TORNADO WARNINGS TO TX, LA AND ARK NOW!!!

AccuWeather.com‏@breakingweather

For updates on the snowstorm across New England, check out our live blog. [link to ow.ly]

6 minWBZ Boston News‏@cbsboston

Winter storm warning in effect for most of Mass. through 7 p.m. - [link to shrd.by]

This is the JTWC latest discussion that mantains as low chance for 98W to develop.

AN AREA OF CONVECTION HAS PERSISTED NEAR 5.3N 136.9E,
APPROXIMATELY 185 NM SOUTHEAST OF PALAU. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY SHOWS A BROAD, ELONGATED LOW LEVEL CIRCULATION
CENTER (LLCC) WITH SPORADIC CONVECTION. A RECENT 170013Z ASCAT PASS
MISSED THE CENTRAL PORTIONS OF THE LLCC, BUT DOES INDICATE THE WINDS
ALONG THE WESTERN PERIPHERY ARE BETWEEN 10 AND 15 KNOTS.
ADDITIONALLY, IT INDICATES STRONGER GRADIENT INDUCED WINDS ARE
LOCATED TO THE NORTH OF THE LLCC AND ARE HELPING TO FUEL RECENT
CONVECTIVE ACTIVITY ALONG THE NORTHERN PERIPHERY OF THE LLCC. UPPER
LEVEL ANALYSIS INDICATES THE LLCC IS LOCATED TO THE SOUTH OF A DEEP
LAYERED SUBTROPICAL RIDGE WHICH IS CREATING MODERATE LEVELS OF
DIVERGENCE ALOFT, IN ADDITION TO LOW TO MODERATE LEVELS OF VERTICAL
WIND SHEAR (10 TO 20 KNOTS). SEA SURFACE TEMPERATURES IN THE
VICINITY OF THE LLCC ARE BETWEEN 28 AND 30 DEGREES CELSIUS.
OBSERVATIONS AT KOROR, PALAU SHOW A ONE MILLIBAR PRESSURE FALL OVER
THE PAST 24 HOURS, WITH THE CURRENT SEA LEVEL PRESSURE AT 1005 MB.
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 10 TO 15 KNOTS.
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1004 MB. THE
POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE
WITHIN THE NEXT 24 HOURS IS LOW.

Concerning Thursday...

From Jackson, MS NWS:

"GIVEN THE AMOUNT OF DRY AIR AND COLDER TEMPERATURES THAT WILL BE IN PLACE THURSDAY MORNING FROM THE PREVIOUS FRONT...WE WILL NEED TO UNDERGO A PRETTY SUBSTANTIAL SURGE OF MOIST UNSTABLE AIR. THIS IS NOT COMPLETELY OUT OF THE QUESTION BUT MAY BE TOUGH TO FULLY ACHIEVE. TIMING THOUGH CONTINUES TO BE ROCK SOLID BETWEEN MODELS AND FROM RUN TO RUN. TAKING A LOOK THIS MORNING AT SOME ANALOGS FOR THIS EVENT...THE TOP ONE THAT MATCHES IS IN LATE FEBRUARY 2007 WHICH PRODUCED SOME SEVERE WEATHER IN OUR AREA INCLUDING THREE TORNADOES...AND A RATHER SIGNIFICANT TORNADO IN LITTLE ROCKS AREA. THERE ARE SOME DIFFERENCES IN THE AMOUNT OF INSTABILITY PRESENT BUT OTHER PARAMETERS LOOK SIMILAR."

Forecast discussion out of Des Moines anticipating a mess:

