From the ABC 7 Weather team

Archive for September 2014

Only A Few Days of Summer Left Before Autumn Begins

September 19, 2014 - 02:19 PM
0 Comments

Enjoy this last weekend of summer - because it is going to feel more like summer here in the Washington D.C. area! Temperatures throughout this last week of summer have been running below normal giving us a little taste of Fall.  However, by the time we head into this weekend, temperatures will top out in the 80s for much of the region thanks to high pressure clearing out cloud cover and helping us boost into the 80s with a light southeasterly flow.

A cold front will cross the area Sunday which will give way to some clouds and about a 30% chance of showers in the afternoon and evening hours moving from west to east. This cold front will also sweep away any of the summer-like weather we have left and leave us with another spell of Autumn weather around the region.

This is happening right in time because the autumnal equinox arrives at 10:29 p.m. on Monday! People celebrate this moment across the world and really the precise moment is when the sun passes directly over the equator! This happens twice a year as you may recall (the "spring equinox" and the "autumnal equinox"). 

 

ZZZZZ

 

In latin, the word "equinox" means "equal night" --"equi" meaning "equal" and "nox" meaning "night". This signifies the equal parts of daylight and darkness.

However, this is not always so "matter-of-fact." The sunrise on Monday is 6:55 a.m. and the sunset is 7:07 p.m. This isn't exactly equal. In fact, we have to wait until Tuesday, the first full day of Autumn to get the full equal light-equal night. The sunrise on Tuesday is 6:56 a.m. and the sunset is 7:06 p.m.

My colleague Eileen Whelan summed it up correctly when she wrote:

"We have the atmosphere to thank for this oddity. Also, the definition of sunrise and sunset. Sunrise occurs the moment the tip of the sun can be seen on the horizon and sunset is the last minute the sun can be seen before it dips below the horizon. Also, keep in mind our atmosphere refracts, or bends, light, which makes it appear as if the sun is rising or setting earlier.

The true equinox occurs when the center of the sun's disk crosses the celestial equator and this occurs at 10:29 p.m. EDT on Monday, September 22. At the same time the equinox occurs in D.C., it occurs across the globe."

Either way, you won't notice a different from Monday to Tuesday, from Summer to Autumn. However, you will notice that the hours of daylight start getting shorter until the Winter Solstice which begins on December 21, 6:03 P.M. EST (which is also the darkest day of the year meaning the day with the least amount of daylight.

However, as we make the transition into Fall, it may seem a little cooler according the outlook by the Climate Prediction Center:

 

ZZZZZ

But, also according to the Climate Prediction Center for the 8-14 day outlook, temperatures may be a little on the warmer side!

 

ZZZZZ
So don't pack away those flip-flops yet for those boots. Fall is here to stay but bouts of summer may stick around until early October!

 

 

 

Continue Reading

Dry start to September in the D.C. area, dry outlook ahead

September 16, 2014 - 12:06 PM
0 Comments

Over the past few weeks, a few locations saw some moderate to heavy rainfall from storms but they were highly localized. Here are some of the locations that have seen decent rainfall this month on our WeatherBug Network.

Monthly Rain and temps as of Noon Tuesday on our WeatherBug Network

Other parts of the area haven't been quite as lucky as of late, with official reports at the local observation stations capturing relatively little rain for the month of September. Officially, precipitation totals so far this month are running anywhere from 1" to 1.5" below normal. Unfortunately, the current outlook isn't going to bring appreciable rainfall anytime soon.

Rainfall by the numbers this month and for the year

Above is a look at how the region is faring as far as precipitation this September. Dulles Airport is struggling the most, with only 0.21" of rain in the first 16 days. The observation station is running over an inch and a half below average for the month.

BWI Marshall has been the closest to average precipitation but is still running around an inch below for the month.

Maryland Drought Monitor

As far as the drought monitor is concerned, the region isn't even abnormally dry. This may change over the next week or two, but looking at the statistics for Virginia and Maryland, there aren't any regions with drought in Maryland and only a few abnormally dry spots south of D.C. in Virginia.

Virginia Drought Monitor

Much of this is due to the fact that the region has such a big surplus for the year and stayed around normal over the summer months. Precipitation is still running nearly 6 inches above average for the year at Reagan National and over 9 inches above average at BWI Marshall.

