Archive for March, 2008

Early Spring Extremes
March 30, 2008

March is almost over and the region continues to experience the typical swings in weather conditions that move us from winter to summer.

Today (March 29) is a good example of the extremes that can strike the area this time of year.

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The next several days are expected to be unsettled but nothing like the extremes experienced back in the early 1940s.

John Collins

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Typical Spring…..So Far
March 24, 2008

Spring officially got underway last week and so far the weather has been typical.  In just a few days time afternoon high temperatures have ranged from the upper 40s into the mid 60s and morning lows have ranged from the mid 20s to near 40. Winds have gusted to nearly 50 mph. We have seen both rain showers and snow showers but most of that activity was on the light side.

Speaking of rain and snow, March precipitation is running a little below normal with only 2.97 inches recorded through Sunday, March 23. That is a defecit of .65 inches. So far this year 9.46 inches has been recorded at BWI-Marshall Airport, a deficit of 1.87 inches. There has been no measurable snow this month and that leaves the area 2.3 inches below the 30 year average.

Keep in mind that the area wound up considerably short of precipitation in 2007 and the small defecit this year keeps us behind the eightball in the long term. This is evident if you have driven by any of the area reservoirs. The National Weather Service has come out with its’ “Spring Drought Outlook”. The Baltimore region sits right at the northern tip of the extensive drought area that has plagued the southeastern U.S.

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While we are not experiencing any drought related problems at this time, if rain totals fall too far short of seasonal averages over the next few months, problems could crop up by the end of summer or early fall. As was proven last year, the hurricane season is no guarantee that the remnants of any storms will compensate for a shortage of the usual summertime rainfall. For a look at the complete drought outlook, check out the following web site:

http://www.noaanews.noaa.gov/stories2008/20080320_springoutlook.html

It appears that typically unsettled weather conditions will continue as April approaches. Anything can happen this time of year. For examble, Baltimore’s record snow fell on March 29, 1942 with a total of 22 inches. For at least the next week it appears as though a storm of those proportions is not in the books.

 John Collins

The Inequality of the Equinox
March 20, 2008

Spring is here!  The new season begins Thursday morning at 1:48 a.m. EDT.  This is the Vernal Equinox, the time when the center of the Sun crosses the plane of the Earth’s equator.  Several viewers have written to ask why we don’t have equal amounts of day and night on the equinox.  In fact, sunrise on Thursday morning in Baltimore will occur at 7:09 a.m. and sunset will occur at 7:19 p.m.  The website of the Astronomical Applications Department at the U.S. Naval Observatory is a great source of information for questions about the Sun, the Moon, seasons, time, calendars and other astronomical phenomena.  I have pasted their explanation of this inequality of the equinoxes below.

Tom Tasselmyer

From the U.S. Naval Observatory Astronomical Applications Department:

Day and night are not exactly of equal length at the time of the March and September equinoxes. The dates on which day and night are each 12 hours occur a few days before and after the equinoxes. The specific dates of this occurrence are different for different latitudes. 

On the day of an equinox, the geometric center of the Sun’s disk crosses the equator, and this point is above the horizon for 12 hours everywhere on the Earth. However, the Sun is not simply a geometric point. Sunrise is defined as the instant when the leading edge of the Sun’s disk becomes visible on the horizon, whereas sunset is the instant when the trailing edge of the disk disappears below the horizon. These are the moments of first and last direct sunlight. At these times the center of the disk is below the horizon. Furthermore, atmospheric refraction causes the Sun’s disk to appear higher in the sky than it would if the Earth had no atmosphere. Thus, in the morning the upper edge of the disk is visible for several minutes before the geometric edge of the disk reaches the horizon. Similarly, in the evening the upper edge of the disk disappears several minutes after the geometric disk has passed below the horizon. The times of sunrise and sunset in almanacs are calculated for the normal atmospheric refraction of 34 minutes of arc and a semidiameter of 16 minutes of arc for the disk. Therefore, at the tabulated time the geometric center of the Sun is actually 50 minutes of arc below a regular and unobstructed horizon for an observer on the surface of the Earth in a level region. 

For observers within a couple of degrees of the equator, the period from sunrise to sunset is always several minutes longer than the night. At higher latitudes in the northern hemisphere, the date of equal day and night occurs before the March equinox. Daytime continues to be longer than nighttime until after the September equinox. In the southern hemisphere, the dates of equal day and night occur before the September equinox and after the March equinox.

In the northern hemisphere, at latitude 5 degrees the dates of equal day and night occur about February 25 and October 15; at latitude 40 degrees they occur about March 17 and September 26. On the dates of the equinoxes, the day is about 7 minutes longer than the night at latitudes up to about 25 degrees, increasing to 10 minutes or more at latitude 50 degrees.

Downtown Tornadoes
March 17, 2008

The tornado that hit downtown Atlanta has been the top news story this weekend. The incedent brings to mind the question, “…how often do tornadoes strike the central business districts of large cities?”

Jay Kendrick did a little digging and found that the National Weather Service has compiled a partial list that identifies two dozen such incidents since the late 1800s.

Downtown St. Louis seems to be the most vulnerable with tornadoes recorded in 1871, 1896, 1927 and 1959. The 1896 storm was an F4 on the Fujita scale and resulted in 255 fatalities. The 1959 storm was also an F4 and took 21 lives.

For a look at the complete list check out:

http://www.spc.noaa.gov/faq/tornado/downtown.html

John Collins

Coolest Winter Since 2001
March 17, 2008

The numbers are in and according to scientists at NOAA’s National Climatic Data Center the 2007-2008 winter months of December through February were the coolest across the U.S. and around the world since 2001.