YIELDING THE POSSIBILITY OF LIGHT FREEZING RAIN ON TOP OF THE FRESHLY FALLEN SNOW. THEN...AFTER THE DRY SLOT WORKS THROUGH...ANOTHER BURST OF SNOW IS LIKELY AROUND THURSDAY NIGHT AS THE CENTER OF THE LARGE LOW PRESSURE SYSTEM MOVES OVER THE AREA. THIS WILL RESULT IN SEVERAL HOURS OF ACCUMULATING SNOW AND STRONG WINDS ON THURSDAY...FOLLOWED BY SEVERAL HOURS OF EITHER LIGHT SNOW OR LIGHT FREEZING RAIN STILL ACCOMPANIED BY STRONG WINDS...THEN MORE LIGHT TO MODERATE SNOW THURSDAY NIGHT INTO FRIDAY MORNING WITH WINDS DIMINISHING SLOWLY UNTIL THE STORM PULLS AWAY LATE FRIDAY. ALL IN ALL IT WILL BE A MESSY AND HAZARDOUS STORM SYSTEM AND ALL INTERESTED PARTIES SHOULD MONITOR FOR FORECAST UPDATES AND POSSIBLE WATCHES/WARNINGS OVER THE NEXT SEVERAL DAYS.

wow all the way down to ft meyers............URGENT - WEATHER MESSAGE
NATIONAL WEATHER SERVICE TAMPA BAY AREA - RUSKIN FL
846 PM EST SAT FEB 16 2013

FLZ051-052-055>057-060>062-065-171500-
/O.CON.KTBW.FZ.A.0005.130218T0500Z-130218T1400Z/
HILLSBOROUGH-POLK-MANATEE-HARDEE-HIGHLANDS-SARASO TA-DESOTO-
CHARLOTTE-LEE-
INCLUDING THE CITIES OF...BRANDON...TAMPA...LAKELAND...
WINTER HAVEN...BRADENTON...WAUCHULA...SEBRING...AVON PARK...
NORTH PORT...SARASOTA...VENICE...ARCADIA...PORT CHARLOTTE...
PUNTA GORDA...CAPE CORAL...FORT MYERS
846 PM EST SAT FEB 16 2013

...FREEZE WATCH REMAINS IN EFFECT FROM LATE SUNDAY NIGHT THROUGH
MONDAY MORNING...

* TIMING...LATE SUNDAY NIGHT THROUGH MONDAY MORNING.

* WINDS...NORTHWEST AT 15 TO 20 MPH SHIFTING TO THE NORTH AFTER
MIDNIGHT.

* TEMPERATURE...29 TO 32 DEGREES FOR MANY AREAS SEVERAL HOURS
SUNDAY NIGHT. TEMPERATURES WILL REMAIN IN THE MID 30S FOR
COASTAL AREAS AND IN SOME MORE ELEVATED TERRAIN AREAS ACROSS
THE INTERIOR.

* IMPACTS...SIGNIFICANT DAMAGE IS POSSIBLE TO COLD SENSITIVE
PLANTS SUNDAY NIGHT. PLAN TO COVER OR BRING THESE PLANTS
INDOORS TO AVOID THEM BEING DAMAGED TO DESTROYED. DANGEROUS
BOATING CONDITIONS ON AREA LAKES AND BAYS TODAY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FREEZE WATCH IS ISSUED FOR THE POTENTIAL OF A WIDESPREAD AND
DAMAGING FREEZE WITHIN 24 TO 48 HOURS. DURING THE FREEZE
PERIOD...TEMPERATURES MAY REMAIN BELOW 32 DEGREES FOR MORE THAN 2
HOURS.

&&

$$

URGENT - WEATHER MESSAGE
NATIONAL WEATHER SERVICE JACKSONVILLE FL
905 AM EST SUN FEB 17 2013

FLZ020>023-030-031-035-036-GAZ132>136-149>152-162 >164-180000-
/O.EXP.KJAX.HZ.W.0001.000000T0000Z-130217T1400Z/
/O.CON.KJAX.HZ.W.0002.130218T0300Z-130218T1400Z/
HAMILTON-SUWANNEE-COLUMBIA-BAKER-UNION-BRADFORD-G ILCHRIST-ALACHUA-
COFFEE-JEFF DAVIS-BACON-APPLING-WAYNE-ATKINSON-WARE-PIERCE-
BRANTLEY-ECHOLS-CLINCH-CHARLTON-
INCLUDING THE CITIES OF...JASPER...LIVE OAK...LAKE CITY...
MACCLENNY...LAKE BUTLER...STARKE...TRENTON...GAINESVILLE...
DOUGLAS...HAZLEHURST...ALMA...BAXLEY...JESUP...PE ARSON...
WAYCROSS...BLACKSHEAR...NAHUNTA...STATENVILLE...H OMERVILLE...
FOLKSTON
905 AM EST SUN FEB 17 2013

...HARD FREEZE WARNING REMAINS IN EFFECT FROM 10 PM THIS EVENING
TO 9 AM EST MONDAY...
...HARD FREEZE WARNING HAS EXPIRED FOR THIS MORNING...

