The two-thirds-of-an-inch the airport has recorded will be just a drop in the bucket by Monday if forecasters at the National Weather Service are correct in their predictions for the late-winter rainstorm headed our way.

There are Flood Watches posted for the entire state today through Saturday evening. Forecasters say the heaviest rain is due Friday night and Saturday, with 2 to 4 inches possible by the time things begin to taper off on Monday.

That much rain, coming on top of a heavy snow meltdown that has saturated the soil and kept the creeks full, will mean flooding for small creeks, streams and urban areas this weekend. And when all that reaches the larger rivers, we should expect those waters to spill over their banks, as well. You can track the flooding here.

The Flood Watches for the Eastern Shore call for even more rain - 3 to 5 inches. That's one to two months worth of normal rainfall in just four days. Do not attempt to drive through flooded roadways.

Here's AccuWeather.com's take on the rain, with their rainfall forecast map.

The wet weather is being brought to you by a slow-moving low-pressure system that has been dawdling our over the Central Plains. The counter-clockwise circulation around that low has been dragging warm, moist air off the Gulf and the Atlantic, and delivering about 0.66 inch of rain at BWI-Marshall overnight.

Next up: A secondary low now forming over the southeast coast. The counter-clockwise circulation around that coastal low will begin to throw onshore easterly winds across Delmarva from the Atlantic. By tonight and Saturday, the rains will become heavy at times, delivering the bulk of the weekend rainfall.

The whole mess will be slow to pull away, so we can expect the drip to continue through Sunday and into Monday. We should get back to sunny skies and mild temperatures by mid-week.

(SUN FILE PHOTO)

Posted by Frank Roylance at 10:49 AM | Permalink | Comments (0)
Categories: Forecasts
        

After spending a brief period at the top of the snow pile, it looks like Baltimore sledded to 5th position by the season's end in the competition for the title of "Snowiest U.S. City 2009-10."

Here are the top 10 finishers, according to a Web site called Golden Snow Globe. No idea who they are, so I can't vouch for their numbers. I know the total listed for Baltimore (80.4 inches) is no longer valid. The National Weather Service forecast office at Sterling, Va. has recalculated and cut the official total for BWI-Marshall Airport to 77 inches. That pushed Mobtown to 5th place, instead of 4th as listed on the site.

Here's now it should look:

1. Syracuse, N.Y.: 106 inches 

2. Erie, Pa.:  90.9 inches

3. Rochester, N.Y.:  89.6 inches

4. Philadelphia, Pa.:  78.7 inches

5. Baltimore, Md.:  77 inches

6. Pittsburgh, Pa.:  76.9 inches

7. Buffalo, N.Y.:  74.1 inches

8. GrandRapids, Mich.:  70.2 inches

9. Fort Collins, Colo.:  69.6 inches

10. Lakewood, Colo.:   68.2 inches

(SUN PHOTO: Algerina Perna)

Posted by Frank Roylance at 4:53 PM | Permalink | Comments (4)
Categories: By the numbers
        

You knew this couldn't last. We've had three days in a row, now, with highs in the 60s. That hasn't happened here since last Nov. 8-10.

But sunny days in the 60s will give way this weekend to four days in the 50s, with rain. And, for the western counties, especially, the mild temperatures and rain will combine to melt down the snowpack that remains on the ground there. Forecasters say small stream and creeks will likely overflow their banks, and river flooding could follow.

The National Weather Service has already issued Flood Warnings for portions of West Virginia southwest of Maryland's Garrett County. There are Flood Watches up from Garrett east to Washington County, including the cities of Cumberland and Hagerstown, where as much as 4 inches of rain could fall through Saturday.

East of the mountains, there are Hazardous Weather Outlooks posted as far as Carroll, Howard and Montgomery counties.

UPDATE: 6 p.m.: Flood watches are now posted for all Maryland counties west of the bay, plus the Upper Eastern Shore

For Baltimore, the rain is forecast to begin late Thursday night into Friday, with more than an inch expected by early Saturday morning. The rain could be heavy at times late Friday and Saturday, with another two inches possible. Rain chances continue into Monday, so it appears the weekend will be a washout. But at least it's not snow. And our snow cover is gone, except for some lingering piles. So we won't have to add that water to the runoff. The rain will be quite enough, thank you.

