From the ABC 7 Weather team

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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Rip Currents: A Deadly Ocean Phenomenon

August 27, 2014 - 12:45 PM
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We definitely have been lucky in the tropical storm department for the most of this year along the eastern seaboard (with the exception of Hurricane Arthur in early July which did lead to some flooding). Hurricane Cristobal, which is churning just about 300 miles of Cape Hatteras, North Carolina, Hurricane Cristobal will continue to move north-northeast avoiding the east coast of the United States.

ZZZZZ

 

However, areas along the eastern seaboard will still indirectly get in on some of the action of Hurricane Cristobal and beachgoers are already starting to feel the effects.

All along the eastern seaboard, from Florida up through New York and Boston, a moderate to high risk for rip currents are being forecast as well as high surf advisories with large crash waves. Rip currents could occur so frequently that a lot of beachgoers for this last week in August are forbidden to enter the water considering the threat for rip currents is so high that it would be life-threatening to anyone entering the surf. These forecast include local Maryland, Delaware and Virginia beaches.

Heading into Labor Day weekend and with the unfortunate and untimely death of an 18 year old whom drowned Tuesday night in Ocean City, Maryland from getting caught in a rip current, I think it would be great to revisit rip current safety: how to recognize a rip current and how to properly save yourself. These currents can occur along any beach that features breaking waves (including the Great Lakes) and they are unfortunately subject to formation at any time during the day and more likely right before or just after low tide. The swells generated by Hurricane Cristobal and brisk onshore flow are creating the environment for a higher risk of rip currents.

According to the U.S. Lifesaving Association statistics, rip currents cause more than 100 drowning fatalities each year and 80% of all rescues on surf beaches nationwide are rip current related. Now, rip current speeds can vary and although rip currents at any speed are particularly dangerous for weak or non-swimmers, some have even been measured as fast as 8 feet per second-which is faster than an Olympic swimmer can swim! Generally though rip current speeds are typically 1 - 2 feet per second.

 So how do these things form and why? Well first what is a rip current? It can be summed up as a fast-moving narrow section of water that travels in the offshore direction. In some cases, the width of the rip current can extend to hundreds of yards.

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(Photos courtesy of National Weather Service)

Now how do these rip currents form? As waves near the shore and heads from deep water to shallow water, they break. As the waves break, they generate currents that flow in both offshore/seaward (away from the coast) and alongshore directions. Currents that flow away from the coast are called rip currents.

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(Photos courtesy of National Weather Service)

Although all beaches are susceptible to rip currents, the shape of the shoreline, the location of jetties, sandbars, groins and piers and the nearshore bottom design or bathymetry can all influence rip current development. Therefore, there are some beaches that are more prone to rip currents due to their topography.

So how to you identify rip currents?

Look for either one or more of these clues:

1. a channel of churning, choppy water

2. an area having a notable difference in water color

3. a line of foam, seaweed or debris moving steadily seaward

4. a break in the incoming wave pattern

Some rip currents can be weak and slow and be little to no threat for experienced swimmers, however, that can all change with a size or intensity of the next incoming wave. A strong wave can causes pulses in the strength of a rip current-so always be aware although most of the time, rip currents are not easily identifiable. *Safety tip - Polarized sunglasses make it easier to see rip currents*

Now on to the next: How do you survive rip currents?

First thing first: if you find yourself caught in a rip current, REMAIN CALM. A rip current is a horizontal current. They do not pull people under water but instead, pull them away from the shore. Most of the deaths that occur from rip currents happen when people are pulled offshore and are unable to keep themselves afloat because they can't swim to shore.

So here are some tips: Once you calm yourself, you can think more clearly so remaining calm is number one!

Secondly, DON'T FIGHT THE CURRENT. Swim out of the current parallel to the beach/shoreline. When you feel that you are out of the current, swim back towards the shore. If you are unable to swim out of the rip current, float or calmly tread water until you feel that you are not being pulled anymore. Don't exert any extra energy. Now, if these tips do not work, draw attention to yourself: face the shore, wave your arms and yell for help.

 

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(Photo courtesy of National Weather Service)

 Contact a lifeguard or 911 if needed! Many people drown while trying to save someone else from a rip current. The best thing you can do it throw the victim something that floats and yell instructions on how to escape.

ZZZZZSo enjoy the beach for the rest of this summer but remember that rip currents can happen along any beach with breaking waves! Keep you and your family safe and take the warning seriously.

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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.

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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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Ragweed pollen in Washington D.C.

