"...the eye in the sky."
- Alan Parsons Project, in their 1982 album Eye in the Sky
6:00 AM Tuesday 12-8-09 [revised from 6AM & 9PM 12-7] Overview of storm ideas for the Tuesday-Wednesday Mid-Atlantic Wintery Mix:
The student climate collaborative provides all of us many additional "eyes in the sky" to track multiple indicators of stormy weather. A quick scan of student analysis thus far:
1. Mr. Foot's 9th graders at the BCPS Crossroads Center were highly skeptical of the National Weather Service's "100% chance" call for anything so early. Student responses: "How can they (the NWS) be SO sure it's 100% freezing rain, like 2 DAYS from now?" Students were also questioning availability of cold air, given the unfavorable position of the "blue lines" (2m temp and 5,000 ft level). They saw the possibility of school delays but didn't buy into it. The take away message here might be that Baltimore County teachers should not bank on extra free time Wednesday to polish up those interim grades.
2. Ms. Abrahm's 9th graders at Mount Saint Joseph's High in southwest Baltimore report that better snow cover would have suggested that early precipitation falls as freezing rain or sleet. Students did tend to believe that as sunrise approaches, this looks to be more of a rain event. Will conditions at 7:00 AM cause enough concern to delay the school day?
3. Ms. Gerst's 5th graders at Perry Hall Elementary agree this will be better handled as a nowcast event, and will be turning their attention to a potential snow event this weekend. They're examining some twists in the North Atlantic and Arctic Oscillation Indices, which suggest the cold air coming behind this week's storm may lay important groundwork for a "semi-Kahuna" this weekend.
Any science teacher in the Mid-Atlantic remains welcome to join our climate collaboration team. We would be thrilled to have sophomores, juniors or seniors on board to help, because if this were a round of golf, we just finished with hole # 1. I am available by email, and will get back to you in a few hours if a response is not received right away.
PREVIOUS STORM TIMELINE & ANALYSIS
The student climate collaborative provides all of us many additional "eyes in the sky" to track multiple indicators of stormy weather. A quick scan of student analysis thus far:
1. Mr. Foot's 9th graders at the BCPS Crossroads Center were highly skeptical of the National Weather Service's "100% chance" call for anything so early. Student responses: "How can they (the NWS) be SO sure it's 100% freezing rain, like 2 DAYS from now?" Students were also questioning availability of cold air, given the unfavorable position of the "blue lines" (2m temp and 5,000 ft level). They saw the possibility of school delays but didn't buy into it. The take away message here might be that Baltimore County teachers should not bank on extra free time Wednesday to polish up those interim grades.
2. Ms. Abrahm's 9th graders at Mount Saint Joseph's High in southwest Baltimore report that better snow cover would have suggested that early precipitation falls as freezing rain or sleet. Students did tend to believe that as sunrise approaches, this looks to be more of a rain event. Will conditions at 7:00 AM cause enough concern to delay the school day?
3. Ms. Gerst's 5th graders at Perry Hall Elementary agree this will be better handled as a nowcast event, and will be turning their attention to a potential snow event this weekend. They're examining some twists in the North Atlantic and Arctic Oscillation Indices, which suggest the cold air coming behind this week's storm may lay important groundwork for a "semi-Kahuna" this weekend.
Any science teacher in the Mid-Atlantic remains welcome to join our climate collaboration team. We would be thrilled to have sophomores, juniors or seniors on board to help, because if this were a round of golf, we just finished with hole # 1. I am available by email, and will get back to you in a few hours if a response is not received right away.
PREVIOUS STORM TIMELINE & ANALYSIS
TUESDAY: I hypothesize that ice storms are more about the daytime high and less about the overnight low. It does not appear Monday's overnight temps dropped as low as everyone expected. That means today's high temps are likely to be in the mid 40's instead of the upper 30's-low 40's as projected earlier. For Central PA, Western MD and into the Appalachian region, highs in the upper 30's will permit the surface to remain cool enough that come nightfall and onset of precipitation, dropping to 32 or just below can occur. For Central Maryland, the Baltimore-Washington NWS is leaning toward a warmer solution, so for example, the forecasted daytime high of 41 F in Towson, MD may end up higher given it is already 40 F at Baltimore Harbor as of 6:00 AM. That will make dropping all the way back down to 32 F more difficult.