* TEMPERATURE...LOWS AROUND 20 TO 25. UPPER TEEN READINGS
POSSIBLE IN NORMALLY COLDER LOCATIONS.

* FREEZE IMPACTS...COLD TEMPERATURES WILL LIKELY DAMAGE OR KILL
CROPS AND OTHER SENSITIVE VEGETATION IF NOT PROPERLY PROTECTED.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THOSE WITH AGRICULTURAL INTERESTS IN THE WARNED AREA ARE ADVISED
TO HARVEST OR PROTECT TENDER VEGETATION. ALSO...POTTED PLANTS
NORMALLY LEFT OUTDOORS SHOULD BE COVERED OR BROUGHT INSIDE AWAY
FROM THE COLD. IF YOU MUST GO OUTSIDE IN SUB-FREEZING
CONDITIONS....SEVERAL LAYERS OF CLOTHES AND A HAT WILL PREVENT
THE LOSS OF BODY HEAT.

A HARD FREEZE WARNING MEANS THAT TEMPERATURES LESS THAN
27 DEGREES ARE EXPECTED FOR AT LEAST 2 HOURS.

&&

$$

The Weather Channel‏@weatherchannel

Philosophy pun alert: #Plato will take the "form" of a #blizzard by this afternoon in New England. Details: [link to wxch.nl]

AccuWeather.com‏@breakingweather

Logan International Airport in Boston, Mass. reports 101 flights canceled so far today, according to [link to flightstats.com]

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE TAUNTON MA
417 AM EST SUN FEB 17 2013

MAZ022>024-171730-
/O.CON.KBOX.WS.W.0003.000000T0000Z-130218T0000Z/
BARNSTABLE MA-DUKES MA-NANTUCKET MA-
INCLUDING THE CITIES OF...CHATHAM...FALMOUTH...PROVINCETOWN...
VINEYARD HAVEN...NANTUCKET
417 AM EST SUN FEB 17 2013

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 7 PM EST THIS
EVENING...

* LOCATIONS...CAPE COD AND NANTUCKET.

* HAZARD TYPES...HEAVY SNOW AND STRONG GUSTY WINDS.

* ACCUMULATIONS...SNOW ACCUMULATION OF 6 TO 10 INCHES.

* TIMING...ANY MIXED PRECIPITATION SHOULD CHANGEOVER TO SNOW THIS
MORNING. THE SNOW MAY FALL HEAVILY FOR A TIME FROM 7 AM THROUGH
2 PM.

* IMPACTS...UNTREATED ROADS AND WALKWAYS WILL BECOME SNOW COVERED.
STRONG WINDS WILL DEVELOP THIS MORNING AND CONTINUE EVENING.
THIS MAY RESULT IN NEAR BLIZZARD CONDITIONS FOR A TIME. IN
ADDITION...THE INITIALLY WET SNOW COMBINED WITH THE WIND COULD
RESULT IN SOME DOWNED TREE LIMBS AND A FEW POWER OUTAGES.

* WINDS...NORTHWEST 30 TO 40 MPH WITH GUSTS UP TO 55 MPH.

* VISIBILITIES...ONE QUARTER TO ONE HALF MILE AT TIMES.

Eric Fisher‏@EricFisherTWC

Blizzard is 1/4 mile visibility and frequents gusts over 35mph (not snowfall total dependent). On the Cape, you've got it. #Plato

7 minEric Fisher‏@EricFisherTWC

According to ASOS, #Plato is officially a #blizzard in Hyannis: [link to 1.usa.gov]

AccuWeather.com‏@breakingweather

Latest snow total: 7.3" at Caribou, Maine.