Needless to say, though, we'll need to be on the lookout for wet basements, leaks through ice-damaged roofs and gutters, overflowing creeks and street flooding. And that can collapse roads, as this amazing video from Freeport, Maine demonstrates.

Never drive through flooded low spots. It's amazing how little water it takes to float a car and carry it downstream. I suspect we will be reading about water rescues, anyway, this weekend.

All this rain is approaching as a low-pressure system moves very slowly toward us out of the Midwest. The counter-clockwise flow around the low is drawing mild, wet air north from the Gulf and, eventually, the Atlantic.

The heaviest rain will arrive late Friday and Saturday. Here's a bit of this morning's forecast discussion from Sterling:

"ONE BATCH OF RAINFALL ONGOING FRIDAY MORNING MAY LIFT NORTH IN THE AFTERNOON...LEAVING CLOUDS AND DRIZZLE BUT ANOTHER MORE SIGNIFICANT AREA OF RAINFALL IS STILL ON TRACK TO AFFECT THE [FORECAST AREA] FRIDAY NIGHT AND SATURDAY. RAINFALL TOTALS OF 1 TO 3 INCHES...WITH POTENTIAL FOR HIGHER AMOUNTS IN UPSLOPE AREA...ARE LIKELY WITH THIS SIGNIFICANT AREA OF RAIN FRIDAY NIGHT INTO SATURDAY."

The chances for rain will continue into Monday as the storm makes its leisurely exit.

Posted by Frank Roylance at 10:49 AM | Permalink | Comments (2)
Categories: Forecasts
        

AccuWeather.com's hurricane forecasters believe the 2010 Atlantic season will be "much more active" than last year's relatively meek performance. A rapidly weakening El Nino event in the tropical Pacific, unusually warm surface waters in the Atlantic's key hurricane nursery, weakening trade winds and higher humidities, they said, are all pointing to increased activity.

"This year has the chance to be an extreme season," said forecaster Joe Bastardi, who led the company's hurricane forecast team. He also correctly forecasted a very snowy winter season for the mid-Atlantic states in 2009-2010, although his predictions were far short of the actual, record-breaking totals.

The new AccuWeather.com hurricane forecast, out Wednesday morning, calls for 16 to 18 tropical storms this season (the average is 11; last year saw just nine, and only three became hurricanes).

Of the 16 to 18 he expects, Bastardi believes 15 will occur in the western Atlantic. He predicts seven landfalls, five of them hurricanes, of which two or three will come ashore in the U.S. (about average).

Bastardi sees similarities in this year's setup to those in 1964, 1995 and 1998. In 1964, Hurricane Cleo struck near Miami as a Cat. 2 storm and killed 217 people. In 1995, Hurricane Opal struck the Florida panhandle and caused $3 billion in damages. And in 1998, Hurricane Bonnie (photo) came ashore near Wilmington, N.C. as a strong Cat. 2 storm and caused $1 billion in damage.

The hurricane season begins officially on June 1, and continues through November.

(SUN PHOTO: Karl Merton Ferron/Bonnie whips Ocean City, Md. in 1998)

Posted by Frank Roylance at 9:00 AM | Permalink | Comments (2)
Categories: Hurricanes
        

The winter of 2009-2010 will still go down in the history books as the snowiest on record for Baltimore. But in the end it will be three inches less stupendous than we thought.

Meteorologists at the National Weather Service have just finished adjusting their snow tallies to account for measurement problems at BWI-Marshall Airport. Officially, at least - the winter delivered 77 inches, not 80.2 inches as the weather service first reported.

And the big storm in December will be recorded officially as an 18-inch snowfall, not 21.1 inches as the first reports stated. December's monthly total has been similarly reduced from 23.2 inches to 20.1 inches, according to the Baltimore-Washington Forecast Office in Sterling.

The changes don't affect any of the records broken in December. The Dec. 18-19 snowstorm remains the biggest December snow on record for Baltimore, and the month remains Baltimore's snowiest December.

And even at a mere 77 inches, it's still the snowiest winter on record for the city. The annual average for Baltimore is 18.2 inches.

The reduction in some winter snow totals was made late last week as Sterling reviewed each of the season's snowfalls to adjust for measurements that were not in compliance with the weather service's protocol.

