Wednesday, January 30, 2008
Friday, January 25, 2008
Tuesday, January 22, 2008
Monday, January 21, 2008
Sunday, January 20, 2008
In case no one noticed yesterday, you went about you day underneath one of the longest-duration "vlizzards" I have ever seen. (That's a virga blizzard). I mean it snowed like mad for at least 9 hours straight, giant invisible flakes coating everything in a blanket of vapor. Actually, it was a virga storm. All that beautiful white and blue on the radar yesterday was snow falling but evaporating before reaching the ground. Whodunit? Dewpoint depression. Boundary layer moisture content was too low to be overcome, and the dryness prevented any of that snow from reaching the ground. Had it reached the surface, we could have called it a "flizzard."
Saturday, January 19, 2008
Thursday, January 17, 2008
FOLLOWUP OBSERVATIONS ON TODAY'S EVENT:
1. My start time was much earlier than news and weather outlets, and I can see why it took until mid morning (at least in southeast Baltimore County). I would surmise the immediate boundary layer was still quite dry, and several hours of virga (when precip is falling but evaporating before reaching the surface), delayed the onset.
2. However, the very nature of what "virga" does is what I believe enabled the snow to reach greater intensity once it began. The atmosphere became sufficiently chilled and moistened to the point that snowfall rates were very high from the start. Combined with the fast moving shield of snow that overspread the area, I knew that once it got started, the snow would make up for lost time by accumulating more quickly.
3. I wore a special tie I reserve for these occasions.. the dark blue one featuring my 2 skiing snowmen. My wife asked what the tie meant this time, and I told her that the 2 snowmen on the tie indicated schools (at least the ones that have some sense to make the right call ...Frederick County...ahem.. Bueller...anyone?) would close 2 hours early. To this she remarked: "Of course, when I bought this tie for you 4 years ago, I had this exact date in mind, January 17, 2008. Riiiight."
HAVE WE LEARNED OUR LESSON FROM PREVIOUS STORMS?
It's obvious now this storm is turning out to mimick it's December 5 cousin, aptly named "The Little Storm That Could" by faithful powderhound Mr. Ligner, the Athletic Director at Sparrows Point High School. That means the 2-4" could end up closer to 5" in some parts of northern and western Baltimore County. I suspect Carroll and out-in-left-field-they-must-have-hired-their-transportation-folks-from-Buffalo- Frederick County will see amounts on the high end of their Warning criteria... with widespread 6-7-8" likely. Of course I adore my job, my students, my employer and the nice summer 2-month bonus I get every year, so you can be sure that MY COUNTY will always make the right call, no matter what. ;-) I leave all the bad weather related decision making to other places, like Howard and Anne Arundel Counties, for starters. No offense and kudos to my Ho Co colleagues who quickly pointed out they are on an exam schedule this week..so they were scheduled to get out early ANYWAY!
There have been several times in the past 5 years that school systems were burned for making a call based on the BELIEF that dire predictions of weather agencies would come to fruition, and didn't. The one that sticks out in my mind most recently is late February 2005, when NWS had posted a Heavy Snow Warning for most of Maryland. You might have thought it was going to be "Day After Tomorrow, Part 2." Everyone closed from bow to stern. The snow started... at 10 AM. Oh it was heavy all right, and started to stick on the parking lot here in southern Balto County, around 3 PM. I know because I was working in the school greenhouse that day, watching the heavy white clumps land on the grass and MELT. It was so unfortunate how that that storm turned out, because in reality we could have squeezed a full school day out of that. The ground was too warm to support accumulate UNTIL the sun angle decreased, once it did, snow started to stick like glue, but roads were still just slushy and not frozen over by any means.
Since that time, I believe school systems have been following a Revolutionary Era to making the call. You've heard the old saying from the Battle of Bunker Hill in 1775.. "Don't fire until you see the whites of their eyes!" I think we are seeing proof of that proverb here in Maryland. We can identify 3 storms tied to the dubious distinction of being a "Whites of their Eyes" Storm:
- Feb 12-14 Valentine's Day Massacre of 2007
- December 5, 2007 Little Storm That Could
- January 17, 2008 Frederick Co. Honorable Mention "What's a Winter Storm Warning?" Storm
GET TO THE POINT WILL YOU?
