Archive for June, 2013

Lightning Safety Tips
June 26, 2013

June 24-30, 2013 is Lightning Safety Awareness Week. Here are some answers to frequently asked questions about lightning.

What causes lightning and thunder?

Lightning is a bright flash caused by the discharge of electricity during a thunderstorm. It happens when imbalances in positive and negative charges occur between the earth and atmosphere. While it’s not always the case, the air inside a thunderstorm usually carries a negative charge, while the earth carries a positive one. The lightning strike makes a connection between the two, and therefore briefly neutralizes these charges. As the electricity travels through the sky, it heats the air around it to 50,000 degrees, causing the air to explode and expand into a shockwave. Thunder is the sound made by the shockwave. Light travels faster than sound, which is why there is always a delay between lightning and thunder.  The shorter the delay, the closer you are to the thunderstorm, and the greater the danger.

When should you take shelter from a thunderstorm?

To be as safe as possible, you should start moving indoors anytime you see lightning or the skies become threatening. At the very least, you should take shelter as soon as you hear thunder. Once you can hear thunder, the storm is usually 10-15 miles away, which is close enough to be struck by lightning. Once you take shelter, wait 30 minutes after the last clap of thunder until you go back outside, to make sure the storm has completely moved away.

Where is the safest place to be during a thunderstorm?

The safest place during a thunderstorm is inside a sturdy building or house, with running water and electricity, away from any windows or doors. In the event of a direct lightning strike, the plumbing and electrical wires help ground the electrical surge, preventing any of the electricity from reaching the people inside. This is why you should avoid using electrical appliances or running water during a thunderstorm. You may also want to unplug any valuable appliances like your TV and computer to protect them from a power surge.

If the forecast calls for thunderstorms, but I have outdoor plans, what should I do?

On days when the forecast calls for the possibility of thunderstorms, it is best to stay alert while doing outdoor activities. Plan ahead on where you’ll take shelter in the event of thunderstorm. Keep an eye on the sky for lightning or darkening clouds. You can also get weather alerts and watch the radar on your smart phone through the WBAL TV mobile app.

What happens if I’m caught outside during a thunderstorm?

Being outdoors during a thunderstorm puts you in great danger of being struck by lightning. That’s why you should start taking shelter as soon as you see lightning, and especially by the time you hear thunder. Keep in mind, that if you’re out on a lake or in a field, it can take a while to get to a safe place. The safest place to shelter is inside a sturdy building with electricity and plumbing. At a park, the only option may be the bathroom facility. If there isn’t a shelter nearby, you can take shelter in your vehicle. It’s a myth that the rubber tires will help ground your vehicle. It’s actually the metal roof overhead that offers some protection in the event of a lightning strike. While sheltering in your car, avoid leaning on the metal steering wheel or car doors.

What if I’m outside during a thunderstorm and I’m not close to any shelter?

This is a situation you want to prevent getting yourself into in the first place. However, if you find yourself out in the open during a thunderstorm, quickly start making your way to a sturdy shelter. Avoid taking shelter under open porches or pavilions, as they offer no protection from a lightning strike. And never take shelter under a tree. Lightning tends to hit the tallest objects. And when a tree is hit, the energy travels through the truck, and through the ground around it. Also, a lightning strike is so hot it can cause branches to break or cause the entire trunk to explode.

If you’re in route to shelter, and you start to feel the static electricity build up around you and your hair starts to stand on end, you are extremely close to getting struck by lightning. At this point, the safest thing to do is crouch down, grab your knees and balance on the tip of your toes. Essentially, you’re trying to make yourself as small as possible, while trying to touch as little of the ground as possible. This is obviously a last resort option, should avoid ever having to resort to this.

How many people are injured or killed by lightning?

The most recent lightning injury in Maryland occurred on June 13, when a young female was struck by lightning at the Plumpton Park Zoo in Rising Sun. She was reportedly standing near a large tree at the time, and is still recovering from serious injuries. Every year, dozens of people are killed by lightning nationwide, with hundreds more subject to lifelong injuries.

If I see someone get struck by lightning, what should I do?

Call 911 immediately. Most victims can survive lightning strikes if they receive immediate medical attention. In many cases, their heart or breathing may have stopped, in which case, CPR may be needed. Do not hesitate to approach and help the victim; they will no longer be carrying an electrical charge.

If you have any more questions about lightning or weather safety, you can contact the WBAL TV meteorologists at http://www.wbaltv.com/tv/about

By Meteorologist Ava Marie

Another Round Of Storms Thursday
June 13, 2013

The stormy leading edge of a collapsing Mesoscale Convective System (MCS), with origins Wednesday in Iowa and Illinois, moved across the Baltimore area Thursday morning. The heaviest rains along with some hail were north of I-70, Baltimore City and I-95.

The track of this storm complex was similar to last year’s derecho but the system was not nearly as strong so it did not meet derecho criteria.

The area is still under the gun for some heavy weather on Thursday.

7:00 AM Thursday Surface Map / Source: NOAA

7:00 AM Thursday Surface Map / Source: NOAA

Maryland is in the warm, humid airmass. A deep low pressure area will track across Pennsylvania with a cold front trailing to the southwest. This system will likely trigger strong storm activity in the warm, humid, unstable airmass this afternoon.

The morning storms did help to stabilize, to some extent, the airmass in northern Maryland. This has most likely shifted the highest severe weather probabilities a bit to the south of the Baltimore/Washington metro areas but it doesn’t mean the area is completely out of the woods.

The two charts below show CAPE and Lifted Index values as of mid-morning.

