From the ABC 7 Weather team

Archive for June 2014

Tropical system may impact the D.C. area for the 4th of July

June 30, 2014 - 11:37 AM
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All interests in the Mid Atlantic and East Coast are turning to the Atlantic Ocean off the coast of Florida, as a weak area of low pressure continues to sit over the area. Conditions aren't expected to be conducive to tropical development with wind shear hampering development, but there are already reports of tropical storm forced winds in the system.

Visible satellite image of the disturbance

Above is a look at the system, which has very little thunderstorm activity at the moment. Much of the storm activity is situated south and east of the center of circulation, which is very poorly defined at the moment. An Air Force Reconnaissance Aircraft is on the way to investigate the system for the next few hours.

Model track guidance depicting the system to move north the rest of the week

Model guidance is depicting this system to drift southward a bit today before moving north along the east coast through the week. The timing brings the possibility of the system to the Mid Atlantic region by Friday morning and out of the area by Friday night.

Model intensity guidance depicting possibility of a Tropical Storm

Intensity forecasts depict the potential for a Tropical Storm by Wednesday or Thursday. This would make for a poor 12 to 24 hours if you are at the Outer Banks, Virginia Beach or north to the Delmarva and Jersey Shore.

While the track forecast doesn't directly impact D.C., the combination of a possible tropical storm along with the interaction of a frontal boundary and approaching region of high pressure from the northwest would result in clouds, the chance for rain as well as breezy winds.

QPF through Saturday morning

The heaviest rain should be limited to the coastlines. Sorry beach-goers. Gusty winds will also be possible along the coasts, though confidence is still rather low.

Your best bet as of now will be to monitor the latest forecasts through the week. We will be sure to keep you updated with the latest information

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Two Year Anniversary of the Derecho

June 29, 2014 - 05:00 AM
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It's a name and date we'll always remember.  June 29, 2012.  The derecho. 

Before that day, most of us had never even heard the term 'derecho'.  After that storm, it's a name we all remember. 

That Friday was one of the hottest days of the year.  In fact, one degree shy of the hottest temperature recorded at Reagan National.  The high reached 104 degrees (a record for the day).  With such high temperatures and humidity, the atmosphere was primed for severe weather.  Little did we know how widespread, and devastating, the severe weather would be.

The line of severe storms originated in Indiana, moved through Ohio and parts of West Virginia, before slamming our region between 9 p.m. and 11 p.m. that Friday night.  Check out the radar composite and infrared satellite from that night.


CIMMS (Cooperative Institute for Meteorological Satellite Studies

Here are a few stats from the meteorologists at our local NWS forecast office in Sterling, VA.  They have a thorough storm summary powerpoint you can view here. 

National Weather Service - Sterling, VA

Winds upwards of 70 mph brought down many trees, thousands were without power for days, and it was a long road to clean-up after the devastating storm. 

Fortunately, derecho's are not a common phenomenon in our area.  Here's a climatological derecho frequency graphic created by the Storm Prediction Center.  The SPC also has an extensive link on derecho's within the site.

SPC

It's one of those day's we'll all remember and a weather term we'll never forget.  I'll leave you with a link from the "Surviving Severe Weather" special the station aired last year.  Meteorologist Brian van de Graaff looks back at the infamous storm.

 

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Lightning safety awareness week: Local lightning detection

June 27, 2014 - 11:33 AM
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A few local golf courses have lightning detection systems, including Congressional Country Club, which is hosting Tiger Woods tournament the Quicken Loans National. With vivid lightning displays the other night which featured plenty of dangerous cloud-to-ground lightning, we wanted to re-post a video from our Surviving Severe Weather Special that aired last summer.

For your own lightning detection needs, there are a few places you can go. First, you can always download our Stormwatch 7 mobile app to your phone, which will send you a message if a dangerous thunderstorm is approaching. You can also check everything from our daily forecast, to our blogs and a radar map.

Another good app to have is the WeatherBug app, which has a an embedded feature showing you how close the nearest lightning strike is to your location. As of Noon on Friday when I wrote this blog, the closest strike was 332 miles away from my location. I think I am safe.

There are a few other places online you can go before heading out the door. Of course you can check our Live Doppler radar, but you can also check these lightning detection sites too.