August 3, 2014 - 11:15 AM
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Ragweed is the highest cause of allergenic rhinitis in North America and will be making its annual visit to the D.C. area in the next couple of weeks. Thus far, pollen counts for Ragweed are relatively low.

Susan Kosisky, the Chief Microbiologist at the US Army Centralized Allergen Extract Lab stated in the pollen count last week, "I thought I was sneezing a bit more than usual this past weekend and concluded there just may be some ragweed in the air. Today we saw the first ragweed pollen of the season, which is not unusual for the last week in July. Ragweed is our most prolific area weed pollen producer. We document about 39% of the total annual ragweed pollen load in August, 57% in September, and 4% in October."

From a pollen report last season, she stated, "The first week of August is when we usually start to see the first glimpses of ragweed season. By the second week in August, daily average totals are around 4 grains/cubic meter of air."

She did note, however, that the latter part of August through early September is usually the point when ragweed really begins to increase in the D.C. area.

Ragweed plant

Ragweed, shown above, are annual or perennial herbs that range from small plants 3 feet tall up to 13 feet tall (Great Ragweed). 21 species of ragweed occur in North America, but most allergy problems are caused by just two species which account for more hay fever (bodies reaction to the pollen) than all other plants together. One single plant can release up to a billion pollen grains in a season. Pollen grains have been recorded around 400 miles out at sea and up to 2 miles up in the atmosphere, so the pollen can travel exceptionally far.

How can you beat the pollen? Here are a few tips.

Stay indoors as much as possible during high pollen days (We will let you know when those days are!)

Keeps windows in your house and car shut as much as possible

Change clothes after being outdoors for a prolonged period of time

Shower before bed to wash off pollen

Equip your home with HEPA air filters

Remember to take your allergy medications (Claritin is my friend during the late summer and early fall!)

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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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Rain back in the forecast for the beginning of August

July 31, 2014 - 04:33 PM
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The past few days have been just about perfect as far as the end of July is concerned. Low humidity levels and below average temperatures have made for very comfortable conditions. One thing has been missing now for a while through the majority of the D.C. area... rain.

Taking a look at some of the area climate reports, you wouldn't think the region has been hurting for precipitation. Reagan National has recorded over 4.5 inches of rain for the month of July. Even the drought monitor shows our area is doing well for precipitation. But taking a closer look, the area has been dry for the second half of the month.

Since July 16, Reagan National has only recorded 0.11" of rain, Dulles 0.13" of rain, and BWI Marshall has seen the most at 0.23" of rain. With the pattern changing as we speak, this should change over the next few days.

WPC Precipitation Outlook through Sunday evening

A frontal boundary south of the D.C. area is expected to push north along the east coast, which will help become the focus for showers and a few storms to ride along. The heaviest rain is expected to remain south and east of D.C., with upwards of 4 inches of rain possible over eastern portions of North Carolina and over 2 inches possible towards the Delmarva Peninsula.

Timing:

Don't expect the weekend to be a complete washout just yet. Not all modeling is in agreement, but as of now, the highest likelihood for steady rain appears to be Friday night into Saturday morning.

Breaks in the overcast will be likely Saturday afternoon and through the day on Sunday. Temperatures will remain slightly below the average of 88 this weekend with highs only expected to reach the low to mid 80s.

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Record low this morning, but was it a chilly July?

July 30, 2014 - 08:22 AM
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The debate around town this morning has been about the best way to describe this morning's temperatures. Would you call it cool? Chilly? Crisp? Pleasant? Perfect? Well, if you live around Dulles Airport, you could call it record-breaking cold. The temperature briefly dipped to 48 degrees.

 

(Dulles Temperatures and Dewpoint this Morning)

 

Here's a look at morning low temperatures across the area.

 

(Morning Lows)

 

The old record at Dulles for July 30 was 51 degrees, set in 1981. The unusually chilly temperatures also managed to break the July 29 record, dipping below the previous mark at 11:58 p.m. Tuesday night. National Airport bottomed out above its record low of 56. Martinsburg, W.Va., hit a record low and Baltimore broke its record low with 55 degrees. 

 

(Records at Dulles)

So why has this fall-like weather made a mid-summer appearance? A trough in the upper atmosphere has drawn in cooler air from the north into the Mid-Atlantic. It has made it's way unusually far south for this time of the year. Many records were broken in the East.

