The Science of Fireworks

Washington, D.C. July 4th fireworks

It’s the sign that Fourth of July is right around the corner – fireworks. The light displays decorate the skies across the United States every year to celebrate our Independence Day. All of the beauty and marvel that comes with fireworks displays is actually due to science.

Chemistry is behind the vivid displays of fireworks in a few ways. The basic formula to create fireworks combines an oxygen rich chemical with burning fuel. Additional chemicals within the package can create the different colors seen in the displays. Strontium will create red colors, titanium causes white and copper produces fireworks with a blue tint. Blue is one of the more difficult colors to achieve because the copper needs to reach a certain temperature (after all, what’s Fourth of July without red white and blue?). Fireworks produce an exothermic reaction, which means that they release energy as heat. That heat turns into the lights and colors we see in the sky.

While chemistry is responsible for many processes during fireworks explosions, physics also plays its own role. The final height of the firework depends on its initial speed. Fireworks are launched using force from an explosion, accelerating it upward. Pressure causes the fireworks to fly upwards and eventually explode outward.

Hundreds of people are injured due to fireworks. Even the handheld sparklers can burn at a temperature of 2,000°F+. Those types of temperatures can melt certain metals, so it would do similar damage to skin.

Meteorology can also affect a fireworks show. Higher humidity may tone down the otherwise vivid colors that decorate the sky. Lightning could hit an unused firework and cause injuries to any bystanders. Strong winds pose a fire hazard – and drought makes things even more dangerous. Too little wind cannot clear smoke after the explosions. When the temperature increases with height (called an “inversion”) instead of decreasing as it usually does, smoke from the fireworks display could decrease viewing quality.

Eastern Iowans should prepare for isolated showers and storms for the afternoon and evening of Fourth of July 2018.

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Posted under Educational, Optics

This post was written by Rachael Peart on July 3, 2018

Winter Solstice

The Winter Solstice occurs at 10:28 AM on December 21st, marking the astronomical start of winter.  This is the exact moment that the sun’s rays are directly over the Tropic of Capricorn.  The sun is at its lowest point in the sky at noon over the northern hemisphere at this time.

This also marks the day with the least amount of daylight, and most amount of darkness.  So, the good news is, more daylight is coming in the days ahead.  In fact, there’s approximately 9 hours, 3 minutes and 44 seconds of daylight on the day of the winter solstice — that’s about 6 hours and 14 minutes left since the summer solstice!  Track the sunrise and sunset times for your hometown by clicking here.

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Posted under Educational, Winter Weather

This post was written by Kyle Kiel on December 20, 2017

Precipitation Type

Here is a look at how the different precipitation types form. Way up in the sky the air is below freezing (below 32°F or 0°C). In some cases there is a warm layer closer to the ground. Exactly how thick that warm layer is and how close to the ground impacts the type of precipitation we receive.

I will start with snow (left side of the graphic below). As the snowflake above falls toward the ground, the temperature through out the travel toward the ground remains below freezing not allowing it to melt. So the snowflake stays a snowflake from top to bottom.

Now for sleet. The snowflake falls through a warm layer (above freezing) and the snow melts and turns to a raindrop. The raindrop than falls through a pretty thick layer of cold air. This allows the raindrop to freeze. By the time it reaches the ground it is sleet.

Compare that with freezing rain. That same warm layer is now thicker leaving a very small layer near the ground below freezing. There is less time for the raindrop to freeze and turn to sleet so it falls as rain and freezes on impact to anything on the ground.

Now if that layer is above freezing all the way to the ground it stays as rain and doesn’t freeze. The air closest to the ground is above freezing and the ground is above freezing. The result would be rain.

Precip Type

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Posted under Education, Educational, Ice, Winter Weather

This post was written by Schnack on January 12, 2017

Iowa Heat Awareness Day 2016

June 9, 2016 is Iowa Heat Awareness Day. There are many dangers that come along with warmer weather. Just in 2015 alone, 24 children died in vehicles on hot days. Remember – “Look before you lock” to check for children and pets. It doesn’t take long for the inside of a car to warm up to over 100° when the outside temperature is 80°.

