Friday, December 30, 2011

Weather Blog: Thoughts Heading into 2012

I went running before work today through the Museum District and The Fan, and was reminded of how great a variety of weather we get each year in Richmond. It's the next to last day in December, and the high was nearly 60 degrees with lots of sunshine. Four days from now, we'll be lucky to hit 35, and the wind chill will stay below freezing. I came to the River City in 2007, and was told by several of my colleagues in Plains that the experience of being a chief meteorologist would be good, but that I would soon become bored with the weather. They were half right. I witnessed some wild weather in my 8 years of working in Tornado Alley, the stuff that gives you nightmares, and while we don't see the extremes here in The Commonwealth, we see a greater sampling of weather types than most areas in the country. In 2011, we had a couple of minor snows, several tornado outbreaks, a hurricane, an earthquake, and a good mix of hot and cold days. Then you throw in days like today, and I have nothing to complain about. I'm married with three small children now, and the quiet days are as exciting for me now as the big weather events. I feel fortunate to be here.
A few notes on the weather over the next week: the disturbance tonight will bring little more than a few showers to the area, and no wintry weather. The cold blast is still on schedule to arrive Monday and stay in place through late Wednesday. There continues to be a signal for a disturbance to move through the area on Thursday, possibly bringing the area a few flurries or snow showers, but nothing to write home about. The storm track will become more meridional "north/south" over the next two weeks, which should result in more temperature swings and perhaps a storm system in there as well. Nothing points to any key storm at this time, but as time goes on, a storm will eventually show itself. Have a fun and safe holiday weekend, and make a resolution this year to better your life and those around you. I'm going to refrain from blogging over the weekend, but I'll be back at it on Monday. In the meantime, I'll post quick updates on my FACEBOOK and TWITTER pages. Hope to see you there. -Zach

Thursday, December 29, 2011

Tracking the Cold & Chances for Snow

I awoke this morning to the rumbling of an idling oil truck in the alley behind my home, perhaps a sign that the word has spread that colder days are ahead and it's time to fill up. The deep trough that will dig into the eastern U.S early next week will bring an air mass with a real bite into the region. It's likely that much of central and northern Virginia will see highs remaining in the upper 30s, which isn't at all unusual for the first week of January, but an abrupt change from the relatively mild fall and winter we have seen to this point. The overnight lows during this period will fall into the upper teens and low 20s. As I mentioned in my post from yesterday, the chance for snow with this pattern change appears slim to none, with only a slight chance of seeing a quick burst of light snow early Monday. If you're scheduled to be at work that day, you'll be working. We'll have another possibility for snow later in the week that looks pretty interesting. Both the GFS and Euro operational models are indicating the presence of an upper-level wave that will dive south out of the upper Midwest and move just south of Virginia on Thursday. This isn't an ideal setup by any stretch for snow, but it's the type of scenario that can become more favorable with time. You'll note my confidence in seeing anything isn't very high by the 20% chance I have in my 7-day forecast. I'll peruse the model suites again this evening and track the movements of birds and small rodents in the morning. Check back for another update tomorrow, and if you haven't already done so, click here to drop by my facebook page and click the "like" button. Have a great Friday. -Zach

Wednesday, December 28, 2011

To Snow or Not to Snow...

That is the question, and it appears as though we'll be left high and dry. The Euro model must have finally awakened from its post-holiday leaded-eggnog stupor, because as quickly as one can say La Nina, the computerized pundit reversed its thinking on next week's nor'easter. Even more disappointing to snow lovers, is the strong agreement of all the medium range models of a deep and cold trough digging into the eastern half of the nation January 2nd-4th. Cold is good, yes, but not cold AND dry, and it appears as though that is what we will likely be dealing with. It was fun while it lasted, but big swings like this are very common, as I touched on in my blog entries from the past couple of days. The image below indicates the Euro model from yesterday morning (12z) and just below that image is the GFS model from the same time. The solutions are completely different, with a nor'easter indicated by the Euro, and a dry and cool setup shown by the GFS.The next two images show the same two models 24 hours later (12z this morning), and while both have shifted considerably, they now are in very good agreement. The big u-shaped area over the eastern U.S. is the deep trough, which this time of year translates to a very cold and dry air mass. The shades of yellow, orange, and red within the trough highlight areas of vorticity, and the vorticity pattern is relatively smooth throughout the trough, with very little concentrated maxima. A strong and isolated vorticity maximum, also called a short wave, upper-level disturbance, or vort max, is often necessary to bring our region snow. A strong vort max can create snow through lift directly attributed to the disturbance, and can also result in surface cyclogenesis that strengthens into a nor'easter. The latter was the solution the Euro was teasing us with over the past couple of days, but now neither scenario appears possible without a concentrated upper disturbance.We could certainly see a return to more of a pattern conducive for snow, but the current consistency of the most reliable suite of models makes any big change very unlikely. 'Tis the season for model flip-flopping and looking ahead for our first snow with great anticipation. I'll continue to track this situation closely and will have updates on any potential for another one headed this way. Check back again tomorrow for another update. -Zach

Tuesday, December 27, 2011

Our Potential for Snow: Part 2

The possibilities for what happens next week still range from sunny and mild to a heavy snow, with one medium range model staying bullish on developing a Nor'easter for the Mid-Atlantic and Northeast. I'm big on consistency when it comes to longer term forecasting, but each model seems consistent in its own way. The GFS continues to show nothing, while the Euro is going gangbusters. The Euro is many times the big winner in medium range solutions, but I've seen it be consistently wrong on a system before. So with a good measure of cautiousness, and a heck of a lot of optimism, I'll put forth my expectations for next week based only on what the Euro is showing. After all, what's the fun of blogging about a non-event? Yesterday I mentioned the possibility of a big snow, citing the pattern change the Euro was depicting. There has been a change between yesterday's model run, and the runs from last night and this morning. That change?...colder and snowier to put it succinctly. The 500 mb low is slower and farther south and the surface low develops a little farther offshore. The overall amount (QPF) of moisture has increased, and more of that moisture falls into an air mass supportive of snow. So for you snow lovers, it continues to look better and better for a decent snow in the Jan 3-4 time frame. The next run of the Euro will begin a little after midnight. Check back here for my analysis. -Zach