Lightning Detection Map

D.C. Area Lightning Mapping Array

 

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Comparatively slow start for 90 degree days this year

June 26, 2014 - 11:09 AM
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This year has only experienced six 90 degree days so far, which is slightly behind the pace of the past few years and well behind the pace the the record year of 2010 which had a total of sixty-seven 90 degree days.

The past two years had an average start, with ten 90 degree days by June 26th. 2011 was slightly ahead of the pace with twelve by the 26th, and the record year of 2010 had an astounding twenty by the 26th.

Number of 90 degree days

Above is a look at where we have been by the 26th of June over the past 5 years and the corresponding total number of days.

With D.C. currently at six, this puts the location at the lowest number of 90 degree days to start the year since 2009 when there were only three by June 26th. 2009 also only featured twenty-two total 90 degree days for the year. The fewest for a year was seven in 1905 and 1886. The least number of 90 degree days for a year recently was eleven in 2004.

Looking back, 3 of the past 4 years have been well above the seasonal average of thirty-six 90 degree days besides last year, which only had thirty-five.

Per Ian Livingston with the Capital Weather Gang, July averages just over fourteen 90 degree days per year and August averages nearly ten, so the big months still lie ahead of us. The second link has fantastic information on 90 degree days in the D.C. area, so kudos to Ian for putting this together a few years back.

Forecast high temperatures for next Wednesday (Courtesy 0Z ECMWF via WeatherBell Models)

Looking ahead, the D.C. area has a good chance to hit 90 a few times next week. Tuesday and Wednesday appear like they will be very hot, with a chance to reach the mid or even upper 90s. A threat for storms also exists both days as a frontal boundary approaches from the west. We'll narrow this down as it gets closer early next week.

Will this year be below average for 90 degree days? Not necessarily even with our slow start. Looking back to 2012 and 2013, each had ten 90 degree days by June 26, but July 2012 doubled July 2013 with twenty-two days compared to eleven days, thus helping 2012 amass fifty-three total 90 degree days for the year.

We haven't really seen a Bermuda High set up just yet which helps bring a warm southerly return flow into the region, but there's still plenty of time for that to happen and it may even set up for a few days next week. Regardless, the Weather Prediction Center continues to place our area in above average long range temperature outlooks, I guess time will tell.

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Lightning Awareness Week

June 25, 2014 - 05:00 AM
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It's that time of the year again. Wet weather mainly comes in the form of  thunderstorms in the Mid-Atlantic. While we focus a lot on severe thunderstorms that contain damaging wind, hail and tornadoes, a storm only needs lightning to become deadly.

 

(National Weather Service)

This week is National Lightning Awareness Week, always a good time to be reminded about our safety rules. As I was pouring through some "fun facts" about lightning to pique your interest, my attention was drawn to a relatively new statistic from Vaisala (a lightning detection company) that shows Maryland in the top ten states of lightning fatalities with 126 deaths in the past 50 years.

(From: Vaisala)

 

There are fewer in the state of Virginia, but it is a serious risk in the Commonwealth and D.C. as well.  Virginia averages 35-45 thunderstorms days per year with peak activity in June, July and August.   

(Virginia Lightning Statistics)

Some other interesting lightning statistics show that  80 percent of lightning victims are men who are doing some type of leisure activity, 37 percent of which are water related.

(National Weather Service)

While the science behind lightning is cool, I want to focus on safety because I think the risk of lightning is underrated and often ignored. If you're a science geek like me and want to know more about how lightning occurs, check out this link.

Have you ever been at the pool or at a sporting event and everyone around you seems to be ignoring the sound of thunder? This has happened to me many times. You just have to encourage others to seek shelter with you and they will follow suit the large majority of the time. The motto on lightning safety from the National Weather Service is a good one: When Thunder Roars, Go Indoors!  No place outside is safe, especially not under trees or in water. You should wait 30 minutes after the last sound of thunder before you can safely go back outside.

(Lightning Safety Outdoors)

When indoors during a lightning storm, stay away from windows, doors and porches. Don't touch electrical equipment or cords. Avoid plumbing, including washing your hands, taking a bath or washing the dishes (I never need an excuse to shy away from that last one). One of my favorite tools to use during threatening weather is the StormWatch 7 App. You can download it here if you don't already have it. I also love this new website with real time lightning displayed on an interactive map that you can zoom in on anywhere in the U.S. So, the next time you find yourself caught outside when thunder roars, make sure you go indoors. And tell your friend or neighbor who may be reluctant to do so, that you'd rather not get hit by something that is 5 times hotter than the surface of the sun and can light up a compact fluorescent light bulb for an entire year.

