Power still out for hundreds of thousands in our area and the Heat Index is going to be 100º or higher again today.  But what is the "Heat Index" and where did it come from?

I’m going to date myself with this post, but here goes. I grew up before there was such a thing called the “heat index.” (I almost grew up before there was a “wind chill,” too. Almost.) And yet I still sort of knew how hot it was during summertime in the beautiful Hudson Valley. At least my body did, and that’s what the heat index is all about, a “feels-like” temperature.

But how hot would you think it was if you didn’t know the temperature? The great baseball player Satchel Paige – baseball has never been the same for me since the Dodgers left Brooklyn – once tackled this sort of question when he was asked how old he was. Paige replied, “How old would you be if you didn’t know how old you are?”

Similarly, the answer for temperature is you will think it’s as hot as your body feels. When the air is hot (forget about humidity for one moment), you perspire. Your body does not want you to be broiled in the sun. That perspiration evaporates from your skin and removes heat. How's that? Gas, in this case water vapor, has more heat energy than liquid water (sweat) and liquid water has more heat energy than ice. It takes heat to change water from liquid to gas (think about heating water on the stove) and when your sweat evaporates, it moves heat from your body into the air.

When the air is very dry, you may actually feel chilled by moisture evaporating from your skin. But not this July. That's because there is lots of water to the air – yes, that sticky humidity. Oh no, he’s going to use that dreaded term “dew point”! You bet, and now look at this dew-point chart.

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Yes, the title says heat event. I didn't to call it a heat wave as the past 12 days haven't all been abnormally hot. As some of the days have, that's what I'll be addressing in this blog. I wanted to come up with a list of 10 things that you may not know about this current stretch of hot weather.

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Every 10 years climate averages, called “normals” are calculated and then used by weather service offices across the U.S. These numbers are then integrated into consumer climate products through every National Weather Service Office webpage and displayed on almanac pages at local TV stations, such as here at ABC7 during each newscast. These averages are compiled from 30 years of consecutive weather data.

The current climate normals are based on the 1971 to 2000 time period and were released in 2001. Prior to this, the numbers were crunched from the 1961 to 1990 period. Climate normals first started in 1956 after the 1921 to 1950 period.

The freshest 30-year period of 1981 to 2010 normals were published by the National Climate Data Center in Asheville, N.C., earlier this month. Starting on Monday, August 1, 2011, each National Weather Service office across the U.S. will begin using these updated climate normals in daily operation. Therefore, average yearly, monthly and daily highs and lows and precipitation will be updated by our local National Weather Service in Sterling, Va., at the start of the new work week.

When comparing the 1971 to 2000 normals with the fresh 1981 to 2010 normals for Reagan National Airport that will be released Monday (numbers listed are in degrees Fahrenheit), average temperatures for each month of the year have increased, with the most significant change noted in January:

There are a few important weather events that could have skewed the numbers for this new set of normals in the Washington/Baltimore area.

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Attention, residents of Jim Hogg County! A major storm roaring out of the Gulf of Mexico is about the take your 10-gallon hats and fling them up into sky like so many skeet pigeons. Strap 'em down, boys!

And while you're at it, strap down those mobile homes and shrubbery as well. When Tropical Storm Don's winds begin to crank up after midnight tonight, the National Weather Service is warning that

MINOR DAMAGE MAY OCCUR TO OLDER MOBILE HOMES. RESIDENTS SHOULD MOVE LOOSE ITEMS INDOORS... SUCH AS GARBAGE CANS AND OUTDOOR FURNITURE...AS THEY WILL BE BLOWN AROUND. NEWLY PLANTED OR YOUNG TREES AND SHRUBS MAY BE UPROOTED IF NOT SECURED PROPERLY. ISOLATED POWER OUTAGES WILL BE POSSIBLE.

Don's twirly center is located right now 120 miles east/northeast of Brownsville, Texas, which itself is about 160 miles south of Corpus Christi. While not of hurricane strength, Don does have winds spinning at nearly 50 m.p.h., enough to create a minor risk of tornadoes, as well as a significant payload of precipitation. Some areas south of the tropical storm could get up to 7 inches of rain this weekend, enough to cause roadway flooding. That's probably a good thing in the long run for Texas, where three quarters of the state is in the worst stage of drought.

