Archive for April, 2011

Another tornado confirmed…MD/VA total up to 11
April 29, 2011

With the finding of tornado damage near Reston in Fairfax County, VA, the Baltimore/Washington Forecast Office of The National Weather Service has updated the number of confirmed tornadoes that touched down in Maryland and Virginia last Wednesday and Thursday, April 27th and 28th…the total now stands at 11.  Their complete report can be found here:  Confirmed Tornadoes.  Most of the tornadoes were on the weaker end of the Enhance Fujita Scale with maximum winds of 65-110 mph.  The strongest tornado was an EF-2 storm with winds near 130 mph and tracked for over 33 miles through western Virginia from near Fulks Run in Rockingham County to St. Luke in Shenandoah County.  So far the team of National Weather Service meteorologists has confirmed four tornadoes touched down in Maryland; one near Andrew’s AFB, one near Breton Bay in St. Mary’s County, one in Westminster, and one just east of Hampstead on Mt. Carmel Road in northwestern Baltimore County.

Nationwide the tornado investigations continue as well, with the second EF-5 tornado of the historic outbreak confirmed in Mississippi.  For reports on the two confirmed EF-5 tornadoes click here:

Hackleburg, Alabama EF-5 Tornado

Smithville, Mississippi EF-5 Tornado

Tom Tasselmyer

April 28, 2002: F4 Tornado Hits La Plata
April 28, 2011

NASA satellite image of La Plata tornado track April 28, 2002

As the recent round of severe weather will verify, Spring is the season for violent thunderstorms and tornadoes in the eastern two thirds of the United States.  And, nine years ago one of those devastating Spring tornadoes ripped through La Plata, MD in Charles County.  It was only the third known F4 tornado to touch down in Maryland (Frostburg on June 2, 1998 and another in La Plata on November 9, 1926), and it had winds estimated up to 260 mph.  The thunderstorm that produced the tornado developed far to the west, in the mountains of West Virginia, then raced east at speeds of nearly 60 mph across northern Virginia toward southen Maryland.  Along with the deadly tornado, the thunderstorm produced hail 4.5″ in diameter.  The tornado did further damage in Calvert County then crossed the bay and headed for Dorchester County on the eastern shore.

Tom Tasselmyer

Happy Easter
April 24, 2011

With the exception of a few predawn sprinkles and showers, Easter Sunday morning turned out quite nice with sunshine and mild temperatures.

The mid morning NASA satellite image shows the nearly cloud free conditions over the Chesapeake Bay region. The cloudiness to the northwest of the Bay is associated with a frontal boundary that will likely affect the area later Sunday.

The National Weather Service map above shows the frontal boundary position Sunday morning. The Map below shows the forecast map for later Sunday.

Waves of energy moving along the front could very well stir up some thunderstorm activity later in the day Sunday.

The National Weather Service Storm Prediction Center has identified the area along and ahead of the front as having a slight risk for severe weather. This includes northern Maryland.

The Precipitation Accumulation forecast map indicates that the heaviest rains will stretch from the Ozark Mountains into the lower Ohio River Valley. The Chesapeake Bay area could receive around .25 inches of rain in any storm activity that may develop.

Check in later on wbaltv.com for updates and join me tonight at 6:00pm and 11:00pm for the forecast for the week ahead.

John Collins

Tornado Confirmed
April 18, 2011

Mother nature went on a rampage across the central and eastern U.S. Thursday, Friday and Saturday. When the complex storm system arrived in the Mid Atlantic region on Saturday it produced a day of rain and numerous severe thunderstorms. One of those storms generated a tornado in Carroll County. The confirmation message is below.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
806 PM EDT SUN APR 17 2011

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0756 PM     TORNADO          1 SW DEEP RUN           39.68N  77.00W
04/16/2011                   CARROLL            MD   NWS EMPLOYEE

            TORNADO CONFIRMED EF-0. MAX WINDS 80 MPH. MAX WIDTH 200
            YARDS. PATH LENGTH 2 MILES. NUMEROUS TREES UPROOTED AND
            SNAPPED. ONE TREE INTO HOUSE. TWO BARNS PARTIALLY
            UNROOFED.

The following is a listing of rainfall reports around the area.

