Sunday, February 1, 2009



GROUNDHOG DAY DRILL: UPDATE # 2

CURRENT SYNOPSIS: MON FEB 2 - 3:45 PM. A TOTAL OF FOUR OR MORE inches across the Baltimore Metro region, with possibly higher amounts first in far western counties of the Blue Ridge, and then later in areas adjacent to the Chesapeake Bay.

The cold front in central Maryland, which may shortly go stationary, will usher in colder air by the evening commute. What little rain that occurs will quickly mix with and change to all snow before midnight. Snow may be intermittent into Tuesday morning, until moisture from one or more waves of low pressure developing along this front moves along the Mid-Atlantic coast. Despite today's warm temperatures, dynamic cooling coupled with evaporative cooling will provide an upper level environment conducive for snow. The bulk of accumulation should occur Tuesday, but could extend into the evening hours. Little or no risk of frozen precipitation until the very end of the event. Below normal temperatures will be in place Wednesday and Thursday, causing overnight re-freezing of standing water on sidewalks, bridges, overpasses and untreated roads.

MON FEB 2 - 1:45 PM. This is a quick update to let you know there are no changes to my forecast for amount and timing of snow. However as you can all tell just by looking out the window, things are not working out today as many forecasters had planned (That could be a good thing for powderhounds). Even I had to take an umbrella with me this morning to shield against the uh, rain er, um the blazing sunshine. I've been watching a variety of data just briefly, and what I see suggests the Mid-Atlantic is still in for a surprise tonight and tomorrow. Question is, will the surprise be a picture of me wearing a grocery bag? Or will it be a "children sleeping, snow is softly falling" kind of surprise? DISCLAIMER FOR STUDENTS AND TEACHERS: None of my forecasts are a suggestion to discard preparation for school the following day. Just adhere to the rule set forth by my esteemed colleague Mr. Terpguy (a Baltimore County science teacher for 39 years) : Be prepared (also known as the Boy Scout motto.)

Observations since 12 noon today: Deep convection in the Gulf and over Florida; There's a ton of moisture headed this way, and it is NOT just happily flowing into the Atlantic, an 850 mb upper low in northern Gulf; Where is the rain for Maryland? The front is almost on top of Baltimore; For concerns the ground is "warm" I decided to check. Here's what I found:

1:30 PM Mon 2-2: The ground on my south facing yard in Dundalk was so hard I had trouble inserting a thermometer. At last check the subsurface temp about 1/2 inch down is ::get this :: 37 F! This is in FULL SUN with no shade and it's been there over an hour now. That tells me once the front arrives as sun angle dips lower, temps will tumble. i was walking on another large field in town a few hours ago. The top 1/2 inch was moist, but you could feel under that a rock solid layer of basically semi-permafrost.

Lastly.. how about the surface lows currently on the live, real, actual, in-front-of-our face maps that ARE NOWHERE TO BE FOUND ON THE HPC SURFACE LOW TRACKING MAP? I guess a low that pops in Pennsylvania and delivers several inches of snow, snarling traffic, is not significant?

Previous discussion from 5:45 AM follows:

SCHOOL: If my snow forecast of 4 inches verifies, then most Maryland districts from Frederick County, MD eastward to the MD-DE line will close once snow is falling Tuesday morning. The same will be true for Northern Virginia, the WV panhandle, and York County, PA eastward to Philadelphia. Wednesday may bring school delays due to re-freezing, black ice and the added potential for a shortwave touching off more snow showers. For Thursday and Friday, roads will be clear and thus, it is expected that schools open on time both days.

ANALYSIS: My research indicates the potential for several inches remains unchanged, despite inconsistencies in computer models. I calculated the amount by taking just the general liquid equivalent projected by an average of the QPF map and the models, but I added the likelihood of "Bay-effect enhancement" if banding sets up from northeast to southwest. With this approach, you arrive at roughly .50 inches of liquid. Translated directly by the standard snow-to-liquid ratio of 10:1, (lowered to 8:1 due to marginal temps) delivers a general 4 inches across Central Maryland, lesser amounts west of Baltimore, higher totals near the Chesapeake Bay and northeast toward Elkton and Philly.