This is the fourth tropical storm for 2011's hurricane season, which is expected to be a frenzied one. Watch Don whistle over the Gulf toward the mainland in ABC7's hurricane cam. Below is the latest image of the storm taken today by NASA's Terra satellite:

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A sticky, white-hot thermometer over at Reagan National just hit 102 degrees. That reading slaughtered the old 1993 record high of 99 degrees. The rising heat has also beat the 97-degree record at Dulles and is sliding up to knock over the 99-degree record at BWI. Going outside feels like sticking your head into an oven.

Should we get used to it?

Yes indeedy, say scientists from the U.S. government, Cambridge University and elsewhere. They've compiled a few illustrative, sweat-inducing maps showing two different scenarios in the near future, depending on how much we control greenhouse gases. (The maps are included the 2009 report, Global Climate Change Impacts in the United States.) First, take a look at the number of days from 1961 to 1979 where the heat surpassed 100 degrees:

Slices of California, the Southwest and the Southern Plains in Texas and Oklahoma had several weeks of above-100-degree days. Everybody else, including the District, was lucky to get 10 days where the heat maxed out above 100, and many states didn't get any. Nice. Now let's see what could happen as the climate timeline begins to split.

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Yes, another day, another record high temperature in the D.C. area. Seems like a bit of a broken record (pun intended?) with the past 12 days being at or above 93 degrees. Well here is the nice forecast for the beaches this weekend, just remember to liberally apply the suntan lotion!

Saturday

Mostly Sunny, Nice

Highs: Lower 90s

A cold front will lie across the region on Saturday bringing with it a few added clouds, but overall I still think we can call it mostly sunny. High temperatures should top out in the lower 90s and a northerly breezy will help make it feel quite nice if you're out on the beach.

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In what might be a first for many digesters of weather news, a consternating phenomenon best described as a "mineslide" has just occurred in South Korea.

According to varying estimates, Seoul has received between 17 and 26 inches of rain since Tuesday, an amount putting to shame the 18.4 inches of precipitation that D.C. has gotten since the beginning of 2011. The almost 12 inches of rain that dropped on Wednesday reset Korean records for one-day rainfall. The result has been raging floods and powerful mudslides that have killed more than 50 people, destroyed thousands of buildings and strolled away with some of the country's strategic ordnance. The L.A. Times' John Glionna reported from Seoul yesterday (which was actually today, in Korea):

Military officials scrambled to retrieve explosives swept away by the storm. In one incident, a military ammunitions depot collapsed under a landslide, and officials said only half of the explosives, including 93 land mines, had been found.

They also worked to retrieve numerous Korean War-era land mines that were dislodged by the storm from grounds near an air-defense unit outside Seoul. The officials warned residents that 10 of those mines remained missing.

Glionna then goes on to quote a military flack saying how they don't expect to find many of these errant mines. Perhaps in cases like this, when mines leave the nest you just have to respect their decision and let them be?

Oddly enough, the Korean meteorological agency doesn't have a lot to say about the cause of this rain, in English at least. (It does have a very cool English page devoted to local dust storms that can turn snow bloody red, which were called Woo-To in 174 A.D.: "At that time, the people believed that the God in the heaven became so angry that they lashed down dirt instead of rain or snow.") But The Hankyoreh delivers the meteorological dirt in this story on Korea's "perfect storm":

The monsoon season finished on July 17, but now Seoul has been hit by a deluge due to a strange distribution of air pressure.

The main cause of this downpour was unstable air in the skies above the central region of South Korea. Generally, warm, light air stays in the upper layer of the atmosphere and cold, heavy air in the lower layer. This time, however, warm air from a northern Pacific anticyclone flowed into the mid and lower layers, causing further instability. When this happens, heavy rain falls for a short period in specific areas. Because of this, new hourly precipitation records were set in several areas.

Want to see what those landslides look like? Follow the jump for an uneasy video taken from an apartment balcony of a brontosaurus-sized wall of muck overtaking a South Korean roadway.