Monday, December 26, 2011

Tracking Richmond's First Chance of Snow

It looks fairly certain we'll finish up December 2011 without a trace of snow, something we haven't seen since 2006. The pattern looks like it could finally make a big shift in early January, bringing much colder air, and possibly the first snowflakes of the season to the area. The various models solutions continue to hint at both colder and snowier weather for the area during the period of January 2nd-7th. Model reliability is typically poor that far ahead, and there have been many departures from the cold solution over the past couple of days. What has drawn my eye has been the persistent signal of a deep and very cold trough digging into the eastern U.S. in response to a negative shift in the North Atlantic Oscillation (NAO). The European Model has been pretty consistent over the past few runs will the colder air, while the GFS has flip-flopped a couple of times and can't seem to settle on a particular pattern for early January. Most recently, and perhaps the most alarming, is the loose agreement of a full-blown Nor'easter on January 5th. We'll certainly see some changes in the solutions over the next few days, and what is there today, could very easily be gone tomorrow. From the signals I've seen over the past several days though, winter could finally make an appearance during the first week of 2012. Check back for another update. -Zach

Thursday, December 8, 2011

Last Total Lunar Eclipse Until 2014 On Saturday Morning

The last Total Lunar Eclipse until 2014 will occur this Saturday morning, favoring viewers all along the Pacific Rim, including the Western U.S. However, those of us on the East Coast will not be able to see this eclipse because our moonset time is before the eclipse begins. The first hints of the "red shadow" will not be visible until 7:45 AM EST.
(Click here to see a map of where the eclipse will be visible in the World).
In Richmond, the moon sets Saturday morning at 7:12 AM, about the time the Sun rises at 7:13 AM. So even if we could see some of that initial shadow being cast by the Earth onto the Moon, it will be nearly impossible to see because of the Dawn.

On the West Coast, though, the Moon will enter "totality" of the eclipse at 6:05 AM PST (which is 9:05 AM EST, well after we can't see the Moon anymore on the East Coast). West Coasters will see a pre-sunrise eclipse of beautiful proportions. Atmospheric scientist Richard Keen of the University of Colorado predicts, "I expect this eclipse to be bright orange, or even copper-colored, with a possible hint of turquoise at the edge." The reason why these colors hue the Moon from our perspective here on Earth is because of our own stratosphere. As the Moon's light is scattered through the Earth's atmosphere back to our eyes, the light waves that "survive" the scattering are reddish.

Watch this NASA video to learn more:

Because we will miss watching the eclipse on the East Coast, you can click here to watch this animation demonstrating what it will look like to our western neighbors.

--Meteorologist Carrie Rose

Wednesday, December 7, 2011

Update on rain and snow Wednesday in Virginia

A slow-moving storm system will finally clear the eastern U.S. by Thursday morning. This Wednesday morning, though, rain continues to track northeast through the western and northern parts of our state, producing some flooding problems in low-lying areas and along creeks and streams. Storm total rainfall should range one to two inches in this part of Virginia, which is why a Flood Watch will remain in effect until 7PM.

For the southeastern half of Virginia, rain totals will remain an inch or less, with the lowest totals at just a quarter-inch in Hampton Roads.

As the surface cold front sweeps southeast this afternoon and evening, much colder air will surge into the region behind it. Winds will shift to the northwest behind the front, with deep, cold air reaching western Virginia before the precipitation ends. This will change the rain to snow, allowing for as much as three to six inches of snowfall accumulation in elevations above 1500 feet! Therefore, a Winter Storm Watch is in effect for that part of Virginia through tonight.

It still looks like the rain will end in central Virginia before the deepest, cold air can settle into the region. There will be a tiny window of opportunity between 10 PM to just after Midnight for the ending rain to briefly change over to snow. Nothing will stick, though, as both air and ground temperatures will still be well above freezing in central Virginia, and remain above freezing into Thursday morning. Here's one forecast demonstrating what snow may fall, but likely not all of this will end up sticking (except in the higher elevations of western VA):

Stay with CBS 6, we'll keep you ahead of the storm!
--Meteorologist Carrie Rose

Monday, December 5, 2011

Rain/Snow Mix Possible Early Thursday

This definitely won't be one to write home about, but enough cold air could arrive in central and western Virginia early enough Thursday morning to change rain to snow or a rain/snow mix before ending. While it looks like a good bet for snow across northern and western Virginia, our chances of seeing anything in the metro are much lower. Above is one model depiction of accumulated snowfall. I agree with the totals across northern and western Virginia, but surface temperatures will be far too warm (37-42 degrees) across central sections for the snow to stick. For reference, the pinks are a trace to 2", cyan 2-3", yellow 3-4", and on up. At least we have a chance to see a little wet snow if nothing else. The forecast atmospheric temperature profile (sounding) in the metro area Thursday around sunrise is favorable for snow to fall while in the process of melting, if there is still rain falling at that time. There's a good chance most, if not all ,of the rain will move northeast of the area by sunrise Thursday, so most of us will miss seeing whatever happens. I'll have another update on this tomorrow. Have a great Tuesday! ZD