Car Heat Awareness

Even outside of cars, there are many health risks that come with prolonged exposure to heat. Limit time in the heat or take frequent breaks and stay hydrated in order to avoid these serious – and possibly fatal – illnesses.

Heat Illness Symptoms

Heat index measures how it feels (known as the “apparent temperature”) based on the air temperature and the current dew point. Dew point is a measure of moisture in the air as well as the main indicator for how humid it is. The higher the heat index, the higher the possibility of developing a heat related illness.

Heat IndexTd

Temperatures this weekend could exceed 90° and the forecast stays warm through next week.

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Posted under Educational, Heat

This post was written by Rachael Peart on June 9, 2016

What was That?

Just got a report of soft snow pellets in Cedar Falls. This is called “graupel”.
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Posted under Educational

This post was written by Schnack on January 25, 2016

Minnesota Tornado Friday Night

UPDATE

NWS DAMAGE SURVEY FOR 07/17/2015 TORNADO EVENT...

EF-1 TORNADO OCCURRED WEST OF WATERTOWN IN CARVER COUNTY
MINNESOTA...

A LINE OF SEVERE THUNDERSTORMS TRACKED EAST ACROSS MOST OF CENTRAL
MINNESOTA DURING THE LATE EVENING OF JULY 17TH. A TORNADO
DEVELOPED ON THE LEADING EDGE OF THIS LINE AND IMPACTED PORTIONS
OF NORTHERN CARVER COUNTY. NWS DUAL POL RADAR OBSERVED TORNADIC
DEBRIS...AND A DAMAGE SURVEY CONFIRMED A 4.3 MILE LONG TORNADO. 

RATING: EF-1
ESTIMATED PEAK WIND: 105 MPH 
PATH LENGTH /STATUTE/: 4.3 MILES
PATH WIDTH /MAXIMUM/: 500 YARDS 
FATALITIES: 0 
INJURIES: 0

START DATE: JULY 17 2015
START TIME: 1158 PM CDT
START LOCATION: HIGHWAY 33 AND 30TH STREET... 3N HOLLYWOOD
START LAT/LON: 44.9488/-93.9715

END DATE: JULY 18 2015
END TIME: 1202 AM CDT
END LOCATION: NORTH OF ROSE AVENUE AND COUNTY 122... 2WSW
WATERTOWN
END_LAT/LON: 44.9532/-93.8846

SURVEY_SUMMARY: TORNADO SPUN UP 3 MILES NORTH OF HOLLYWOOD AND
CONTINUED EAST NORTHEAST TO 2 MILES WEST SOUTHWEST OF WATERTOWN.
THE MOST DAMAGE OCCURRED AS THE TORNADO CROSSED VEGA AVENUE WHERE
NUMEROUS TREES WERE SNAPPED AND SOME MINOR STRUCTURAL DAMAGE WAS
FOUND. THERE...A HOME WEATHER STATION RECORDED A 99 MPH WIND
BEFORE IT BLEW OFF THE HOUSE. THE WEATHER STATION REPORT...IN
ADDITION TO THE DEGREE OF TREE DAMAGE...SUPPORTS AN ESTIMATED
MAXIMUM WIND SPEED OF 105 MPH.

EF SCALE: THE ENHANCED FUJITA SCALE CLASSIFIES TORNADOES INTO THE
FOLLOWING CATEGORIES.

EF0...WEAK......65 TO 85 MPH
EF1...WEAK......86 TO 110 MPH
EF2...STRONG....111 TO 135 MPH
EF3...STRONG....136 TO 165 MPH
EF4...VIOLENT...166 TO 200 MPH
EF5...VIOLENT...>200 MPH*

There are reports of cars flipped, structural damage, and large trees down about 4 miles west southwest of Watertown in Carver County, MN. Radar observed a tornado in this area for 2 to 3 minutes around midnight. Looking at different modes of the radar data can tell us many things about what is happening. The image below is a good example of that.
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Posted under Educational, Severe Weather

This post was written by Schnack on July 18, 2015

No Data from Charles City

You might have noticed there has been no data being plotted for Charles City lately on our maps.
There is a reason for that. According to the Northeast Iowa Regional Airport Manager (William R. Kyle) in Charles City the AWOS (Automated Weather Observing System) has been taken down for replacement with new equipment. This project is being conducted by the IDOT. The equipment replacement will take about one week. After that it will take about two weeks to test the equipment. After that the FAA will have to certify it. Hopefully this will all be complete and back up and running around Thanksgiving.

