From the ABC 7 Weather team

Archive for May 2012

Today: 124 Year Anniversary of the Infamous Johnstown Flood

May 31, 2013 - 05:00 AM
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On this day in 1889… heavy rain had already fallen and continued into the daylight hours across west-central Pennsylvania’s small, but booming steel-producing town at the time, Johnstown.

“It commended to rain here on Thursday night at 9 o’clock, May 30, 1889. It rained very hard up till Friday noon, May 31st. All the streams that empty into the reservoir were overflowed; large trees and logs of all kinds went into the reservoir; it took logs away from my place that had been here for forty years,” said John Lovette, a sawmill owner along the South Fork Creek.

weather map

Story Image: Weather map from May 31, 1889 courtesy of NOAA's Central Library showing low pressure across the Great Lakes with rain showers and a southeast wind for much of the northern Appalachians. Johnstown, Pa., is highlighted on the map.

What many didn’t realize is that a lake 450 feet higher in elevation than the downtown and several miles northwest of the city was filling up to its limit and was at the verge of bursting at the seams.

Shortly after Noon EST on May 31, 1889, a message in Morse code from someone at the South Fork Fishing and Hunting Club at Lake Conemaugh was sent to officials in downtown Johnstown advising residents that the lake's dam was going to break and send a wall of water down into the valley. So many false alarms on the potential dam breakage had been sent time and time again in the past that everyone blew this one off without even second guessing.

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Venus Transit: A Once In A Lifetime Astronomical Event

June 5, 2012 - 05:00 AM
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It's been quite the year for spectacular astronomical sights.  There was the supermoon, annular solar eclipse, and now the transit of Venus, which will occur tonight.  This is when Venus passes directly between the earth and the sun and we see the distant planet, as a small dot passing slowly across the face of the sun.  You can actually see this unusual alignment later this evening and through sunset (between about 6PM and 8PM).  The weather in D.C. looks fairly good for transit gazing; however, there may be a few clouds that could block the view. 

Best Time To See Venus Transit In D.C.

Interestingly and historically, this rare alignment is how we measured the size of our solar system. For those of you who have smart phones, there’s an app for this. The phone app is creatively called the VenusTransit phone app and will actually allow everyone to send their observations of the transit to participate in a global experiment to measure the size of the solar system.

The last Venus transit was in 2004.  After tonight's transit, we won't see the transit of Venus, again, until 2117.   If you missed the transit viewing in 2004, this is a once in a lifetime opportunity!

Do not try to observe the transit of Venus directly! You must use proper eye protection at all times with the proper solar filters. You still have time to order a pair of glasses online and here is a place where I know you can get them dirt cheap.  Enjoy the show!

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Severe weather outbreak possible Friday

May 30, 2012 - 09:53 PM
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All the ingredients could be coming together for a large scale severe weather outbreak in the region late Friday. As a matter of fact, some of the factors are falling in line with a past episode of severe weather that occurred at almost exactly the same time of the year back in 1998.

First of all, at the surface, a strong cold front separating warm, humid air from much cooler, drier air will be a driving mechanism for storms to build across western Pennsylvania and carry over the mountains into the District. All the forecast models agree the timing of the storms to be during and just after the warmest part of the day; mainly between 4 p.m. and 10 p.m. This could significantly impact the evening commute.

FrontForecast

(This image shows an average model solution for Friday evening. The front noted with the edged line likely moves through before Midnight. The bright yellow blobs show where the best potential for severe storms would be along the front.)

The front has significant upper-level support. Aloft, winds will be diverging allowing air at the surface to rise. The storms will easily be able to tap strong winds aloft around 50 mph. Significant updrafts going well into the atmosphere, bypassing the freezing level at 10,000 feet will be enough to support large hail. Additionally, winds turning with height (or changing direction) could be enough to generate a few tornadoes.

The threat is great enough that the Storm Prediction Center has much of the East Coast in a slight risk for severe weather two days out already.

Ironically, the forecast for severe weather on Friday, June 1st comes within 24 hours of the 14-year anniversary of the major outbreak on June 2, 1998 across the Mid-Atlantic. A similar situation happened with a strong cold front plowing east from the Ohio Valley. Very warm temperatures ahead of the front were replaced by much cooler, breezy weather in the 1998 set up.

Notice the similarities in the weather map from the morning of June 2, 1998 (below) and where the forecast models show a similar strong front this Friday morning (second image below). The low pressure is forecast to be only 250 miles southeast of the June 2nd outbreak.

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(Archived weather map from 8 a.m. June 2, 1998)

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(Long-term GFS forecast model shows the placement of the cold front on Friday morning)

The wind profile from Dulles International late on June 2, 1998 is seen below. The winds up to 5,000 feet in this sounding are 29 knots with mid-level winds (on the same horizontal line as the number 50 on the diagram) are 46 knots. The strength of the wind field through the atmosphere between the June 2, 1998 outbreak and what is forecast for Friday afternoon (second image below) is very similar as well.