Jim Cantore‏@JimCantore

Up next, widespread Heavy #snow for the heartland by midweek: [link to po.st] #newx #sdwx #kswx #iawx #wiwx #mnwx #ilwx

Eric Fisher‏@EricFisherTWC

Like with #Nemo, an 'eye' has formed with Winter Storm #Plato. Impressive. [link to twitter.com]

1 minAccuWeather.com‏@breakingweather

Dramatic changes are on the way--Downtown Los Angeles warmed to 82 F yesterday, but will only have a high of 58 on Tuesday....

Thanks for posting this - i love weather doom porn. It never turns out to be anything, but its fun to masturbate to.

The Northeast is very fortunate Winter Storm Plato is tracking farther east. It's of equal intensity to Nemo and would have been a significant blizzard if it would have tracked closer to the coast.

AccuWeather.com‏@breakingweather

Chief Meteorologist Elliot Abrams discusses Northeast snowstorm and what is to follow. [link to ow.ly]

Ryan Maue‏@RyanMaue

RAP forecasts sub-zero dewpoints later in the day along Space Coast. [link to twitter.com]
1 hRyan Maue‏@RyanMaue

Very dry air over Florida. Dewpoints in the single digits. Daytona Beach dewpt. is 9°F temp is 46° [link to twitter.com]
1 hRyan Maue‏@RyanMaue

Washington, Oregon Cascades to see very snowy pattern, many feet during next week's cold. [link to twitter.com]

For this I am thankful!!

Yes, thank God! Next week there are another in the models, but too early to know!

6-12 inches in Mass. We have about 4-6 right now outside of Boston. Wind advisory until 10pm tonight with gusts to 50mph. It's not a big storm.

that's good!

Okay maybe I spoke too soon cause the winds just picked up. LOL!

Regardless, I don't foresee many issues arising from it.

NWS New York NY‏@NWSNewYorkNY

Its very windy out there today. Here is our latest report of sustained winds, wind gusts and snow from this am [link to ow.ly]

Ryan Maue‏@RyanMaue

Current Florida dewpoints: 6°F Daytona Beach, 8°F in the swamp (Gainesville), 17°F Ft Laud. Arctic airmass to Keys [link to twitter.com]

February 21-23 High-Impact Significant Winter Storm
By Andrew at 12:41 PM
Have removed the 'Potential' from the storm title, as the event is within the timeframe of reasonable certainty.

Satellite imagery shows the storm system of interest is in the Gulf of Alaska and nearly onshore in Alaska at this time. Analysis of the infrared field determines that the center of low pressure is on the coast of Alaska, with a very ragged comma shape still present in association with this storm. Surface analysis indicates the storm is in the 990 millibar range, so it is a fairly decent storm at this point in time.

Model uncertainty still remains a priority to deal with at this time, as it does appear there are two possible solutions evolving. Shown above are 500 millibar height anomalies for Hour 120, or 5 days away. Cold colors suggest the presence of low pressure, while warm colors favor areas of high pressure. The bottom image shows 850 millibar temperatures and mean sea level pressure for Hour 132, meaning it is 5 days and 12 hours away. This model is the North American Ensemble Forecasting System (NAEFS), a set of ensembles which I understand is derived from the Canadian and American ensemble forecasting systems. The NAEFS has done very well in the past two years for predicting temperature anomalies during the winter, this will be my first time seeing how it fares with storm systems. The NAEFS is predicting the storm system to ride east-northeast through the Plains and into the Midwest. This is not what recent model trends have been showing- the latest forecast models have taken it further north.

The issue with the models is how strong that high pressure system will be in both Canada and the East US. If we look at the top image of the NAEFS, we can see that the high pressure system is strongest from Canada into Greenland. Models and ensembles differ as to where the center of this high pressure system will be. The NAEFS proposes the high pressure system to be centered in north Canada, which then allows the storm system to progress further east and into the Midwest. The European model, as you will see below, takes a much different track.

