Dan's Wild Wild Science Journal

To me the most fascinating part of synoptic forecasting is Satellite Meteorology. I can still remember working in Tulsa at KJRH TV where we had a GOES Unifax machine. Every 15 minutes a high resolution image would spit out. During the day the resolution was 1 km on a visible image. This was good enough to see jet contrails at times.

Jet Contrails from the NASA Modis Satellite- It sees true colour. GOES does not. These contrails keep the nights warmer and days slightly cooler over much of America.

One afternoon a large contrail was visible across Northeast Oklahoma and I ran outside the station and there it was! I was looking at the bottom of it, the satellite was seeing the top from 36,000km away. This seems like no big deal now, but in 1978, it was a very big deal!

TV viewers have since grown very accustomed to seeing satellite images on TV weather reports and now even online. What the average person does not know is just how incredibly valuable these images are.

It was once said that if the GOES Satellites could see nothing but hurricanes in the ocean, they would be worth 100 times the money spent to build them and put them in orbit. I certainly agree.

They do however see MUCH more than just hurricanes. Read on learn some of the incredible ways these satellites are making accurate forecasts and early severe weather warnings possible.

First some misconceptions.

1. Satellite images are not in colour. TV Weather graphic equipment remaps the cloud images over colour maps. The next generation of weather satellites GOES R will be able to see almost true colour. It is really not that necessary to forecasting anyhow.

2. These satellites are VERY high. About 1/10th the way to the moon. The reason is that at 36k km they orbit the earth once a day, and since the Earth turns once a day, they appear to hover over the same spot. If one breaks, the Space Shuttle cannot even get one tenth of the way up to fix them.

3. They are called GOES for Geostationary Operational Environmental Satellite. We use two if them in the USA. Goes East and GOES West. They are in orbit over the Equator and cannot see well in the high latitudes because of the curve of the Earth. Alaska, and Northern Canada forecasters use the Polar Orbiting satellites, but only get a few pics a day. The current operational east satellite is GOES 12. GOES 13 and 14 are in orbit, but in storage until needed.

GOES Water Vapor IR imagery Image from July 4 05Z

4. They take mages every 15 minutes and can do an image over a small area every 7 minutes in rapid scan mode.

5. They do not have cameras per say. They have sensors that detect electromagnetic radiation. The visible light that your camera records when you take a picture is electromagnetic radiation. It’s light in the visible part of the spectrum.

X-rays and the radio waves from your favourite FM station are “light” as well. We humans just cannot see that light. So is infra-red radiation that “night goggles” use. You can buy video cameras now that see in the IR wavelengths.

The GOES imaging sensors actually see electromagnetic radiation in 5 different bands. One visible and 4 in the infra red. The GOES also has another sensor called the sounding radiometer. The sounder imager can actually detect temperatures and moisture at different levels in the atmosphere. Even under clear skies.

We can actually take a sounding without launching a weather balloon. (They cost you the tax payer about 100$ a pop too)

Even in daytime we get both the IR and visible images. At night we only get the IR of course. The visible channel can resolve objects bigger than about 1 km square. The IR imager is 4 km. One image you see rarely on TV is the Water Vapor IR images. These images look almost like an atmospheric X-ray and are very valuable to forecasters like me.

IR Image from GOES East Midnight 4 July 2009. See the storms in Kansas!

Using water vapor imagery we can see the outlines of troughs and even upper level low pressure centers called vorticity maximums. These “vort maxes” can kick off convection or intensify a low pressure system. Skies may clear suddenly behind them. Knowing their position also allows us to compare the real world with a forecast model. If the model has forecasted it well,then confidence in the models forecast is increased!

Since the amount of radiation an object gives off is related to it’s temperature, the IR images also can tell us the height of clouds and thunderstorms! The colder the cloud, the higher it is! High ice crystal cirrus clouds show up bright white on IR images, where ground fog is sometimes hard to see since it’s the same temp. as the ground.