CAPE

CAPE  (Source: SPC/NOAA)

Lifted Index

Lifted Index  (Source: SPC/NOAA)

CAPE is, in essence, an expression of energy in the atmosphere for making storms and when values are in the thousands there is a severe potential. As of mid-morning the highest values have been pushed south by the early morning storms.

Lifted Index is an expression of stability/instability in the atmosphere. Negative numbers are unstable indicators. As of mid-morning the higher valued negative numbers are also concentrated to the south of the metro area because of the morning storm activity.

The bottom line, the Baltimore area will likely be on the northern edge of severe storm activity this afternoon and evening. It all depends on how much destabilization can occur before the cold front comes in. Sunbreaks will help but cloud cover will be considerable for the rest of the day.

The National Weather Service has issued a Severe Thunderstorm Watch for the area until 7:00pm.

Thunderstorm Watch area PINK / Flood Watch area GREEN

Thunderstorm Watch area PINK / Flood Watch area GREEN     (Source: NWS/NOAA)

As storm activity develops, the Watch area could be extended to the Eastern Shore counties.

The latest updates are available anytime on the web at wbaltv.com/weather. Join Tom Tasselmyer for the latest at 5-6 & 11pm on WBAL-TV 11 and at 10 pm on WBAL+.

John Collins

Bumpy Weather Ahead
June 12, 2013

The atmosphere around the Mid Atlantic is becoming primed and ready for stormy conditions over the next couple of days.

A stalled front reaches from New Jersey to low pressure in Iowa. Dewpoints south of the Front are in the 60s to around 70 (very humid). North of the front dewpoints are in the 50s.

Wednesday Midday Surface Map / Source: NOAA

Wednesday Midday Surface Map / Source: NOAA

The thin cloud deck over the Chesapeake Bay area at midday will allow heating and destabilization of the atmosphere during the afternoon. The boundary just to the north is a focus point and strong upper air winds will help energize any storms that develop or move into the area.

BWI Forecast Sounding for Wednesday Evening / Source: NIU

BWI Forecast Sounding for Wednesday Evening / Source: NIU

The right edge of the BWI forecast SKEW-T chart for Wednesday evening indicates that there will be some directional and wind speed shear. Other values on the chart are indicative of storm potential.

Wednesday Storm Outlook / Source: SPC/NOAA

Wednesday Storm Outlook / Source: SPC/NOAA

NOAA’s Storm Prediction Center places the highest chances for severe weather on Wednesday between the Ohio River Valley and the lower Great Lakes with a bullseye near Chicago. The Chesapeake Bay area is in the “Slight Risk” area.

Thursday Storm Outlook / Source: SPC/NOAA

Thursday Storm Outlook / Source: SPC/NOAA

By Thursday the focus moves east with the low pressure system and storms. The Chesapeake Bay area is right in the middle of the “Moderate Risk” target for severe storm potential. It will all depend on the timing of the approach of the cold front and the degree of the destabilization of the atmosphere.

Check out the forecast at anytime on the web at wbaltv.com/weather

John Collins

More Storms On The Way
June 11, 2013

Monday (6/10/13) was a very active day for storms around Baltimore. A waterspout and several possible tornadoes were reported/sighted. The National Weather Service will be a several locations nearby on Tuesday to investigate storm damage.

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1050 AM EDT TUE JUN 11 2013

...PRELIMINARY STORM SURVEYS UNDERWAY TODAY...

THE NATIONAL WEATHER SERVICE OFFICE IN BALTIMORE MD/WASHINGTON DC
WILL CONDUCT STORM SURVEYS OF AT LEAST FIVE AREAS TODAY IN CONCERT
WITH STATE AND COUNTY EMERGENCY MANAGEMENT. THESE LOCATIONS ARE
FORK MARYLAND IN BALTIMORE COUNTY...BALTIMORE CITY NEAR LOCUST
POINT... WOODBINE MARYLAND AND THE ROUTE 94 CORRIDOR IN HOWARD
COUNTY INTO NORTHERN MONTGOMERY COUNTY... COLTONS POINT IN SAINT
MARYS COUNTY... AND CHARLES COUNTY BETWEEN LA PLATA AND WALDORF.

THESE SURVEYS ARE IN RELATION TO THE SEVERE THUNDERSTORMS THAT
MOVED THROUGH THE AREA YESTERDAY.

A FINAL ASSESSMENT INCLUDING RESULTS OF THE SURVEY ARE EXPECTED
TO BE COMPLETED AND TRANSMITTED VIA A PUBLIC INFORMATION STATEMENT
THIS WEEK... POSSIBLY AS EARLY AS LATE TODAY FOR SOME OF THE
DAMAGED AREAS.

IT WILL ALSO BE AVAILABLE ON OUR WEBSITE...WHICH CAN BE FOUND AT
WEATHER.GOV/WASHINGTON.
 One of the areas to be investigated will be western Howard County where a storm cell generated a tornado warning. Some damage was reported. Radar at the time displayed a “velocity couplet” that is a signature for possible tornado activity.
Highlighted point is an indicator of a possible tornado

Highlighted point is an indicator of a possible tornado

The brighter green spot at the tip of the arrow along side an area of red is an indicator of rotating winds at an increased velocity. This “couplet” moved into south central Carroll County over a twenty minute period before dissipating.

The front that generated Monday’s storms has moved east but another system will be approaching late Wednesday into Thursday. Another round of storms is likely in that time period and the Storm Prediction Center in Norman, OK has targeted the Mid Atlantic region with the potential for a slight risk of severe storms.

Convective Outlook for Thursday

Convective Outlook for Thursday

Ceck out our web site    wbaltv.com/weather    for updates.

John Collins