When doing these observations, we put the Kestrel setup on an island of grass out in our small parking lot. Now, most meteorologists and weather buffs may scoff at even the idea of taking weather observations that don’t meed the World Meteorological Organization’s standards (eg. temperature measured at 2 meters, wind at 10 meters, away from buildings, etc.), but we wanted to make observations of what the weather really feels like. Not the weather taken at the airport next to the tarmac, but the weather you feel when you go outside. Makes sense, right? This is why the Kestrel meters offer a more true environmental snapshot of exactly where you are- it measures the conditions right where you are- not miles away at the airport or another weather station hub.

A quick note about the thermistor (temperature sensor): at all angles, the thermistor stayed in the shade of the Kestrel unit. So while we did not measure the temperature within a Stevenson screen or within a fan-aspirated radiation shield, the temperature is accurate to what you would feel while outside, at that exact minute. This is why the temperature has so much variation on the charts below.

When first investigated the data, the first thing we looked at was what the difference between the two days was. We knew the first day was warmer, but that hardly tells the whole story.

Recorded temperature during the afternoon on July 6 and 7, 2010 in Boothwyn, PA (just outside of Philadelphia).

In the graph, the darker line is the 6th and the brighter line is the 7th. At first glance, it looks like the temperature can really vary during the day. And in reality, it does. Most of the rises and dips in temperature can be explained by some passing clouds and winds (explained later). Even though the thermistor was not directly in the sun, when the sun went behind the clouds temperatures drifted down until the sun came back out. The high temperature recorded on the 6th was 105.5 F, while the high temperature recorded on the 7th was 104.5 F. Compare this to the local airport high’s of 102 and 103, respectively.

Now about that wind. I figured the wind had an influence on the temperature because to our west is a small woods area, and to the east is a large asphalt parking lot. I figured the temperature would become cooler with an easterly wind and warmer with a westerly wind. To investigate this, I took a day (the 7th) and plotted the temperature and wind direction on separate axes. The result is below, with wind direction in green and temperature in red.

Temperature vs. Wind Direction for a small period of time on the 7th.

Temperature vs. Wind Speed on July 7.

I noticed that there was a slight correlation between the direction and temperature, but it was not consistent. Also, I only took a small sample of the data where this effect looked better- in some segments of the data it was hardly noticeable. However, for times when the data did seem to align it was almost always the same. Temperatures rose with an Easterly wind, and temperatures decreased with a Westerly wind. After seeing this, I decided to compare the Temperature and Wind Speed during this same time period (below).

Now, the wind speed correlation seemed much more defined. As winds increased, the temperature reading dropped from the mixing going on in the air.

Looking closer at the data, I calculated the correlation factor for both variables with respect to temperature. (For those unfamiliar with correlation factors, -1 means a complete negative correlation, 1 means a complete positive correlation and 0 means no correlation at all.) Comparing the temperature to wind direction for the period graphed, the correlation factor was a measly -0.03. The wind speed had a much better correlation with temperature with a correlation factor of -0.69. For the entire day, temperature and wind had a correlation of -0.46 on the 6th and -0.50 on the 7th. Not an exact match, but a pretty strong observation that I wouldn’t be surprised to see during the summer.

Have questions? Want to know more? Comment below, tweet at us or check out our Facebook page.

This summer has proven to be one of the hottest on record, and we’re only now in mid-July! Even when the weather is mild, temperatures in cars can soar to dangerous levels within minutes.

We decided to do an experiment with the Kestrel 4500 Bluetooth unit to see just how hot the inside of a car could get during one of the hottest day of the summer. Check out the latest episode of KestrelTV where Kestrel Weather girl Monica Devlin shows you how your car becomes an oven under the hot sun.

It should be noted that we did place the Kestrel in direct sunlight. In meteorology, temperature sensors are always placed in the shade with good airflow. We did this because we were measuring the temperature on the dashboard. Temperature measurements in other parts of the vehicle were likely less than measured on the dashboard, but still significant. The dashboard surface is said to be similar to the hard parts of a child’s car seat in terms of how it much it can heat up.