 

(Preliminary Record Lows via CoolWx.com)

 

Typically, high temperatures are in the upper 80s in late July in D.C. While we will gradually see temperatures warm up today and tomorrow, the overall pattern keeps us cool to near average through mid-August.

(6 to 10 day Temperature Outlook NOAA)

If you're thinking to yourself that this is a cool July, you're right. As of this morning, Dulles has averaged 74.7 degrees this month, about two degrees cooler than normal. At Reagan National, the average temperature is a bit warmer at 79.8 degrees, right about average. Still, this July is the coolest we've enjoyed since 2009. There were nine days of 90 degree or higher temperatures at National Airport this month, including a high of 99 on July 2nd.  At Dulles, there were just five 90 degree days this month.

If we look ahead to August, climatologically speaking, we will start the month with an average high of 88 degrees and end it with an average high of 84. August is the last meteorological month of summer, with slightly fewer minutes of daylight.

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Haze in D.C. today most likely smoke from Canadian wildfires

July 29, 2014 - 11:45 AM
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What a beautiful morning it has been, with lows in the 50s and 60s across the region, including a record-tying low of 59 degrees at BWI Marshall. With such low humidity levels across the region though, you would expect to see deep blue colored skies with now a few white puffy cumulus clouds. Instead, a haze has settled in over the region.

Visible satellite image after 11am

Take a look at the visible satellite image above. Just by looking at this image by itself without motion, it is very hard to see anything that may signify smoke over the D.C. area. But click here to see the satellite in motion. Did you happen to see the very light colored area over D.C. right after sunrise? This is showing the possibility of either some extremely thin clouds, or more than likely, a very thin layer of smoke in the atmosphere.

Courtesy: NASA MODIS

A number of fires have not only been burning in the Pacific Northwest, but also well north of the border in the Northwest Territories of Canada. Above is a look at the NASA MODIS satellite world view which I stumbled upon while perusing the web. I circled the regions of smoke that were showing up yesterday in Northern Canada and over the Hudson Bay. Given the flow of the atmosphere, much of the smoke more than likely was pushed south and eventually southeast into the Midwestern U.S., Northeast and Mid Atlantic States.

Water Vapor Imagery Tuesday Morning the 29th

The upper-level flow shows a large trough through the eastern part of the U.S. and a large ridge over the western U.S. The resulting steering flow has been from Northern Canada southeast through the Midwestern States and directly into the D.C. area. Check out the water vapor loop here. Keep in mind the orange, black and dark grey show very dry air while the purple, blue and white areas show increased levels of atmospheric moisture.

The effects from smoke in the D.C. area will be minimal and air quality is still expected to be good through the next few days, though the haze may hang around tomorrow and Thursday.

NASA MODIS image from July 23rd

The fires have burned over two million acres of land in the Northwest Territories and are thought to have been caused by lightning.

Photos of the fires near Yellowknife, Canada.

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Cooler and comfortable end to July

July 26, 2014 - 06:00 AM
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After a hot start to July with eight of the first fourteen days above 90 degrees, the pattern shifted. Since then, high temperatures topped out in the low to mid 80s seven times and reached 90 degrees only once.

Looking ahead to the end of July and the beginning of August, temperatures are still expected to be cooler than normal. Once we get through the weekend, which will feature more heat, humidity, and the chance for showers and the possibility of severe storms, cooler air is forecast to filter in next week.

500mb vorticity plot for next Tuesday

While a large ridge is expected to continue to build over the southwestern U.S., a potent shortwave will move through the Midwest and into the Northeast this weekend bringing the potential for severe storms.

This shortwave will spin around an area of low pressure centered over the eastern part of the Hudson Bay in Canada (above), which looks like it will be blocked from moving anywhere as high pressure sets up east over Canadian Maritimes and the northern Atlantic.

6 to 10 day temperature outlook from the CPC

In reality, what does this mean for the D.C. area? Temperatures may only approach the 80 degree mark Tuesday and low to mid 80s Wednesday through Friday of next week. In addition, humidity levels should be low, with dew points in the 50s expected Tuesday through Thursday before more moisture slides back into the region Friday.

Tuesday afternoon 2-meter temperature anomalies (Credit: WeatherBell Models)

With record heat dominating the headlines, including the hottest global June on record per NOAA, this will most certainly be enjoyed throughout the eastern half of the U.S. next week. Portions of the eastern U.S. will enjoy afternoon temperatures 10 to possibly 20 degrees below the seasonal average.

