What the Hell is Phasing and what does it mean to us!

You will hear alot of talk about phasing in the coming weeks with the pattern change in full effect. First of all, what is Phasing?

Basically, in simple terms, Phasing is when two low pressure systems combine into one low pressure system. Lows that combine can be stronger and more intense creating more dangerous winter conditions this time of year. One excellent example of a recent Major Phasing event would be Sandy. We all know what the end result was.

Sandy was an incredible force of nature. Tropical Storm wind covered almost 600,000 square miles



While some notable Doctors instantly put language in their blogs such as " we also must acknowledge that climate change could have played a role " while describing why such a storm could happen. There is no evidence what so ever that immediately support this. What we do know, there were a series of meteorological events that took place. I was following a number of NWS Chats days before impact in the N.E discussing the potential major phasing of Sandy and the potential impacts that such an event would have.

This was one post, two (2) days before landfall that was very accurate.

Two of the major players in the potential event will be the blocking in the Atlantic as well as the positioning of the ridge out west. The 12z GFS, despite a different handling of the ULL near Newfoundland, shows the blocking in the higher latitudes very well. Pretty impressive, even for October, all potential phasing systems aside.



Phase at 204, surface low with a major tug north and west...surface low looks to be in the 950's and moving northwest towards the 40/70. The trough wraps and phases with "Sandy" around the Newfoundland ridge:

The trough wraps and phases with "Sandy" around the Newfoundland ridge:



Notice the area of Low Pressure along the coast of North and South Carolina. This the the area that got phased into Sandy. This was 192 hours out.

OK, you all get the picture on what phasing is. It happens alot during the Winter Storm Season as Nor-Easters move up the coast and react to other ripples or troughs of low pressure that are moving across the country. This is why a lot of these storms blow up as they move to the North.

Now, lets look at the current scenario. While things will be relatively quite for the next ten days or so, we will see little events take place. Looks for things to pick up in the January 12 to 14th time frame.

As i mentioned a couple of days ago the stratosphere has been warming for several days. It takes time for the effects of such warming to rear it's head at the surface. But it is coming.

A total dislodging or destruction of the stratospheric PV is better to relocate cold from the higher latitudes to the lower latitudes. However..there is alot that has to happen for the Arctic cold to be relocated southward. Mainly..the warming has to work its way down to the troposphere and that means anticyclonic flow becoming stacked or more organized through the various levels of the atmosphere. The +AO/NAO signal that we are seeing is in response to the 500mb vortex relocating itself around Baffin island. The 500mb Baffin island vortex could be in response to the warming seen in the stratosphere. If this is the case, like is being indicated, its going to get brutally cold after the second week in Jan!



The CFSv2 ensemble mean shows a warmup occuring during the first half of January but it also shows the Arctic air gates are wide open the second half January! If one looks close enough one can see the dual blocking signals of negative EPO and negative NAO/AO with the warmth centered on the Gulf of Alaska and the Baffin island/Greenalnd area due to blocks in the polar jet stream at those particular locations.



Now getting back to Phasing. Here is today's outlook from :

NATIONAL WEATHER SERVICE MORRISTOWN TN
235 PM EST WED JAN 2 2013

.LONG TERM...(THURSDAY NIGHT THROUGH MONDAY)...MAIN WEATHER CONCERN
IS THE AMOUNT OF PHASING BETWEEN THE NORTHERN AND SOUTHERN STREAM
WAVES AND EXTENT OF GULF MOISTURE RETURN INTO THE TENNESSEE VALLEY
FOR SATURDAY NIGHT AND SUNDAY. GFS AND ECMWF AGREE FAIRLY WELL WITH
A GOOD DEAL OF PHASING BETWEEN THE TWO SYSTEMS...BUT THE GFS IS WEAK
IN RETURN OF GULF MOISTURE. THE ECMWF AND NAM MODELS SHOW A GOOD
DEAL MORE MOISTURE/ISENTROPIC LIFT AND ASSOCIATED PRECIPITATION
MOVING NORTHEAST INTO THE TENNESSEE VALLEY SATURDAY NIGHT AND SUNDAY.

SINCE MODELS ARE IN PRETTY GOOD AGREEMENT WITH THE PHASING OF THE
TWO WAVES...I PREFER GOING WITH THE HIGHER POPS. INTERESTING THAT
THE GFS POPS ARE IN THE 30S AND 40S...BUT SHOW LITTLE IN THE WAY OF
QPF. LATER SHIFTS WILL LIKELY HAVE TO BUMP UP THE POPS.

THE TEMPERATURE PROFILE SHOWS A MIX BAG OF SNOW..SLEET..RAIN AND
POSSIBLY FREEZING RAIN WITH THIS SYSTEM. SINCE DEWPOINTS WILL BE
INITIALLY QUITE DRY..A GOOD DEAL OF EVAPORATIVE COOLING EXPECTED
WHICH WILL HELP COOL COLUMN.





Two Lows in close proximity of each other



Phased together



Here is the animation. I am to lazy to make one. LOL

http://raleighwx.americanwx.com/models/gfs/00zgfs500mbHGHTNAGFSLoop.html

So stayed tuned for the rest of the winter. You will here the term Phasing a lot, I promise.

Going back a few days ago in chat in reference to Stratospheric warming, here are the temps today, and the projected temps in 10 days.



If you go by climatology, this signal, which has been steadily warming over the past week or so, should bring some bitterly cold weather to the South . How far it moves towards us here is yet to be determined. The stratosphere is a area one would think that is not looked at to predict weather events. The vast majority of the weather that impacts us at the surface occurs in the lowest layer of the atmosphere: the troposphere. The stratosphere is the next layer up, and while storms don’t occur there, research has shown that temperature changes in the stratosphere often signal changes in the troposphere as well. They are opposite each other, though! Warming in the stratosphere can be a clue to significant cooling in the troposphere.

