Summer is here–at least for us Northern Hemisphere humans. And that means it’s time for beaches, barbecues, and a brief batch of summertime science from your friends at StormForce 31.  Why does summer sizzle so? Our simmering minds want to know!The basic player in summer heat is, you guessed it, the sun. It must be a lot closer to us in the summer than in the winter, right? Not true.

Astronomically, Earth’s a little off-kilter, rotating on its axis at an incline, or tilt, of 23.5 degrees. Why the La-Z-Boy position? Scientists think that sometime early on, Earth got absolutely clobbered by a Mars-sized protoplanet in a spectacular collision of worlds. That collision knocked Earth into a tilted rotational axis.Earth stays in this 23.5-degree tilt no matter where it is in its annual orbit around the sun. In fact, the northern end of the Earth’s tilted axis more or less points toward the same place in space throughout the year–at Polaris, the aptly named North Star.

Because of this tilt, Earth’s north pole leans 23.5 degrees toward the sun on the summer solstice (around June 21), while the south pole leans 23.5 degrees away. On the winter solstice (around December 21), the south pole leans toward the sun and the north pole leans away. Whichever hemisphere leans toward the sun gets pool parties and picnics. The other hemisphere hauls out parkas. But let’s be clear here. The pool-party hemisphere doesn’t heat up because it’s closer to the sun. It heats up because that hemisphere receives the sun’s solar energy at a more direct angle, which affects both the duration and intensity of your daily bake.

The hemisphere leaning into the sun gets a whole lot of daylight every day, while its pasty counterpart gets less tanning time and more starry sky. In fact, because of the Earth’s tilt, the north pole gets 24 hours of daylight every summer day, while the south pole sits the season out in darkness. (The equator, on the other hand, is Earth’s Even Steven, with 12 hours of daylight every day of the year.)You get a more intense bake in the summer, too. Think of summer as a sort of seasonal high noon. Like the hot, directly overhead, noontime sun, the summer sun points right at you. And that means more intense solar energy. It’s the same if you angle your reading lamp at the wall. Not much heat in that oval patch of light, is there? Now point it straight at the wall. A bit warmer, even if you pull the lamp back a bit.

                                  With the sun more directly overhead–like at noontime, in summer, or at the equator–sunlight effectively tunnels straight into our air. At the poles, during the morning or evening, or in the winter, it has to slug through far more atmosphere, as much as 40 times more. Sure, it gets to the same place eventually, but at the expense of a lot of energy.

Gary Dobbs, Meteorologist / Storm Force 31

We now are officially in the summer doldrums…weather-wise and work-wise.

Now, work-wise is another story. Sure, counting teachers and others who generally are off for the summer, 20-25 percent of the population is likely on vacation any given week between the beginning of June and the end of August. Peak vacation periods seem to come around July 4, which this year is conveniently on a Friday, and the first week of August, when most kids’ summer baseball leagues are over and families can finally pack all the kids up for that getaway.

We all need, and deserve, vacations. So take what you’re due and don’t take your computer, your work cell phone or your Blackberry with you unless you’re president of either your company or the United States (or running for either.)

This is a great opportunity to bring back out my favorite forecasting tool……it’s very elemental and is virtually always accurate. 

Gary Dobbs, Meteorologist / Storm Force 31

That Tuesday morning cool front really made a difference with our weather here in the TennesseeValley.  Not only will we enjoy cooler temps on the thermometer but we’ll enjoy much less humid air to our bodies.  But did you know humid air is lighter, or less dense, than dry air?  How can the air become lighter if we add water vapor to it?

Scientists have known this for a long time. The first was Isaac Newton, who stated that humid air is less dense than dry air in 1717 in his book, Optics. But, other scientists didn’t generally understand this until later in that century.

To see why humid air is less dense than dry air, we need to turn to one of the laws of nature the Italian physicist Amadeo Avogadro discovered in the early 1800s. In simple terms, he found that a fixed volume of gas, say one cubic meter, at the same temperature and pressure, would always have the same number of molecules no matter what gas is in the container. Most beginning chemistry books explain how this works.

Imagine a cubic foot of perfectly dry air. It contains about 78% nitrogen molecules, which each have a molecular weight of 28 (2 atoms with atomic weight 14) . Another 21% of the air is oxygen, with each molecule having a molecular weight of 32 (2 atoms with atomic weight 16). The final one percent is a mixture of other gases, which we won’t worry about.