Until the problem was discovered in the wake of the Feb. 5-6 blizzard, contract observers working for the Federal Aviation Administration were making only hourly snow measurements, and taking storm totals after the flakes stopped falling - called "snow depth" measurements.

The technique, which complies with FAA rules, is considered invalid by the NWS for climatological data, because it does not allow the snow to compact.

The weather service requires that snow measurements for climatological purposes be made one every six hours. Because of compaction, the totals are usually smaller. That's what the FAA contractor was supposed to have been supplying to the weather service.

So, with no six-hour data, Steve Zubrick, Sterling's science and operations officer, elected to use the FAA's snow depth data instead of the hourly measurements, because it is the most conservative solution.

He and forecaster Jared Klein combed through the data and made the changes. Some snowfalls were unaffected. Most turned out smaller. A few increased due to rounding of snow depth numbers to the nearest inch.

Here are the original and revised numbers for BWI:

December: Original:  23.2 inches  Revised:  20.1 inches

January:  Original: 7.5 inches  Revised:  6.9 inches

February:  Original: 49.5 inches  Revised:  50 inches

Season:  Original: 80.2 inches  Revised: 77 inches 

Major storm totals:

Dec. 18-19:  Original:  21.1 inches  Revised:  18.0 inches

Feb. 5-6:  Original:  24.8* inches  Revised:  25 inches  

Feb. 9-10:  19.5 inches (no change; measured properly) 

* This was the original snow depth measurement. The FAA's total from one-hour measurements was 28.8 inches. 

(SUN PHOTOS: Top: Algerina Perna/Bottom: Karl Merton Ferron)

Posted by Frank Roylance at 4:20 PM | Permalink | Comments (9)
Categories: By the numbers
        

Enjoy the mild weather and abundant sunshine today and tomorrow. The National Weather Service says the above-normal temperatures will remain, but forecasters predict substantial rains by later this week and lingering through the weekend. And that is raising new worries about flooding, especially in Western Maryland, where there are still several feet of snow on the ground.

The problem lies with a low-pressure system that will be organizing over the Central Plains later this week. As it crosses the continent and approaches the East Coast, it will draw southerly winds north ahead of it, and with that air comes lots of Gulf moisture.

Light rain could start falling west of the Blue Ridge as early as late Tuesday night, with more heavy rain possible later in the week east of the mountains. The NWS says: 

"INITIALLY...FLOODING WILL BE A CONCERN BY THURS ACROSS THE POTOMAC HIGHLANDS AND ESPECIALLY WEST OF THE ALLEGHENY FRONT WHERE 20-30 INCHES OF SNOWPACK STILL EXISTS
AS OF YESTERDAY MORNING."

"INCREASED PROBABILITIES OF PRECIPITATION LIKELY FRI AND FRI NIGHT AS SURFACE LOW PRESSURE DEVELOPS OVER THE MID-ATLANTIC STATES. LONG-RANGE DETERMINISTIC AND
ENSEMBLE [COMPUTER] GUIDANCE HINTING AT ANOTHER ROUND OF HEAVY RAIN FRI NIGHT.
CONFIDENCE IN TIMING THIS FAR OUT IS LOW BUT ANY HEAVY RAIN WOULD
POSE A THREAT FOR WIDESPREAD RIVER FLOODING ACROSS THE ENTIRE
REGION."

Here's Eric the Red on the soppy forecast. He says the storm's progress will be blocked by the same North Atlantic blocking high that helped bring us so much snow in February. This time it's rain. Lots of it:

"Tuesday looks good. Wednesday ... eh. Maybe a little light rain as a warm front tries to lift north through the region. Thursday, I'm hoping we sneak in some decent hours during the afternoon before the leading edge of rain spirals at us from the west, which models have happening in the late afternoon or evening.

"Friday ... Saturday ... and Sunday: Doh, Doh and Doh. Storm stalls over the region, maintaining periods of rain. Some models have 2 to 4 inches of rain for that three-day stretch. Maybe more? Geeesh."

(SUN PHOTO: Frank Roylance/Last snow in my front yard melted Sunday)  

Posted by Frank Roylance at 10:32 AM | Permalink | Comments (1)
Categories: Forecasts
        

Okay, so we don't want to think about snow anymore this season. But just to tie a ribbon on the season ...