IADSounding(The wind profile from Dulles International on the evening of June 2, 1998. Courtesy of the National Weather Service in Sterling, Va.)

 

ForecastSounding(The forecast wind profile for Friday afternoon)

The June 2, 1998 outbreak produced Maryland’s first F4 tornado (before the Fujita Scale was renamed to the Enhanced Fujita Scale) in a small western Maryland town of Frostburg. In total, 7 tornadoes touched down in the Baltimore-Washington Forecast Office’s area of responsibility on that day.

All-in-all with a severe weather outbreak possible Friday, you should stay tuned to ABC7 Weather Team and WTOP for the latest forecasts and any watches and warnings that could be issued on Friday.

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The dangers of heat and how to stay safe

May 29, 2012 - 12:33 PM
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The heat index reached 95 degrees on Tuesday, prompting a hyperthermia alert.

This week we had our first taste of summer heat and humidity hitting the 90 degree mark for the first time this year. Our local criteria for a Heat Advisory is when the heat index value is expected to reach 105-109 degrees within the next 12-24 hours.

A Heat Advisory may be issued for lower criteria if it is early in the season or during a multi-day heat wave. That is why a Heat Advisory was issued on Memorial Day because it is early in the season, a holiday and because we are not yet acclimated to the heat/humidity.

This recent blast of heat is of course only a prelude to what will likely be another sizzling summer with heat waves that will push the mercury well into the 90’s and perhaps even the triple digits. The combination of heat and humidity can be deadly and while the elderly, infants, children, and people with chronic medical conditions are more susceptible to heat related illness and death, even young healthy individuals can succumb to heat related illness.

So, before we get into the daily blazing heat and humidity of summer, I thought it would be a good time to review the dangers of heat and how to stay safe.

There are four main dangers of heat that include heat cramps, heat syncope or fainting, heat exhaustion and heat stroke.

-Heat cramps can occur when you exercise in hot weather which may lead to muscle cramps. This occurs because of brief imbalances in body salts but cramps can become less frequent as a person becomes used to the heat. Additionally, drinking sports drinks, keeping yourself hydrated and taking it easy can keep this from happening.

-Heat syncope or fainting can happen when someone who is not used to exercising in the heat. This occurs when a person experiences a quick drop in blood pressure but as with heat cramps this can be combatted by taking breaks and keeping properly hydrated.

-Heat exhaustion is also another major danger of heat and occurs when a person losses fluid and salt through perspiration and doesn’t replace them. The body temperature may rise, but not above 102 degrees and in some cases hospitalization is necessary especially for the elderly. The last and most serious danger from heat is heatstroke.

-Heatstroke is when the body’s thermostat gets thrown off and the body temperatures can rise to 105 degrees or higher. Symptoms of heatstroke are confusion, unconsciousness, and lethargy. If you or someone thinks they may be suffering from heatstroke they need to seek medical attention immediately as death can result if not treated.

While the heat can be dangerous, if you use common sense and follow some simple preventative rules, you can stay safe and cope with the heat.

First, make sure that you drink plenty of fluids and don’t wait until you are thirsty to drink. During heavy exercise in the heat you need to drink two to four glasses (16-32 ounces) of cool fluids each hour. Sports beverages can be used to replace the salt and minerals you lose when you sweat.

Next, wear appropriate clothing and sunscreen. Choose lightweight, loose fitting and light colored clothing. Sunscreen is important because if you get sunburn it affects your body’s ability to cool itself and actually causes loss of body fluids. If you must be outdoors try to be outside either in the morning or the evening hours.

You need to pace yourself, take frequent breaks, and try to find a shady place to rest. Of course the best way to avoid heat related health issues is to stay indoors and soak up the air conditioning.

Please remember never to leave infants, children or pets in a parked car, even if the windows are cracked open. There is no excuse for this. Even with the windows cracked open, interior temperatures can rise almost 20 degrees within the first 10 minutes. Also, if possible bring your pets indoors. If that is not an option make sure they have plenty of shade and fresh, cool water.

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Memorial Day Sunrise over Washington, D.C. (TIMELAPSE)

May 28, 2012 - 07:11 AM
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It'll be a hot and humid Memorial Day in our nation's capital with high temperatures around 90°.  Here's a timelapse of the sunrise (5:46 a.m.) over Washington, D.C. this morning.

 

 

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First 90° Day In D.C. On This Unofficial Start To The Summer Season

May 28, 2012 - 04:00 AM
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We're feeling the HEAT and HUMIDITY this Memorial Day Monday -- highs climbed into the upper 80s and into the 90s in some spots.  In fact, here in Washington, we made it to our first 90° day!  Not only are temperatures close to 10 degrees warmer than average, but you factor in the humidity and it feels like the upper 90s! 

NOAA Heat Index

Hot Memorial Days can be good if you plan to head to the beach or kick-start the summer season at the pool.  Keep in mind, the 2012 summer solstice doesn't arrive until June 20th at 7:09 PM, but it certainly feels like summer with the heat and humidity.

