From the ABC 7 Weather team

Archive for August 2014

Labor Day Weekend 2014 weather forecast

August 28, 2014 - 04:07 PM
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Labor Day Weekend. For as long as I can remember, it has never been an easy forecast and has rarely featured perfect weather. Last year was really hot, with Saturday through Monday seeing temperatures of 92, 93 and 92 respectively. 2012 recorded 1.64" of rain to start the holiday weekend, 2011 ended the weekend with 1.36" of rain, and 2010 was near perfect, with plenty of sunshine, temperatures in the 80s and low humidity with dew points in the 40s and 50s.

That leads us to this weekend. The forecast has been favoring higher levels of heat and humidity to return to the region this weekend and hanging around for the start of September.

A warm front will be knocking on D.C.'s doorstep Saturday and high pressure will be centered in the northern Atlantic. This will lead to the aforementioned increase in humidity levels, meaning more clouds and dew points back in the mid to upper 60s. At this point, Saturday looks to be the coolest part of the weekend with highs in the mid 80s under partly sunny skies. It may even be mostly cloudy to start the day, but sunshine should filter overhead by midday. Even with the frontal boundary, Saturday should feature the lowest threat for rain, with the highest possibility in the mountains.

Temperatures should be the highest on Sunday (Image Courtesy WeatherBell.com)

By Sunday, the warm front will move north bringing in warmer air overhead. OK, let's call it hot air, as high temperatures are forecast to be in the lower 90s by the afternoon hours (See image above). Combine that with high dew points and energy sliding in from the west and afternoon thunderstorms appear to be a solid bet. Some storms may also be heavy rainmakers, as there will be abundant moisture in the atmosphere.

Below is a look at the forecast precipitable water values for Sunday, which when are this high in the 2 inch range, may mean the potential for some very heavy downpours. Be sure to keep an eye on Doppler Radar this weekend, and if you're out at the pool, find us on your phone!

Precipitable water values forecast for Sunday per the ECMWF Model (Image Courtesy: WeatherBell.com)

Monday will have similarities to Sunday, as the heat and high humidity won't be going anywhere fast. Troughing east of the mountains will set up by the afternoon again allowing for storm chances later in the day. Highs Labor Day aren't forecast to be quite as hot, topping out in the upper 80s to near 90 degrees.

Labor Day Weekend forecast updated Thursday Evening

 

Delmarva Beach Forecast

Rehoboth Beach, DE HD Camera  |  Ocean City, MD HD Camera 

Rehoboth Beach HD Camera Thursday Afternoon

How will the beaches fare this weekend? With the slight easterly component to the wind on Saturday, it may be on the cooler side to start, with highs around 80 degrees under partly sunny skies Saturday.

Sunday and Monday do look pretty nice at the beach. Temperatures should be in the low to mid 80s each day under partly cloudy skies. There is a slight chance for a few showers and storms late in the day, but right now the possibility is only around 20-30%.

Beach Forecast as of Friday morning

The rip current risk should subside by Friday and ocean conditions should calm down through the weekend. Regardless, you may want to double-check with the lifeguard before entering the water if you're not a strong swimmer.

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Hot End to Summer, What's Ahead?

August 28, 2014 - 07:47 AM
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August has been a crazy cool month, but we get one last hurrah from summer as the month ends.  So far there have only been two days when the mercury has reached 90 degrees or better in D.C. and none at Dulles.  Reagan National is running about a degree below average while Dulles had the 3rd coolest first half of August on record, and the month is ending about 4 degrees below average as of today.  However, the tables are turning and we will be close to 90 starting Saturday and continuing at least into the middle of next week.  Check out the latest 6-10 forecast showing well above average (85) temps.

 



6 to 10 day Outlook NOAA

 Typically as we enter September the temps wane.  Days get shorter and shorter with a loss of more than an hour of daylight by month's end.  Less heating of the earth means the average temperature drops from 84 at the start  of September to ten degrees cooler when it ends. 