James E. Lee, meteorologist-in-charge out at the National Weather Service forecast office in Sterling, Va., says both big storms that struck the region in February will go down in the weather history books, at least preliminarily, as blizzards.

The weather service announced soon after the Feb. 5-6 storm that blizzard conditions were recorded at BWI-Marshall Airport from approximately midnight on Feb. 6 until 5 a.m., with winds gusting to 37 mph and visibilities reduced to one-eighth of a mile in heavy snow.

Blizzard conditions occur when falling or blowing snow reduce visibilities below a quarter mile for three hours - not necessarily consecutive hours.

Today, Lee confirmed that blizzard conditions were also reported at BWI-Marshall during the Feb. 10-11 storm, at 10 a.m., 2, 3, 4 and 6 p.m.

We already know this was the snowiest winter, the snowiest February and [February was] the snowiest month on record for Baltimore. Here are a few other winter weather trivia from this meteorological winter just ended, just published in the NWS Monthly Climate Report for BWI-Marshall in February:

1. Baltimore recorded two separate, two-day, double-digit snowfalls in the same month (Feb. 5-6 and Feb. 9-10) for the first time since record-keeping for snow totals began in the 1880s.

2. The two big February storms dropped a combined 44.5 inches of snow at BWI in just six days. It was the most snow ever to fall for any 7-day period on record for Baltimore. The previous record weekly snowfall was 32.6 inches, in Jan. 6-12, 1996.

3. The daily 7 a.m. "climatological snow depth" - the snow measured on the ground at BWI - on Feb. 11 was 34 inches, setting a new record. The old snow-depth record was 30 inches, recorded on Jan. 18, 1957. 

4. The average snow depth for Baltimore in February was 11 inches, the highest average monthly snow depth ever recorded for the city. The previous record was 7 inches, in January 1996.

5. There was at least an inch of snow on the ground at BWI on 22 dates in February. That's the third-highest number of February days with an inch of snow or more on the ground for Baltimore. The highest number is 27 days in 1934, followed by 25 days in 1905.

6. The maximum daily temperature at BWI failed to reach 50 degrees for the entire month. That's the first time that's happened in any month since January 1977, and only the 10th time on record. Even so, February 2010 ranked as only the 22nd coldest February on record here. 

(SUN PHOTOS: TOP: Karl Merton Ferron/BOTTOM: Kenneth K. Lam)

Posted by Frank Roylance at 5:02 PM | Permalink | Comments (2)
Categories: By the numbers
        

The National Weather Service has hoisted a string of sun and moon icons across the five-day forecast today. It's a reminder that there is plenty to see up there if we would just lift our eyes above the grimy snow piles and glaring street lights.

The weather forecast looks pretty good, right through the middle of next week. Sterling is looking for sunny days in the 50s by this weekend, and partly cloudy to mostly clear nights.

It's an opportunity to get reacquainted with the night sky after a month of cold and snow and ice.

On the way home the other night I noticed that Venus has returned to the evening sky. It's still very low in the west, setting about an hour after the sun. And it's not yet as brilliant as it will be by the end of March, when it will set more than an hour and a half after sunset.

But it's been quite a while since we've had Venus (left, in ultraviolet) as our evening star, and it will be a welcome sight for commuters and evening dog-walkers. Late in March we'll get a chance to see Mercury rise out of the sun's glare and get pretty close to Venus prior to a nice conjunction in early April.

Mars (right) is fading this month, but it remains a prominent presence high in the eastern sky each evening. Look for it just below the twin stars of Gemini - Castor and Pollux. It is noticeably redder than the bright stars of the winter constellations, and hard to miss.

And in case you missed Thursday's night's flyover by the International Space Station, the ISS will make a very similar pass on Saturday evening. Thursday's appearance was notable for the station's ability to gleam right through the scattered thin clouds that spread over much of the Baltimore area.

Look for the ISS again Saturday evening as it rises above the southwest horizon at 6:08 p.m. This pass will be nearly as bright as Thursday's, but probably with fewer clouds. The station will climb  even higher - to within 3 degrees of the zenith at 6:11 p.m. From there it will slide off toward the northeast, disappearing from view at 6:14 p.m.

