT
TO SEE OR HEAR IT COMING...IT WILL BE TOO LATE TO GET TO A SAFE
PLACE.

IF YOU SEE WIND DAMAGE...HAIL OR FLOODING...WAIT UNTIL THE STORM HAS
PASSED...AND THEN CALL THE NATIONAL WEATHER SERVICE TOLL FREE AT 1 8
6 6 7 6 3 4 4 6 6. YOU CAN ALSO TWEET YOUR REPORT USING HASHTAG GAWX.

A TORNADO WATCH REMAINS IN EFFECT UNTIL 1000 PM EDT MONDAY EVENING
FOR NORTHWESTERN GEORGIA. A SEVERE THUNDERSTORM WATCH ALSO REMAINS IN
EFFECT UNTIL 1000 PM EDT MONDAY EVENING FOR NORTHWEST GEORGIA.

March 18-20 Significant Northeast Snowstorm

A significant snowstorm looks to impact much of the Northeast with accumulations exceeding one foot in many locations.

High resolution model forecasts, like the one pictured above, show a significant snowfall event is in the making. Current indications are that snow amounts will exceed one foot in much of Maine, New Hampshire, Vermont, New York and even into parts of Pennsylvania. Coastal areas, like New York City and coastline towns wil receive lighter accumulations, possibly nothing at all if you are in areas like southern New Jersey. For the inland areas that do receive snow, isolated amounts of up to 18 inches are possible, especially in Maine and portions of Vermont and New Hampshire. This potential is not all that great outside of Maine, but there is still potential.

Andrew

Supercells Erupting Over Alabama, Georgia

An absolutely vicious cluster of supercells is erupting over Mississippi and Alabama, partially into Georgia as well at this time.

Radar imagery indicates isolated supercells are blossoming over the aforementioned states this afternoon as instability and shearing become conducive for severe weather. An overview of instability parameters reveals the strongest buoyancy is to the south of these supercells, but a sufficient level of energy is on hand for these cells to really get going. Wind shear analysis shows that these storms are pumped with 40-60 knots of shearing- more than enough for severe weather. Composite analysis by the Storm Prediction Center tells me the highest tornado threat is not centered in the supercells crossing into Georgia, but is actually centered over central Alabama. A combination of enhanced spinning and additional instability in the midsection of AL is allowing an increased tornado potential to evolve, making for a very dangerous situation over much of the Gulf Coast this afternoon.

Andrew

Colder Weather On The Way - And It's Here to Stay

"He said I wanna see you again

But I'm stuck in colder weather

Maybe tomorrow will be better

Can I call you then"

(From Zac Brown Band song, Colder Weather)

As the Zac Brown Band tells in Colder Weather, it looks like the majority of the nation is going to be stuck in colder weather. Unfortunately, tomorrow will not be better- if anything, it will be even colder.

Shown above is the European model's projected 850 millibar temperature anomaly forecast for 6 to 10 days away from today. The 850 millibar level is commonly referred to as one of the lower levels of the atmosphere. The European model is very clear with its intentions over the next 10 days. The projection is for harsh cold to start out in the North Plains and Upper Midwest, where anomalies of 10 degrees (C) below normal will be commonplace. As time progresses towards that 10 day forecast mark, we start to see the cold slide south, into the midsection of the nation by the time the weekend is around, and penetrating the South US 10 days from today.

The long range American temperature anomaly forecast is no more comforting. This forecast is from the American ensembles and is forecasting surface temperature anomalies in Celsius. From the next 8-16 days, the ensembles are pretty firm in saying that all areas east of the Front Range in Colorado should be able to achieve below normal temperature anomalies. The atmospheric set-up favors frequent cold shots into the Mid-Atlantic and Southeast as a result of the suppressed jet stream, and the American Ensembles latch onto that idea quite well. The Northern Plains also experience a solid degree of below normal temperatures.

So what's causing all of this cold to suddenly evacuate the Arctic and ruin the onset of spring? As you see in the 2-6 day forecast of 500 millibar height anomalies from the European model above, record-breaking high pressure in the Arctic Circle is causing the Arctic Oscillation to go negative. For those unfamiliar with the term, the Arctic Oscillation involves a positive and negative phase. The positive phase has strong low pressure over the Arctic that locks cold up in the higher latitudes and allows warmth to prevail in the US. The negative Arctic Oscillation (AO) permits strong high pressure to take over the Arctic, which in turn allows cold air to flow freely into the United States. The Arctic Oscillation is forecast to reach a negative level that is so low it has not been seen since 2010. If the AO goes as low as the most extreme forecasts are calling for, we could see a negative level not experienced since 1985. Regardless of how low the Arctic Oscillation will go, the big picture is that cold weather will dominate the nation for the rest of March, likely into at least the first week or two of April. This event is not just a few days of chilly weather- we're talking multiple weeks of below normal temperatures. There is no end in sight to this colder weather at this time. I suppose this winter cold just got backordered.

For those of you who follow the idea that above normal snow cover in Siberia during October can make the Arctic Oscillation go negative in the following winter, this is a direct byproduct of that idea. The last third of October 2012 had way above normal snow cover, meaning we could be in for a month or more of below normal temperatures. Happy Spring!

Andrew