Updates Below (most recent 10:15am)
Good Thursday morning to one and all :-)
If you've been following any sort of weather headlines over the last 24-hours or so, you will have seen a whole lot of talk about this big New England blizzard.
Well, before it gets there it has to scrape by here. It's not going to be that big of a deal, just some rain showers following today's mild temperatures:
|NAM - Friday Morning||NAM - Friday Evening|
Following that though, the game changes...
It all has to do with the Atlantic Ocean providing a huge amount of source moisture for the storm to feed on, and the fact that we'll unite the southern and northern stream flows for a good "bomb" cyclone event. A "Bomb" is when the central pressure of a storm deepens more than 24milibars in 24-hours. By most accounts, this will happen-- and then some.
<Tangent> One Way To Get A Lot Of Snow -----
One of the ways we can see ahead of time to know that a lot of snow may be coming to a region is to analyze the internal properties of a storm system and its clouds. When it comes to the flakes, you obviously would need to have a good solid region in the clouds where snow-growth is encouraged. In a recent example from our own region, it would look like this:
Those horizontal gray lines represent the 10,000 and 15,000 foot markers. So within that region of the clouds in this example, snowflakes are forming. Then the question becomes: How much snow? Essentially you want to try to see a factory being set up, where rising air motion pushes moisture into this zone and flakes come out. Our last snow event locally looked like this:
The red contours represent vertical air motion, which also happens to be measured in negative numbers (forces of gravity and downward motions are positive numbers). In this example, we were able to get 2" of snow to come down.
Using these same tools, this is what the model dynamics are spitting out for this upcoming storm in the Boston area Saturday morning:
There's a bulls-eye of some serious vertical air motion right through the snow-growth zone Saturday morning that may well cause 2" of snowfall per hour. What a difference in the two systems, eh? Now, a meteorologists would be much more comfortable seeing this sort of signature in the models with 24-36 hours to go, but since it's already appeared with 72-hours to go there comes a battleground where you're worried about hyping this up and seeing something change or not deliver, or not hyping it up and missing the boat. Then there's always the concern of what your audience wants to talk about. Everyone's antennae fly up when there's talk of snow, and your boss knows it :-)
But for us, we're not going to see much of anything wintry come from this storm system. In fact, one limiting factor on the snow for New England could also be due to the same thing: the progressive nature of the air flow aloft.
|GFS - 500mb Chart - Friday AM||GFS - 500mb Chart - Saturday AM|
(Yep, there I go again with those vorticity maps)... If you recall from Superstorm Sandy, we had a much deeper plunge aloft at the hands of colder air, and it was able to take that hurricane and draw it inland. These values are also attempting to phase two separate systems, but it does not occur until the melded storm is already off-shore. In fact, instead of the system over the Great Lakes maintaining dominance, the coastal storm will take over and our little system will appear to "jump" the mountains to strengthen on the other side.
From the same maps on the GFS:
|GFS - Surface Chart - Friday Morning||GFS - Surface Chart - Saturday Morning|
Even by Friday morning this transition of energy is taking place, where the parent storm moving through the Ohio Valley realizes the grass is oh so much greener by the Atlantic Ocean. By the time Saturday hits, there's only one system, and it's tearing up the New England Coastline with a central pressure in the 980s (or perhaps even lower).
The GFS is attempting to put some snowflakes back our way in this same environment Friday night, and we may get a flurry or two, but I would not be surprised at all to see the moisture appear to fly away from us and flock toward this deepening coastal low. Temperatures are going to stay cold on Saturday as well, being in the cold air return flow of this strong Nor'easter, but our next system is headed in on Monday, so during the day Sunday our moderating southerly winds will pick back up.
And, just for fun, here's what the NAM is calling for in terms of snowfall in the Boston area:
A 20"+ snow event for the entire I-95 corridor would be historic, and possibly approach all-time levels. I'd still be more tepid about making this call, because the models have shown this sort of thing more than a few times before, but the results were disappointingly low in the end. However, since more people have access to data these days, you know that so many of your viewers are going to be in tune with the possibilities, so they want you to talk about them. Then old folks get scared, grocery stores get cleaned out, and then they blame you when it doesn't materialize ;-) But, these are also those challenging times that being a meteorologist becomes so much more meaningful (and even fun).
Update (10:15am) - I wanted to bear out this point about energy transfer a little more, because it shows up real well by looking at wind "streamlines". You're going to see during the day Friday our little system that comes across our area almost simultaneously cede itself to being absorbed by the rapidly intensifying low off the coast. Here's what the NAM is showing with this:
|NAM - Friday Midday||NAM - Friday Evening||NAM - Early Saturday Morning|
I think this stuff is kinda neat, so I thought I'd share it so you can see a good example of one storm melding into another as it continues to intensify. For clarity, the first low pressure center (marked by converging airflow) is moving up through Lake Erie into western NY, while the other more obvious one is paralleling the Atlantic coast.
Now, another element brought out by these streamlines is the eventual result overnight Friday that puts a solid fetch of wind-flow from directly over Lake Erie onto the WV Mountains east of Charleston. We will be seeing snow from this, though so far is still looks to be light. Notice how the territory covered by those lake-borne winds is fairly restricted, so back off toward the west (aka, Huntington, Kentucky, etc.) should not expect any snow-- and more likely will get sunshine overhead by Saturday morning.
It'll be fascinating to watch, especially when things finally start happening ;-)
|Regional Radar/Satellite with Warnings Tracking||
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Have a great day everyone!