So does this Memorial Day stand out with the hot, summer-like temperatures?  Not quite!  In fact, last year, Memorial Day Monday climbed to 96° in D.C.!  No record, though.  The record for May 30th (when Memorial Day fell in 2011) is still 98° set back in 1991.  The record for this Memorial Day is 97° (1941). 

Here's how high temperatures got over the last few years on Memorial Day:

2010 -  91° 
2009 -  82° 
2008 -  85° 
2007 -  86° 

It was certainly a hot Memorial Day in Washington, and again, our first 90° day!

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Memorial Day Weather: D-Day Forecast and the Sands of Normandy

May 28, 2012 - 12:45 AM
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Each Memorial Day we honor and remember the service and sacrifice so many have given to our country. I was struck by a reminder of that sacrifice by a recent study that found about 4% of the sand on Omaha Beach in Normandy was pieces of shrapnel still left from the invasion of 160,000 Allied soldiers and battle of Normandy, June 6, 1944, almost 68 years ago. That D-Day landing was postponed by one day by one of the most historic weather forecasts of all time. The invasion was originally scheduled for June 5, but 24 hours before on June 4, three teams of meteorologists, somewhat divided on opinions, recommended that the invasion be postponed for 24 hours because of a forecast of a very bad storm that day. 

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Weather map of June 5, 1944

That forecast proved correct. An invasion on June 5, in hindsight, would have been a catastrophe with the rains and gale winds. The forecasting teams, one American and two British, were coordinated by Group Captain James Stagg. The forecasting teams were not in agreement about the forecast for the next day, but one of the leaders of the team from the UK Meteorological Office was a Norwegian meteorologist Sverre Petterssen

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Sverre Petterssen a Norwegian meteorological officer

who based his forecast on fundamental physics and upper air observations from Allied aircraft over the Atlantic, rather than just looking at analogous weather patterns as was the more general way of weather forecasting by the American team. Petterssen’s forecast along with other meteorologists working as a team proved correct and the break in the weather gave the D-Day landing a critical element of surprise.  Within a few days, the change of tides would have meant a postponement of an invasion by a month. Two weeks after the invasion and after the Allied forces were moving forward, another fierce storm hit Normandy, but the invasion, though not in ideal weather had been a success. 

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Almost 25 years after contributing to one of the great weather forecasts of all time, Dr. Petterssen, was a visiting professor at the State University of New York at Albany and taught a course in synoptic meteorology.  

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Synoptic meteorology the analysis and prediction of storms and large-scale weather features. I was indeed fortunate to be student in Dr. Sverre Petterssen’s course that year and was reminded of it when I saw the story on the sands of Omaha Beach today.

 

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Ball Lightning: A mysterious phenomenon!

May 25, 2012 - 05:00 AM
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Lightning captured by Raul Heinrich striking the CN Tower in Toronto July, 23rd 2008

Let's just make this clear from the get go: we know little to nothing about this phenomenon. In fact, for many years ball lightning was thought to be something made-up or misinterpreted by eye witnesses. Through the rapid increase in photographic and video technology, we've added many more cameras to the world and through these observations scientists have begun to acknowledge that ball lightning exists... but now the real questions arise: what is it, and how does it form?

So we’ll start with the basics. Regular lightning itself is still quite an enigma to researchers, but at least we feel we’re beginning to grasp the foundations of how it’s created. It’s generally accepted that as a thunderstorm begins to form from a rapidly rising current of air (updraft), the water droplets eventually reach the freezing level where ice begins to form. Scientists now believe it’s the interaction between ice and water in a thunderstorm where electrical charges are exchanged and eventually dispersed into the cloud. In the most basic sense, most storms gather a positive charge at the top of the cloud while a negative charge forms at the base. Knowing that opposite charges are attracted to each other, the negative charge at the bottom of the storm induces the ground below it into a positive charge. If the storm eventually builds up enough of a charge, the energy is released as a lightning bolt from the cloud to the ground. Remember how we just talked about the negative and positive charge in the cloud itself? This difference can also create a lightning bolt within the cloud. In fact, most lightning bolts are intracloud lightning… roughly 75%-80% of the lightning a cloud produces. 

Lightning strike panorama over Bucharest, Romania on June 26th, 2007 by Catalin.Fatu at en.wikipedia
Lightning captured by Raul Heinrich striking the CN Tower in Toronto July, 23rd 2008

That’s basically how lightning forms, so what about “ball lightning”?

Since the dawn of man, people have given many descriptions of ball lightning. Most accounts talk about the sight of a glowing ball of light (about the brightness of a 100 watt bulb) anywhere from the size of a tennis ball, to the size of a beach ball. Almost all accounts talk about seeing some sort of glowing ball in the air. Sometimes reports have the ball dropping towards the ground and moving around very quickly and erratically. Some people say the ball travelled from outside to inside a house or building through and open door or window, sometimes scorching the floors and walls on its way before it vanishes. Other stories tell tales of the lightning balls fusing metal together, disrupting electrical wiring and/or equipment, and even scorching or killing people! Ball lightning accounts range from people experiencing highly electrical thunderstorms, to others saying the ball burst out of “thin air” from a gentle rain on a cloudy/cool day.