September Climatology

 Two other notables for the first meteorological month of fall...  hurricanes and allergens.  First we'll talk hurricanes as Cristobal continues to churn in the Atlantic today.  Click here for the latest advisory from the National Hurricane Center. A high risk of rip currents continues on the Mid-Atlantic coast. Check out Lauryn's blog on that.  September is the peak of hurricane season. More major hurricanes are recorded this month than any other.  Conditions so far haven't been that favorable for tropical development with wind shear and coolish temperatures.  However, there is still time for that to change. There are a few areas of possible development. One in the Gulf of Mexico and the other in the Caribbean. 



Areas of Possible Tropical Development- NHC

 Here in the Mid-Atlantic we should always be prepared for a hurricane this time of the year. 

     September is also a bummer of a month for allergy sufferers.  While pollen has been moderate, the peak of ragweed season is here.  The first week of September usual has the highest pollen count for ragweed in the D.C. area.

 

 

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Fog Season Arriving in the Washington Area

August 24, 2014 - 06:22 PM
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Fog is a subtle weather condition that can quickly become dangerous for commuters, walkers, bikers and runners without advanced warning. It doesn’t come with a bang like a thunderstorm or can be seen slowly piling up like snow, but rather slowly and quietly develops, usually at night, and can cause serious and abrupt visibility problems the following morning.

Fog is typically found in the cooler season because of the longer nights, which allow the temperature to drop to the dew point and condense suspended moisture in the air. Also, stronger storm systems often occur later in the fall (November particularly) which can produce foggy scenarios.

A recent study from the National Weather Service in Blacksburg, Va., showed that nearly 65% of fog events for the Blue Ridge foothills and Piedmont occurred November through February. Only 13% widespread dense fog events happen in the spring and summer.

Fog graph

In most of the fog events studied, a key feature was the position of a strong surface high pressure. High pressure produces sinking air, which results in clear skies and light wind (the perfect recipe for fog). When high pressure is anchored along or off the East Coast, the Mid-Atlantic tends to have foggy nights.

The upcoming pattern this week favors a similar set up where high pressure will be focused across the Mid-Atlantic and southern New England.

Surface map

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Tropical Storm Cristobal Forms

August 24, 2014 - 09:00 AM
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An Air Force Reserve Hurricane Hunter aircraft investigating a disturbance near the southeastern Bahamas determined that the system has become organized enough with a well-defined circulation to be classified Saturday night and as of Sunday Cristobal becomes our third tropical storm of the season.

Enhanced Satellite Loop

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The Threat of Rain Continues This Week

August 19, 2014 - 02:42 PM
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If you like cloudy, muggy and gloomy weather then this week is your week. Fortunately, temperatures will be held at bay, only reaching into the lower to mid-80s for daytime highs Tuesday, Wednesday and Thursday but the humidity will continue to stream into viewing area as the region is wedged between an area of high pressure to the north and an area of high pressure to the southwest (take a peek at the graphic below).

ZZZZZ

Courtesy of The National Weather Service Baltimore-Washington

A frontal boundary will also continue to be draped across our region and will continue to meander in the vicinity of central Virginia and the D.C. metro area at least through Thursday. That frontal boundary will be the main forcing mechanism for any showers or small thunderstorms that pop up around the region Tuesday afternoon. This means that generally any rain that pops up will be around the stationary front getting caught up in our easterly flow and will preside mainly just south of the Washington D.C. metro area on Tuesday afternoon and evening. Unfortunately, since there is so much moisture and the fact that there is no element that is moving these cells along quickly, are few could contain isolated downpours. Good news is that I don’t anticipate any widespread severe weather for Tuesday evening and into Tuesday night.

ZZZZZ

The frontal boundary is just to the south of Washington D.C. on Tuesday afternoon, draped across Fredericksburg through Southern Maryland and back to the west around the Eastern West Virginia Panhandle.

If you are headed out to Nats Park tonight, just know it will be a little on the steamy side but I do believe that we will remain dry. Plenty of clouds will stick around through the duration of the game against the Arizona Diamondbacks as temperatures drop through the 70s. There could even be some areas of fog that form while you make your way home from the stadium.

ZZZZZ

Overnight temperatures on Tuesday will only fall to right around 70 degrees in most locations and warm back up into the mid-80s once again tomorrow. There could be a few peeks of sunshine once again Wednesday but an upper level low, diving out of the northwest, will be headed this way.