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Summer starts with showers

June 20, 2014 - 05:44 PM
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High pressure ushered in cooler and drier air Friday behind the showers and storms Thursday afternoon and evening. Temperatures even reached a scorching high of 97 degrees on Tuesday, the hottest temperature since August 5th, 2012 when it reached 98 degrees. The 97 degree reading was also a record for the 17th of June. After beautiful conditions Friday, changes will enter the region in the form of a stationary boundary which will hang around this weekend.

Rainfall forecast Friday evening through Sunday evening

Rainfall totals are expected to be on the order of a quarter of an inch to a half of an inch, with higher totals possible south of D.C. for Central Virginia and the Tidewater. Areas in those locations have the potential for over an inch of rain. Also, sorry in advance if your headed to the Outer Banks this weekend.

Temperatures are expected to be rather cool tomorrow, only reaching the low to mid 70s in the D.C. area as easterly winds set up along with scattered showers.

18Z 4km NAM forecast temperatures for Saturday evening at 7pm

Questions still remain as to Sunday's forecast, which may not see noticeable improvements until later in the day. Clouds are expected to hang around the region for much of the morning before the high-angle summer sunshine burns through the overcast later in the day. Highs should settle around the 80 degree mark.

Duration of Daylight

Don't forget, tomorrow is the first day of summer, as astronomical summer begins at 6:51am. Sorry it won't feel like summer, but I think we've had our fair share of the heat and humidity earlier this week. Have a nice weekend.

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Longest duration of daylight today through Monday the 23rd

June 18, 2014 - 04:00 AM
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With the summer solstice readily approaching this Saturday at 6:51am, the area is finally at its peak for daylight with 14 hours and 54 minutes today through Monday the 23rd. This is a stark contrast to just 6 months ago, when there was 9 hours and 26 minutes of daylight December 20-22, 2013.

With the high heat and humidity, summer feels like it is in full swing, but the average high right now is only 85 degrees. The highest average temperature jumps to 89 degrees from July 7-22.

Duration of Daylight in Washington, D.C.

The sunrise is currently at 5:43am and the sunset is 8:36pm. By the end of June, we'll only lose 3 minutes of daylight, but by the end of July, D.C. will be down to 14 hours and 12 minutes of daylight. We'll remain above 12 hours through September 25th. The Autumnal Equinox is on Monday the 22 of August.

Find the duration of daylight table for D.C. here.

D.C. Sunrise/Sunset times

 

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Code orange: Air quality alert across D.C. area

June 17, 2014 - 09:37 AM
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As temperatures continue to rise in D.C., we have more to worry about than just overheating. Monday was the first time this year that Washington, D.C.'s air quality degraded to Orange - the level considered unhealthy for sensitive groups. An air quality alert has been issued for today and Wednesday for much of the metro area as warm temperatures, stagnant air and light winds hover over the Mid-Atlantic.

(Wednesday's code orange)

Air quality in our area primarily depends upon the level of two pollutants: extremely small particles of dust,  like metals and chemicals and ground-level ozone. Most of the very small particles, referred in the environmental world as particulate matter, originate from our use of fossil fuels like gasoline and diesel for transportation and coal for the production of electricity. Ground-level ozone also has it’s origins in our use of gasoline and diesel to get around town, this form of ozone is not associated with the ozone layer in the atmosphere that protects us from UV light.

Poor air quality for the D.C. area is mainly seasonal (May through September) and is worst during the hours of 3 p.m and 7 p.m. when temperatures are warmest and there is the most activity/industry.
It’s during our summer months where weather patterns often lose their progressive characteristics: the large-scale movement of weather systems and ultimately wind, and it’s this lack of air movement that increases the amount of pollution in the air. Those really windy conditions that develop as strong cold fronts move through are fantastic at pushing and diluting air pollutants away thus we usually see fewer air quality issues during the fall, winter, and spring.

(Stagnant pattern this afternoon)

When gasoline and diesel are burned in the engine of a car, several of the chemicals that are given off in the exhaust are nitrogen oxides. These nitrogen oxides go into the air, and through a series of chemical reactions involving sunlight, ozone is produced. It usually takes several hours of sunlight to form higher levels of ozone thus air quality around D.C. is at its worst during the afternoon and evening.