Here is what to expect. Mark your calenders. LOL

In the Mid and Deep South, the next week or so will feature chilly weather with a gradual moderation.

Just beyond the seven day period, a significant flip to very cold weather is possible. The odds are better than 60% that we will see some of the coldest weather since January 2011. As we get closer to the cold period, we will be able to see more clearly if this could actually rival some of the January 2003 or 1994 cold weather when highs were in the 10s and lows were near zero.




A big rain event will occur in the South as we make the change to the colder pattern. That rain will come between Thursday, Jan. 10th and Saturday, Jan. 12th. How far South is unknown at the moment. Will have to keep an eye out for the potential of some Severe Weather even tho at the moment, not thinking it will be a big, wide spread issue.

A big Southern Snow? Too early to know for sure, but snow-lovers like me will be glued to the models and observations looking at the pattern between Saturday, Jan. 12th and Tuesday, Jan. 16th. If we’re going to get any (and it’s a big “if”), that looks like about as good a set-up as we could get. It is a long way off.

Here is another thing to look for that I forgot to add above. 500 millibar spaghetti plot of ensemble forecasts.



Each individual set of red, light blue, and dark blue lines indicates a possible position of particular 500 millibar height levels from the various models. The more variation you see in those lines means there is more uncertainty in the forecast. When they start to show more of a pattern, confidence grows that one particular solution is more accurate than the rest. Based on this run of the GFS model (12:00 AM today), there is a lot of uncertainty, but there is increasing consistency in the long-term showing those lines dipping south over the East. That indicates where a future deep trough will set up opening the door for some very cold air.

Here is a quick explanation from the University of Illinois of what the 500 mg heights and temperature means to the forecast.



The above panel shows 500 mb forecasted fields for geopotential height, temperature and wind vectors. 500 mb charts depict conditions in the middle troposphere (roughly 5000 meters).

Geopotential height approximates the actual height of a pressure surface above mean sea-level and is represented by the solid white contours. The geopotential height field is given in meters with an interval of 60 meters between height lines. The 500 mb height field encircling the globe consists of a series of troughs and ridges, which are the upper air counterparts of surface cyclones and anticyclones. The distance from trough to trough (or ridge to ridge) is known as the wavelength. Typically waves at 500mb are known as long waves. Embedded within the long waves are short waves, which are smaller disturbances often responsible for triggering surface cyclone development.

Wind vectors provide information about wind direction and wind speed and are drawn here as tiny red arrows. Wind vectors point towards the direction in which the wind is blowing and the longer the wind vector, the stronger the wind. The unit of magnitude for wind speed as depicted by the wind vectors is meters per second.

Temperature is represented by the color filled regions and the associated values are indicated by the color code located in the lower left corner of the forecast panel. Temperatures are given in degrees Celsius with an interval of 5 degrees Celsius between temperature contours, also called isotherms.

In this particular image, the important features are the two closed lows in the western half of the continental United States. Notice that the temperature is relatively cold in the center of the troughs. These cold temperatures can act to intensify upward motion caused by the troughs.

When cold advection occurs into a trough (and warm advection into a ridge), this acts to amplify the wave in the geopotential height field. When the wave is amplified, vertical motions intensify, providing energy for a developing cyclone.

Neat little graph Met. Rob Guarino, made.



We are gonna start the year with a positive NAO. We have a few stormy periods in January but also a few breaks from winter. The overall idea is to watch 1-2 weeks out at a time. The chart above is more like projections based on the ebb and flow of the NAO and AO.



MY THINKING AT THIS POINT...

The cold air in the east and Midwest will actually slow the stormy pattern down for the first week of January.

After that the pattern may try and get a few storm either near the East Coast or come in through the Midwest. This period has one of change as the NAO and AO start to dip again into a stormy period.

Later in the month will feature a few stormy periods but a period of warmth too. I find the later part of the month one of wide swings in the weather esp. in the south with severe weather...a severe/bliizard outbreak in one storm and colder weather near February.

The west coast will continue a parade of storms the next few weeks.

BEST CHANCE OF WINTER STORMS THIS MONTH...
AFTER JANUARY 10... 40% CHANCE
AFTER JANUARY 15... 55% CHANCE
AFTER JANUARY 20... 64% CHANCE

Credit:, Entire post. Rob Guarino

Hmmm. Excellent and on point read of whats to come. IMO

http://theweathercentre.blogspot.com/2013/01/multiple-stratospheric-warmings-confirm.html?m=1

Great blog post today, e !!

And thanks for posting that link to that other blog.....his explanations are very similar to the way you try to explain things, to us novices!!!

Based on the graphic, after the second warming, it looks like that brrrrr.....cold moves way south, but stops just at the FL line........ do you think we could feel the effects, here in FL? (not counting Aug....LOL)

Day time highs during the day on the 19th. Brrr!



Look at Tennessee, highs in the teens. WOW

Arctic plunge...then a low forms in the gulf and moves northeast. Can you say major snow storm if that plays out.



From HUN this afternoon:

CONSIDERABLY COLDER CONDITIONS WILL EXIST POST FROPA
BY LATE IN THE WEEK AS A DEEP TROUGHING PATTERN SETS UP FOR MUCH OF
THE EASTERN CONUS. THIS WILL OPEN THE DOOR FOR THE ARCTIC CANADIAN
AIR TO OOZE SOUTHWARD, MAKING FOR A BELOW-NORMAL END FOR THE FORECAST
PERIOD.