TUESDAY NIGHT: Throw three processes in a mixing bowl: radiational cooling (RC), evaporative cooling (EC), and latent release of heat (LR). What do you get? A cooler and drier than expected airmass (RC) a few hours longer than expected ahead of the storm. This would thicken the surface cold layer slightly once rain begins by late evening. As precipitation begins, some will evaporate while falling through this cool, dry layer (EC); actually cools the air layer further. However, indications this morning show that perhaps the opposite may be setting up: a layer of cold air at 5,000 feet promoting more sleet than snow, with easterly winds off the Bay to scour out the low-level cold air quickly. This is why your local NWS forecasts have removed the 100% chance of just freezing rain and replaced with sleet and snow transitioning to some freezing rain, then over to plain rain by 3 AM. (White Marsh, MD / Columbia, MD / Frederick, MD)
TUESDAY NIGHT: Throw three processes in a mixing bowl: radiational cooling (RC), evaporative cooling (EC), and latent release of heat (LR). What do you get? A cooler and drier than expected airmass (RC) a few hours longer than expected ahead of the storm. This would thicken the surface cold layer slightly once rain begins by late evening. As precipitation begins, some will evaporate while falling through this cool, dry layer (EC); actually cools the air layer further. However, indications this morning show that perhaps the opposite may be setting up: a layer of cold air at 5,000 feet promoting more sleet than snow, with easterly winds off the Bay to scour out the low-level cold air quickly. This is why your local NWS forecasts have removed the 100% chance of just freezing rain and replaced with sleet and snow transitioning to some freezing rain, then over to plain rain by 3 AM. (White Marsh, MD / Columbia, MD / Frederick, MD)
WEDNESDAY: From Frederick County, MD on west - the threat of freezing rain remains in place. Once rain freezes on contact, even though the temperature might be less than 32, this change of state from liquid to solid is a condensation (or heating) process believe it or not. The act of "freezing" requires energy, and thus the surface temperature will rise to near 32. Once slightly past that, the ice begins to slowly melt, and the liquid can also slowly evaporate - back to a cooling process. This is the latent release of heat (LR): an equilibrium can keep a freezing rain regime in place longer than computer models or human forecasters alike can predict accurately.
BOTTOM LINE FOR SCHOOLS: Depending on how quickly frozen precip transitions to liquid early Wednesday morning, will dictate what ground crews and transportation officials do. They'll have to salt roads and walkways regardless, but will a change to rain come quickly enough to wash away any concern for school delays? From Carroll County, MD on west it will be a dicey call but 2-hour delays are not unrealistic. Areas not under a Winter Storm Watch/Winter Weather Advisory will experience some overnight frozen precip. Large school systems such as Baltimore County will experience a plethora of conditions, from just rain the Southeast area, to a longer period of snow/sleet/freezing rain between Reisterstown north east well into the Hereford Zone. A transition to rain by 3AM as the NWS projects would make the June calendar watchers happy, but powderhounds know it's only early December - and paybacks will be coming!
Student climate collaboration teams will continue examining this storm, as well as the weekend semi-Kahuna. Until then, let's revisit a Maryland school closing rule: "Storms from the west don't bring extra rest."
PREVIOUS INTRODUCTION: The season's first significant coastal snowstorm has given way to a multi-day period of cold in advance of stronger and more widespread system by mid-week. The power of this storm, now causing severe problems along the West Coast and throughout the Rockies, is partly due to its origins as former
Pacific Super Typhoon Nida. At one point in its late November ocean trek, this storm had winds clocked at 203 mph. The remnants became a surface low pressure system, and have now reached the US mainland. Combining a pulse of Arctic air with El-Nino enhanced moisture from the subtropical jet will create expansive and significant problems for most of the nation this week. This is a storm only for extreme weather watchers, the rest of us will gladly duck and cover.
BOTTOM LINE FOR SCHOOLS: Depending on how quickly frozen precip transitions to liquid early Wednesday morning, will dictate what ground crews and transportation officials do. They'll have to salt roads and walkways regardless, but will a change to rain come quickly enough to wash away any concern for school delays? From Carroll County, MD on west it will be a dicey call but 2-hour delays are not unrealistic. Areas not under a Winter Storm Watch/Winter Weather Advisory will experience some overnight frozen precip. Large school systems such as Baltimore County will experience a plethora of conditions, from just rain the Southeast area, to a longer period of snow/sleet/freezing rain between Reisterstown north east well into the Hereford Zone. A transition to rain by 3AM as the NWS projects would make the June calendar watchers happy, but powderhounds know it's only early December - and paybacks will be coming!
Student climate collaboration teams will continue examining this storm, as well as the weekend semi-Kahuna. Until then, let's revisit a Maryland school closing rule: "Storms from the west don't bring extra rest."
PREVIOUS INTRODUCTION: The season's first significant coastal snowstorm has given way to a multi-day period of cold in advance of stronger and more widespread system by mid-week. The power of this storm, now causing severe problems along the West Coast and throughout the Rockies, is partly due to its origins as former
Pacific Super Typhoon Nida. At one point in its late November ocean trek, this storm had winds clocked at 203 mph. The remnants became a surface low pressure system, and have now reached the US mainland. Combining a pulse of Arctic air with El-Nino enhanced moisture from the subtropical jet will create expansive and significant problems for most of the nation this week. This is a storm only for extreme weather watchers, the rest of us will gladly duck and cover.
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