A piece of energy out in front of that low will move into the region Wednesday afternoon through Wednesday evening. This means we have a good chance to see some showers and thunderstorms around the region. Most of the activity will die off in the evening hours as we lose our heating from the day but there is a about a 20% chance that a few showers or storms could linger into the late evening hours leading into Thursday.

By Thursday morning, that upper level low (reference the first graphic from the National Weather Service for more information on the upper level low) will be nearing our area, crossing through during Thursday afternoon and Thursday evening bringing us yet another chance of some showers and thunderstorms. This time, there is about at 50% chance of scattered showers and thunderstorms around the region on Thursday.


The best chance for a good soaking rain comes on Thursday but all in all expect less than a 1.00” in total rain accumulation from Tuesday throughThursday night. This will be good because if you have found yourself sniffling a little through the weekend and into the first part of this week, around the D.C. region mold, grasses and weed pollen is all running a little on the elevated side. So it will be good to get some rain to alleviate some of those allergies.

 

ZZZZZQPF or Quantitative Precipitation Forecast shows 1.00” of less of rain accumulation around the WJLA viewing area from Tuesday through early Friday morning

Due to the rain that we received through the first half of August, we are well over our normal averages for rain during the summer (June – August 19th) at Reagan National Airport as well as Baltimore-Washington Airport (in fact, the rain that fell on Tuesday, August 12th put BWI +4.38” over their normal rainfall amount for the summer). Dulles International Airport could still use some rain however, as they are behind a little over 1.50” for rain accumulation for the summer months.

And while we are at it, to be completely honest, I am still not sold on keeping Friday through the weekend dry. I have continued to have it dry in my forecast for the last two days but I believe it is going to be a wait and see game to if this pattern sticks through Friday and into the weekend or to see if high pressure can edge out bringing some more pleasant conditions. Either way, we will keep an eye on it for you and let you know as the picture becomes clearer.

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3rd Coolest August on Record at Dulles and Baltimore

August 16, 2014 - 09:15 PM
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While we have experienced some seriously beautiful weather so far this August we have also had several very chilly mornings in the Mid-Atlantic.  When you average the high and low temperatures together, we rank in the top three coolest months of August up to this point at Dulles and Baltimore.  Here is a graphic from the National Weather Service that shows our average temperature so far from August 1st through the 15th compared to the averages and records for the month.

 

 

 


August Statistics- National Weather Service

 

 

 

 

 Not once did the thermometer at Dulles or BWI reach 90 degrees in August of 2014.  87 was the hottest day of the month at Dulles, VA on the 5th.  If we take a look at Reagan National, while it was also cooler than average, it definitely tells a different story.

 

 

 


August Statistics at Reagan National Airport

 

 

 

  The average temperature here is less than two degrees below the normal of 77.1.  It did hit 90 degrees, but only once on the 5th.  And it doesn't even make the top ten coolest Augusts on record.  It really goes to show you how different weather can be just a few miles apart in our region.  Now that the month is half over, what can we expect as we end it?  Will there be a big warm up? 

 



6 to 10 day Outlook

Well, at least a bit of one...   The medium range forecast has temperatures near the seasonal average with above average temps nearby .  We could hit 90 in there for a day or two if we're lucky (yeah, I wouldn't mind one more).  So far, D.C. has had 16 days at 90 degrees or above.  On average, we get between 25 and 30 of them in a year.  The summers with the fewest 90 degree days were in 1905 and 1886 when there were only 7 days. (Thanks to Alex Liggitt and a previous blog for those last two stats). 

 

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Rain to return to the region next week

August 15, 2014 - 09:48 AM
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At this point in time, I think a lot of us Washingtonians are wondering where the summer has gone. With temperatures in the 50s to low 60s this morning, and highs only near 80 this afternoon, we'll be 7-10 degrees below average across the area. Looking ahead to the 7-Day forecast, summer is expected to return by the end of the weekend. But with the increasing levels of heat and humidity will come a higher likelihood for showers and thunderstorms.

Morning lows Friday, August 15

The eastern part of the U.S. has been beautiful this morning due to high pressure filtering in behind yesterday's weak reinforcing cold front. Temperatures were thought to possibly break into the 50s at Reagan National this morning, which would have been the first time in 10 years that has occurred, but low and behold, it only dropped to 62 degrees. I'm guessing chalk that up to the warm water temperature at 77 degrees in the Potomac next to the sensor.