Oh sorry, got carried away with reminiscing about climatology. Okay, the point is for tomorrow:
If two-thirds of your geographical scope of authority receive at or above the projected snow amounts, and a changeover to rain is delayed or denied, the likelihood of your school system calling for a delay or closing is inversely porportional to the decision made the day before and the parent reaction to that decision. Without delving too far into the political gooeyness (sp?) of this, let's break it down like such:
IF YOUR SCHOOL SYSTEM WAS.. TODAY YOU RECEIVED... TOMORROW YOU WILL BE..
a Winter Storm Warning area... No early dismissal... Closed, for various reasons.
a Winter Weather Advisory area... A 2 hour early dismissal... 1-2 hour late opening
a Winter Weather Advisory area... No early dismissal... On time, No late opening
Not in any warning or advisory area... Snow but no dismissal... 1-2 hour late opening
WHEN'S THE NEXT STORM?
There is potential for a coastal system to surprise the Mid-Atlantic yet again on Saturday. With cold air in place and models continuing to back the shield of precip more westward with each run, I could see a Special Weather Statement coming out on Friday for the Saturday system which has the potential to deliver the same amount or greater than what the Mid-Atlantic saw Thursday.
And then there's Kahuna potential lurking in the near future, as early as Tuesday and perhaps again on Friday. I will endeavor to stay on top of these developing winter weather events and bring you the latest scoops of truth as time and family permit. As I said in the heading, those of you who were honking for snow, be careful what you wish for, because Mother Nature is about to make up for lost time.
As always, please post your observations in the comments, and feel free to send me a snow pic that I can use to beautify the site: email@example.com. Enjoy the snow while it lasts!
Wednesday, January 16, 2008
WED 1/16 - 6:00 PM: I figured you'd be back here before long. Perhaps you were wondering if I would ever be back, but since the weather has provided us a new topic, as Captain Kirk might say: "Well, now you have something new to talk about." As many of you already know, the Baltimore/DC NWS issued a Winter Weather Advisory for the most of Maryland west of the Chesapeake Bay, including the DC and Baltimore Metro areas. I've been watching their discussions, the observations, satellite, and of course our old friend, the computer models, for several days now in anticipation this storm was going to deliver some sort of winter precipitation on Thursday. Those in this region whom follow winter weather are beginning to suspect that this system is not turning out as expected, and I anticipate a diversity of surprise closings and delays throughout the DC-Baltimore Metro areas are on tap Thursday morning. Low level cold air appears entrenched into the deep South, as evidenced by the extent of NWS winter weather advisories from here to Georgia.
This fast-moving system will display unique impacts across the Mid-Atlantic area (specifically in Maryland west of I-95, south central Pennsylvania, Northern Virginia, the West Virginia Panhandle, and of course the Shenandoah region):
1. Persisent high pressure "centers" in the Mid-Atlantic will allow temperatures overnight to drop below freezing. By daybreak, whatever precip that begins to fall will freeze on contact, allowing slippery travel conditions to develop quickly, and catch unsuspecting motorists/walkers off guard.
4. Changing and unresolved precipitation timing concerns that may disrupt school schedules.
5. A fast moving system that WOULD become a major snowstorm were it not for lack of access to an Arctic high in Southeast Canada. (actually there is one there, but the timing and orientation are not right this round)
The biggest concern which prompted NWS to hoist advisories for the Maryland region is that computer models do not see to be handling the presence of low level cold air across the region. Secondly, the eventual intrusion of warm air aloft may be delayed such that frozen precip is now more likely over a wider area than originally thought, and for a longer period of time. Accuweather, on the other hand has been downplaying the potential for ice or mixed precip. As I remind my students in situations like this, the amounts sometimes does not matter if we have a mixture of frozen precip, because even one tenth of an inch of ice as you all know can wreak far greater havoc than just one inch of snow. The movement of this storm can be seen in a computer model animation from a site I've recently discovered: coolwx.com