The leading theories around ball lightning all eventually point to the formation of something called “plasma”. Plasma is something thrown around in all sorts of science-fiction books and films, but it is a real thing - most recently associated with flat screen televisions. Plasma (as defined by dictionary.com) is “a highly ionized gas containing an approximately equal number of positive ions and electrons.”

WHAT??? 

Let’s look at something you’re probably a bit more familiar. You’ve seen one of these, right? 

Photo courtesy: Luc Viatour / www.Lucnix.be

I like to sum up the notion of plasma as electrified gas/air that acts more like a fluid. Now imagine taking the “electrical strands” you see in the toy plasma lamp, scrunch them up into a ball and that’s pretty much what experts believe to be ball lightning. 

So imagine that you’re just minding your business, when all of a sudden you see a bright flash, hear a tremendous boom, then see a glowing ball in the air! I find ball lightning so interesting because it’s seems to be a phenomenon that people rarely even think about, and when it does occur it’s a complete surprise! 

Ball lightning stories even have a local flavor. Our own chief meteorologist Doug Hill has a family account of witnessing a ball lightning event! According to his mother and her brothers and sisters, when living just right off the Inner Harbor in Baltimore a lightning ball came right through a wooden framed screen door in the front of the narrow, shotgun style home, travelled down the wooden floor leaving scorch marks in its wake, before exiting through the back screen door! 

Through researching this topic, I found a great website that has an extensive log of personal ball lightning accounts: http://amasci.com/weird/unusual/bl.html
There also happens to be a really cool case study that was performed on a ball lightning account in Queensland, Australia back in 2002. Here’s a link to their page: 

http://www.ernmphotography.com/Pages/Ball_Lightning/BL_Gallery1.html 

Lucky for us, a photographer caught the event! Here are some of his photos:

Courtesy of: ERN Mainka
Courtesy of: ERN Mainka
Courtesy of: ERN Mainka

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Memorial Day Weekend Beach Forecast

May 24, 2012 - 03:15 PM
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Some changes have been starting to take place in the weekend beach forecast. Overall it still looks like it will be nice for the Delmarva Beaches down to Virginia Beach. There are questions though as a new system has developed just to the east of Florida which may become another tropical system. This could really put a big question mark for the forecast for the Outer Banks and the Southeast. Here are our latest thoughts.

All the information you need to know about the beaches here!

Delmarva Beach Resource Guide

Saturday & Sunday Beach Forecast

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2012 hurricane season forecast: Near normal hurricane season, NOAA says

May 24, 2012 - 12:42 PM
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Well, it’s that time of the year again when we will be monitoring the tropics daily for potential tropical development. The 2012 Atlantic Hurricane Season officially begins June 1st and will conclude November 30th. However, storms can and have formed both before and after the official season just like we saw already this year with Alberto. Tropical Storm Alberto formed off the South Carolina coast on Saturday May 19th and then weakened into a post tropical depression as it moved back into the cooler waters of the Atlantic by May 22nd.

The official forecast from the National Oceanic and Atmospheric Administration (NOAA) was released this morning, May 24th at 11:00 EST. Their forecast is for a near normal hurricane season with a 70 percent chance of nine to 15 names storms. Of those, four to eight will become hurricanes with maximum sustained winds of 74 mph or higher. From the four to eight hurricanes they believe that one to three of those storms will become major hurricanes, which are category 3 or greater. An average hurricane season produces 12 named storms, 6 hurricanes and 3 major hurricanes.

It is important to note that no matter if the official forecast is for an above, below or average number of hurricanes that preparation is paramount. For example, in 1992 that hurricane season only produced six names storms however one of those storms was Andrew. Andrew made landfall in south Florida as a Category 5 storm that devastated that region. A quote that is always in my head is that it only takes one and with memories from Irene still fresh in resident’s minds everyone should have a hurricane plan and be prepared to use it should a storm take aim on our area once again.

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D.C. Thunderstorm: Arlington Timelapse - Awesome Lightning Bolt!

May 23, 2012 - 07:40 PM
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Heavy rain, thunder, and LIGHTNING... oh my! 

Check out this timelapse from atop our ABC7 Studio in Arlington (courtesy of our WeatherBug camera). As a strong storm cell moved over the area, you can see the dark skies, raindrops on the camera lens, and an awesome end frame... take a look!

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Timelapse of colorful sunrise over Washington, D.C.

May 23, 2012 - 09:13 AM
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The clouds and partial clearing set the stage for a picture perfect sunrise over our nation's capital this morning.  If you hit the snooze button and missed the spectacle, the WJLA roofcam has you covered and captured the scene in this timelapse video.  Enjoy!