YOU: "WHAATTT????? 4 INCHES??? WHAT COMPUTER MODEL ARE YOU LOOKING AT??"

ME: I'm not looking at ANY computer model. I'm relying on that which Justin Berk suggested we all do.. (read next section for context) use my own knowledge, intuition and experience.

If NWS and TV forecasters have seemed unwilling to commit on amounts until now, it may have been due not only to misguided model data, but the memory of embarrassing outcomes in the past decade: (Too low-January 25, 2000) (played catchup-February 14, 2003); (Too high-March 3, 2001). (Caveat: I've had a number of them myself, and will relate those stories to you because none of us are immune to making vast, catastrophic mistakes.) There is more discussion of this in my "statement on the models" below.

Since it's been 5 years from when this site began, perhaps it is time you get some background on "the man behind the curtain" so you can better understand the methods behind the madness. Scroll to the next post for three true stories of life without computer models.

STATEMENT ABOUT "THE MODELS." Expecting more "GoDaddy" goofiness during the Superbowl, my wife and I conveniently blocked the TV during commercials for sake of the children. Oh, sorry, that was the wrong intro. I meant to talk about computer models.

The other game may be over, but the real game in town is just starting. I wonder if the computer model whiplash confounding forecasters is from data so corrupted for this event that NOAA would rather let it go than admit they're unwilling to rely on traditional meteorological techniques. Justin Berk of ABC2 News said it best in his post earlier today, with regard to the possible data gap caused by diverted air traffic over Alaska's Mount Redoubt: "many forecasters have relied too much on computers and not enough on their own knowledge and intuition. I often say that if computers were perfect, we would be out of work." I for one appreciate his candor, and if I had a choice between laying off meteorologists, or shutting off computer models, he'd be among the ones I'd keep!

Case in point from the Baltimore/Washington NWS at 8:50 PM Sunday. Note that I've converted the abbreviated text to full words for clarity:

WE'RE GETTING A FAIR NUMBER OF CALLS REGARDING THE LATE MON/TUE EVENT. I'M HAVING TROUBLE GETTING WOUND UP ABOUT IT. ALL MODELS I'VE LOOKED AT SHOW THE LOW STAYING OFF THE COAST AND TRACKING STEADILY TO THE NORTHEAST AS SHORT WAVE DRIVES SOUTH EASTWARD INTO THE UPPER TROUGH WHICH WILL HELP TO KEEP THE COASTAL LOW OFFSHORE.

I still have a lot of misgivings with the picture being painted by NWS and higher offices. There is so much erroneous information scattered throughout the playing field, and I think they realize this to the point that even though the computer projections "appear" to have settled on a solution, doesn't mean the programs have initialized all the pieces to make an informed decision. That last critical part is up to US, the CREATORS of the program.

MY LIST OF CONCERNS:
(1) Radar shows convection and thunderstorm cells in the Gulf of Mexico. This was NOT predicted by the models. It is clear some of the models did not even include this data in their most recent runs.
(2) Moisture is feeding into the upper level flow already ahead of the cold front sliding south across the Midwest. This moisture cannot be ignored and will be involved in the end game.
(3) Upper level low at 500 mb is moving out of southern Canada. The models do not have a good handle on it's direction and destination.
(4) The very unusual precipitation forecasts for the Mid-Atlantic suggest there will be this "hang-back" of moisture from Baltimore north to Philly and New York. There is also odd placement of convective activity off the Carolina/Florida coast.
(5) Finally, it appears that the placement, strength and destination of several shortwaves have been so problematic that no one can figure out what they're going to do once they encounter the base of the trough over the Mid-Atlantic by Monday night.

In conclusion, if I'm wrong, then there will be a full accounting on this site, and you will thoroughly enjoy the way in which we do this. It is the same technique I've had to use in class in previous years for failed forecasts: I wear a brown paper bag over my head, with the forecasted amount written next to the actual amount. If it happens this time, I'll post that picture of myself here for all to see!

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