Breathing air that contains higher levels of particle matter and ozone is unhealthy for many reasons. Younger children and older adults are more susceptible to the ill effects of exposure as pollution levels increase (thus the alert today for “unhealthy air for sensitive groups”), we are all at risk for developing respiratory health issues as air pollution levels rise and go beyond the code orange thresholds.

(Clean Air Partners action guide)

So today’s abundant sunshine and lack of wind will unfortunately couple with the pollutants produced by our daily activities to degrade the air we breath. You can always monitor air quality conditions through a variety of resources: www.airnow.gov and http://www.mwcog.org/environment/air/ are great websites to stay informed. 

Meteorologists Ryan Miller and Jacqui Jeras contributed to this report.

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Washington Summer Scorcher on the Horizon

June 15, 2014 - 05:57 PM
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A Canadian high pressure has been supplying the Washington metro area with a cooler Northwest wind that has cleared the air and provided low humidity. The weather pattern will change early next week as the high pressure slides off the coast. A Southwest breeze will pump in much warmer lower 90s on Monday with the humidity creeping back.

A weak upper-low will move from the Midwest into the Upper Ohio Valley and then off the Northeast on Monday afternoon. While Washington will likely stay dry, a brief thunderstorm could develop ahead of this feature north of Interstate 70 during the afternoon.

The atmosphere will get primed for heat Tuesday and Wednesday. Below are two upper-level charts comparing the forecasted mid-level pattern Wednesday with the pattern from a mid-July heat wave that produced a record 102 degrees on July 23, 2011.

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Superstitious celestial event tonight

June 13, 2014 - 10:12 AM
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Are you superstitious? Well, not only is it Friday the 13th, but there's also a full moon tonight. 

It's a rare celestial occurrence when the two coincide, but it does today.  The last time this happened was on October 13th, 2000. We'll have to wait more than 14 years for the next full moon on Friday the 13th. In fact, the next time this occurs won't be until August 13, 2049. Yep, 35 years!

The June full moon is known as the "honey" or "strawberry" moon. The honey moon name comes from the yellow glow the full moon takes on, since the June moon is the lowest in the sky. It's also because so many weddings take place in June and people are going on honeymoons. You may have also heard of the strawberry moon. This comes from June being peak strawberry season.

The moon rises tonight at 9:04 p.m. and will set tomorrow morning at 7:23 a.m. 

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Flash Flood Watch through this evening in the D.C. area

June 12, 2014 - 11:23 AM
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After storms dropped multiple inches of rain last night across the D.C. area, numerous showers and storms are anticipated again through this evening. An upper-level disturbance continues to spin to the southwest of D.C., ensuring plenty of moisture from the Atlantic into the region.

With this pattern, showers and storms will also tend to steer over the same areas as they travel from south to north, creating a process we call training, as they follow one another like train cars. This may add to flooding troubles when showers and storms develop later today.

The Flash Flood Watch officially calls for one to two inches of rain in locations today, with the potential for isolated higher amounts. Over the past few days, parts of the region have received over two inches of rain, so the area is already primed. Flash Flood Guidance shows many areas only need a few inches of rain within a three hour period in order to flooding to occur. Be sure to take precautions later today while on the roads and if you encounter high water, be sure to turn around to find another route.

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Tornado Watch Wednesday in the D.C. area

June 11, 2014 - 03:05 PM
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DOPPLER  |  HD CAMERAS  |  WATCHES & WARNINGS  FACEBOOK

A Tornado Watch is in effect until 9pm for the majority of the D.C. area and points to the west. Here is a look at the watch shaded in yellow.

Tornado Watch until 9pm tonight

A boundary remains across the region stretching from western Pennsylvania to eastern Maryland which may enhance thunderstorm activity later this afternoon and evening. As additional shear is located along this boundary, locations near it would have the greatest threat for rotating thunderstorms and the potential for an isolated tornado. Otherwise, thunderstorms through the evening will have the potential to produce damaging winds, large hail and heavy rain.

If you can do so safely, please share any storm reports or damage reports to our Facebook page or any of our twitter accounts.

Be sure to keep an eye on Doppler radar through the afternoon and tune in to ABC 7 News at 5pm and 6pm for the latest breaking weather. In addition, Newschannel 8 will be covering any severe weather through the afternoon and evening as well.