Molecules are free to move in and out of our cubic foot of air. What Avogadro discovered leads us to conclude that if we added water vapor molecules to our cubic foot of air, some of the nitrogen and oxygen molecules would leave — remember, the total number of molecules in our cubic foot of air stays the same.

The water molecules, which replace nitrogen or oxygen, have a molecular weight of 18. (One oxygen atom with atomic weight of 16, and two hydrogen atoms each with atomic weight of 1). This is lighter than both nitrogen and oxygen. In other words, replacing nitrogen and oxygen with water vapor decreases the weight of the air in the cubic foot; that is, it’s density decreases.

Wait a minute, you might say, “I know water’s heavier than air.” True, liquid water is heavier, or more dense, than air. But, the water that makes the air humid isn’t liquid. It’s water vapor, which is a gas that is lighter than nitrogen or oxygen.

Compared to the differences made by temperature and air pressure, humidity has a small effect on the air’s density. But, humid air is lighter than dry air at the same temperature and pressure.

So enjoy the lower humidities even if it is more dense out there!

Gary Dobbs, Meteorologist / Storm Force 31

Early dawn. Late sunset. Long day. Short night. For us in the northern hemisphere, the June solstice marks the longest day of the year.

It’s your signal to celebrate the first day of summer in this hemisphere. South of the equator, winter begins.

When is the solstice where I live?

The solstice happens at the same instant for all of us, everywhere on Earth. But our clocks say different times.

This solstice takes place on Friday, June 20, 2008 at 23:59 Universal Time. If you’re not accustomed to the 24-hour designation, the June solstice falls at 11:59 p.m. Universal Time and 6:59 p.m. Central Daylight Time.

To find the time in your location, you have to “translate” to your time zone.

Here’s an example. In the central United States, for those using Central Daylight Time, you’d subtract 5 hours from Universal Time. That how we get 6:59 p.m. Central Daylight Time as the time of this solstice.

Want to know the time in your location? Check out EarthSky’s article How do I translate Universal Time into my time? And just remember: you’re translating from 23:59 Universal Time, Friday, June 20.

What is a solstice?

The earliest humans knew that the sun’s path across the sky, the length of daylight, and the location of the sunrise and sunset all shifted in a regular way throughout the year.

They built monuments, such as Stonehenge, to follow the sun’s yearly progress.

Today, we know that the solstice is an astronomical event, caused by Earth’s tilt on its axis, and its motion in orbit around the sun.

Because Earth doesn’t orbit upright, but is instead tilted on its axis by 23-and-a-half degrees, Earth’s northern and southern hemispheres trade places in receiving the sun’s light and warmth most directly.

At the June solstice, Earth is positioned in its orbit so that the North Pole is leaning 23-and-a-half degrees toward the sun. As seen from Earth, the sun is directly overhead at noon 23-and-a-half degrees north of the equator, at an imaginary line encircling the globe known as the Tropic of Cancer. This is as far north as the sun ever gets.

All locations north of the equator have day lengths greater than 12 hours at the June solstice. Meanwhile, all locations south of the equator have day lengths less than 12 hours

Where should I look to see signs of the solstice in nature?

Everywhere.

For all of Earth’s creatures, nothing is so fundamental as the length of daylight. After all, the sun is the ultimate source of all light and warmth on Earth.

If you live in the northern hemisphere, you can notice the early dawns and late sunsets, and the high arc of the sun across the sky each day. You might see how high the sun appears in the sky at local noon. And be sure to look at your noontime shadow. Around the time of the solstice, it’s your shortest noontime shadow of the year.

If you’re a person who’s tuned in to the out-of-doors, you know the peaceful, comforting feeling that accompanies these signs and signals of the year’s longest day.

Why is the solstice a big deal?

Cultures universally have had markers, holidays and alignments . . . all related to the solstice.

It has been universal among humans to treasure this time of warmth and light.

For us in the modern world, the solstice is a time to recall the reverence and understanding that early people had for the sky. Some 5,000 years ago, people placed huge stones in a circle on a broad plain in what’s now England and aligned them with the June solstice sunrise.

We may never comprehend the full significance of Stonehenge. But we do know that knowledge of this sort wasn’t isolated to just one part of the world. Around the same time Stonehenge was being constructed in England, two great pyramids and then the Sphinx were built on Egyptian sands. If you stood at the Sphinx on June 21 and gazed toward the two pyramids, you’d see the sun set exactly between them.

How does it end up hotter later in the summer, if June has the longest day?

People sometimes ask, “If June 21 is the longest day of the year, why is it that we usually receive the hottest weather not on that day, but in late July and August?”