Graph of Temp (F) and Relative Humidity (%) of our Kestrel in a Car experiment. The data before the temperature begins to rise is from using the Kestrel on a tripod and vane mount to monitor conditions during the early afternoon.

Notice how there is hardly any humidity in the vehicle. Since the low humidity would encourage efficient sweating, any person or animal placed in the car would be dehydrated very fast. Also notice not just how hot it gets but how fast the temperate rises just within the first ten minutes.

Jan Null, Adjunct Professor of Meteorology at SFSU has done extensive research on this topic and provides an up-to-date page on the current statistics and research. His experiments covered a large range of temperatures and he says that “‘cracking the windows had little effect.”

You can download the data from our experiment below. The file is split into four sheets: an introduction, the raw data, the raw data with explanations and finally, a graph. You can investigate the data yourself and make graphs of different things. (Note, we took out data like wind speed that didn’t make any sense to include.) Download the data here (.xls file)

You can find more details for Jan Null’s website here: http://ggweather.com/heat/

Have questions or comments? Share them below, on Facebook or tweet at us!

I was very excited to visit NCAR this summer! As a student of meteorology, I knew some things about this giant center for research, but I was really excited when I was selected to attend this workshop. A few facts about NCAR/UCAR:

• UCAR was established by the University community to further the advancement of research in the atmospheric and related sciences
• UCAR created and manages NCAR, which is located across four campuses at and around Boulder, CO
• NCAR/UCAR employ around 1,500 people (including management and support staff)
• NCAR/UCAR is funded mostly through the National Science Foundation
• NCAR scientists research things such as climate change, hurricane development, severe weather warning systems, supercomputers, aircraft-based instrumentation and more!

The NCAR Mesa Lab in Boulder, CO.

During the workshop we attended, our first stop was the NCAR Mesa lab, which was designed by world-famous architect I.M. Pei. The structure can be seen while approaching Boulder, as it sits 600 feet above the city.

NCAR has a very large supercomputing facility to meet the needs of scientists who must run computer models which simulate things in the atmosphere- everything from pollution to severe thunderstorms to the earth’s climate. The Mesa lab also is host to the Visualization Laboratory, which is a high-tech conference room capable of displaying 3D simulations.

The Gulfstream-V, one of two research aircraft used by NCAR, sits in its hanger undergoing preparation for a hurricane research project later this summer.

Another one of the labs I got to visit was the Research Aircraft Facility. We were lucky enough to catch one of the airplanes- the Gulfstream-V- was in the hanger, being prepared for a project called PREDICT which will deploy late this summer to research pre-development of tropical systems in the Atlantic. It was really cool to see scientific research on this scale, with so much coordination between everyone. Many of the instruments they take up on the plane and developed at RAF because a scientist wants to measure a certain atmospheric variable in-flight.

We also visited the National Renewable Energy Laboratory’s National Wind Technology Center. There were many different types of wind turbines being tested, and it was very interesting for me to see how NREL works with industry to develop and market the technologies it develops. In addition to harnessing the power of wind, the facility made use of a large solar array to power its operations.

Of course, it wasn’t all research science at the workshop. We were fortunate enough to be able to take a trip up to Rocky Mountain National Park where we had to walk across some snow to get to a lookout point. It was beautiful and really a treat for someone like me who normally doesn’t see mountains of this size.

Overall, I had a lot of fun at NCAR. I was able to meet my peers at other institutions and also meet some of the top atmospheric scientists in the world! While I’m back at Kestrel now for the rest of the summer, I was able to make some great connections at NCAR and I hope our paths cross again in the future.

For more information about the NCAR Undergraduate Leadership Workshop, check out the workshop page at NCAR’s website. You can find out more about NCAR and UCAR at their websites.

Wondering about weather words? Check out the Kestrel weather glossary online.