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Totally not awkward.

Was Newt Gingrich popping Teamocil back in 2008? Because he certainly seems to be acting all warm and fuzzy and kind of out of character in this TV spot about climate change, starring no other than GOP arch-nemesis Nancy Pelosi.

This week, the hangover seems to have hit him. On New Hampshire radio station WGIR, Gingrich said that he "probably wouldn't" do another global-warming spot, because this last one had been "misconstrued." Gingrich claimed: "Look, I was trying to make a point that we shouldn't be afraid to debate the left, even on the environment."

So who misconstrued the ad? Well, probably the same Tea Party folks that Gingrich is hoping will support him in his 2012 presidential run. And it's no wonder why: He certainly sounds like a man who believes the government should dive with both hands into this climate-change problem. Take a look at the ad below, which was sponsored by Al Gore's Alliance for Climate Protection (now the Climate Reality Project), and see how little "debate" is going on.

(At least on his website Gingrich is keeping it real: His "American Energy Plan" would kill off the Environmental Protection Agency and force the losers of environmental lawsuits to pay all legal bills of the opposing side.)

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Yesterday I talked about the intense drought in the Horn of Africa that's enabling the spread of famine and in general making life increasingly unbearable for east Africans. We in America are lucky to come across a news story a week about the enduring misery of eastern Africa, but it's something our government has kept a steady eye on.

Ever since the NOAA-7 satellite launched in 1981, world scientists have monitored soil moisture and plant growth and death in Africa. The continuous measuring has allowed for the construction of a map-in-time of the region's hardship. In the past three decades, as you can see in the above image, the Horn of Africa has suffered "extreme" drought (the second-worst form) for about 15 years. The darkest areas represent zones of greatest aridity, and Kenya, northern Somalia and Djibouti all seem particularly prone to hellish climate patterns.

With the current weather outlook, there's not much relief on the horizon, a dismal fact that NOAA calls "another reason for great concern." (Hi-res map here.)

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After another hot week across the D.C. area, what kind of weather can you expect at the beaches? We'll start off by taking a look at Friday in case you are heading down a bit earlier than everyone else.

Friday

Mostly Sunny, Hot & Humid

Highs: Low to Mid 90s

Friday will be the hottest day of the week locally and also the hottest day at the beach if you are headed there through Sunday. Highs should top out in the low to mid 90s under mostly sunny skies. Heat index values should approach the 100 degree mark and winds will be out of the southwest around 5-10 m.p.h.

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Public fountains and reflecting pools will look mighty appealing today as steady deliveries of hot air begin to arrive in the District.

If you were upset during last week’s heat wave, which may have caused 64 deaths countrywide, then you certainly will find the rest of this week extremely disagreeable. Go ahead – leap into the Tidal Basin for a preemptive cool-off.

The culprit behind this heat repeat is an atmospheric ridge drifting across the southeast U.S. that’s blowing warm, moist wind our way. This afternoon, temperatures will crawl up into the mid-90s to make for an eleventh straight day in D.C. above 90 degrees. It’s growing more and more likely that this month will be the hottest July on record for this blighted city. And you’ll feel every hundredth of a degree Fahrenheit of it, thanks to humidity levels that seem to emit from god’s clothing iron.

Oh, and if you have asthma or other respiratory conditions, don't forget not to breathe today. There's a Code Orange air-quality alert in effect.

Friday is best not to speak about. But here goes: The heat index will hit the ceiling and a heat advisory will no doubt be issued as actual temperatures buzz around 100 degrees, melting ice-cream cones and faces across the region (or so it might seem to non-natives). The record high of 99 degrees in 1993 could very well topple as temperatures boil up in the heat-shrouded afternoon.

In times like these, don’t forget to hose down your leafy progeny. This is not good plant weather, unless you're a cactus farmer. Already about a quarter of Maryland is locked into some form of drought.

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Here we are enduring another July of weather records and you, like others, may think it must be because the climate is changing. And that is true, the climate is changing. But it won’t happen until August.

What?

