First Trackable event...

In my winter outlook-- I targeted December as the coldest month and the most likely to be colder than normal AND have some type of snow and cold.

Attached are the 9 and 10 day maps from the ECMWF--the most reliable longer range model.

This is a classic look for a good snowstorm here. If THIS were to play out as shown, it would bust my 5-10 inch winter total forecast.


Of course--this is 9-10 days out. In a La Nina winter, its harder to hold the block in place--if you note there is a storm in place to the NE of Maine. That feature most hold to suppress this storm and hold the cold air in place. If that feature is not there--this event will be MUCH different.

** In a La Nina pattern, the pacific jet is stronger (faster) making blocking harder to hold**

Winter Outlook 2010-2011

I'm running a day later than I had promised--but the crisp cool day today inspired me to put my thoughts and forecast on paper. I've had my general ideas for several weeks, was just waiting for a little more data to trickle in to double check things.


Winter 10-11

Quite the shift from last winter where we had 200% normal of snow

Season Temp. Forecast +2 above normal

Seasonal Snowfall 5-10 inches. (Same forecast for Roanoke, 2-5 inches for the Danville region) 10-18 inches for the NRV, The favored high elevations of the region get more due to upslope snows. (AKA, places were I doubt anyone will read this blog)
Higher risk for ice storms. 

Monthly breakdown temp bread down

December-

-2 below normal

January

Starts cooler but ends warm

+2

February

+4
Still has some colder outbreaks, just warmer overall.

As the long wave pattern adjusts to spring, March will feature rapid swings (Normal to some extent in March) with a higher then normal risk of wintry weather.

Technical talk--

This may bore you if you don't enjoy weather. (I need to post a glossary of terms for those who may care--but if you google these terms you can find them)


I derive my outlook by many means-- First and foremost I read as many detailed outlooks from REAL meteorologists as possible. From there, I study the global patterns based from the El Nino/La Nina regions and other terms such as GLAAM, Mountain Tourque, PDO,QBO, MJO, AO  the past season's hurricane pattern and even snow cover in Eurasia this time a year. From this information I can get a set of years that had similar pre season patterns and check the climo records for those seasons. Its not an exact science, nor do I claim to be my one and only source. With more qualified people creating these "usable comparable years" I see little sense in recreating the wheel as a less qualified forecaster.


Last year, the west based moderate el Nino made it somewhat of an easy call and I'd rate my call an A--- didn't foresee the big snow in December and missed the extreme cold in early January--but other then that it was excellent. The big factors all lined up and I went big and scored big.

This winter's outlook has half the confidence as last years--

Why?

In favor of warmth--
Strong La Nina, The Indian Dipole, Positive QBO

In favor of colder--
Long term pattern of the NAO being negative
Snowcover in Eurasia being above normal.
Some research shows that re curving hurricanes from the east coast may be an harbinger of the -NAO being negative in the winter.


We don't have many close analogs because the El Nino went rapid to La Nina and is currently strong. This COULD disrupt the forecast because the norm is a colder December transitioning to warmer as the winter progresses. (If the La Nina has peaked sooner--does the December climo norms not matter is the thought here)

Piecing this together--

Strong La Nina's don't usually bring big snows to our region. Hence, I'm starting cold and moving warmer and expecting below normal snow. However, the snowcover in Eurasia, Re-curving hurricanes and longer term trend of the NAO I expect us to end up in the battle zone between colder air that spends much of the winter bottled up well to our north.

Monthly break down--

December-- Cold pattern develops late November and is strongest until middle of the month. The pattern begins to adjust to a warmer and by early Jan we are in a warmer pattern.


January--

Early month cold gives way big and its a good month- Late month holds chances for a few severe cold outbreaks, but warm wins the month.

February-
Warm pattern holds on with still the occasional risk of a couple cold days with trailing storms as cold fronts clear (See Feb 89 as example)


Storm pattern---

Last season the mean storm track for our region was to our south and east, hence most events were mostly snow and a ton of it. This season, I expect the mean storm track to go to our west placing us in the warm sector. However, the Appalachian Mountains play a role here where the cold air gets trapped against the mountains and we end up with an ice event. Strong La Nina = south east ridge= Warmer temps on the east coast, especially south of 40 latitude. Cold air damming plays BIG role in our ice storms.

These events can be subtle--For example.

Monday is a great day- High 61, low 32
Tuesday feels a little cooler--52 high but the relative humidity drops and the dew point is 8.
Clouds come in Tuesday night and sleet develops. Temp falls down to 25 with the sleet. By the next morning it is 29 with freezing rain. On the other side of the blue ridge towards Tazwell its 44, Charleston WV is 48 and to our east Richmond is 36 and south Danville is 38. Freezing rain lingers all day. The next day the temp is back into the upper 40's. 2 days later temps are back in the 60's.

These type storms come out of the SW--- and can head up into Ohio then reform well to our northeast. That low level cold air being trapped along the Appalachian mountain (There are three types of this "cold air damming" that causes aides in these ice and snow storms) places us in a unique spot for these ice events. If we tap into the colder air that build up over the Arctic (And didn't build up last year because of the pattern) we could see a nasty ice event or two.

For the record, LYH has one of the highest "per hour" freezing rains in the nation--close to 50 hours a year of freezign rain. I use to have a map of the hours. This is a unique climate trait to our region due to the proximity of the Blue Ridge which creates the inability to remove cold air at the bottom 2k or often less feet of the atmosphere.

