Dan’s Wild Wild Science Journal

The American Meteorological Society has thousands of members in all types of atmospheric disciplines. The smallest group is likely the broadcast Meteorologists. We have a little over 100 attendees here in Portland at the the 37th annual AMS Conference on Broadcast Meteorology. I know what you are thinking. A room full of 100 people with very good haircuts.

You might be surprised though. We come in all colours, shapes and sizes. I even have a slight green tint to my hair due to a hotel pool in Seaside Oregon. It’s a long story, and believe me, it was a real shock, considering I was three days away from presenting at a Climate Seminar that kicked off the conference!

Online remedies included white vinegar, and crushing a bunch of aspirin up, and mixing with shampoo. Mixed results, but it seems a bit better. Apparently this is a result of my attempt to hold off my rapidly greying hair with a grocery store product! I haven’t told my News Director about this yet, but someone at the station will read this and pass it on I suspect!

The conference has been quite good today. We had an update on the GOES satellite program. Almost all of the weather satellites you see on TV, or online are from the GOES. GOES stands for Geostationary Operational Environmental Satellite.

They are at the same altitude as the satellites that are used for TV signals. At 35,780 km high they take exactly 23 hours, 56 minutes and 47 seconds to orbit the Earth. This is precisely how long it takes for the Earth to turn once on it’s axis. They therefore, hover over the same spot, and with infrared sensors, you can get satellite images of any spot in the USA, every 15 minutes. Around the clock. In rapid scan mode, every 7.5 minutes. (The more observant of you might be wondering why your clock takes exactly 24 hours to go around, not 23 hours 56 mins. and 47 secs.! You should!- Here is a hint: SUN)

A new GOES will be launched in a few days. GOES O will likely become Goes 14. They are given a letter before launch, but once operational, they are given a number. The current GOES satellite, that covers much of the Eastern 2/3rds of North America, is designated as GOES 12. GOES 13 is already in orbit, but in storage. This new GOES will not significantly improve our abilities to monitor the weather.

The big improvement will come with the GOES R series in 2015. The next generation of satellites will have higher resolution and sensors capable of “seeing” much more, in the non visible wavelengths. It will also be able to give a close to true colour look at the Earth. The reason you cannot get true colour now, is that there is no sensor for the green wavelengths. (True colour requires Red, Green and Blue) Money is the reason. Big cost for little gain according to what was said today by James Gurka, of NOAA NESDIS.

Perhaps the greatest advance will be the new GLM. That stands for Geostationary Lightning Mapping sensor. We will be able to see real time lightning data across the entire western hemisphere. Not just cloud to ground data like you see on TV during stormy weather now, but cloud to cloud, and in cloud lightning. (Yes that is what it’s really called, I am not simplifying names here!)

I am asked often about the lack of lightning warnings. We warn for severe storms and tornadoes, but why not for lightning?? It’s a good question and there is not one single answer. The gist of it though, is that we do not have enough data or knowledge to do a decent job of it. We should though, because lightning kills more people in the USA, in an average year, than hurricanes or tornadoes.

Portland sunset Monday night from my balcony. Click for full pic.

That is changing though, and by the end of the next decade, I think we will indeed have the ability. Frankly, we should have already had GOES R in orbit. The USA is falling behind Europe in remote sensing. Many grad students now go there to work on their research, because they have satellites with the newest technology up already.

A satellite built to gather information on climate crashed into the ocean recently. Who knows if a replacement will be built. Science has truly suffered in this country. I have written before about the war on science, the fact that GOES 14 will not go up for 6 years is at least partially a result.

These satellites cost each American a few pennies per day to operate, and it has been said that if they could see only hurricanes and nothing else, the cost would have been worth it, ten times over! They see much more though. I will do a post soon and show you just how much information is available in one satellite image!

G’nite from a cool and green Portland. Green, in more ways than one!

ps “colour” is correct with or without the u, and I like it with the u. So get over it!

It sounds like something right of an episode of Doctor Who. High winds arrive suddenly, and disappear 4 hours later in a flash. That’s just what happened over North Alabama Sunday night. Sonic screw drivers, and a Tardis might help explain it, but I have a pretty good idea, just the same. I can promise that the Daleks had nothing to do with it. (Although I would not put it past the Cybermen).