PUBLIC INFORMATION STATEMENT
SPOTTER REPORTS
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
506 PM EDT SUN APR 17 2011

THE FOLLOWING ARE UNOFFICIAL OBSERVATIONS TAKEN DURING THE PAST
25 HOURS FOR THE STORM THAT HAS BEEN AFFECTING OUR REGION.
APPRECIATION IS EXTENDED TO HIGHWAY DEPARTMENTS...COOPERATIVE
OBSERVERS...SKYWARN SPOTTERS AND MEDIA FOR THESE REPORTS.  THIS
SUMMARY IS ALSO AVAILABLE ON OUR HOME PAGE AT WEATHER.GOV/BALTIMORE

********************STORM TOTAL RAINFALL********************

LOCATION          STORM TOTAL     TIME/DATE   COMMENTS
                     RAINFALL           OF
                     /INCHES/   MEASUREMENT

MARYLAND

...BALTIMORE COUNTY...
   1 SW PERRY HALL       1.00   555 PM  4/16  TRAINED SPOTTER

...HOWARD COUNTY...
   2 WSW ELKRIDGE        1.25   512 PM  4/16  TRAINED SPOTTER

**********************24 HOUR RAINFALL**********************

LOCATION              24 HOUR     TIME/DATE   COMMENTS
                     RAINFALL           OF
                     /INCHES/   MEASUREMENT

MARYLAND

...ALLEGANY COUNTY...
   1 SSE CRESAPTOWN-BEL  1.25   700 AM  4/17  COCORAHS

...ANNE ARUNDEL COUNTY...
   1 SE DEALE 0.9 SE     1.48   700 AM  4/17  COCORAHS
   2 W SEVERN 2.0 W      1.32   700 AM  4/17  COCORAHS
   1 NNW PAROLE          1.25  1000 AM  4/17  TRAINED SPOTTER
   1 SE PASADENA 0.7 SE  1.10   700 AM  4/17  COCORAHS
   2 NNE CROFTON 1.5 NN  0.96   700 AM  4/17  COCORAHS
   1 WSW ODENTON 0.8 WS  0.96   700 AM  4/17  COCORAHS
   3 SSW SOUTH GATE 3.0  0.94   800 AM  4/17  COCORAHS
   3 ESE PASADENA 2.6 E  0.72   800 AM  4/17  COCORAHS

...BALTIMORE COUNTY...
   1 SW JACKSONVILLE 1.  1.79   800 AM  4/17  COCORAHS
   4 N COCKEYSVILLE 3.7  1.74   900 AM  4/17  COCORAHS
   3 WNW BALDWIN 2.7 WN  1.64   800 AM  4/17  COCORAHS
   1 SW LONG GREEN 0.6   1.57   700 AM  4/17  COCORAHS
   1 SW TOWSON 0.8 SW    1.42   830 AM  4/17  COCORAHS
   1 E KINGSVILLE 1.2 E  1.38   700 AM  4/17  COCORAHS
   1 SE GWYNN OAK 1.2 S  1.23   700 AM  4/17  COCORAHS
   NE REISTERSTOWN 0.4   1.20   700 AM  4/17  COCORAHS
   2 WNW CATONSVILLE 1.  1.09   700 AM  4/17  COCORAHS
   2 ESE WHITE MARSH 2.  1.00   600 AM  4/17  COCORAHS
   1 ENE CATONSVILLE 0.  0.97   800 AM  4/17  COCORAHS
   1 NNE ROSEDALE        0.95   800 AM  4/17  TRAINED SPOTTER

...CALVERT COUNTY...
   1 W PRINCE FREDERICK  1.48   700 AM  4/17  COCORAHS
   2 SW CHESAPEAKE BEAC  1.36   700 AM  4/17  COCORAHS
   6 E MARLTON 6.0 E     1.06   700 AM  4/17  COCORAHS

...CARROLL COUNTY...
   4 NE TANEYTOWN 3.7 N  1.77   700 AM  4/17  COCORAHS
   3 NE TANEYTOWN 3.2 N  1.68   700 AM  4/17  COCORAHS
   SE MOUNT AIRY 0.2 SE  1.65   700 AM  4/17  COCORAHS
   2 SE ELDERSBURG 2.0   1.62   730 AM  4/17  COCORAHS
   1 W WESTMINSTER 1.0   1.32   600 AM  4/17  COCORAHS