 

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Global Warming

May 23, 2012 - 05:01 AM
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“THIS IS AN EXTREMELY DANGEROUS TORNADO WITH COMPLETE DEVASTATION LIKELY. … SEEK SHELTER NOW! … MOBILE HOMES AND OUTBUILDINGS WILL OFFER NO SHELTER FROM THIS TORNADO — ABANDON THEM IMMEDIATELY.” Pretty ominous statement but this and other similar apocalyptic statements from the National Weather Service have been, and will be issued experimentally this tornado season in Missouri and Kansas in an effort to have us make a better life or death decision. Yet only 60 years ago, the then U.S. Weather Bureau would not issue a tornado alert for fear of causing widespread public panic.

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The first public tornado risk statement was given by broadcast meteorologist, Harry Volkman in March 1952, who was afraid of being arrested by the government for communicating (correctly) there was a tornado “risk” for central Oklahoma. My  science of meteorology has made incredible advances in understanding and forecasting short-term life threatening weather such as tornadoes. Do we know everything? Is the science of tornado prediction “settled”?  In Joplin, MO, in 1970, in 1990 or now? Of course not. There is much to learn and still about 70% of tornado warnings are false alarms- there is no tornado. But we make a decision. Sometimes as many tragic stories from the devastating tornado season last year, the decision was not take shelter. Lives were lost. But the terrible tornado season last year also lead thousands of Americans in or near “tornado alley” to make the decision to purchase a “safe room” for their home. Joplin, Missouri, the city almost destroyed by a rare EF-5 monster one year ago, will spend $26 Million (with federal funding) for safe shelters for their schools. A good decision? Probably after the tragedy and near tragedy of last year, yes a good decision. Forecasting tornadoes still has many uncertainties, yet if a tornado warning is issued, we all have to make a short-term decision. Now more of us will head to a safe room and not worry if this is another false alarm. There will never be 100% certainty in forecasting tornadoes, but we will make a “best”decision.

The science of meteorology through satellite observations, computer “models” and continuing basic and applied research has also made impressive progress in forecasting the track and intensity of hurricanes.

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Rather than minutes or hours, Americans in the possible path of a hurricane have to make a decision. Days ahead.  Do I evacuate? Do I believe the forecast? There is that cone of uncertainty . . . do I take a chance? Is the science of hurricane forecasting, “settled”? Again of course not, but decisions, human and economic decisions effecting sometimes millions are made, knowing the exact outcome is uncertain.

Supposedly the great Yogi Berra said, “It’s tough making predictions, especially about the future”. However, we make decisions every day about some prediction whether it is the traffic during rush hour, canceling a weekend picnic or headed with my family to a shelter when I hear a tornado siren.

Why should a decision about what action we take based on expert outlooks for our climate and national, regional and local changes 50 or 100 years from now be any different than making a decision, taking actions, minutes, hours, days or even a week from now knowing the tornado or hurricane, snow storm or seasonal forecast is also uncertain. The science is not settled but the modern science of forecasting short term weather is solid and the modern science of estimating long term climate changes (yes global warming and it impacts) is solid.  Are either 100% accurate?  Do we require 100% accuracy before making a decision or taking action?  Ask folks in Joplin what they will do the next time a tornado warning siren sounds.

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We make decisions every day without 100% certainty, other than the sun will come up. The science of short-term weather and longer-term climate is solid. Neither is 100% certain but look where we have come in 60 years from no alerts to “You could be killed if not underground or in a tornado shelter”. Where will we be in making climate related decisions 60 years from now? Let’s hope history gives us some perspective for our future shared decisions.

 

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Joplin Tornado: One Year Later

May 22, 2012 - 10:42 AM
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It was a Sunday afternoon, 5:34 PM, one year ago from today, when a supercell thunderstorm spawned an EF5 tornado over Joplin, Missouri.  In just over a half hour, residents' lives changed drastically.  Despite fatalities, property destruction and damage, and a forever changed landscape, the people of Joplin and surrounding communities have come together to show the true power of Americanism. 

Going back to that devastating day, we start with a look at the radar and storm relative velocity at 5:48 PM on May 22, 2011.

NOAA Radar  

The radar (left) is extremely impressive.  The higher/brighter reflectivity shows the extremely heavy rain and hail.  The area circled is the debris ball from the tornado itself.   A hook echo can also be made out surrounding the debris ball.  The storm relative velocity depicts inbound (green) and outbound (red) winds.  The tight couplet shown on the right indicates strong rotation. 

Over 200 mph winds, tracking six miles across the city of Joplin, caused more than a thousand injuries and 160 fatalities.   The Joplin tornado is the deadliest tornado on record since modern tornado record keeping began in 1950 and falls 7th on the list of deadliest in U.S. history.

Google Maps - Path of Joplin Tornado 

 

 

 

 

 

 

 

 

               2011 was an unusually active year for tornadoes.  It ranks second as the most active year for tornadoes with 1691 tornadoes recorded (2004 most active year with 1817 tornadoes).  In May 2011, 326 tornadoes were reported.  There were 178 fatalities in May 2011, with 158 of those fatalities due to the Joplin tornado.