A word of explanation: I and other meteorologists in D.C. rely on the National Weather Service for data on the region’s “normal,” or average, temperatures. (If you want to see my problem with the word “normal” in meteorology, click here.) The NWS averages are based on temperatures over 30 years, which in today’s world means from 1971 to 2000. But that three-decade range shifts as time goes by, and on Aug. 1 the NWS will begin to use a new set of averages based on observations from 1981 to 2010. So this year the climate for all cities, states and most countries will be “changing,” although you probably won’t feel it in any substantial way.

You might wonder, Why 30 years? Why not pick 20 years, 40 years or even a century to form a “climate average”? Well, a story I’ve heard that I can’t verify for certain (but it is a good story), is that the 30-year period was chosen by the German government in the early 1900s for health resorts that claimed to have beneficial weather and needed to show climate data for evidence. For some reason, the Germans decided upon 30 years. Anyway, that amount of time has now been used for many years as an internationally agreed-upon climate-average standard.

So what do the updated averages mean for Washington?

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This epic photo of a storm cloud might make you wet your pants with majesty, but is it real? No source information is available at its home on Digg, although one commenter does point out a seeming resemblance to a "huge angry chicken." It certainly looks like it's been Photoshopped. But then again, so does a lot of nature's best work. What are your thoughts?

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The drought that you may or may not have heard of in the Horn of Africa – it's difficult parsing all the droughts that spread in one of the driest regions out there – is proving to be an enduring, worsening crisis for millions of starving Africans.

Some are calling it the worst drought that eastern African has suffered through in 60 years. Livestock are dropping dead, food prices are through the roof and more than 11 million people (a number that is growing) are in need of food assistance in Somalia, Ethiopia, Kenya and Djibouti. The arid conditions are feeding famines in Somalia, where the United Nations says malnutrition rates have approached 50 percent in some areas, the highest rates in the world.

Tens of thousands of people have died in the past few months. East Africa right now is the world's "worst humanitarian disaster," according to the chief of the United Nations' Refugee Agency. Here's a taste of what's happening:

But maps only say so much. To get a grasp on the human toll of the disaster, try reading this AP account of children left for dead along the roadways. There are also illustrative posts from Mercy Corps about starving cows at the markets and people wandering the desert for weeks looking for food and water. If you're inclined to shed a few bucks for humanitarian aid, head on over to Oxfam or to the International Federation of Red Cross and Red Crescent Societies' donation page.

Politics and warfare play a big part in the famine, but as this is a weather blog, here's what is happening in the climate to account for the parched earth.

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The rush of 300-plus tornadoes in the Southeast this April spread carnage on an order that's difficult to imagine. With nearly 350 fatalities, the epic storms rank as the fourth deadliest U.S. tornado outbreak. Many communities still look fresh from a team of hard-charging wrecking-ball operators.

So, was there anything meteorologists could have done to better prepare for this weather assault?

The folks at NOAA are continually working on that question. To predict severe, tornadic systems of the kind that popped up from April 25 to April 28, one of the things they're looking at is the behavior of lightning as the storms develop. Here's why: Violent supercells that can spawn tornadoes have thick columns of rising air inside their murky boundaries. These powerful updrafts create bursts of lightning in clouds high in the sky, while at the same time cloud-to-ground lightning grows less frequent. By noting this pattern, meteorologists get a good idea of when a storm could drop a twister onto communities below.

One of NOAA's next-generation GOES-R satellites, on target to launch in 2015, will carry a nifty Geostationary Lightning Mapper to sense electric bolts in the clouds and on the ground over the entire United States. For now, meteorologists can use the SPoRT Lightning Mapping Array (part of which is based in Washington, D.C.) to track potentially dangerous systems. Below you can see what the April tornado outbreak looked like through the mechanical eyes of the North Alabama Lightning Mapping Array. The storm that generated the destructive EF-5 tornadoes in Tuscaloosa, Birmingham and Madison, Ala., starts to kick off 40 seconds into the video. Explains NOAA:

The data visualized here are much like those stars, and represent 10,405,546 points that make up thousands of individual lightning bolts from the ground up to an altitude of 9 miles. Each frame of the animation shows all of the measured lightning points in a one minute interval, and the total time span of the animation is 24 hours, starting from 7:00 pm CDT on April 26th. Notice that the large clusters of data points are extremely dense and are located at higher altitudes. These points coincide with observations of almost no lightning ground strikes during severe weather.