We are writing to notify you of an accuracy issue we have discovered in certain Kestrel 4000 series weather meters.  For the majority of Kestrel customers, this issue will not impact the ability of the Kestrel to provide the accurate environmental readings they require for their applications.  In fact, only two customers to date have actually reported seeing the impact of this accuracy issue in their application.  However, because we are committed to ensuring the Kestrel line’s absolute accuracy and adherence to specifications, we are providing notice to you and providing test, repair and recalibration of any Kestrel meter displaying this flaw at our expense.
All Kestrel 4000 series meters manufactured after 3 February 2006 make use of a temperature sensor inside the relative humidity housing (the white cylinder) to provide accurate humidity readings more quickly in changing conditions. Due to a supplier error, certain units were manufactured with an internal thermistor with response characteristics that did not match the external thermistor.  The result of this is that at very low temperatures the Kestrel displays higher values for relative humidity than the true value, and at very high temperatures the Kestrel displays values lower than the true relative humidity.

Please note that at room temperature, the Kestrel is within specifications, and deviates only at the extremes of the temperature range.  Note also that only humidity and humidity related measurements (heat stress index, evaporation rate, dewpoint, humidity ratio, relative air density, wet bulb, and density altitude) are affected.  Wind speed, temperature, wind chill, pressure and altitude are unaffected and perform within specifications throughout the specification range. This problem impacts only Kestrel 4000 to 4500 models and does not affect the Kestrel 3000 or 3500.  Please refer to our list of possible scenarios to get a better idea of how this problem may affect the measurements you use in your application.

Fahrenheit

Celsius

Affected units will have serial numbers between 571631 and 608738 (manufactured between April 2008 and April 2010).  We would like to request that you check your unit(s) for this serial number range. If you have a unit(s) in this range, please visit our online return authorization page to obtain a RA number.  You can request a prepaid UPS return label at the bottom of the page.  Please contact us if you have any questions or problems with the return authorization page.  Once received, we will repair and return your unit(s) as soon as possible. If you have any questions, please do not hesitate to ask.

Thank you for your time and we apologize once again for any inconvenience. 

Please see below for specific examples of how the Kestrel is used and how it may affect you:

Long-range Shooting: I use my Kestrel 4000 to take measurements relating to ballistics performance – specifically wind, temperature, barometric pressure and density altitude.  How will this issue affect the accuracy of my firing solution?

Wind, temperature and pressure are all unaffected, so these readings will be completely within specifications.  Relative humidity has an extremely small effect on air density (whether input as density altitude or humidity into your ballistics calculator), so the humidity inaccuracy is unlikely to impact the firing solution result at all. If this is the only context in which you use your Kestrel 4000 (or 4500), you can safely continue to use it for this purpose.

HVAC: I rely on my Kestrel to give me the necessary information to aid in appropriately sizing AC units and humidification/dehumidification requirements.  Could I have sized a unit incorrectly as a result of this thermistor issue?

For residential/commercial AC, an error is very is unlikely because you almost certainly took your measurements at or around room temperature (70-80° F /21-27° C).  In this temperature range, the relative humidity measurements are within the +/- 3% accuracy range even with the thermistor mismatch.

Racing: I use my Kestrel to determine air density impact on my ET in bracket races, or to tune my car to the perfect fuel/air ratio.  Could the thermistor mismatch have impacted my results?

As discussed above, relative humidity has a very small impact on air density compared to temperature and pressure.  So, whether you were referring to density altitude or inputting absolute pressure, temperature and humidity into an ET calculator, your results are unlikely to have been impacted.  Furthermore, the errors are only seen at the extremes of the  temperature range.  At 100° F and 40% relative humidity (true), the Kestrel would measure 36.1%.  Less than 1% more than the specified accuracy.

Concrete Pouring: I’ve used my Kestrel to determine if my concrete will dry too fast due to evaporation.  Did the Kestrel cause me to compromise the integrity of the concrete?

Highly unlikely.  At the temperatures suitable for pouring concrete, the Kestrel would either be within specifications or would under-report humidity, thereby erring on the side of caution.  If it was extremely hot at the pour location, the Kestrel would read a lower relative humidity (and a higher evaporation rate in a 4300) than actual.  At worst, you may have taken steps to reduce evaporation (covering, misting, add-ins) that were not necessary because the Kestrel showed a faster drying rate than actual.