NOAA - Joplin Damage

In an effort to prepare and protect people in the wake of severe weather situations, many new initiatives are evolving.  The federal and local (Missouri) goverenments are coming together to fund "weather safe rooms" in new Joplin schools being built.  NOAA continues the "Weather-Ready Nation" intitiative to help spread better information, so people make better decisions.  

Among the overwhelming images of a city succumb to a natural disaster of this magnitude, come images of renewal and revival. The StormWatch7 weather team compiled a photo gallery on the one year anniversary.

On this one year anniversary of the Joplin tornado we remember all those who lost their lives and loved ones in this tragic weather event and the people who continue to pick up the pieces after a life changing event. More photos in this gallery of before and after and today in Joplin

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Early Season Tropical Scare

May 20, 2012 - 10:32 PM
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A low pressure that sat and spun over the Gulf Stream off the South Carolina Coast officially became named Tropical Storm Alberto on Saturday. The storm will start to move away from the Carolina Coast next week, eventually fading into the distance in the cooler water of the North Atlantic by the middle and latter half of the work week. Of course, Alberto formed two weeks before the official June 1 start to the Atlantic hurricane season.

Alberto

Story Image: Visible satellite imagery from Saturday, May 19th showing Tropical Storm Alberto forming off the South Carolina Coast. Courtesy of the Space Science and Engineering Center (SSEC) at the University of Wisconsin-Madison.

Prior to Alberto, Tropical Storm Aletta stirred things up in the Eastern Pacific at the beginning of the week....forming just one day shy of the start of the Eastern Pacific’s hurricane season. That storm was hundreds of miles from Mexico and the southern California Baja and posed no threat to land.

What we may think of as an “active” start to the tropics actually awakened a “tropical drought” on Earth! Believe it or not, Aletta broke what had been a 41-day streak with no tropical cyclones on the globe! According to the U.K. Met Office, this was the longest stretch without a tropical cyclone in at least 70 years!

Speaking of tropical withdrawl, a record number of days have passed between major U.S. hurricane landfalls. As a matter of fact, that record was shattered even before Christmas! 2,232 days had passed way back on December 4, 2011 since Hurricane Wilma made landfall along the Gulf Coast as a category 3 storm in 2005. Previously, it was between September 8, 1900 and October 19, 1906 where no major hurricanes made landfall in the U.S.

record

Graph courtesy of Roger Pielke, Jr., professor of environmental studies at the Center for Science and Technology Policy Research at the University of Colorado at Boulder.

So, with two tropical systems kicking things off early this year, should we be extra cautious of how the 2012 Atlantic Hurricane Season might turn out this year? Not necessarily. Let’s look back at two other seasons in recent times where an early start didn’t necessarily equal a busy season.

In 2009, the first tropical depression of the season formed in the same vicinity as Alberto on May 29th. The storm only had a life cycle of one day as a vigorous upper disturbance kicked it off into the cooler water faster than Alberto will be next week. In the 2009 season though only 9 named storms developed. This is two less than the average of 11 for a season.

In 2003, Tropical Storm Ana was the first tropical storm on record in the North Atlantic basin. It became a subtropical storm early on April 20th then later that same day transitioned to a tropical storm as microwave data suggested it had a warm core. Ana formed within 300 miles of Bermuda and then wondered east through the Atlantic, so it posed no threat to land.

An early named storm in that season (2003) lead to an active year with 16 named storms.

The major factor at stake for the upcoming 2012 season is a transition to a weak El Nino which tends to increase upper-level wind shear in the Atlantic, suppressing tropical formation a bit. Therefore, the forecast is for an average to slightly below average season for tropical storm formation. So, while we got an early start, things could level off as the season wears on and El Nino tries to make an appearance.

Of course, stay tuned to the ABC7 Weather Center and WTOP Radio for the latest on any tropical development that may head our way this summer and fall!

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Summer Outlook : Another Very Hot One? What the Team Thinks

May 18, 2012 - 05:50 PM
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Here we are only 1 week away from the Memorial Day Weekend, the "traditional" beginning of summer. After so much record heat last summer (remember 104° July 29?)  many folks are not ready for heat and humidity. Look at our recent poll.  Boy only 15% say, "Bring it on"

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But ready or not, we can't escape summer heat and humidity completely in Washington. So what will the coming summer be like? Another scorcher such as last July, out hottest month ever, with 25 90° days and that high of 104° on July 29th?  Or a break in hot humid summers?  Four of of the last five summers have been hotter than average. Each of our entire weather team has an opinion and the elements we look at include ocean- atmosphere links such as El Nino and La Nina . . . ENSO is neutral right now.   

 

 

 

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One element I look at is soil moisture and drought and right now much of the south and southwest soil is dry and much of the area in drought.

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It’s conditions like this that can give what we meteorologists call “feedback”. The soil, being very dry, does not absorb heat the way wet soil or the oceans do, but rather reflects heat back into the air and thus the heat feeds back or builds.