Saturn, too, is visible in the evening sky this weekend as it nears opposition on the 22nd. Look for it low in the east southeast later in the evening, say, 10 p.m. It has a steady light and a slightly yellowish tint compared with the stars.  

Clear skies!    

Posted by Frank Roylance at 12:02 PM | Permalink | Comments (0)
Categories: Sky Watching
        

Space Cadets! If skies stay clear enough, we'll have a fine opportunity this (Thursday) evening to watch the International Space Station fly almost directly over Baltimore.

The ISS will be cruising up the East Coast around dinner time. We'll catch our first glimpse as it passes 220 miles over Georgia, and we'll be able to watch it until it disappears in the Earth's shadow off the coast of Maine.

Look for a bright, star-like object rising above the southwest horizon at 6:53 p.m. If it has multiple lights, colored or blinking lights, it's an aircraft. Keep looking.

The ISS will climb toward the zenith, passing above the bright winter constellation Orion at about 6:56 p.m. From there, the station will fly above the twin stars of Gemini and - just below Gemini in the eastern sky, reddish Mars - before vanishing in the northeast at about 6:58 p.m.

As always, take the kids outside with you. They're great at spotting this thing. And then come back here and leave a report to share the experience.

Got the stargazing bug? Head out to the Community College of Baltimore County, this Friday evening for a Star Party being thrown by the school's Astronomy Dept. Here are the details:

"Star Party, from 7 to 9 p.m. at the Observatory at CCBC, 7200 Sollers Point Road. If conditions appear cloudy, rainy or snowy, please check for cancellations by calling 410 282-3092 approximately 45 minutes before the scheduled start time.

"Visit the CCBC Web site for additional information about star parties, or call 443 840-4216." The star parties are free.

Posted by Frank Roylance at 12:52 PM | Permalink | Comments (4)
Categories: Sky Watching
        

All that wishing and hoping last month has finally gotten some traction. The National Weather Service is serving up almost a full week of fine late-winter (or early spring) weather for Central Maryland as stormy weather moves farther out to sea, and high pressure builds in from the northwest.

After the snowiest February on record, and one of the coldest in the last 40 years, we're looking at six straight days of sunshine ahead, with daytime highs in the 40s today and tomorrow, snapping to 50 degrees or more through the weekend and well into next week. The average high for this time of year in Baltimore is 50 degrees. Overnight lows will rise above freezing by next week.

It's going to feel positively spring-like, except for the huge piles of snow and ice that persist on parking lots, along roadsides and in shaded spots all across the region.

We still have a small pile on our front yard, and a big one in the rear, where we threw the snow we shoveled off the WeatherDeck, and where sunshine doesn't penetrate until afternoon.

Kinda makes you wonder whether any of the heaps will survive until April 1. If you'd like to register a candidate snow pile, keep an eye on it this month, and report back to the WeatherBlog when it vanishes, feel free to send me a note.

Please include your name and email address, and the precise location of the heap. A picture would be fine, too. That's the Loveton Business Park in Sparks at right, sent to me by L.J. Kirk.

Let's see if we can identify the last remnant of February's storms (in the city and five surrounding counties) when it finally trickles off into history.

No prizes. Just glory for the last pile standing.

(AP PHOTO/Rob Carr at BWI-Marshall)

Posted by Frank Roylance at 10:44 AM | Permalink | Comments (3)
Categories: Forecasts
        

The big low-pressure system riding up the east Coast today is driving northeast winds onto the mid-Atlantic beaches this Wednesday morning. The National Weather Service has posted Coastal Flood Advisories for the Maryland shore:

"AT OCEAN CITY INLET...HIGH TIDE ON WEDNESDAY WILL OCCUR AT 917 AM
EST. THE WATER LEVEL REFERENCED TO MEAN LOWER LOW WATER IS
EXPECTED TO RISE TO NEAR 5.0 FEET. MINOR FLOODING AT OCEAN CITY
INLET BEGINS AT 4.0 FEET MLLW."

For a look at the surf, check out the Kite Loft web cam in Ocean City. Looks like those folks have installed a higher definition camera. First time I've seen it, but it's a much better picture than I've noticed before. Or maybe it's my imagination.