A new technique has been developed that subtracts one channel from another and makes it possible to see fog at night. We call it the “fog Product“. High clouds over a fog layer will usually keep it from dissipating as fast so seeing the different layers of clouds is very important.

Lines of building cumulus clouds can be seen long before radar echoes show up. Many times when the atmosphere is unstable, these building towers are the first clue that severe convection is imminent and a tornado watch may be issued.

Geostationary weather satellites are over Europe and Asia, along with the Middle East, So we can actually see every corner of the globe. Not the high latitudes though, we only get images of the poles a few times a day. Forecasters in these high latitudes get very good at interpreting the lower and higher resolution images from the polar orbiting satellites. If you have the money, you can download the images from these satellites as they pass overhead. Lots of people do it!

Temperature structure of the atmosphere near Huntsville AL. From GOES. Numbers on the right are indexes that tell the forecaster about instability etc.

There are other sensors on these satellites as well. If you crash in a remote island, your plane will have an ELT on it. This Emergency Locating Transmitter will be picked up by the GOES. Detection of solar storms is also made possible by GOES along with other satellites. Arctic Ice in shipping lanes is also monitored with GOES. If there were GOES in 1912, maybe the Titanic would have missed that berg.

Yes, it cost a lot of money to put these satellites up in space and even more to build them, however the images they provide are very nearly priceless.

Yes there really is such a thing and you can join too. I warn you, a membership card will mark your final descent into geek-dom. So clean the screen on your Mac, and dust off your entire collection of Doctor Who episodes, and accept the fact you’re a geek and be happy about it. I am!

There is actually some big news in the cloud world as of late. There is a new one! Not world, we still have the same one, and it’s ecosystem is in a very iffy state. What we do have is a new cloud type. Maybe.

The Royal Meteorological Society is working with the founder of the cloud appreciation society (CAP) to get it recognized officially by the World Meteorological Organization (WMO) of the UN. I think they have a pretty good chance too. I myself have seen them and could not identify them either! They are very beautiful and memorable.

The working name is ASPERATUS. Latin for rough and they do indeed appear rough! You can see an example of the cloud on the image below. Click to go to the CAP website.

Asperatus? Is the cloud of the month at the Cloud App. Society. Image is hyperlinked.

Cloud types are not that hard to learn. Here is an easy way to do it.

4 main categories:
1. Low 2. Middle 3. High 4. Tall
Each of these categories can have flat clouds or puffy clouds. Flat clouds are status. Puffy are cumulus. Middle clouds have the prefix Alto. High cloud has the prefix Cirro. There is only one tall cloud, a cumulonimbus. Commonly called a thunderhead and it is indeed likely a thunderstorm, or about to be one! Sometimes you will see a low cloud that seems to be a bit of stratus and cumulus together. Call it stratocumulus and you will likely be right.

One last thing. If it’s producing rain, add the word NIMBUS. Nimbus means rain cloud. As in cumulonimbus!  So a puffy middle cloud is an alto-cumulus and a high thin flat cloud is a cirrostratus. (I pronounce it cirro stray tus.)

Flying Saucer Lenticularis- Click image for more at Sci. Ray.

My favourite type of cloud is a LENNY. Technically it’s an Alto-cumulus Standing Lenticularis. (ACSL). They sometimes look like flying saucers hovering over a mountain top. There was a great display around Mount Rainier recently. Lennies are caused by invisible waves in the atmosphere. As air rises and cools, at the top of the wave, it may condense and form a cloud. As it descends, the air warms, and the cloud disappears. The visible part of the cloud will tend to stand over one spot!

173232main_noctilucent_clouds_nasa-webv_1

The link here is a great time lapse of these clouds from NASA.

Noctilucent Clouds- from NASA See description. Click image for more.

There is actually another type of cloud. Very rare, and very high. So high, it’s in the Mesosphere between 45-80km high. At the edge of space itself.

Noctilucent clouds are seen usually in the polar regions after dark. They are so high, that they can be lit by the sun, after it’s totally night at the surface. NASA is studying them with the AIM satellite. Check out the movie. I think I have seen Noctilucent clouds once, but I cannot say for sure.