This effect is called “the lag of the seasons.” It’s the same reason it’s hotter in mid-afternoon than at noontime. Earth just takes awhile to warm up after a long winter. Right now, ice and snow still blanket the ground in some places. The sun has to melt the ice – and warm the oceans – and then we feel the most sweltering summer heat.

Ice and snow have been melting since spring began. Meltwater and rainwater have been percolating down through snow on tops of glaciers.

But the runoff from glaciers isn’t as great now as it’ll be in another month, even though sunlight is striking the northern hemisphere most directly around now.

So wait another month for the hottest weather. It’ll come when the days are already beginning to shorten again, as Earth continues moving in orbit around the sun, bringing us closer to another winter.

And so the cycle continues.

Gary Dobbs, Meteorologist / Storm Force 31

While it looks as if we will be out of a thunderstorm threat for a few days, it is the time of year when families are spending a lot of time outdoors, here are some tips from the National Weather Service on what to do if you’re outside when a storm does hit:

• The safest place when outdoors during a thunderstorm is a large, enclosed building not a picnic shelter, shed, baseball dugout, or tent. The park restroom might not be pretty, but it might be your best option to stay safe from a lightning strike.
• If a building is not available, the next best choice is a hard topped vehicle, not a convertible or motorcycle.
• If you don’t have a building or vehicle available, do NOT seek shelter under a tree. Lightning prefers tall objects.
• Avoid touching metal objects during a storm. This includes: baseball bats, fences, golf clubs, poles, backpacks, and bicycles.
• Wait until 30 minutes after you last heard the last roll of thunder before leaving your shelter.

Of course, the best way to ensure the safety of you and your family in the event of a storm is to pay attention to weather reports and avoid outdoor activity when severe weather is predicted. It’s way more fun to watch a storm when huddled under a blanket on the couch with a bowl of popcorn then when outside in the midst of it!

Gary Dobbs, Meteorologist / Storm Force 31

Before facing major surgery, wouldn’t you want a second opinion?  When a nation faces an important decision that risks its economic future, or perhaps the fate of the ecology, it should do the same.  After the United Nations-sponsored Intergovernmental Panel on Climate Change (IPCC) concluded man is responsible for global warming, an organization called THE HEARTLAND INSTITUTE (www.heartland.org) formed its own group called the Nongovernmental International Panel on Climate Change. (NIPCC) While the governmental group concluded anthropogenic greenhouse gases are likely the dominant cause of global warming (and man’s contribution), the nongovernmental group reached the opposite conclusion- namely that natural causes are very likely to be the dominant cause.

 The public’s fear of anthropogenic global warming seems to be at a fever pitch.  Polls show most people in most countries believe human greenhouse gas emissions are a major cause of climate change and that action must be taken to reduce them, although most people apparently are not willing to make the financial sacrifices required.

THE HEARTLAND INSTITUTE  hopes their latest study will help bring reason and balance back into the debate over climate change, and by doing so perhaps save the peoples of the world from the burden of paying for wasteful, unnecessary energy and environmental policies.

I just finished reading their latest publication, “Nature, Not Human Activity, Rules the Climate” (yes, I KNOW I need to get a life).  I recommend it to you if you are curious about the topic or just want to have some factual information the next time you get in a heated (”heated; get it) global warming discussion over the backyard fence.

Just click on the HEARTLAND link above and enjoy !!

Gary Dobbs, Meteorologist / Storm Force 31

As we sit and simmer with July weather in early June in the Tennessee Valley, it is a good time to check out how hot it CAN be.  For example, the statewide hottest temperature ever recorded in Alabama was 112 degrees. 

The coolest two statewide high records, shown here, aren’t as obvious. Alaska in the far north and Rhode Island, with no part of the state far from the cool Atlantic, are no surprises.

But tropical Hawaii, with the same high record as Alaska, isn’t as obvious. Credit the ocean. Even in the tropics, ocean waters stay cooler than land. Almost all of Hawaii is cooled to some extent by ocean breezes.

The complete list of state records below shows that the Plains states, far away from the ocean, can be hotter than the humid Southeast.

The USA’s highest temperature, 134° on July 10, 1913 in Death Valley, Calif., is also the official highest temperature in the Western Hemisphere.

Ordinary summer heat makes much of the Southwest, including Death Valley, sizzle from June through August. But, Death Valley’s unique geography turns this hot weather into extreme heat.

Winds off the higher surrounding land, known as the Great Basin, often blow hot, dry air thousands of feet down into the long, narrow valley, which is 282 feet below sea level.