Heat index and wind chill are two of the most popular “apparent temperature” indexes which try to convey a more useful temperature to the general public. Most people understand the basic premise of these indexes (wind makes cold temperatures feel even colder, humidity makes it feel hotter), but did you know that because of how heat index was developed, the heat index can be lower than the actual air temperature?

Heat index was developed by R. G. Steadman in a 1979 paper published in the Journal of Applied Meteorology titled, “The Assessment of Sultriness. Part I: A Temperature-Humidity Index Based on Human Physiology and Clothing Science.” As a researcher in the Textiles and Clothing Department at Colorado State University, his paper takes into account a number of factors to form what we know today as the Heat Index. These factors that Steadman accounted for include include:

• “Basic Dimensions” – A typical human, either sex, height of 1.7m (5’ 5.8”), 67kg (147.7lbs), which gives a person’s surface area of 1.78 square meters (19.1 square feet)
• “Effective radiation area” – The amount of radiation exchange between radiant heat and surroundings. Steadman uses the average ratio of 0.79 for clothed parts of the body, and 0.85 for bare (unclothed) parts under mild conditions.
• “Clothing cover” – The amount of clothing and the thickness of the clothing, which is assumed to be “long trousers and a short-sleeved shirt of blouse” to cover 84% of the body’s surface. While there can be differences in the exact apparel worn along with hair length, Steadman points out that these effects impacts are similar to individual variations in skin insulation.
• “Core temperature” – The comfortable body temperature (which the body is trying to achieve in equilibrium) is 37 C (98.6 F).
• “Activity” – The amount of actively a person in engaged in. Steadman uses a person walking at a rate of 1.4m/s (3.1 mph), which generates 800 W/m^2 of energy from the human body.
• “Effective wind speed” – This is the wind speed on the body. Meteorologists measure wind speed (Eg. At your local airport) at a height of 10 meters (33 feet). Using the average wind speed at 10 meters, and factoring in the diminished winds that actually reach the surface, Steadman uses an effective wind speed of 1.32 m/s (3 mph).
• “Ventilation rate” – The amount of heat exhaled by a person. For summer conditions, this is estimated to be about 8% of heat from the body lost through the lungs.
• “Skin resistance to moisture transfer” – What most people would call the effect of humidity on the skin.
• “Clothing resistance to heat transfer” – The amount of heat not escaping through garments.
• Along with a few other complex factors

Heat Index Chart (Courtesy National Weather Service)

It is important to note that there is no “official” formula to calculate heat index exactly. This is because heat index is a value from a table. Your Kestrel unit looks up the table value using a complex polynomial equation that gives a very accurate value from the table. This is why, if you use the temperature and dew point from the Kestrel and plug it in to some online calculators, you may see a difference in the heat index value. Rest assured, your Kestrel unit is using the most accurate method possible. (Most online calculators of Heat Index, such as this one on the national weather service website, use a modified formula which carries an error of +/- 1.3F. The Kestrel uses a much more sophisticated formula that is nearly identical to the index table.)

(From top to bottom) Temperature, Relative Humidity and Heat Index. Notice the Heat Index is less than the air temperature. Is that right?!

Looking at the official chart (or at your Kestrel indoors) you notice what seems to be an anomaly-the heat index may be lower than the current temperature. I noticed it this morning on the Kestrel meter I use at my desk. (See image on the right.)

The reason for this is that the index assumes a small amount of wind, and also assumes the person is walking. Note, the amount of wind and the walking speed (defined as “Activity” in the list above) is a constant value throughout the table. So in many low-humidity situations (under 30% humidity) with an air temperature of less than 98 F, the heat index will always be lower than the actual air temperature, as explained above. In the US, this can be common in desert areas that are very dry such as places in Arizona, New Mexico and Nevada.

For more information about Heat Index, check out this great resource from the National Weather Service: http://www.srh.noaa.gov/jetstream//global/hi.htm

To learn more about humidity and other environmental conditions that your Kestrel meter measures, check out Knowledge Center.

Check out our entry below. Maybe you could convince your company to sign up? Post your best tips for staying active in between work, family and life in general. Tell us how you fit in fitness while juggling a busy schedule and you could win an NK hoodie!