...CHARLES COUNTY...
   2 E WALDORF 2.2 E     1.12   700 AM  4/17  COCORAHS
   3 WNW LA PLATA 2.6 W  1.04   332 AM  4/17  COCORAHS
   4 SSE WALDORF 3.6 SS  1.00   500 AM  4/17  COCORAHS
   1 SW BRYANS ROAD 1.0  0.70   700 AM  4/17  COCORAHS

...FREDERICK COUNTY...
   1 SSE THURMONT 0.8 S  4.08   700 AM  4/17  COCORAHS
   2 ESE MIDDLETOWN 1.8  1.85   700 AM  4/17  COCORAHS
   3 NW FREDERICK 3.1 N  1.83   700 AM  4/17  COCORAHS
   5 WSW NEW MARKET 4.8  1.30   700 AM  4/17  COCORAHS
   4 SSW FREDERICK 3.5   1.09   600 AM  4/17  COCORAHS

...HARFORD COUNTY...
   SE WHITEFORD 0.3 SE   1.91   800 AM  4/17  COCORAHS
   4 WNW HAVRE DE GRACE  1.71   700 AM  4/17  COCORAHS
   3 WNW FALLSTON 2.6 W  1.65   700 AM  4/17  COCORAHS
   3 NNE KINGSVILLE 2.5  1.54   700 AM  4/17  COCORAHS
   2 W BEL AIR 1.7 W     1.32   700 AM  4/17  COCORAHS

...HOWARD COUNTY...
   3 NW COLUMBIA 2.6 NW  1.43   730 AM  4/17  COCORAHS
   3 SE SYKESVILLE 2.6   1.43   700 AM  4/17  COCORAHS
   2 SSE SYKESVILLE 1.7  1.40   700 AM  4/17  COCORAHS
   2 W COLUMBIA 1.7 W    1.39   700 AM  4/17  COCORAHS
   1 WSW ELLICOTT CITY   1.38   815 AM  4/17  COCORAHS
   2 N COLUMBIA 2.3 N    1.31   700 AM  4/17  COCORAHS
   1 SE MARRIOTTSVILLE   1.30   800 AM  4/17  COCORAHS
   2 WNW ELLICOTT CITY   1.26   700 AM  4/17  COCORAHS
   2 SE WOODBINE 1.6 SE  1.26   700 AM  4/17  COCORAHS
   2 N ELLICOTT CITY 1.  1.18   700 AM  4/17  COCORAHS
   2 W ELKRIDGE 1.8 W    0.90   700 AM  4/17  COCORAHS

...MONTGOMERY COUNTY...
   1 NNW POTOMAC 0.9 NN  1.60   700 AM  4/17  COCORAHS
   2 W ROCKVILLE 1.8 W   1.45   700 AM  4/17  COCORAHS
   5 NNE GERMANTOWN 4.6  1.36   700 AM  4/17  COCORAHS
   1 ESE NORBECK 1.1 ES  1.25   700 AM  4/17  COCORAHS
   2 W COLESVILLE 1.7 W  1.19   700 AM  4/17  COCORAHS
   2 NNE WHEATON-GLENMO  1.17   700 AM  4/17  COCORAHS
   1 ESE ROSSMOOR 1.3 E  1.10   700 AM  4/17  COCORAHS
   1 SE OLNEY 0.6 SE     1.04   700 AM  4/17  COCORAHS
   2 NW WHITE OAK 1.7 N  1.02   700 AM  4/17  COCORAHS
   1 N WHITE OAK 1.2 N   0.99   700 AM  4/17  COCORAHS
   1 NNW TAKOMA PARK 0.  0.87   700 AM  4/17  COCORAHS