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I’m afraid with that pattern now established and our warm pattern (12 of 13 months now above average) we are in for another hotter than average summer. But not as hot as last summer (+3.4°) or the summer of 2010 (+3.6°). I know that is being darning. So here is the rundown of what we all think about the coming summer.


Myself – Another hot one - temperatures above average and 35-45 90° days for the summer


Doug - I think it will not be a long, hot summer. Rather a “normal” summer is more likely, I think. If anything, might be a fraction below average temperature wise. Rainfall subject to tropical effects.

Alex - I'm a statistics guy and will go with persistence here. 7 of the past 10 summers have been above normal. I'll continue that but not nearly as hot as the last two. The normal is 77.7 degrees but the last two years have averaged above 81 degrees. I'll go with 78.5 degrees, nothing too excessive!


Adam –I think it'll be a slow start to the summer. We'll have a typical amount of heat and humidity, but I anticipate the final tally of 90 degree days to be near or slightly below average.  To be honest, I don't put much energy into the summer forecast because it's always hot and humid here in the D.C. area - you can't escape it. Sure, some summers are hotter than others and will have a greater impact on sensitve groups of people and some are cooler, but it's still just hot. You'll need your A/C and a pool will always feel refreshing in July in Washington no matter the final statistics.

Brian- Not an extremely hot summer with above average rain. 
Coming off a historically warm March, one may want to leap to the conclusion that the summer will be unbearable. Looking over the past statistics, we have actually had years with below-average summer temperatures following unusually mild, late winter/early springs so don’t fret the cooling bills just yet. Much like we’ve seen the repetitive pattern as of late with extended dry stretches followed up by periods of soaking rain.

Chris - I'm forecasting Summer temperatures that will run "+1.0 degrees above normal."  All told, it will feel like a “typical Mid-Atlantic Summer.” Additionally, I DO NOT think we will have more than one or two periods of prolonged heat (IE: Heat waves) and those periods, IF we see them, would last a week or less. Getting to specific numbers (31-36) 90° d or greater days this Summer, with the majority occurring in July.  I will add that I think this Summer will be rather active in terms of severe weather and storms, so make sure have your emergency kit in order and ready to go. Last, I believe that precipitation this Summer will be average or slightly above average. The wild card in all of this, of course, would be the impact of any tropical system.

Eileen - slightly above average temperatures overall with average to slightly below precipitation

Devon – I'd take a wild stab and say our summer will average "above" for temperatures and average "below" for total rainfall at Reagan National by the time we tally up the initial info. What do I think that REALLY means? I'd say a stretch or two (one or two weeks) of very hot weather, with generally a bearable summer but lacking in total rainfall... if I'm right, get ready to water!


Ryan Miller - I'm going slightly above average temps due in part to neutral ONI and slightly below rainfall values which could aid in bumping temps up.

Steve-I don’t think it will be as hot as last summer, but don’t look for prolonged periods of below average temperatures either. Around 40 90-degree plus days with at least 10 in the upper 90s and a few "super ugly hot days." Total number of days with rain or showers will be limited, but when it does rain, look for significant totals quickly. "

So the final tally is roughly 7 to 3 for a hotter than average summer in the DC area.  A guarantee?  Surely you jest.  There is no skill in day to day forecasts beyond about 7 days so all we can really talk about is the general outlook for the coming summer.

And can't forget what our colleagues at NOAA's Climate Predictiion Center think. The very latest outlook 

ZZZZZ

 

So be prepared, but if you don't like heat,  hope that this at least comfortable, low humidity pattern continues . . .and Doug, Adam and Brian are correct and myselfI and 5 of our team are wrong.  Of course keep watching Channel 7, News Channel and right here on WJLA.com.  We'll keep you posted throughout the summer hot, humid or cool and comfortable.

 

 

 

 

 

 

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Delmarva & Outer Banks Region Beach Forecast 5/19 & 5/20

May 18, 2012 - 01:33 PM
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If you are heading to the beach this weekend, I'm sorry to tell you but it won't be warm and sunny. The pesky low which has been sitting off the southeast coast will have an affect on the Eastern Shore, bringing breezy winds and cooler temperatures as the air flows off the cool ocean. Water temperatures are still in the lower 60s so it makes sense why the air will be so cool. If you are going, Saturday will be the nicer of the two days with a little more sunshine and warmer temperatures than Sunday.

Saturday Beach Forecast for Delaware & Maryland Beaches

Sunday will only be a few degrees cooler overall but the added cloudcover will make it feel even cooler. Be sure to bring the sweatshirt and pants if headed down to sit on the beach. We'll be adding a forecast for the Virginia Beach area and Outer Banks for next weekend's Memorial Day Weekend Beach forecast. Sorry you can't enjoy a warm weekend the quiet week before Memorial Day! Early model guidance is depicting a very warm weekend next week!

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Sun chasing the moon (TIMELAPSE)

May 18, 2012 - 10:06 AM
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There was just enough of today's waning crescent moon left (6% illumination) to see the sun chase it into the sky early this morning. Enjoy this timelapse from the WJLA roofcam:

By the way, there will be a solar eclipse on Sunday, but we won't be able to view it here on the east coast.