The Mesosphere is the least explored part of our atmosphere. It’s extremely difficult to get there! You can pass rapidly through it on the shuttle heading into orbit, but you are there only for seconds. Too high for balloons and planes!

Some recent research is indicating that an increase in the appearances of these clouds may be due to climate change. While the troposphere is warming, the layers of the atmosphere above it are predicted to be cooling. That very thing is happening.

Clouds are the great leveler. Rich or poor, we can all see them and there is no charge. Those who live in the haze free areas of the world away from air pollution are the luckiest, and your chance of seeing Noctilucent clouds is much higher in polar regions. Lennies are very rare outside of mountain regions, but I have spotted them even here in the Southeast in winter.

These Cirrus aren't Near us. Click for details from NASA JPL.

Earth does not have a lock on clouds, with Venus covered in clouds made of sulfuric acid. Jupiter has clouds made of methane and Saturn’s moons Titan is also covered in exotic clouds. There has even been speculation that life might exist in the Jovian clouds, at just the right pressures and temperatures.

Yes, Mars has cirrus clouds!  They are made of ice crystals and look just like our cirrus.

I love clouds so much, I frequently show pictures, that viewers send me, on my daily weathercasts.

So look up in wonder every now and then!

Later,
Dan

The title of this may confuse you, and believe it or not, to accomplish it, you have to do nothing at all!

However, you would make your local weather geek even happier if you would type the words hoax into your email app. and hit send!

Let me explain.

I get hundreds of emails a week/sometimes each day. I try to answer as many as I can, but I and hundreds of my fellow Meteorologists (especially those like me who work on air) are getting the same pictures sent to us over and over. If you see any of these pictures or hoaxes in your email, do us all a favour and hit REPLY ALL. Then type the words HOAX. That’s what I do.

So here is what truth I know behind these images and hoaxes.

This is not Hurricane XXXXXXX. It's a shelf cloud ahead of a thunderstorm. I bet it was taken on the Great Lakes.

This is not even a tornado! It's a waterspout and it was taken by Fred Smith in 1993 near Okeechobee, Florida. Oh, and there was no oil rig anywhere near. Someone added that, and a tall tale later. Lovely shot though. Oh, and Fred owns the copyright on the picture!

Mars will never look as big as the full Moon unless you are looking through a good telescope. This hoax repeats every year in August because of the original email. It never happened and it never will. (NASA image.)

These hoaxes get more active depending on weather and the time of year. If a hurricane develops in the Atlantic, I will start getting the picture taken from ship. If a tornado wreaks havoc on some poor town, I will get the picture of the tornado. Especially if the twister hit Oklahoma or Texas, because as everyone know, that’s where the oil is!

The Mars hoax peaks in August every year, because it got started in 2003, when Mars made a rare close approach to Earth. In 2003 it was  a little over 55 million kilometers away.  Very close by Astronomical standards, but Mars get nearly this close every 18 months or so.

I purposefully made the tornado photo small because Fred Smith has a right to be paid for his image.

Update: I received another hoax email today, but this one is not weather related. It’s an email that contains images of the attack on Pearl Harbour 7 Dec. 1941. It claims the images were just discovered and devleoped from a “Brownie” camera.

This pic is from Pearl Harbour, but it's been in Naval Archives for 65 + years.

This pic is from Pearl Harbour, but it’s been in the Naval Archives for 65 + years.  So have all of the other pictures in this email. More here.

Dan

fin

Good Friday 2009 will long be remembered in Alabama and Tennessee. Huge hailstones, and violent tornadoes pounded the region. Only two deaths, and some 50 injuries, but a lot of destruction. It certainly could have been worse, and to families that lost loved ones and homes, it is a tragedy that will be remembered for a life time.

Many times, when severe storms hit, the only view of hail or tornadoes for most people, is on TV. Not this time. The news room was inundated with calls from viewers, watching large hail stones dent their car, and ruin their roofs. Local car dealers here have over 300 damaged cars.