...PRINCE GEORGES COUNTY...
   1 E BOWIE 0.5 E       1.07   700 AM  4/17  COCORAHS
   7 ESE BRANDYWINE 6.7  1.02   700 AM  4/17  COCORAHS
   ESE CAMP SPRINGS 0.1  0.87   800 AM  4/17  COCORAHS
   2 SE FOREST HEIGHTS   0.86   700 AM  4/17  COCORAHS
   2 SE SUITLAND 2.1 SE  0.86   800 AM  4/17  COCORAHS
   1 W OXON HILL 1.1 W   0.85   700 AM  4/17  COCORAHS
   2 S LAUREL 2.0 S      0.83   800 AM  4/17  COCORAHS
   2 NNW CAMP SPRINGS 1  0.82   700 AM  4/17  COCORAHS

...ST. MARYS COUNTY...
   2 W CALIFORNIA        1.30   700 AM  4/17  TRAINED SPOTTER
   4 ENE CHARLOTTE HALL  1.22   700 AM  4/17  COCORAHS
   4 E HOLLYWOOD 3.5 E   1.16   700 AM  4/17  COCORAHS
   SW PARK HALL 0.2 SW   1.02   700 AM  4/17  COCORAHS
   SSE TALL TIMBERS 0.3  0.89   800 AM  4/17  COCORAHS
   1 NE LEONARDTOWN 0.6  0.86   600 AM  4/17  COCORAHS
   1 NNW COLTONS POINT   0.85   700 AM  4/17  COCORAHS

...WASHINGTON COUNTY...
   3 NNE SMITHSBURG 3.1  2.66   700 AM  4/17  COCORAHS
   2 ESE WILLIAMSPORT 2  2.31   700 AM  4/17  COCORAHS

PUBLIC INFORMATION STATEMENT
SPOTTER REPORTS
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
236 PM EDT SUN APR 17 2011

THE FOLLOWING ARE UNOFFICIAL OBSERVATIONS TAKEN DURING THE PAST 25 HOURS
FOR THE STORM THAT HAS BEEN AFFECTING OUR REGION.  APPRECIATION IS EXTENDED
TO HIGHWAY DEPARTMENTS...COOPERATIVE OBSERVERS...SKYWARN SPOTTERS
AND MEDIA FOR THESE REPORTS.  THIS SUMMARY IS ALSO AVAILABLE ON OUR
HOME PAGE AT WEATHER.GOV/PHI
********************STORM TOTAL RAINFALL********************

LOCATION          STORM TOTAL     TIME/DATE   COMMENTS
                     RAINFALL           OF
                     /INCHES/   MEASUREMENT

DELAWARE

...KENT COUNTY...
   DOVER AFB             1.31   800 AM  4/17

...NEW CASTLE COUNTY...
   WILMINGTON AIRPORT    1.95   800 AM  4/17
   BLACKBIRD             1.77   900 AM  4/17
   LONGWOOD              1.76   900 AM  4/17
   NEWARK                1.60   700 AM  4/17

...SUSSEX COUNTY...
   REDDEN                1.33   900 AM  4/17
   PRIMEHOOK BEACH       1.31   900 AM  4/17
   GEORGETOWN AIRPORT    0.95   800 AM  4/17
   BETHANY BEACH         0.47   900 AM  4/17
   MILLSBORO             0.46   900 AM  4/17

MARYLAND

...CECIL COUNTY...
   CONOWINGO             2.10   900 AM  4/17
   FAIR HILL             1.50   900 AM  4/17

The following maps outline the severe weather reports for the three day period. Take note of the red dots on the maps. These indicate the location of reported tornadoes. There were 248 reports of tornadoes over the three day period. Many were multiple reports for a single tornado and a final tally of the actual number of  tornadoes should be forthcoming.

John Collins

Wet & Stormy Saturday
April 16, 2011

I very large spring storm system is marching across the eastern U.S. Saturday.

Late Saturday Morning GOES Image Courtesy: NASA

For the past several days this system has been producing heavy rains and severe storms across the nation’s mid section.

The biggest impact on the Mid Atlantic Region Saturday will be heavy rainfall.

The graphic above shows one computer model’s estimated rainfall totals through Sunday morning. The map is a little hard to read without close examination. It targets the heaviest rains from the Baltimore area westward. 2-3 inches of rain is possible with a few areas receiving as much as 4 inches. A Flash Flood Watch is in effect for areas west of the Bay. A Coastal Flood Watch & Advisory are in effect west of the Bay as well due to the combination of high tides and strong winds.

Severe storms are also possible with this weather system.