So what did happen to cause roaring winds of up to 70 mph that knocked down trees and power lines across 5 counties? Simply put, mother nature through a rock in the pond!

Base Reflectivity 11:58 pm Sunday 12 April. From NOAA & Plym. St.U. archive data. High winds developed, on the back edge of the rain shield.

The heavy rain Sunday evening was the key, but you may have noticed that the winds followed, behind the rain. This is the big clue. It’s rare, but sometimes a large band of convection can act a barrier to the winds aloft.

As the wind flows over the thunderstorms, a wave develops in the atmosphere. Just like any wave, it has a high point and a low point. As the wind flows to the lowest point, it can reach the surface. This can bring the strong winds aloft, down to the ground.

John McLaughlin of KCCI TV in Des Moines Iowa captured a gravity wave event on his stations tower cams, a few years ago. Take a look. You can clearly see the waves.

There is growing interest in understanding these events, and in the operational forecasting of them.

Here is what we do know.

They tend to occur, when there is a stable layer of air near the ground, and unstable air aloft. Meteorologists call this elevated convection. IF, the depth of the stable layer is just right, then a wave can set up, that accelerates winds, in this stable layer, toward the surface.

Clues to an event include a jet stream pattern, with a trough to the west and a ridge to the east. A warm front, is usually located to the south of the area, affected by the gravity wave. A Wake low also develops behind the rain bands. The change in pressure, tends to track with the increase in winds.

So did we see that here Sunday night??
You better believe it.

Surface Map from 2:15 AM Monday 13 April 2009. The warm front is south of the Tennessee Valley. The dark red, is the cold cloud tops, associated with the rain bands.

Still, these conditions happen frequently, and they do not all bring 100 km/hr winds! Understanding, is the first step in forecasting them though.

You can find out more here.

For fellow nerds:

This is quite good.

It’s been a crazy Spring so far. It may not be over yet!

UPDATE: Dr. Tim Coleman is the expert on these events and has written a guest post about this event here. Check it out!

Further update on Monday April 20:
The local Metr. community is still discussing this event, and an analysis by the Huntsville NWS office has some interesting information. The winds peaked before the lowest pressures were recorded. This seems to indicate that this was primarily a wake low event, rather than a gravity wave. As I wrote above, these things are still poorly understood, and believe me, this is the kind of thing that gets we weather nerds very excited.

Later,
Dan

300 millibar chart for 00z Monday 13 April. (Jet stream winds for 7pm Sunday night. The spreading (diffluence) of the winds shows up clearly with a trough West, and ridge to the East of Alabama.

Pressure Trace (Red) and Average Wind Speed (Blue) from our Monte Sano Weather net station. Notice the winds increase as the pressure drops rapidly. The event begins around 10 PM, and ends by 3 AM.

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

His name was Richardson.

Lewis Fry Richardson. He was a British mathematician, and as a Quaker, also a pacifist. When World War one began, he enlisted as an ambulance driver to serve his country while adhering to his ideals.

Richardson had the bright idea that the mathematical equations that govern the air, could be used to predict the weather. He decided to make a forecast, and divided the forecast area into squares.  Then he assigned such variables as current temperature, pressure, and humidity to each of these grids. He believed that if he solved all the equations for each grid, he would come up with a forecast of the weather 8 hours in the future.
It took him months! No computers around in World War One, and no one really wanted to help him!

Lewis Fry Richardson- Ctsy UK Met. Office

Did it work??

Total failure dude. (I can relate my friend, I can definitely relate!)

He did not give up though, and kept working on it for years. He had the idea of having thousands of people in a stadium, who would each do one calculation, and pass it on to the next person. This would make it possible to solve all of the complex calculus equations, in a short period of time, and produce an accurate forecast!

With the advent of computers in the 1950’s, this idea took on a whole new meaning.  While Richardson’s first forecast failed spectacularly, the attempts showed much promise by 1960. If only Richardson could see the models I look at every day now!