The map below shows where all of the other AWOS stations are across the state are located.
Click on image to enlarge.
Images below are courtesy of Iowa Environmental Mesonet.

The map below shows you where the instruments are located at the airport. 

 

 

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Posted under Educational

This post was written by Schnack on November 7, 2012

Shorter Days Ahead

It is getting to that time of year  where the days are getting shorter.  Take a look how fast the sunset times change during the next few months. The data is for Waterloo.

8:02 PM August 20
7:09 PM September 20
6:19 PM October 20
4:43 PM November 20
4:39 PM December 20

The two maps below show the direction the Sun rises and sets on the horizon. The green line is the sunrise and the red line is sunset. The map on the left is August 20 and the map on the right is December 20. The change

The image below shows what the path of the sun looks like as it travels from horizon to horizon from June to December.

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Posted under Astronomy, Educational

This post was written by Schnack on August 20, 2012

Different Scenario this Evening

Last night I posted about how there was a “CAP” that prevented any storms from developing Wednesday evening. This evening is a different. Showers and thunderstorms have developed in the last hour…notice the radar image below.


The Davenport sounding shows no “CAP” and therefore allowing the air to rise rapidly producing thunderstorms. The red line in the sounding represents the temperature as you go up in the atmosphere. The temperature continues to cool off all the way up to the jet stream. There is now warm layer like there was Wednesday evening.

 

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Posted under Educational, Severe Weather

This post was written by Schnack on May 3, 2012

Finding Clouds at Night

The sky is clear in some locations and cloudy in others across Iowa this evening. During the day it would be easy to see this with a visible satellite image but at night it is a bit more difficult. There is no visible satellite image available because the sun has set. So this product is really good at indicating what the sky conditions (clouds and/or fog) are at night. I circled the area with a clear sky over Iowa and Wisconsin with a green line.

The locations with colored dots indicate there are clouds or fog. If the circles are empty that means the sky is clear and there is no fog.  The colors correspond with either the how low the base of the cloud is or what the visibility is. See the chart below. Click here for the direct link to the updated image.

Here is more information about the image from the Aviation Weather Center division of the National Weather Service.

Visible/Fog

The vis/fog satellite images are generated from visible geostationary satellite images during local daylight hours, and from a derived “fog” image at night that emphasizes the low clouds (Note the saw-tooth boundary between the different images).During the day the visible image is brightness normalized by dividing by the cosine of the solar zenith angle. This removes most of the image dependence on sun angle, such as brightness changes at sun rise and sun set and differences between winter and summer image brightness. The visible brightness depends primarily on the thickness of the cloud. The visible image is used when the sun is higher than 3 degrees above the horizon.

At night there are no visible images, so a derived “fog” image is substituted for the visible. The “fog” image is generated from the temperature difference between the 3.7 micron images and the 11 micron infrared images. The temperature difference depends primarily on emissivity differences caused by different physical characteristics of the radiating surfaces. The brightness of the image is set up so that low clouds are white, ground is gray, high clouds are black, and very high cold thunderstorm tops are a salt and pepper black and white. The “fog” image is not very sensitive to the temperature of the low clouds except for extremely cold surface temperatures below -40 degrees, when it starts to show some of the salt and pepper appearance. The ground generally shows up as a gray color, except for a few areas in the west, such as the delta of the Colorado River which shows up white because of the soil emissivity there. The white “fog” low clouds start to show up on the images when the low clouds are wider than 2 miles, and are thicker than about a hundred feet. Hence it will generally pick up widespread IFR condition, but may not show small, thin local fog or haze conditions.

 

 

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Posted under Education, Educational

This post was written by Schnack on November 22, 2011