QPF today through next Tuesday morning from the WPC

The forecast looking ahead over the next few weeks doesn't look to good for rainfall chances in the D.C. area. The WPC forecast above only brings about a chance for light rain over the next week, and other modeling continues to depict dry conditions even through next week. A few showers may be possible with a cold front next Monday into Tuesday, but beyond that the region may not see decent rainfall until after the following weekend of the 27th and 28th. We'll of course keep you up to date with our latest 7-Day Forecast.

Continue Reading

Sunday Night "Mysterious Flash of Light" in the Sky

September 15, 2014 - 07:53 AM
0 Comments

Many reports have been coming in of people in the D.C. region seeing a bright flash in the sky last night. It happened just before 11 p.m. Eastern Daylight Time. Most reports on the American Meteor Society website are described as a bright white or yellow flash that lasted around one second. Here is a map of all of the reports:

(Meteor Sightings via American Meteor Society)

So, what was it? Most likely, it was a meteor. Meteors are pieces of rock, ice and dust, usually from a comet, that explode and burn up as they enter the Earth's atmosphere. There are two meteor showers taking place in the month of September. First, the Southern Taurids, which are active for two months from Sept. 7-Nov. 19th. According to the American Meteor Society, they tend to produce few "shooting stars" but can be rich in fireballs and often responsible for an uptick in fireball reports to the society's website. In addition to the Southern Taurids, the less known Piscids will be near their peak in September and continue through October.  Check out this article from In-The-Sky.org. Let us know if you saw anything: Just go to our Stormwatch7 Facebook page and leave a note. 

Update:

This video was taken from Jesse Ferrell who works for Accuweather in State College, PA. You can see how the fireball completely lit up the night sky.

Here's another look at the meteor from Jeremy Settle, Assistant News Director at News 12 in New Jersey.

 

Continue Reading

Roller coaster temperatures this week, strong storms possible Thursday

September 9, 2014 - 08:46 AM
0 Comments

The weather picture is rather complex this week and we've got a little bit of almost everything in the forecast, even SNOW! (Ok, the snow is for Canada, Montana and maybe the Western High Plains, but now I have your attention!)

Low pressure has been keeping us cloudy and cool in the Mid-Atlantic since Sunday night. The high in D.C. yesterday was 77 degrees and with mid-upper 70s again today, it will be the coolest stretch of temperatures since late May (thanks to Ryan Miller for that nugget). All of this is happening on the average last date of 90 degrees at Reagan National.

 

(This Afternoon)

 

As the low pressure system departs tonight, our focus turns to a potent cold front that is currently in the Midwest.  MUCH cooler air is coming in from Canada behind it where they have been seeing some snow!

 

(GFS Model showing possible snow in Western NE Thursday)

 

The cold front drops through the plains and spreads toward the east. Check out the chilly nights ahead for our friends to the north!

(Flirting with Freezing Thursday AM Midwest)

Notice on that forecast model that as the cool air invades the nation's mid-section, warm air will be drawn in ahead of that front it the east. It will be muggy in D.C. Wednesday as it warms up to around 80 and by Thursday we reach the top of the roller coaster with  highs back in the mid to upper 80s. Here's a look at highs from the North American Model.

 

(NAM Temperatures Thursday)

 

By the time it arrives in the D.C. area, this storm system will already have a history of producing severe weather. Today it will hit the Midwest and then the Great Lakes/Ohio Valley on Wednesday. By the time it reaches us, much of the energy will be to the north. However, with a strong jet in the upper levels of the atmosphere, the thunderstorms that develop over the D.C. region could produce damaging winds Thursday afternoon/evening. 

 

(Storm Prediction Center Severe Outlook Thursday)

 

This all should pass us overnight on Thursday and stall in the southeastern U.S. That puts us in the cool sector with 70s again for highs and overnight lows in the 50s even inside the beltway. The core of the cool air evades us, but it sure will feel like fall. In addition, a reinforcing cold front comes in on Saturday (bottom of roller coaster) with a few showers. Expect below average temperatures into next week.

Continue Reading

Shelf Clouds Common Prior to DC Storms Lately

September 7, 2014 - 07:58 PM
0 Comments

Many social media sites have spotlighted these saw-like storm clouds. Just this past weekend, a north to south line of storms produced a long shelf cloud as it hurled from the Cumberland Valley to the nation’s capital.

What does it look like? The image below shows the low, horizontal wedge-shaped cloud. It forms along the leading edge of a thunderstorm’s gust front.

shelf cloud

To understand a gust front, consider the mechanisms in play in a storm. In a thunderstorm downdraft, heavy rain forces the cool air in the atmosphere’s upper-levels to spread to the ground. The air then fans out in all directions once it reaches the surface (since air can’t exactly dig into the ground). The leading edge of this cool air outflow ahead of the storm is called the storm’s gust front.