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Wet end to the work week in the D.C. area

June 10, 2014 - 08:09 PM
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Flooding rains were the story of the day on Tuesday as Flash Flooding stranded motorists, flooded streets, businesses and residences east of D.C. in Prince Georges County. Rainfall amounts were an inch or more with radar estimated totals over two and a half inches in isolated locations. More rain is in the forecast over the next few days as a frontal boundary approaches from the west. Take a look at some of the local WeatherBug sites that recorded some heavy rainfall today.

Tuesday rain from the WeatherBug Network

Wednesday will feature heavy rain once more, but there is also a threat for severe storms with damaging winds and large hail. The Storm Prediction Center placed the D.C. area in a "Slight Risk" for severe storms tomorrow which is highlighted below. This includes areas along and west of I-95, south into North Carolina and west into the Ohio Valley.

Slight Risk for severe storms Wednesday

The timing for storms looks to be starting in the early afternoon and continuing through the evening. There is a good bet we'll be dealing with watches and warnings tomorrow so be sure to keep a close eye on forecasts through the day.

In addition, heavy rain appears possible in the region which could exacerbate flooding concerns once again. A look at the 3-hr flash flood guidance, depicts the amount of rain in a 3-hr period that would bring the potential for flash flooding. This is anywhere between 1.8 and 3 inches, meaning any heavy rain makers could return the possibility for flooding. Keep that in mind for the commute home Wednesday evening.

Forecast precipitation 8pm Wednesday through 8pm Friday

This is a look at the precipitation forecast through Friday evening. Areas just west of D.C. area forecast to receive an additional 1-2+ inches of rain. A cold front is expected to push east of the area Friday night into Saturday morning, dropping humidity and allowing for slightly cooler temperatures with highs in the low to mid 80s both Saturday and Sunday. Could this be yet another beautiful weekend? All of our fingers here in the weather center are crossed!

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Astronomy Festival on the National Mall

June 6, 2014 - 12:27 PM
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Tonight will feature everything from exhibits, to hands-on activities, telescopic viewings, and a presentation from astronomers. The festival is put together by Dr. Donald Lubowich, who is the Coordinator of Astronomy Outreach at Hofstra University. Last year, even with little publicity, over 1500 people came out for the event, and with the weather expected to be perfect with clear skies and mild temperatures, this year should be great.

The event website can be found here. Around 20 local amateur astronomers will be on hand showing everything from sunspots while the sun is still up, to the moons of Jupiter and rings of Saturn after sunset. Enjoy if you plan to attend!

 

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Thunderstorms for D.C. Wednesday

June 4, 2014 - 08:53 AM
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A large complex of thunderstorms is taking aim at the Mid-Atlantic and has everyone in D.C. wondering just how concerned we should be about the risk of severe weather here.

The answer is not simple.  We should be on alert, but I don't expect a long-lived, widespread, damaging wind event. The Mesoscale Convective System (MCS) developed in the Midwest yesterday. That's a fancy term for a medium-sized cluster of thunderstorms. It produced more than 400 reports of severe weather including tornadoes, winds in excess of 60 mph and very large hail. 

 

 


Storm Reports- SPC

 

Check out the baseball size hail from twitter:

 


And this semi-trailer in Nebraska was blown over by strong winds.

 


The MCS has held together for more than 600 miles and is now in the Ohio Valley. Some cities at greatest risk today include Cincinnati, Louisville, Lexington, and Nashville. Notice that much of our area is highlighted in the brown. The Storm Prediction Center has the D.C. region at a 5-percent chance of damaging winds within 25 miles of any point. We are also at 5-percent risk of large hail. 

 

 


Severe Wind Outlook- SPC

 

While that threat sounds pretty low, there remains some uncertainty on how this system will behave as it gets close to us. The Stormwatch 7 team is currently predicting that most of the showers and storms will not be severe, but a few could reach dangerous levels. The MCS should weaken as the sun goes down. The mountains can help knock it down a bit, too. In addition, the present forecast track has the low moving right over us, which would bring the stronger storms south of our region.

 


Futurecast

 

As for timing, we could see some development of showers and storms this evening, but the main event comes while you are sleeping between 10pm and 7a.m. Expect the early part of the morning commute to be wet, with improving conditions through the morning.  Partly sunny skies by the afternoon and a pleasant end to the week.  Make sure you watch Good Morning Washington starting at 4:30 a.m. for the latest weather information and how it will affect your drive to work or getting the kids to school.

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