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Severe Storms Possible Sunday and Monday

July 25, 2014 - 03:07 PM
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Say goodbye to the beautiful weather of Friday and hello again to summer in Washington, D.C. for the weekend. That means a return of heat and humidity as well as a return of summertime thunderstorms. Saturday will feature very warm temperatures, right around 90 degrees for a daytime high with increasing clouds and increasing humidity late in the day. Another thing that will increase on Saturday will be the chances of showers and thunderstorms. Albeit, it is only a slight chance of showers and thunderstorms through the PM and overnight hours on Saturday, but still a chance.


An upper level piece of energy will approach the region on Saturday night. Mainly our western areas will be the breeding ground for any action, but by Sunday, we all have equal chances to see showers and thunderstorms across the area as that disturbance passes through the D.C. area.

ZZZZZ

 

Also what we are watching after Sunday’s disturbance is a very strong cold front will be dropping out of the upper Midwest and down into the region for Monday. Therefore, we have a chance of showers and thunderstorms Saturday night – Monday, some of which could be strong to severe.
Above graphic, at the top, shows the slight risk area for severe weather Saturday through Monday. The risk moves from the Ohio Valley Saturday to our area on Sunday and Monday. On the bottom of the graphic, the surface features show an area of high pressure overhead bringing us very pleasant on conditions on Friday. Then through 8 p.m. Saturday, the area of high pressure scoots off the coast giving us a southerly flow bringing humid air from the south and transporting it right here into the D.C. area as a warm front approaches the region. By Sunday and Monday morning, the strong cold front is still to the north and west of the area.


So now that we know what is going on, what can we except through the weekend? Well considering that warm front is just to the south on Saturday night, lift from warm advection around the warm front and the piece of energy approaching us from westerly flow aloft will give us that about a 20% chance of storms on Saturday afternoon and evening continuing through the overnight hours. There will be a good chance of severe weather across our area through the day on Sunday as that disturbance moves through the region. One thing that still remains a question is temperatures on Sunday. Right now I have temperatures fairly warm, nearing 90 degrees. But, if we get some thunderstorms in the morning hours, that could down our temperatures for the afternoon and lessen the instability in the atmosphere. Either way, it will still be very muggy outside through the day on Sunday with mainly clouds hanging around. Some of our models do suggest that we get some thunderstorms during the first part of the day on Sunday.

 

ZZZZZ

 

Caption: Showers and thunderstorms around the region weaken slightly as they travel to our area from the north and west. This is around 11a.m. on Sunday.

We do know that any of these storms could produce damaging winds, possible hail and heavy rain. There will certainly be substantial moisture around the region given the nice southerly flow, therefore localized flash flooding is definitely a concern. Take a look at our precipitable water values:

 

ZZZZZ

 

You may have heard this term or “PWATS” quite a bit this summer. Really what preciptable water values are are the amount of water within a vertical column above the surface if it were all precipitated out. These values are over 2.00” in some spots and when we see that, we know there is enough moisture available to create flooding conditions.


By Monday, the chance of showers and storms remains through the day as the cold front finally travels through the region. Again, some of there could be strong to severe but by Tuesday, we are in for another treat.

ZZZZZ

A nice refreshing airmass moves into the region bringing low humidity and refreshing temperatures. Daytime highs on Tuesday are in the upper 70s to lower 80s! We just got to make it through some summertime storms to get the reward by mid-next week!

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Cherrystone tornado rated EF-1

July 25, 2014 - 11:46 AM
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The National Weather Service office in Wakefield, VA surveyed the damage from yesterday morning's storm in Northhampton County in southeastern Virginia and determined the damage was due to a tornado, straight line wind, and a large swath of hail.

Path of the tornado, straight line wind and large hail

Above is a look at the path of the tornado, wind and large hail. The tornado originated in the Chesapeake Bay as the storm rapidly intensified. The EF-1 tornado had estimated maximum wind speeds of 80 to 100 mph and was on the ground for 8 miles over a span of 15 minutes. It's maximum width was 150 yards. The tornado wasn't the only feature that caused damage in this storm.

A downburst resulting in straight line winds was observed in the yellow wind damage swath. Wind speeds were estimated between 65 and 75 mph and downed numerous trees and even contributed to overturning several camping trailers in the Cherrystone Campground.

The hail core fell mainly within the blue lines (first image above) in the size of golfballs to a few reports of baseball size. This caused considerable tree and leaf debris, crop damage and siding damage on homes in the path.

The storm caused 36 injuries and 2 fatalities.

See the rest of the preliminary storm survey here.

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