As the air moves downhill it encounters increasing atmospheric pressure, which squeezes the air, warming it at a rate of 5.5° for every 1,000-foot drop in elevation. Some of the mountain ranges around Death Valley are 7,000 – 9,000 feet high, and the surrounding land between the ranges is 4,000 – 5,000 feet above sea level, which means the air can warm at least 20-25° by the time it reaches the bottom of the valley.

In addition, the steep walls of the valley heat up and radiate that heat back into the valley, causing the already hot air to grow even hotter. July’s average high in Death Valley is 115°, but nearly every year the temperature reaches 125°, or higher.

The world’s highest official temperature is 136° recorded at El Azizia, Libya, on Sept. 13, 1922.

Not everyone agrees that the Death Valley and El Azizia records are valid. Some meteorologists say that a sandstorm was going on at the time 134° was measured at Greenland Ranch in Death Valley and that very hot sand and dust could have hit the thermometer inside its shelter, pushing its measurement higher than the actual temperature of the air.

The Weather and Climate Extremes booklet published by the U.S. Army Corps of Engineers has more information on these and other records. This booklet is available for download from the U.S. National Technical Information Service.

We also have a list of each state’s low temperature record.

State high temperature records

State    Temp    Date          Station                   Elevation (feet)
Ala.     112   Sept. 5, 1925   Centerville               345
Alaska   100   June 27, 1915   Ft. Yukon                 420*
Ariz.    128   June 29, 1994   Lake Havasu               505
Ark.     120   Aug. 10, 1936   Ozark                     396
Calif.   134   July 10, 1913   Death Valley              N/A
Colo.    118   July 11, 1888   Bennett                   5,484
Conn.    106   July 15, 1995   Danbury                   450
Del.     110   July 21, 1930   Millsboro                 20
Fla.     109   June 29, 1931   Monticello                207
Ga.      112   July 24, 1952   Louisville                132
Hawaii   100   April 27,1931   Pahala                    850
Idaho    118   July 28, 1934   Orofino                   1,027
Ill.     117   July 14, 1954   E. St Louis               410
Ind.     116   July 14, 1936   Collegeville              672
Iowa     118   July 20, 1934   Keokuk                    614
Kansas   121   July 24, 1936   Alton                     1,651
Ky.      114   July 28, 1930   Greensburg                581
La.      114   Aug. 10, 1936   Plain Dealing             268
Maine    105   July 10, 1911   N. Bridgton               450
Md.      109   July 10, 1936   Cumberland and Frederick  623, 325
Mass.    107   Aug.  2, 1975   New Bedford and Chester   120, 640
Mich.    112   July 13, 1936   Mio                       963
Minn.    114   July  6, 1936   Moorhead                  904
Miss.    115   July 29, 1930   Holly Springs             600
Mo       118   July 14, 1954   Warsaw and Union          705, 560
Mont.    117   July  5, 1937   Medicine Lake             1,950
Neb.     118   July 24, 1936   Minden                    2,169
Nev.     125   June 29, 1994   Laughlin                  605
N.H.     106   July  4, 1911   Nashua                    125
N.J.     110   July 10, 1936   Runyon                    18
N.M.     122   June 27, 1994   Lakewood                  N/A
N.Y.     108   July 22, 1926   Troy                      35
N.C.     110   Aug. 21, 1983   Fayetteville              213
N.D.     121   July  6, 1936   Steele                    1,857
Ohio     113   July 21, 1934   Gallipolis                673
Okla.    120   June 27, 1994   Tipton                    1,350
Ore.     119   Aug. 10, 1898   Pendleton                 1,074
Pa.      111   July 10, 1936   Phoenixville              100
R.I.     104   Aug.  2, 1975   Providence                51
S.C.     111   June 28, 1954   Camden                    170
S.D.     120   July 15, 2006   Kelly Ranch/Usta          2,339
Tenn.    113   Aug.  9, 1930   Perryville                377
Texas    120   Aug. 12, 1936   Seymour                   1,291
Utah     117   July  5, 1985   Saint George              2,880
Vt.      105   July  4, 1911   Vernon                    310
Va.      110   July 15, 1954   Balcony Falls             725
Wash.    118   Aug.  5, 1961   Ice Harbor Dam  475       475
W. Va.   112   July 10, 1936   Martinsburg               435
Wis.     114   July 13, 1936   Wisconsin Dells           900
Wyo.     116   Aug.  8, 1983   Basin                     3,500

*Elevation estimated.