The rapid increase in computing power has revolutionized weather forecasting. In 1979, I was told that an accurate 7 day forecast would not be possible in my lifetime. Computers were just not fast enough. In 1980, an extended forecast was 3 days. I produce a 7 day forecast everyday now, and some stations put on a 10 day forecast. The 5 day forecast is as accurate as a 3 day forecast was just 20 years ago!

Let me explain how they work. No math, I promise!!

Grab a map of North America or Europe, or wherever you are in the world. A map that covers several thousand kilometers. Now get a box of sugar cubes. The kind you put in your tea or coffee. Put them down on the map. Now imagine that the cubes cover the entire map. Now, we tell the computer model what the weather conditions are in every single one of those cubes. We then use the mathematical equations that describe the atmosphere, to move the weather from one cube to another.

If there is a south wind over Texas, then the cubes over Oklahoma will get warmer. How fast they get warmer, will depend on the wind speed, the elevation, and whether or not the sun is shining. Actually there are a ton of variables, and they can all be described using equations of math. Some better than others. We have to decide how often we are going to move the weather, from one cube to another. Modern weather models use a time period of just a few minutes. We call this the time step of the model. We also have to decide how big are cubes are going to be.

Imagine a map covered with sugar cubes

This is very important, because the smaller the cubes, the more accurate the forecast. Imagine we have a cube that is 50 kilometers wide on each side. We will give one value of the current weather to that cube, when we tart the model. Will the weather be the same across that entire cube? No, of course not. We will have to average the weather over the cube and this will introduce error into the forecast. The smaller the cube, the less error.

Here’s the rub.

The smaller the cube, and the shorter the time step, the more time it takes to run the model!

I also neglected to tell you something. We have a map covered with a a layer of sugar cubes right? What about the rest of the atmosphere? What about the weather up high. What about the jet stream? We have to have a bunch of sugar cubes in layers on our map. Each one has to be given a value for the weather happening now, before we can run the model!

The best resolution model run by NOAA over North America is called the NAM. North American Mesoscale model. The cubes are 12 km square in the NAM and there are 70 layers of them. The top layer is over 20 miles high! The model is run 4 times a day on a multi-million dollar supercomputer. It makes a forecast out to 84 hours in the future. Other models have bigger cubes and forecast the atmosphere out to 10 or twelve days. They take longer to run of course.

NWP model forecast of temperatures and winds at 5000 ft. From NOAA and weather.unisys.com

So why isn’t the three day forecast always perfect??

The cubes are still too big for one thing. We also do not know the weather over all of North America exactly is another. The NAM covers large areas of ocean, where there may be no weather observations at all! We have to guess. We do a pretty good job of it too.

There is more error. The equations are not perfect, so even if we did know the weather everywhere, and could tell the model exactly what the weather is doing right now, it would still make a less than perfect forecast! There is more though. what about clouds?? How do you tell the model what a cloud looks like, and how do you tell the model what to do with rain and snow that falls.

The rain will affect the temperature and humidity. If the rainfall is wrong, more error!

Lastly, there is chaos.

If we had perfect equations, and perfect knowledge of the initial weather, the forecast would still go wrong!

The atmosphere is a chaotic thing. This was described brilliantly by Ed Lorenz. He famously asked the question “Does a butterfly flapping it’s wings in Mexico cause a blizzard in Kansas”? Tiny changes at molecular level will eventually add up to big errors.

The current thinking is that the limit to very accurate numerical weather model forecasts is somewhere between 2 and 4 weeks. We have a long, long way to go, to get there though!

You might wonder about Climate models used by the IPCC to forecast climate change. They are similar, but since they must run for hundreds of years, the cubes are huge. Climate scientists are not interested in the weather the model comes up with. They ARE interested in the climate it comes up with, and the changes in climate that it comes up with.
How good are these Climate models??
Look at the image below.

Climate Model Hindcast from IPCC

When we start the models back in the early 1900’s, they do a very good job of predicting the Earths temperature through the 20th century. Notice the difference when we do not include greenhouse gases rising. The model blows it. Only when we include natural and human caused changes in the atmosphere, does the model get it right.