Temperatures will rise slightly into Saturday, back into the mid 80s. By Sunday, a cold front currently situated over Canada will move into the region, bringing a chance for showers and storms by the afternoon and evening. Highs Sunday should reach the upper 80s.

Water Vapor imagery from Friday morning

Beyond Sunday, the forecast can be summed up by the one word many of you don't like hearing...unsettled. Monday and Tuesday will feature a chance for storms from a disturbance currently located over the northern Rockies. By Wednesday and Thursday, we'll be under the influence of a trough which is currently over the Pacific Northwest. This set-up will feature dewpoints in the upper 60s all week, along with showers and the chance for afternoon storms.

Forecast precipitation through Friday morning from the WPC

Taking a look at the precipitation forecast from the Weather Prediction Center above, the D.C. area may see 2 inches of rain or more with locally higher amounts through Friday morning of next week. Not exactly something we really need after the terrible flooding last week. Be sure to dust off the umbrella heading into next week!

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Coolest August morning in 10 years? It's possible Friday

August 14, 2014 - 01:02 PM
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So far, the month of August has been slightly cooler than normal. There have only been two days this month with above-average temperatures. Now, let me set the record straight: It hasn't been abnormally cold so far this month, but it will definitely be much cooler than normal over the next two days.

(Forecast morning lows Friday)

Low temperatures Friday morning and Saturday morning may drop into the 50s at Reagan National Airport. This hasn't happened in 10 years, since August 7th, 2004, when the mercury dropped to 58 degrees. Since 2009, temperatures haven't dropped into the 50s at Reagan National until September 1st, the 11th twice, the 14th and the 15th, so we're nearly a month ahead of where we've been over the past few years.

The average low doesn't eclipse the 50s until September 24th. Looking back a little further into the climate data, temperatures in the 50s in the month of August have been largely absent in D.C. after 2004.

There were numerous times prior to that date though, as Reagan National reached the 50s in August in 2000, 1998, and 1997, four times in 1994, once in 1992 and two times in 1989. That gives 12 occasions in the past 25 years, though none in the past 10. I guess we'll see if we can break the warm streak starting tonight.

(Secondary cold front will move through this evening)

The forecast low tonight for D.C. is 60 degrees. As a secondary frontal boundary pushes through the region this afternoon and evening, drier air will settle overhead along with clearing skies overnight. By the early morning, clear skies and light winds should lead to plenty of radiational cooling, which may help D.C. reach its potential. The wild card: The Potomac's water temperature still stands at 77.5 degrees. A slight shift in the wind could keep the temperature from dropping below 60.

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Washington D.C.'s record rainfall Tuesday

August 13, 2014 - 06:33 AM
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Yesterday's deluge was a significant one, with record rainfall in parts of the area. BWI recorded its second rainiest day in record history with 6.3 inches of rain (BWI's still-standing record is the 7.62 inches of rain that fell on July 23, 1933 during the 1993 Chesapeake-Potomac hurricane).


BWI wasn't the only location to get dumped on by the wet weather. The National Weather Service released additional rainfall totals from weather spotters across the region. Check out some of these impressive totals:
(National Weather Service totals)

Another interesting tidbit about yesterday's rain, this one from ABC 7 meteorologist Ryan Miller:

Yesterday's rain was courtesy of a strong frontal system sliding through the area. Heavy rain continues for New England today, while we begin to dry out.


Breezy winds will usher in lower humidity through the afternoon.  Tonight will be comfortably cool and clear, which should make for great viewing of the Perseid meteor show, which peaked last night.  It may be a little harder to see the shooting starts with the still bright, waning gibbous moon in the night sky, but it will still be a good night sky show.

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Areas of heavy rain in the D.C. area Tuesday

August 11, 2014 - 02:06 PM
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An area of low pressure continues to move into the Great Lakes region today and an associated frontal boundary will bring the possibility of heavy rain through Tuesday. Showers will begin Monday evening, rather light in nature, and will continue to overspread the D.C. area overnight.