Much different than last winter--warmer, less snow and more ice. More rapid shifts and in some sense laster winter was cold with shorter bursts of warmth. This year will on some levels be the opposite. Warm, with short bursts of cold.

My biggest concern is 1-2 nasty ice events, not the nuisance ice events I described-- Also, La Nina's breed drought as the pacific jet dominates and everything is progressive with little interaction from the subtropical jet. This is something to monitor as we head into the spring growing season.
Will update as needed.

Remember to add us to your twitter account at Lynchburgwx

Heaviest snow ever in Lynchburg?

Here is a photo from Jan 30th of this past year---

While working on my winter outlook, I checked on some data from last years various snowfalls. For some reason, I wondered how this heavy snow event compared to others as far as the heaviest snow in an hour and other short specific durations.

In general-

Heavy snow is an inch an hour or more, moderate snow is about a half inch an hour

One unique fact is that the biggest snows on record (Jan 1996, Dec 09, March 93) often give the best depth, but its the duration that wins, not ONE heavy hour. Visibilities associated with these would be Heavy snow--less than a quarter mile, moderate snow-- about a half mile.

My search of the data is limited by the resources online and more importantly, the lack of ALL the hours of data pre 2000--

I'd bet that I am accurate 20 years, likely accurate 30 years and at that point the data is missing WAY to much.


The snow from Jan 30th was about 2 inches an hour between 7 and 8 am, with about 3.3 inches falling between 7 and 9 am.

The heaviest snow of the past 20 years comes down to 2 dates--

1. March 2, 2009. The storm that broke the 13 year double digit snow drought also had ONE of the heaviest snowfalls in the past 20 years. Between 12 am and 2 about 5.1 inches of snow fell. This was part two in a two part system. Part one pass through the area Sunday afternoon. Places Lynchburg south and east had about 2-3 inches of heavy wet snow. As the upper piece of energy passed through, the temps dropped at every level of the atmosphere and the snow bands set up over town for 2 hours. This was a powdery snow--so the liquid equivalent was .27 and the snow ratio was about 19-1. (Inch of liquid would make 19 inches of snow) The heaviest snow fell between 12-1 am with about 2.6 inches falling with a two hour total of 5.1 inches.

2. January 25, 2000- This storm is called the Carolina Crusher as a largely unforecasted and then under forecasted storm developed which brought locally 8-12 inches of snow with upwards of 20 inches in the
Raleigh, NC region.
Local forecasters struggled with a 1-2 inch call issued at 8 PM, upgrade to 2-4 inches at 10 PM and then 6-12 well after the onslaught of snow was on. There was a tremendous amount of dry air to the northwest of this storm, so it only snowed when the heaviest of snows hit the area. From 8 PM on, there was snow in the clouds evaporating as it fell. Snow first trickled out of the clouds around 3 am and it meant business. Between 3:45 and 4 AM a half inch of snow fell. The next two hours 4.7 inches of snow fell-- with 2.6 inches falling between 4 and 5 am.

(On a side note-- My old roomates, Mike, Chris and Jeremy can testify that I was all over this storm, promising them at least 6 inches of snow that night---one look at radar at 2 pm with the classic negative tilt radar presentation sealed the deal for me. I was right, but not by much. 10 miles west of Lynchburg had nothing more than flurries.)

Special mention-
Jan 22 87 had 5 inches fall in 3 hours.

Most other events max out between 1 and 1.5 inches an hour.


Which event had the heaviest---over two hours the March 1-2 09 event does take the cake. However, this was a powdery snow. The Jan 25, 2000 event ended up "officially" as .78 liquid for 7.5 inches of snow. I measure 8.5 inches at my house--which was 4 miles north of the airport. (Not even sure who measured that one)

It is this bloggers opinion that the Jan 25, 2000 storm had the heaviest snow on record for one hour. The fluff from the 09 event was impressive but when you compare 2.6 inches of fluffy snow to 2.6 inches of good ole concrete snow, the concrete wins. However, the 2 hour total of March 1-2 2009 has the 2 hour total lead.

New Home for Lynchburg Weather

As the NFL season starts, fall settles in and its time for me to begin working on my winter outlook. Last years outlook was a slam dunk..
I do enjoy tropical and severe weather, but at some point this hobby can become WAYY to much, so I do place 10x the effort into winter weather.

http://www.facebook.com/notes.php?id=507002058&notes_tab=app_2347471856#!/note.php?note_id=174886414694

I threw out temps at -2 for the winter and it was more like -4 ish region wide. Snowfall predicted 30' in LYH, 35' ROA and 45' down in Blacksburg. My overall feel for the winter was close--with the only bad part was missing the intense cold snap in early January.

We had a 10 ten snowfall winter--but pretty far off the all time mark set in 1995-1996. We did set a record for snow cover--- with the LYH airport reporting an inch of snow 42 days, shattering the old record of 36 days set in 1978

This winter will be a La Nina---the opposite of an El Nino meaning the global pattern will be much different. My early thoughts would hedge towards colder/ice/snow in December maybe into early January. From there, the pattern shifts and we sit on the mild side of things most of January and well into February. During this time, we will see SOME cold air outbreaks, but they won't last but 2-5 days at best.

The pattern MAY shift back late February into March---this is a may, not WILL.

I'm not willing to put any exact numbers, but I'd December comes in colder then normal, January comes in much above normal and February is slightly above. Snowfall is hard to call with one event often making or breaking this number. Normal in Lynchburg is 18 inches.  This winter looks to come in on the low side--with a higher risk for significant ice events.