Those same models say we will see a catastrophic rise in temperature in the next 100 years, if we do not do smething to reduce CO2, and other greenhouse gases.

Yea, it’s scary isn’t it. Now you know why so many climate scientists have a bad feeling in the pit of their stomach, and they cannot seem to convince the public why.

See, I told you this was interesting!

Later,

Dan

Credits:
The Forgiving Air by Richard Somerville (He goes into great detail, and also with no Math! Buy the book.)
COMET NWP Model Matrix
NCEP (National Centers for Environmental Prediction-NOAA)
Unisys

Hundreds of the world’s top Climate Scientists have been meeting in Copenhagen. This is the largest meeting, since the release of the 4th assessment report of the IPCC in 2007. I have written here several times about research, indicating that the situation was worse than thought, just two years ago.

The rate of greenhouse gases in the atmosphere is increasing more rapidly than expected in the worst case scenario. Sea Level is rising more rapidly than expected, and the Arctic ice is diminishing much more rapidly than expected. The IPCC scientists made clear in 2007 that sea level rise was a difficult prediction, and that they might be underestimating it. You could say that. The latest Science is indicating a real possibility, of over 1 meter in rise by 2100. The 2007 report was about half that!

The same week that this conference is held, the Gallup organization released a poll that shows the number of Americans who think the threat from Climate Change is being exaggerated, has increased!

This is the great disconnect, and seems to be a hot topic of conversation in much of the Science world. The public just doesn’t seem to get it. Is this the fault of the Scientists? The news media? Is it the fault of our education system.

The economic catastrophe could be to blame. People are too busy keeping food on the table, and get most of their science from cable news. That’s a BIG mistake by the way, although AM Radio is no doubt worse.

A Scientist I know, has suggested that the answer is much less complex. The cold Winter in the East. This may very well be the answer!

Several times over the last couple of months, I’ve heard, on cable news programs, something along the line of ” a climate protest was held in a blizzard today…” and “Al Gore testified to congress during a snow storm…” in stories on Climate Change.

Even people who should know better , apparently don’t. This week, a Tampa Meteorologist proclaimed, during his weathercast, that Climate Change had stopped in 1998, and used the cold Winter in the East as one of the reasons. (If only he had read my last post! See  ”No, Global Warming didn’t Stop in 1998″ below!)

Just so you know, the planetary temp. is not measured in your back yard.

It’s measured in everyone’s back yard! (Well, maybe not that guy who lives two blocks over, the dogs would tear someone to pieces)

The map below shows the World temps. in January. The bigger the red dot, the warmer it was. Yes, it was cold in the Northeast. However, The rest of the planet had the 7th hottest January on record!! I wonder how many people, under the blue dots, got called by Gallup??

January 2009 Temperatures

The Copenhagen report will be out in a few months, but below are a few of the “Key Messages” from the Scientists.

Key Message 1: Climatic Trends

Recent observations confirm that, given high rates of observed emissions, the worst-case IPCC scenario trajectories (or even worse) are being realised. (my highlights) For many key parameters, the climate system is already moving beyond the patterns of natural variability within which our society and economy have developed and thrived. These parameters include global mean surface temperature, sea-level rise, ocean and ice sheet dynamics, ocean acidification, and extreme climatic events. There is a significant risk that many of the trends will accelerate, leading to an increasing risk of abrupt or irreversible climatic shifts. (My accent here)

Key Message 2: Social disruption

The research community is providing much more information to support discussions on ?dangerous climate change?. Recent observations show that societies are highly vulnerable to even modest levels of climate change, with poor nations and communities particularly at risk. Temperature rises above 2oC will be very difficult for contemporary societies to cope with, and will increase the level of climate disruption through the rest of the century.

Key Message 3: Long-Term Strategy

Rapid, sustained, and effective mitigation based on coordinated global and regional action is required to avoid ?dangerous climate change? regardless of how it is defined. Weaker targets for 2020 increase the risk of crossing tipping points and make the task of meeting 2050 targets more difficult. Delay in initiating effective mitigation actions increases significantly the long-term social and economic costs of both adaptation and mitigation.

The rest are on the conference website.