This is the most recent forecast from the typically-reliable European model. It is called the ECMWF model in the weather world, but for practical purposes we will refer to it as the European model. This forecast also has two images: the top image once again shows 500 millibar height anomalies, while the bottom image depicts 850 millibar temperatures and mean sea level pressure values. The 500 millibar chart is valid for Day 5 (Hour 120), while the bottom image of mean sea level pressure is for Hour 144, or 6 days away. If we do a comparison between the NAEFS and this European model, it's pretty obvious that the European model is stronger with the high pressure in the East than the NAEFS. We see more oranges stretching down south from Canada and into the Eastern US than the ensemble system. The reason for this is a much weaker connection between the high pressure in Greenland and high pressure in Canada. Almost like a bridge, the European model nearly breaks off the connection between these two masses of high pressure, which would allow the Canadian high pressure system to then push further south and allow the European solution to prevail. If the European model solution did prevail, one would expect lower snow totals with any snow further to the north. Quite an odd solution in my opinion, and we will evaluate it further later on in this post.

Something that needs to be brought up is that strong high pressure system in the Pacific. That big high pressure system, combined with the low pressure in the West US creates what's called a negative Pacific North American index, or a negative PNA. The low height anomalies in the West provoke above normal height anomalies (high pressure) to arise in the East US, which typically can push storms into the North Plains in a similar fashion to the European model. The NAEFS ensemble system also has this high pressure system in the Pacific, but is more widespread than the European model. The more widespread it is, the stronger the high pressure is. As a result of a stronger high pressure, the 500mb heights must become lower and this would push the storm track further to the south. However, we now go back to the previously-mentioned high pressure over Greenland. When high pressure is established to the east of Greenland, it is called and East-based Negative NAO; 'East based' for being east of Greenland, and the negative NAO (North Atlantic Oscillation) implies high pressure over Greenland. The negative NAO provokes the subtropical jet stream to become more active and pushes the overall storm track south. It also suppresses the high pressure in the Southeast, which is why I'm not confident in the north-bound European model. Both images above show the east-based negative NAO, but both have different solutions. It all comes down to which factor has the stronger influence. Because the negative PNA is upstream of the Midwest, it will have a stronger effect than the negative NAO, which is far up in Greenland. However, by the time the storm system is able to reach the Plains, the negative NAO will hold some influence and ought to be able to keep the storm system south, definitely further south than the European model's solution.

I can understand why there have been trends north. Shown above are 500 millibar heights (not anomalies, just the regular values) valid for Hour 96 (4 days away). We can see our low pressure system just beginning to emerge from the Rockies. The issue from here is where it comes out of the Rockies. The NAEFS forecast in this image has the low pressure system in far southeast Colorado. When you get storms coming from that area, there is a decent possibility that high pressure could push it north, and I believe this is where the European model is getting the idea of a northward trend from. Additionally, the storm will be reaching what's called a negative tilt by the time it is exiting Colorado. A negative tilt implies that a storm system's highest vorticity values are pointing towards the southeast, and this is where we find the big difference between the southern solution (NAEFS forecast) and the northern solution (European model).

I put together the NAEFS and ECMWF (European) models together for the same timeframe. They are both forecasting 500 millibar values for 4 days away. The black line illustrates the tilt of our storm system, while the red line illustrates the tilt of the high pressure system in the Central US that is preceding this storm. The issue between the northern and southern solutions is that the European model wants to bring the system to a negative tilt faster than the NAEFS ensembles do. This is shown by the ECMWF image's black line tilted to the southeast, while the NAEFS is more neutral-tilted, meaning the highest vorticity centers are not tilted in any particular direction. In response to the negative tilt by the European model, the storm system digs to the Southeast more. This situation then responds similar to if you were to push some form of a wedge (shovel, for example) into the ground- the shovel (storm system) tries to dig down further south, but the ground (high pressure system) is provoked to move north in response, and this is how the European model gets its northern solution.

Considering there are three different ensemble systems rooting for a southern solution and just one model and one ensemble system rooting for a northern solution (the most recent American model jumped south a bit), I'm going to have to go with the southern solution. I am a bit hesitant, because the European model and its ensemble set are very prestigious and reliable forecasting systems, so it's a very tough forecast to make when it's essentially Europe vs. the world.