Surface map for Monday Evening

The Tuesday morning commute may be a wet one, but the heaviest rainfall is expected to fall Tuesday afternoon and evening. A few embedded thunderstorms will be possible, and some locations may see the potential of 1 to 2 inches of rain with isolated higher amounts.

RPM Precipitation Forecast

Our in-house RPM model shows the potential for much of the D.C. area to be closer to the 0.5" to 1" range, with isolated spots mainly north and west of D.C. with the higher amounts. This is in line with other modeling as well as the excessive rainfall discussion, which is pegging the state of Pennsylvania with the potential for the heaviest rainfall.

While ponding on the roadways will be possible, flooding doesn't appear to be a big threat at the moment. However, if some of the heavier showers and storms begin training over the same locations, some localized flash flooding may be possible, especially by the afternoon and evening hours on Tuesday.

Rain should wrap up for the most part overnight Tuesday into Wednesday morning. Drier air will filter back into the area Wednesday afternoon and at this point, conditions look about perfect Thursday through Saturday with plenty of sunshine and comfortable temperatures in the lower 80s.

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Supermoon and Perseid Meteor Shower

August 10, 2014 - 05:00 AM
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A lot going on in the night sky over the next several days.  The August full moon, which occurs tonight, may look a little bigger and brighter than normal.  In fact, it will be 14% bigger and 30% brighter.  The reason is because the moon is at lunar perigee.  This means the moon is about 30,000 miles closer to the Earth than normal.

NASA

You'll have to wait for breaks in the clouds to see the bright moon Sunday night.  If you don't get a chance to see the moon tonight, you'll get another chance at catching a 'supermoon' when it happens again on September 9, 2014.   The August supermoon will be the closest of all supermoons this year.  The moon will not be this close again until the full moon on September 28th, 2015.

NASA

Another fantastic night sky event is the annual Perseid meteor shower.  One of the most vibrant meteor showers of the year with nearly 60 to 100 meteors in an hour from a dark place at peak. The only caveat is the perseids will be competing with the very bright supermoon.  The perseid meteor shower peaks on the mornings of August 11th, 12th, and 13th. 

NASA

As for local weather, conditions won't be ideal for supermoon and meteor shower viewing.  It looks like skies will be rather cloudy for the next few nights with clear skies returning by Wednesday night.  You should still be able to see a few shooting stars by midweek, with the still bright waning gibbous moon.

The Stormwatch weather team would love to see your supermoon pictures.  Upload them to our Stormwatch Facebook page and maybe you'll see them on air! 

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Tropical Storm Bertha is the 2nd Named Atlantic Storm

August 1, 2014 - 04:18 PM
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It has been a relatively slow start to the 2014 Atlantic hurricane season.  We've only had one named storm, so far... Arthur.  Arthur developed as a tropical depression east of Florida on June 31st and strengthened to a Category 1 hurricane by July 3rd and made landfall near Cape Lookout, NC that night.  Check out the track below:


Just as we start the month of August a new tropical storm is upon us.  Tropical Storm Bertha developed late Thursday night and is approaching the Lesser Antilles.  Bertha, as of the 5pm update from the National Hurricane Center has winds of 55 mph and is moving WNW at 24mph.  Check out the storm spinning on satellite imagery. 

Bertha, as of right now, is not expected to strengthen significantly. In fact, the latest track from NHC keeps Bertha at tropical storm strength through the extended forecast time frame.  Here's the latest track:

NHC

If you have travel plans to the Caribbean, Bahamas, etc., you'll certainly want to keep a close eye on the track of the storm.  Bertha is forecast to continue on its WNW track before turning to the NE late Monday after heading farther out to sea.  It doesn't look like Bertha will have an impact on the lower 48.

Remember Hurricane Bertha from 1996?  Bertha reached Category 3 hurricane strength with max winds to 115 mph on July 9th.  Bertha then made landfall between Wrightsville and Topsail Beach, NC as a Category 2 hurricane on July 12th.  Click here for an extensive overview of the storm courtesy of the National Weather Service in Newport/Morehead City, NC.  Check out the track below and the satellite image from when Bertha made landfall:

It looks like this time around Bertha will not have a similar effect on the east coast of the U.S., as it did in 1996. The Stormwatch7 weather team will continue to keep you informed of all tropical updates through the rest of the hurricane season, which goes through November 30th.

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