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Across the lower 48 states the average winter temperature was 33.2 degrees farenheit….the 54th coolest since records began in 1895. On the other hand, on a global scale, this past winter was the 16th warmest when land and ocean surface temperatures are factored together.

Precipitation across the United States this winter was above average in most areas.

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You can check out the complete NOAA report by going to: http://www.noaanews.noaa.gov/stories2008/20080313_coolest.html

John Collins

The Superstorm of ’93
March 13, 2008

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This year marks the 15th anniversary of the Superstorm of March 1993. The storm, acting more like a hurricane than a blizzard, tracked north from the Gulf of Mexico and made landfall on the Florida panhandle in the early morning of March 13th with wind gusts of 110mph in Franklin County, FL and 11 confirmed tornado touchdowns. The storm later produced wind gusts to 101 mph on Flat Top Mountain, NC and a gust to 144 mph atop Mt. Washington, NH. Deep snows accompanied the storm from Alabama to Maine with 50″ at Mt. Mitchell, NC, a Maryland state record of 47″ at Grantsville in Garrett County, 44″ at Snowshoe, WV and 43″ at Syracuse, NY. The rapidly intensifying storm dropped barometric pressures to record lows at several stations, including: 28.52″ at BWI, 28.43″ at Philadelphia, PA and 28.28″at White Plains, NY. Cold air following the storm set 145 record lows including: -12 at Burlington, VT, -10 at Mt. LeConte, TN, +2 at Asheville, NC and +2 at Birmingham, AL. Damage from wind, snow, ice and tornadoes totaled $3 billion and 270 people lost their lives in storm related incidents.

Tom Tasselmyer

Clock Is Ticking For Snow Lovers
March 10, 2008

As we head for mid March, turn the clocks forward to daylight savings time again and the sun starts to feel a little warmer, snow lovers like me start getting antsy.  Time is running out for one last blast of winter!  In fact, with the memory of this past weekend’s storm fresh in our minds, it’s tempting to think, like one emailer today named Fergie, that this winter has been very wet.  However, the statistics listed below, for December, January, February and the first 10 days of March show drier than normal conditions.  Snowfall, while just about half of what is normal (8.5″ vs. 16.7″ through March 10th), is not even in the top 10 for least snowy winters in Baltimore.

As for getting a big snow before spring really takes hold….we’ve had big snowstorms up until the end of March and the latest a snowflake has ever been recorded here is May 9, 1923.  So there’s still a chance, fleeting as it may be, for snow lovers to enjoy one more.

Tom Tasselmyer
Dec.-Jan.-Feb.-Mar. precipitation:  10.74″  which is 0.38″ below normal

Baltimore’s 10 Least Snowy Winters
1949-50        0.7″
1972-73        1.2″
2001-2002    2.3″
1997-1998    3.2″
1958-1959    4.0″
1918-1919    4.0″
1991-1992    4.1″
1931-1932    4.2″
1980-1981    4.6″
1889-1890    4.9″

Stormy Saturday
March 9, 2008

The storm system that produced all of the severe storms in the South and heavy snows in the Midwest finally reached the Mid Atlantic region Saturday. Several clusters of severe thunderstorms developed late in the afternoon. Lightening and thunder reports were minimal. The main feature was wind and hail.

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Wind gusts that ranged from 50 to more than 70 mph were reported across the region.  

Reports of damage to trees and power lines were numerous across the area. There were also several reports of buildings being damaged by trees, blowing debris and the wind itself.

Gusty winds will continue overnight. A High Wind Warning is in effect for the northern tier of counties in Maryland with a Wind Advisory in effect elsewhere.

 By the way, don’t forget to set your clocks AHEAD one hour. Sunday is the first day of daylight saving time.

John Collins

Another Winter Storm Forming
March 6, 2008

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Low pressure organizing over Texas this morning is expected to redevelop on the central gulf coast Friday and track north along the eastern slopes of the Appalachian mountains Saturday. If the storm stays on this track it will dump a swath of heavy snow from north Texas to northwest Arkansas through western Kentucky, southern Indiana and into northern Ohio by midday Saturday.  The heavy snow could shift to northern New England on Sunday. Maryland will likely be on the warm side of this storm as it pushes north, with the potential for more heavy rain Friday night and Saturday. As the storm pulls away from the mid Atlantic region, there is a chance for the rain to change to snow showers Saturday night. Gusty winds and cold temperatures will follow the storm on Sunday.

Tom Tasselmyer

Wild Tuesday
March 6, 2008

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The storm that blew through Maryland Tuesday evening produced a typical variety of March weather. From severe thunderstorms and tornadoes to ice and heavy snow, the eastern 1/3rd of the nation endured some wild weather. The map above shows the severe weather reported to the National Weather Service. There were 271 reports of damaging winds from thunderstorms, 11 reports of hail and 2 tornado touchdowns. One tornado hit 4 miles northwest of Samantha, AL in Tuscaloosa County, damaging six homes. Here in the mid Atlantic, a tornado touched down near Big Stone Gap, VA, which is in Wise County in the far southwestern corner of the state. That storm was 300 yards wide, tracked a mile and destroyed six homes, damaged fifteen others and injured two people. Here in the Baltimore/Washington area winds gusted to 74 mph at Reagan-National airport in D.C., 73 mph at White Plains in Charles County, 66 mph at Andrew’s Air Force Base in Prince George’s County and 43 mph at BWI-Marshall airport. Farther north, it was freezing rain, sleet and snow from northern Ohio to upstate New York and into New England. This latest blanket of snow brought the seasonal snow totals to 163″ at Caribou, Maine, the 2nd snowiest season ever recorded in Caribou, and 109.3″ at Burlington, Vermont, making this the 7th snowiest season on record for that city…and March is typically the snowiest month of the year in northern New England!

Tom Tasselmyer