Shelf cloud 2

Where the gust front meets the warm air ahead of the storm, the air rises and forms shelf clouds. Immediately in the shelf cloud’s wake is where the heaviest rain and strongest winds can be found (such as shown in the image below from the storm that moved through Hagerstown, Md., on Saturday). Shelf clouds are found a few miles ahead of the actual storm.

Shelf cloud 2

Now, shelf clouds don’t precede every thunderstorm. Typically, they are found ahead of thunderstorms that form ahead of a vigorous cold front (like Saturday’s front), an upper-level low pressure or along the leading edge of a derecho. The more powerful the cold front or upper-level disturbance triggering the storm, the better opportunity to see this cloud feature.

So, the next time you see a shelf cloud, remember that often the worst weather is just in its wake. The milky color behind the shelf feature is the heavy rain shaft accompanying the thunderstorm.

Continue Reading

Tags:

Coastal System Brings Clouds and Showers To Start the Week

September 7, 2014 - 05:07 PM
0 Comments

Wow!  What a difference a day makes!  An absolutely gorgeous Sunday follows a hot, steamy, and stormy Saturday.  The cold front that slid through late Saturday night has now stalled off the coast.   That has kept the Carolinas rather warm and wet today, but has allowed much drier and cooler air to greet us in the mid-Atlantic and Northeast. 

Along the front, an area of low pressure will develop along the eastern Carolinas.  That will set the stage for an unsettled start the work week.  Cloudy skies will greet us Monday morning with a few sprinkles around.  With the clouds, and an easterly breeze, temperatures will only climb into the mid to upper 70s.  Here are forecast highs for Monday:

Showers will be sporadic, but it will be good to have the umbrella with you with rain chances possible through Tuesday night.  There is also some discrepancy between the model guidance.  The European model favors heavy rainfall Tuesday morning at 8 am along and east of the I-95 corridor, whereas the NAM has only a few sprinkles around.  See the difference in the snapshots below:

WeatherBell European Model 8am Tuesday
WeatherBell NAM Model 8am Tuesday

Folks along the coast will see the heaviest rain and strongest winds.  The Weather Prediction Center's Qualitative Precipitation Forecast (QPF) delineates the highest rainfall totals to be over the eastern shore of Maryland and VA Beach region through the day Tuesday.

NOAA Weather Prediction Center

One thing is for sure, it won't be a bright and sunny start to the week.  The weather pattern changes by Wednesday, as sunshine and more seasonable temperatures return.  Another strong cold front will slide through by week's end bringing another taste of fall to the air by next weekend. 

 

 

Continue Reading

Tags:

Strong Storms Likely Saturday

September 5, 2014 - 08:19 PM
0 Comments

It says September on the calendar, but it certainly doesn't feel like meteorological fall.  Temperatures have started out well above average for the first few days of the month, but big time changes are on the way!

A strong cold front is currently moving through the Midwest.  Ahead of the front, very hot and humid conditions exist.  Behind the front, much cooler and drier air.

Strong storms have been firing up along the front all day.  Tomorrow, as the front approaches the east coast, scattered strong and severe thunderstorms will develop.  It'll feel like summer tomorrow afternoon with highs back into the lower 90s, but feeling like the upper 90s with very high humidity.  The heat and humidity, combined with the approaching front, will trigger strong to possibly severe thunderstorms.  The greatest threat from the storms will be damaging winds.  As far as the timing, storms could pop anytime after 2pm.  Here's one simulation at 2pm showing a few storms firing up.

WeatherBell - NAM 2pm

A few other simulations suggest the storms will arrive after 6pm.  Check out our in-house computer model that shows widely scattered showers and storms around at 9pm.

Since it will be so hot and humid, you'll want to keep an eye to the sky for ominous looking clouds.  Storms could fire up at any time.  If you're planning on being outdoors, make sure you have the StormWatch weather app downloaded to your phone for radar updates, as well as dangerous storm warning alerts based on your location.  The greatest risk for storms will be between 2pm and 10pm Saturday.

The rain should wrap up overnight Saturday from NW to SE, as the drier air slowly filters in.  Humidity levels will be noticeably lower Sunday with highs around 80 degrees.  Check out a comparison of dewpoint temperatures (measure of humidity/moisture) Saturday and Sunday.