Despite this, I am willing to stick with my prediction that was made yesterday for this system. To me, there are three stages of the models. The first is the Long Range track, where the models get a consensus roughly 10 days away from the event. The second stage is what I like to call the '60 Hours of Chaos', where the storm gets within 8 to 5 days away (Hours 180-120 on the models) and the models go in every which way. The third and final stage is the final track, where the models converge on a solution within 5 days of the storm. This final track can sometimes be nearly the same as the first Long Range track. We already observed the first stage, and are now clearly in the second stage. The system will get on land in the next few days, so model solutions should clear up as the time comes closer. I should mention that the Chicagoland area into southern Wisconsin and north Indiana and southwest Michigan may see that 'Accumulation Possible' dropped if dry air manages to start that region with virga (precipitation is being produced, but evaporates in a dry layer of air before it hits the ground) as some sources are suggesting. There will be a lot of dry air in place just a day or two before the event, and this could very well hinder the already-lowered totals. I will most likely have my first accumulation map out either tomorrow or Tuesday; confidence remains low.

Andrew [link to theweathercentre.blogspot.de]

NWS New York NY‏@NWSNewYorkNY

The nor'easter ~500 mi ENE of NYC has a pressure ~956mb. The pressure at NYC is 1006mb; A 50 mb diff. and the reason why it is windy today!

Eric Fisher‏@EricFisherTWC

#Plato down to 956mb...from 1001mb at 00z last night! Extremely rapid deepening. Good thing this one tracked east of Nemo. h/t @StuOstro

This looks very dangerous... from snow to severe weather [link to i.imgur.com]

[link to synoptic.envsci.rutgers.edu]

URGENT - WEATHER MESSAGE...CORRECTED
NATIONAL WEATHER SERVICE MELBOURNE FL
318 PM EST SUN FEB 17 2013

... FREEZE WARNING IN EFFECT FOR LAKE...ORANGE...OSCEOLA...
SEMINOLE...INTERIOR VOLUSIA COUNTIES EARLY MONDAY MORNING...

FLZ041-044>046-053-144-180445-
/O.UPG.KMLB.FZ.A.0002.130218T0500Z-130218T1400Z/
/O.NEW.KMLB.FZ.W.0002.130218T0500Z-130218T1400Z/
INLAND VOLUSIA-NORTHERN LAKE-ORANGE-SEMINOLE-OSCEOLA-
SOUTHERN LAKE-
INCLUDING THE CITIES OF...DE LAND...LEESBURG...ORLANDO...
SANFORD...KISSIMMEE...ST CLOUD...CLERMONT
318 PM EST SUN FEB 17 2013

...FREEZE WARNING IN EFFECT FROM MIDNIGHT TONIGHT TO 9 AM EST
MONDAY...

THE NATIONAL WEATHER SERVICE IN MELBOURNE HAS ISSUED A FREEZE
WARNING...WHICH IS IN EFFECT FROM MIDNIGHT TONIGHT TO 9 AM EST
MONDAY. THE FREEZE WATCH IS NO LONGER IN EFFECT.

...FREEZE WATCH REMAINS IN EFFECT FROM LATE SUNDAY NIGHT THROUGH
MONDAY MORNING...

* TEMPERATURE...NORTHWEST WINDS WILL DIMINISH AFTER SUNSET THIS
EVENING UNDER CLEAR SKIES. THIS WILL RESULT IN STRONG
RADIATIONAL COOLING OVERNIGHT. TEMPERATURES WILL FALL RAPIDLY
AFTER SUNSET AREAWIDE. READINGS ARE EXPECTED TO FALL BELOW THE
FREEZING MARK IN THE EARLY MORNING HOURS...MAINLY ALONG AND
NORTH OF THE I-4 CORRIDOR.

* IMPACTS...COLD SENSITIVE PLANTS SHOULD BE COVERED OR BROUGHT
INDOORS IN ADVANCE OF FREEZING TEMPERATURES. PETS SHOULD ALSO
BE BROUGHT INDOORS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A FREEZE WARNING MEANS SUB-FREEZING TEMPERATURES ARE IMMINENT OR
HIGHLY LIKELY. THESE CONDITIONS WILL KILL CROPS AND OTHER
SENSITIVE VEGETATION.

&&

$$