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Fed up with this ridiculous heat, a caravan of us traveled to Beckley, W.Va., this weekend for a tour of the defunct Exhibition Coal Mine. Once a crown jewel in West Virginia's coal industry, the mine today functions as a tourist attraction after closing in 1910. But more importantly, it's a lovely 58 degrees in there every month of the year. As long as you don't stand up or breathe too deeply the mine's a great place to cool off during July in D.C. View its dark and deadly mysteries in this photo gallery.

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The color brown marks areas where pop-up lines of bobbing ducklings may appear this afternoon and evening.

The unstable, moist atmosphere above the District has squeezed out so much water today that flash-flood warnings are appearing in several areas in the suburbs. Streams and pooled water will make for a nice obstacle course during your evening commute.

Stay alert under overpasses and in any area where water is running over the road, however small an amount it might be. The National Weather Service already has a report of one vehicle in Howard, Md., washed off of a roadway swamped with knee-deep water.

Here are the details of the standing flood warnings:

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This discouraging footage below shows the mangled remains of two bullet trains after they collided Saturday near Wenzhou in China's Zhejiang province, killing at least 38 people and injuring nearly 200 The cause, according to Chinese authorities, was lightning.

It wasn't that an unexpected bolt from the sky caused a train to go haywire. These conveyances have automatic systems prepared to react in the chance of a lightning strike. In this case, the train that was zapped apparently functioned correctly by shutting down. The second train, however, did not shut down and plowed directly into the disabled vehicle at a substantial clip. Just why that happened is under investigation.

Lightning nailing moving trains isn't unheard of – Japan's shinkansen has gotten toasted before – but if it's happened in D.C. with Metro, I sure can't find evidence of it. Is that because the District has some kick-butt electrical-diffusion technology? Train buffs stay tuned: I have a call out to Metro to find out how our local people-movers deal with surprise electrical attacks.

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At 2 p.m. today, the temperature at Reagan National was just 1 degree below the all-time record of 103 degrees. The heat index, a measure of how scorched your skin feels, was around 120 degrees.

And somewhere out in the midst of this hellish brew, Allyson Harkey is preparing to don an impervious, heat-capturing PVC top for her performance tonight at the Capital Fringe Festival.

“I'm very slick,” says Harkey. “But I don't think I have it any worse than anyone else. We could be naked in there and still be uncomfortable.”

“There” is the Baldacchino Gypsy Tent, the Fest’s central venue and a nexus of misery for festivalgoers and performers alike. The physical specs of the tent make it the perfect heat trap for D.C.’s summer air: It’s set up on blacktop, which radiates warmth like a greasy pizza stone, and during shows flaps come down to block any crosswinds that could clear out the stagnant air.

“There are a couple of fans, but with the lights on it adds few more degrees,” says Harkey, co-artistic director of the musical Cabaret XXX: Les Femmes Fatales. “It's really, really, really hot.” On a scale of 1 to 10, it’s “like, 11.”

As sure as painfully low-budget production values and extreme subjects like dead babies and cannibalism, unbearable heat is one Fringe Fest feature that pops up year after year. The critics carp about it: Maura Judkis, formerly of TBD who now writes for the Post, has created a “Heat Fringedex” that goes up to 2 million degrees, while the City Paper’s Chris Klimek noted that he “had a nice sweat going while standing perfectly still in the Baldacchino Gypsy Tent” last night at 1:30 a.m. (Klimek describes D.C.’s summers as feeling like “a hell-mongrel with halitosis is licking my entire body.”)

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With temperatures topping out around the 100 degree mark again today, the heat is still making its presence felt across the D.C. area. Even the beaches have reached the lower 90s and should hit the mid 90s this afternoon. What about the weekend you say? Don't worry, as promised, we have you covered.

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