WeatherBell - EURO 2pm Saturday dewpoint temperature
WEatherBell - EURO 2pm Sunday dewpoint temperature

Saturday afternoon dewpoints will be in the lower 70s compared to upper 40 lower 50 degree dewpoint temperatures by Sunday afternoon. 

The front will stall off the coast Sunday and will keep temperatures slightly below average for the early part of next week.  We'll have to watch the front closely because an area of low pressure may develop along the front and could bring a few showers by Tuesday.  It's still too early to tell, but one thing is certain -- cooler and drier, more September-like, weather will return by the end of the weekend! 

Continue Reading

Tags:

StormWatch 7 blog: Daylight disappearing quickly in D.C.

September 4, 2014 - 10:45 AM
0 Comments

I've been talking to a lot of people lately that have noticed just how quickly the D.C. area has been losing daylight. In August alone, the area lost over an hour of daylight, from fourteen hours and ten minutes on the 1st all the way back to thirteen hours and four minutes on the 31st. Take a look at the graphic below, which will give you a good idea of the big milestones coming up.

(Duration of Daylight in D.C.)

So far D.C. has lost two hours of daylight since the solstice, but that will jump to over three hours lost by the end of September. Unfortunately the area will be below twelve hours of daylight by then as well. We'll have to wait until October 20th for eleven hours of daylight, and November 17th for ten hours of daylight.

To find the duration of daylight for D.C. or anywhere in the U.S., go to this site here and go to form A, or look around the world in form B.

Continue Reading

Tags:

Lapse of the thunderstorms moving through Frederick, MD Tuesday

September 2, 2014 - 06:18 PM
0 Comments

After seeing the potent line of storms form west of the mountains moving east towards D.C., we quickly scrambled to get all of the necessary information out before clicking a few buttons to record a time lapse! Check it out here.

Did you happen to see it? If you did and took any pictures or video, feel free to share them to our Stormwatch 7 Facebook page!

Here is a great picture sent in from Renee Rohwer from Mount Airy, MD this afternoon.

Shelf Cloud in Mt. Airy, MD from Renee Rohwer

Continue Reading

Severe Thunderstorm Watch until 10pm Tuesday

September 2, 2014 - 04:49 PM
0 Comments

DOPPLER RADAR  |  HD CAMERAS

Numerous thunderstorms have developed across the region and some of them have become strong to severe. This prompted the Storm Prediction Center and National Weather Service to post a Severe Thunderstorm Watch for the D.C. Metro and points north until 10pm.

Severe Thunderstorm Watch until 10pm

Storms will have the potential for damaging wind, large hail, heavy rain and frequent lightning. Stay tuned to ABC 7 News for the latest updates and please follow @SteveRudinABC7, @alexliggitt and @DevonLucie for updates on twitter.

Continue Reading

Hottest stretch so far this year looks to continue into September

September 1, 2014 - 08:16 PM
0 Comments

After a hot end to August, the heat doesn’t want to go anywhere for the beginning of the month. Check out the 7-Day forecast here. Tuesday through Saturday all appear like they will at least be close to the 90 degree mark, with the hottest day for the remainder of the week Tuesday. Oddly enough, Reagan National Airport hasn't recorded four days in a row with highs at or above 90 degrees this year. The 15th through 21st of July 2013 was the last time we've experienced a prolonged period of high heat, with 7 days in a row at or above 93 degrees.

Last September also started off on a hot note, but beyond the first few weeks there was a nice cool down with a long stretch of days in the 70s. The average high is 84 degrees to start the month, but falls to 74 degrees by the end of the month.

90 degree days as of September 1

Temperatures should get back near normal come Sunday as cooler air moves in after a cold front. For the year, D.C. is still below the normal number of 90 degree days, with 19 as of Monday, compared to the 28 we were at by September 1st in 2013, and compared to the 36 average D.C. typically records in a year. With the recent hot summers, however, this is nothing compared to the record 67 90-degree days in 2010 or even the 56 in 2012, so at least it has been nice!

Monday's rainbow over D.C. captured by Richard Barnhill

Check out this beautiful picture from Richard Barnhill. You can find him on social media here and here, and check out his other pictures on flickr here.

What about storm chances the rest of the week? After a stormy past two days in parts of the area, a cold front will move into the region late Tuesday bringing an additional chance for afternoon storms. A break in the action will be likely Wednesday and Thursday before chances return Friday in an isolated nature and more widespread action with a potent cold front on Saturday.

Continue Reading