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Solar Eclipse 2012

May 17, 2012 - 11:39 AM
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After a sighting of the supermoon earlier in May, get ready for another spectacular night sight this coming weekend -- a solar eclipse.  Now before I get your hopes up, if you live on the East coast, you won't be able to see the eclipse; however, people in the West and Southwest will get quite a show. 

Diagram of an eclipse 

The solar eclipse will occur Sunday, May 20, 2012. A solar eclipse occurs when the new moon passes directly in between the Earth and the Sun. Now there are different types of eclipses: partial, total, annular, and hybrid. The eclipse visible for folks on the West coast, Sunday, will be an annular eclipse.  This is when most of the sun is covered by the moon (roughly 90%), but a sliver of the outside of the sun is visible -- resembling a ring and sometimes referred to as the "ring of fire".  It is important to those viewing the eclipse that they wear protective eyewear.  Even though most of the sun is covered, you still want to protect your eyes.  If you think about it, you're still looking at the bright sun (although much less of it) and that exposure can be damaging to the retina.

"Ring of Fire" in China

I found a great quote from NASA's leading eclipse expert, Fred Espenak of the Goddard Space Flight Center, giving us his take on eclipse viewing.  Espenak says, "I like to compare different types of eclipses on a scale of 1 to 10 as visual spectacles. If a partial eclipse is a 5 then an annular eclipse is a 9."  Expenak went on to say  "On that scale of 1 to 10, a total eclipse is 'a million!".   A total solar eclipse occurs when the moon covers the entire surface of the sun, so everything gets dark -- the sun is completely hidden!  The last total solar eclipse seen from the United Sates was 18 years ago - May 10, 1994.  If you want to see a total eclipse in the U.S., your time is getting closer -- only 5 years to go. 

So why won't residents in the East coast get to see the annular eclipse?  Well, the sun will have already set by the time the annular eclipse occurs.  The few that will be lucky enough, in the U.S. to catch a glimpse of the annular solar eclipse will be a swath from Northern California to the Texas Panhandle.  The map below also shows where people in the middle of the country will see a partial eclipse.

Even though we, in D.C., won't get to see the eclipse there will certainly be lots of images circulating the internet that we'll be able to ooh and ahh over. 

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The "Sticky" On Humidity

May 15, 2012 - 05:20 PM
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Humidity -- we talk about it often in weather.  We mostly reference the humidity when the weather gets warm, but there is humidity all the time -- it just depends on whether it's high or low.  That then leads to how it "feels" outside.  For example, the three H's of summer you're probably familiar with in D.C. - Hazy, Hot, and Humid.  It's one thing to be hot in the summer with temperatures in the 80s and 90s, but factor in the humidity and that's when it can feel downright uncomfortable... and don't even get me started on what it does to my hair!

So what exactly is the humidity?  And why does it make the air feel so "sticky"?  Let's break it down a little.  Humidity is the amount of water vapor in the air.  It's measured in different ways, but you'll most commonly hear it referred as the relative humidity or the dew point.  The image below gives you a visual of the temperature and the amount of water vapor present (think of the beakers as the atmosphere).  The lower the temperature, less moisture needs to be present for the air to become saturated.  The same thought can be applied for warmer temperatures, but you can see more water vapor can be present.

FAA - http://www.aviationweather.ws/026_Water_Vapor.php

Let's start off with relative humidity.  The relative humidity is the amount of moisture in the atmosphere relative to the amount that would be present if the air was saturated.  It sounds confusing, I know.  The relative humidity is expressed as a percentage and is based off the temperature.  We tend to associate rainy days or humid days with higher humidity, which can be true, but it can also be misleading.  Often times the humidity is near 100% in the morning.  The reason is the air is typically cooler in the morning and cooler air holds less water vapor - you can go back to the image above to help visualize this.  The relative humidity is a good measure of humidity; however, it can be a little tricky to understand.  I have always been a fan of the dew point.  

The dew point is the temperature the air has to "cool" to, to become saturated.   I put the word "cool" in quotations, since the dew point can be a fairly high temperature.  Now the dew point temperature will never be greater than the air temperature, but the closer the dew point is to the air temperature, the more water vapor in the air, and the more "sticky" or muggy it feels.  Usually when the dew point gets above 65°, that's when it starts to feel uncomfortable.

For example, if the temperature is 86° and the dew point is 70° it will actually feel like 91°!  The reason it feels hotter is because it's harder for our bodies to cool us off when there is higher humidity.  Our bodies use a process of evaporative cooling, so if there's a lot of water vapor in the atmosphere, it is much harder for our bodies to cool off, as compared to a day when there is less water vapor and lower humidity.  The chart below shows the Heat Index which calculates the temperature and relative humidity to determine how hot it feels to our bodies.  Hot temperatures combined with high humidity can be very dangerous.

NOAA Heat Index

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