The Baltimore area is at the northern edge of an area that is at risk for severe thunderstorms Saturday and Saturday night. Damaging winds and lightning are the primary threat but this system has had a history of producing tornadoes and that would not be out of the question. It appears that the highest tornado risk would be south of Baltimore where temperatures will be warmer.

Keep up to date on wbaltv.com and check in with Lowell Melser on WBAL TV-11 this afternoon and this evening for the latest on the storm’s progress.

John Collins

Severe Weather Threat Marching East
April 15, 2011

Severe Weather Reports as of 6pm Friday (click to enlarge)

Severe Weather Outlook Saturday (click to enlarge)

The Severe Storms Prediction Center has indicated parts of the mid Atlantic may be in for severe thunderstorms on Saturday.  The same storm system that has produced more than 50 reports of tornadoes from the mid Mississippi valley south toward the gulf coast, is marching east.  Rain is likely around here Saturday and severe thunderstorms are possible, especially south of Baltimore.  Stay close to a weather forecast and get Insta-Weather updates on WBAL-TV  and wbaltv.com throughout the day Saturday as the storm moves through Maryland.  Much better weather should return for the 2nd half of the weekend.

Tom Tasselmyer

Ozone Hole
April 5, 2011

It has been recently reported that an ozone hole has developed over the arctic region (North Pole). The news release and pictures below are courtesy of NASA.

John Collins

Recent observations from satellites and ground stations suggest that atmospheric ozone levels for March in the Arctic were approaching the lowest levels in the modern instrumental era. What those readings mean for the remainder of the year is unclear. But what they mean for the long-term is that the recovery from human-induced ozone depletion is an uneven climb.

These maps of ozone concentrations over the Arctic come from the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite. The left image shows March 19, 2010, and the right shows the same date in 2011. March 2010 had relatively high ozone, while March 2011 has low levels. The large animation file (linked below the images) shows the dynamics of the ozone layer from January 1 to March 23 in both years.

In mid-March, scientists from Germany’s Alfred Wegener Institute announced that Arctic ozone levels had been cut in half in the waning weeks of winter, according to a network of 30 ozone sounding stations spread around the region. Data from OMI (shown above) also confirmed a depletion. OMI is a spectrometer that measures the amount of sunlight scattered by Earth’s atmosphere and surface, allowing scientists to assess how much ozone is present at various altitudes, particularly the stratosphere.

Ozone is destroyed when chlorine- or bromine-based compounds—especially chlorofluorocarbons (CFCs) —break into their free atoms and combine with the oxygen. That process is amplified when the stratosphere is especially cold, which it has been in recent weeks.

“This depletion is not necessarily a big surprise,” said Paul Newman, an atmospheric scientist and ozone expert at NASA’s Goddard Space Flight Center. “The ozone layer remains vulnerable to large depletions because total stratospheric chlorine levels are still high, in spite of the regulation of ozone-depleting substances by the Montreal Protocol. Chlorine levels are declining slowly because ozone-depleting substances have extremely long lifetimes.”

The concentration of ozone in the Arctic atmosphere varies greatly from year-to-year, and ozone “holes” do not form consistently like they do in Antarctica. “Last winter, we had very high lower stratospheric temperatures and ozone levels were very high; this year is just the opposite,” Newman said. “The real question is: Why is this year so dynamically quiet and cold in the stratosphere? That’s a big question with no good answer.”

Scientists will be watching in coming months for possible increases in the intensity of ultraviolet radiation (UV) in the Arctic and mid-latitudes, since ozone is Earth’s natural sunscreen. “We need to wait and see if this will actually happen,” Newman said. “It’s something to look at but it is not catastrophic.”

On a global scale, the ozone layer is still on a long-term course for recovery. But for decades to come, there remains a risk of major ozone losses on yearly or regional scales.

NASA image by Rob Simmon, with data courtesy of Ozone Hole Watch. Caption by Mike Carlowicz and Kristyn Ecochard.

Instrument:  Aura – OMI
——————–
The image and text below are courtesy of NOAA. The image depicts ozone concentrations worldwide on Tuesday, April 5, 2011. Note the lower ozone levels over northwest Russia and eastern Scandanavia and the elevated ozone levels over the northeast United States.
John Collins