Modern technology is still not good enough to give reliable advance warning of small EF 0 and EF 1 tornadoes. (For those reading from other countries, the U.S. rates tornadoes on the Enhanced Fujita scale. This scale runs from zero to five. Five is very bad.) The large killer tornadoes are forecasted much better now than in the past. I warned viewers Thursday night that we faced such a threat, and showed on a map, where the threat was highest. We made the warning the lead story in our newscast. This kind of detailed forecast was impossible 25 years ago. Science has learned a lot.

Everyone in the path of the tornadoes had several minutes of warning Friday. I would like to think that this explains the low numbers of deaths, and injuries.

Looks like "Cricket ball" size to me.

We have had hundreds of images of the hail and the storms, along with a bunch of questions about the event directed to the Meteorologist. Since that’s me, I spent the day refreshing my memory on the science of hail, and wind. What follows are some answers. I have also written to one of the top experts in the field of hail research, so another post is possible soon.

A lot of the hail on Friday was the size of golf balls, but many reports of tennis ball, and even softball sized hail were reported. Viewers sent me pictures to back up the reports. They sent a LOT of pictures. These images allowed forecasters like me to better predict the size of the hail, in areas further East.

The super-cell storms are constantly being measured, as the tracked across Alabama and Tennessee. One of these measurements is called VIL. It stands for Vertically Integrated Liquid. The VIL is an estimate of the total liquid water in column through the storm.

If you divide the VIL of a storm, by the height of the storm, you get a number called the VIL density. This number tends to be a good measure of hail size. It’s not perfect, and there are other factors that can affect how large the hailstones that reach the ground are. One number we look at is called the “Wet Bulb Zero” height. It tells us how close to the ground the hail stones will start to melt. Detailed info on VIL, and VIL density is available for my fellow nerds here.

When viewers start sending me pictures of golf ball sized hail, and I know the storm has a VIL density of say 4, then I can be quite certain that other storms that day with a vil density of 4 will have larger than golf ball sized hail. These images are very helpful indeed, but I worry that people will get hurt in their attempt to take photos of the hail. There was an injury Friday. A woman was hit in the head with a large hail stone, while running to a car, to get out of the storm.

Coins are a good way of communicating hail size. avoid using the term "marble size". I don't know how big your marbles are! You may have even lost them!

Some of the hail was clear ice, instead of opaque. This clear ice is likely related to the freezing rate, and the amount of supercooled water in the highest reaches of the super-cell thunderstorm. Slower freezing, and slower hail growth, gives clear ice. The amount of supercooled water around the hail stone seems to play a big roll in the determination of clear vs. opaque.

Another viewer asked about the jagged hailstones. These are likely hail stones that are made up of several chunks of ice that froze together. A large stone like this, can only be thrown upward, and held aloft, by an updraft of around 160 km/hr! Stones this size are rarely seen and when they are, a violent tornado is usually close by. The exception is Colorado, where stones this large can form with no tornado. So, that rule is mainly for areas East of the High Plains.

The Hail Friday was Quite Varied In Shape/Size

Several images of hail that was “egg” shaped were sent in. I am not certain how this happens. It may very well be related to the intense low pressure circulation inside the tornadic thunderstorm. Centrifugal force perhaps? You can read more about hail on the UCAR Fact Sheet.

Meteorologists call this the mesocyclone, and Doppler weather radars can detect the strength of the mesocyclone. The mesocyclone near the largest hail on Friday was very intense. So intense, that I was quite certain, a tornado was on the ground, and doing damage. Storms like these we tracked on radar Friday, are seen rarely. In my 30 years of forecasting, I have tracked storms like that on maybe 6 or 7 days.

Wall clouds are very popular with the public. Storm spotter courses show lots of pictures of them, and when we have strong storms, I get many photos from viewers of what looks to them like a wall cloud. I always tell our reporters in the field, that a wall cloud will look just like a wall cloud. If there is doubt, it probably is not one. Wall clouds are the parent cloud of a tornado, and a rotating wall cloud is a sign that you may be about to see a tornado. Best not be in a location ahead of one!