Here's a look at the surf in Rehoboth, Del. I didn't realize they were rebuilding the boardwalk out there. Is that repair work for damage earlier this winter, or routine replacement? Anybody know?

Posted by Frank Roylance at 9:54 AM | Permalink | Comments (3)
Categories: Cool pictures
        

The photo is more than seven years old, but still ... A snapshot of Baltimore under a new blanket of fresh snow, shot from the International Space Station as it flew 220 miles above the city? That's a cool picture in my book, even if it was shot in December 2002. Enjoy.

Posted by Frank Roylance at 5:49 PM | Permalink | Comments (1)
Categories: Cool pictures
        

Although light snow has already been reported in the northern Baltimore suburbs this afternoon, Central Maryland should be spared a difficult time with the approaching storm.

The National Weather Service is predicting less than an inch of new snow at BWI tonight, after a period of rain this evening and a mixture of rain and snow between 10 p.m. and 1 a.m.

Most of the snow from this system will be to our south this time, as the AccuWeather.com snow map (left) shows.

Snow showers are likely after daybreak, changing to rain and snow showers later in the morning. The airport could see another half-inch of snow from that, if the forecast holds up. The mixed showers could continue into the evening as the storm departs and draws cold air in behind it.

The cold and wintry precipitation comes to us courtesy of a low forming off the Carolina coast, and a weaker system moving this way from the Ohio Valley. Late forecast model runs suggest the two storms will phase, or merge their energies a bit more than expected. That could mean the coastal storm will track nearer the beaches, bringing higher winds and heavier precip to Southern Maryland and the Eastern Shore on Wednesday.

Forecasters out at Sterling are having a hard time predicting BWI-Marshall snowfall accumulations for this one. The problem is the usual - timing, storm track and temperatures. "Light snowfall up to one inch seems possible," they say in their afternoon discussion. "But evening shift will need to monitor expected precipitation totals and temperatures in event that headlines become necessary."

One thing they do seem sure of - Garrett County will get more snow.

Wednesday night and Thursday will be windy as the storm departs to the northeast and high pressure builds from the west, forecasters say. That will eventually mean more sunshine and daytime highs stretching into the mid-50s by this weekend into early next week. It will be the first extended period of above-average temperatures since the end of January.

Student forecasters at FootsForecast.org are predicting 1 to 3 inches from DC to south central Pennsylvania. But nudging the storm track to the west a bit, they say, "will greatly enhance snow totals."  

Eric the Red, a professional meteorologist from Baltimore, sounds a little nervous about twitches in the radar and model runs. He's holding his breath, but issued this prediction anyway:

"1 to 3 inches of wet snow north and west of town (I think the 3 might be pushing it, but what's 3 when you've had 30?), with rain possibly mixing with or changing to wet snow elsewhere with little accumulation ... maybe an inch. Weds: Periods of light rain and snow, with no additional accumulation."

I may have a new forecaster to add to the mix here. More on that if we wake up Wednesday to 3 to 6 inches of surprise snow.

Next, forecasters will be watching the snowpack in the western counties for signs of a rapid meltdown and flooding.

Posted by Frank Roylance at 4:05 PM | Permalink | Comments (1)
Categories: Forecasts
        

Water in a hydrological monitoring well in Christiansburg, Va. briefly dropped almost 2 feet in response to the Mag. 8.8 earthquake in Chile on Feb. 27.

The Christiansburg site is well-known to hydrologists for its sensitivity to the seismic waves that travel around the globe after major quakes. It had a similar response to the earthquake in Haiti on Jan. 12 and to others as far away as the South Pacific and the Indian Ocean.

Here's the tracing from the Chilean quake. The regular sine-wave variations are due to the effect of lunar tides on the Earth's crust:

Posted by Frank Roylance at 2:28 PM | Permalink | Comments (1)
Categories: Cool pictures
        

The National Weather Service's Sterling, Va. forecast office has disowned the list of Top 20 Snowstorms for Baltimore that was posted on its Web site for many years. In the wake of the Feb. 5-6 storm, concerns were raised about the scientific legitimacy of the criteria long used for inclusion on the list.