Wall clouds will form under the "rain free base" of a supercell.

Sometimes a pendant will slope down, from the wall cloud toward the rain shaft. This is called a tail cloud. Usually, rotation in the wall cloud is quite apparent.

The tornado that tracked through Marshall, Dekalb, and Jackson counties on Friday has been rated as an EF-3 on the enhanced Fujta scale. This means winds of over 150 mph. The maximum width of the path of damage is nearly 1KM!

The estimate of the tornado’s size, and strength is based on several factors, The width of the path, and it’s length. The maximum winds can be estimated by the damage to trees, and structures. It is important to realize that if a large tornado does no damage, then it cannot be given a rating.

Many times, people will insist that a tornado has been under rated because there are many destroyed homes. If these homes are mobile homes/trailers, then an EF2 tornado will completely destroy them. If there is no major damage to wooden homes, then the tornado rating is likely correct. An EF2 will also usually destroy a garage or out buildings as well.

The EF3 tornado is much stronger, and does much more damage to wooden/ brick structures, on a foundation. An EF2 tornado has winds up to 115 knots or round 219 km/hr. An EF3 has winds from 219- 265 km/hr. That is nearly 160 knots. A category 5 hurricane is another example.

Typical EF3 Damage (From NOAA-NWS)

Heavy cars will be thrown a good distance by an EF3 and walls of well built structures will collapse. Damage in the Sylvania area, of Dekalb County, indicates that the tornado Friday was at EF3 strength. Late word from the NWS survey team tonight, of one home that was picked up, and slammed 4 feet into the dirt in Sylvania. Read the preliminary storm survey here.

The methods of rating a tornado is explained in this slide show. If everyone who lived in a mobile home, left for safer shelter during a tornado watch, the death toll from tornadoes would drop by half in this country. Don’t think that tie downs make any difference. They almost certainly do not.

Thanks to all of our viewers here in Alabama and Tennessee whose pictures and reports helped us track the storms on Friday. If you see your picture in this post-please email me and I will add a credit. We have so many- the names have been separated!

UPDATE SUNDAY EVENING: Donnie Charles of Albertville emailed us this picture. It’s a GIANT wall cloud. Taken in 2006, but a good example.

Huge Wall Cloud Near Albertville, Al 2006.

Notice the striations. Wall clouds like that almost always accompany killer tornadoes.

Now the bad news. More storms Monday.

Keep safe,

Dan

Ask most Meteorologists (including me) what their favorite cloud is, and you will probably get the same answer

Lennys.

That’s slang term for ALTO CUMULUS  STANDING LENTICULARIS

Imagine a blob of air riding along in the wind. Suddenly, you run into a big mountain. As the air stream you are in, rides over the  mountain, the pressure drops and so does the temperature. If it gets cold enough, the moisture in the blob of air can no longer stay in vapor form, and will condense to tiny water droplets. Cloud droplets to be exact.

A cloud forms!

As the air descends the mountain, it warms,  and the pressure increases. The cloud droplets can now go back to invisible vapor, and the cloud disappears. If you think about it, this will lead to a cloud forming near a mountain range that just sits there! Even if the wind is blowing 80 knots across the mountain range, the cloud does not move.

Lenny clouds can develop far away from mountains too.

If you throw a rock into a pond, ripples will will move out in concentric rings far from where the rock fell. The same thing happens in the atmosphere. Wind blowing over a mountain range will start an up and down oscillation. Each time the air rises to the top of the wave, a cloud will form. These “Gravity Waves” can cause lenticularis clouds to form thousands of miles from a mountain range. I once observed lennys in Florida, caused by strong winds across the mountains of Central Mexico!

A very rare type of Lenny that develops only when conditions are just right is called a Flying Saucer Lenticularis. I’ve never seen of these, but I sure hope to someday! There was a SPECTACULAR display of them last Fall in Seattle. One of these shots made the Astronomy Picture of the Day!

You have to see it, and you can RIGHT HERE.

Isn’t that GREAT?

Dan