Jim Lee, meteorologist-in-charge at Sterling, told me that one of the problems is that the list does not discriminate among 1-day, 2-day and 3-day storms, not to mention those that seemed to rage on even longer. The No. 1 ranked snowstorm, before the list disappeared from the Sterling site, dropped snow on Baltimore over four days, from Feb. 15 to Feb. 18, 2003.

But Lee told me a few weeks back that, meteorologically speaking, no snowfall that lasts four days can be considered the consequence of a single storm. And in truth, that 2003 event really was a combination of at least two storms, with some time during those four days when no snow was falling. (The Baltimore Top 20 snowstorm list includes two others, in 1899 and 1892, that stretched over four days.)

So, because climatologists only accept data on 1-, 2- or 3-day storms, the Sterling office will be reassessing its Top 20 list. What we'll probably get will be several lists, broken down by the length of the storm, and ignoring the snow that fell on the fourth day of three former Top-20 storms.

The Sterling office will also be reassessing storms that may have been measured at BWI-Marshall with hourly measurements - in accordance with FAA standards - rather than with the six-hour measurements required by NOAA for climatological purposes. That could reduce official storm totals for BWI going back as far as 1998, when the FAA took over the job of measuring snowfall at the airport from the weather service. There are six Top 20 storms since 1998 at BWI that could be affected.

I'm not sure how all this will come out in the wash. It seems likely that, if the FAA's contractors really have used hourly measurements since 1998, that all our snowstorms since then will get smaller. When the problem was discovered last month, Lee rejected the 28.8-inch total the FAA contractor reported for the Feb. 5-6 storm based on its hourly measurements. He replaced it with the more conservative 24.8-inch measurement the contractor reported as the storm's "snow depth" - the total measured when the snow stopped falling (and after the snow's weight had compacted it). 

On the former issue - revisiting the entire storm record at BWI and Washington and ranking snowfalls in separate categories according to the number of days the snow fell - I suppose they have to abide by the rules set by climatologists.

But, on the latter, it seems to me that those of us who are not climatologists experience snowstorms as discreet events based on how much we have to shovel once the flakes stop falling. I would argue that the February 2003 "storm" - while it may have been two storms - felt like one really long siege to those of us left to dig out from 28 inches of snow.

So, in the interests of continuity ... or nostalgia, or something less than scientific ... here is the old NWS Top 20 Snowstorms list for Baltimore, using the old (now officially discredited) criteria, and updated to include the three big storms from December 2009 and February 2010. Clip and save. You may never see it again after the NWS issues its revised lists.

Some observations: February, while it is not the snowiest month on average at BWI, has seen nine of these Top 20 storms, as many as January and March combined. December has seen just two. But what's most astonishing to me, personally, is that, while the record goes back to the 1880s, my family and I have witnessed 10 of these 20 storms since we moved to Baltimore only 30 years ago. How about you? There should be only three or four that no one living today can recall.

1. Feb. 15-18, 2003:  28.2 inches

2. Jan. 27-29, 1922:  26.5 inches

3. Feb. 5-6, 2010:  24.8 inches*

4. Feb. 11, 1983:  22.8 inches

5. Jan. 7-8, 1996:  22.5 inches

6. Mar. 29-30, 1942:  22.0 inches

7. Feb. 11-14, 1899:  21.4 inches

8. Dec. 18-19, 2009:  21.1 inches

9. Feb. 18-19, 1979:  20.0 inches

10. Feb. 9-10, 2010:  19.5 inches

11. Mar. 15-18, 1892:  16.0 inches

12. Feb. 15, 1958:  15.5 inches

13. Jan. 25, 2000:  14.9 inches

14. Dec. 11-12, 1960:  14.1 inches

15. Feb. 11-12, 2006:  13.1 inches

16. Mar. 5-7, 1962:  13.0 inches

17: Jan. 22, 1987:  12.3 inches

18. Jan. 30-31, 1966:  12.1 inches

19. Feb. 16-18, 1900:  12.0 inches

20. Mar. 13-14, 1993:  11.9 inches  

* Snow depth measurement. The "true" depth, had it been measured every 6 hours, likely would have been more.

(TOP: AP Photo/Rob Carr; BOTTOM: Sun Photo/Gene Sweeney, Jr.)

Posted by Frank Roylance at 10:29 AM | Permalink | Comments (8)
Categories: By the numbers