At the offices of Nielsen-Kellerman Company, competitive spirit is as obvious as overhead lighting, W.B. Mason manila folders, multi colored post-its and swivel chairs. We’re in the business of building tough, long-lasting electronics for extreme outdoor activities and demanding sports. NK designs and manufactures Kestrel Pocket Weather Meters, sports performance monitoring electronics for rowing, and ClearNav soaring instruments for gliders.

The NK employee roster boasts an impressive line-up of jocks that includes nationally and internationally competitive rowers and paddlers, several women with serious shooting skills, a certified wildland firefighter, a triathlete, an ALL lacrosse player, a former NFL cheerleader, a world champion dragon boat drummer, a paintball player, a cross-country soaring pilot (who’s also a marathoner and a yogi), two dressage riders, a CrossFit enthusiast, and a motorcycle mama.
However, being in an office full-time can put even ex-hardcore athletes in a fitness rut. The daily grind of sitting all day at a desk, traveling for trade shows and regattas, taking care of kids and running households can cause fitness to take a back seat. This has happened for many of us here. A competition is just what we need to kick us into high gear. Competition is a part of the NK culture. For example, it’s not unusual to drive by the NK headquarters and see a water balloon toss, relay race, jump rope contest, or heck, even tug-of-war going on in the parking lot. Say what?

Just as our products are niche and unique, our office is anything but your typical cubicle dwelling. Most notably, we have four to six dogs roaming around at any given time. They serve as excellent front door greeters and reduce workplace stress by 42%. Ok, we haven’t done official statistics on this… but how can you be stressed when a wrinkly bulldog puppy bumbles over periodically to snuggle your leg and stare at you with a goofy, toothy, wide-mouth grin? Exactly.
Contests are a regular part of our business activities. We have contests in meetings, at tradeshows, and over morning coffee. The adrenaline rush of a challenge motivates us here at NK. Whether the contest is to beat sales goals, gain market share or DROP pounds and shape up for Be Well Philly, NK will KO the competition…and have some fun while we’re at it.

Ladies & Gentleman Announcing…the NK line up (cue crowd roar):

CEO Top Dog: Alix Kocher

401K Killa HR Manager: Paula Whittaker

Sign-the-Dotted-Line Business Development: Christy Munding

Raise Revenue Czar Sales & Marketing Manager: Katie Godfrey

Production SNAFU Assassin Asst. Engineering Manager: Dan Honeywell

Q & A King Technical Support : Ben Nielsen

Tech Solution Sultan Design Engineering Manager: Michael Naughton

Tweet til Death Marketing & PR Coordinator: Monica Devlin

The Hands Tool and Die Maker: Yohann Rigogne

Git-er-Done Maintenance & Repairs: Tim Godfrey

Your Kestrel Weather Girl,

Monica Devlin

Follow our fab fit (or flub) journey right here on the blog and elsewhere in the cybersphere:
Tweet (or die) @KestrelChick @coxboxdude
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The NK team

BUY NOW

Wherever there’s a need for humidity, wind speed, barometric pressure or temperature readings…there’s a Kestrel Pocket Weather Meter to save the day with accurate, instant measurements!

If I were the casting director for this latest Weather Channel commercial, the above statement is how I would describe the epic role and significance that the scene-stealing Kestrel 4500 plays just at the .08 second mark. Sure, you only catch but a brief glimpse of the Kestrel’s noble, quarter-turned profile, rugged American-made cool, and sturdy exterior which earns its 5-year warranty. However, there are no small parts, only small actors- and weather meters. Positioned between Storm Tracker Jim Cantore’s official “Weather Channel” hat and mic, the Kestrel 4500 is clearly part of his essential gear.

Jim Cantore is kind of a big deal in the weather world. I mean, heck, as this commercial conveys, he’s like the Raging Bull of Meteorology. The undefeated champion of storm tracking!

But, not only superstar meteorolgists use Kestrel Meters to get instant environmental conditions. Just about every TV weather team in the country relies on the Kestrel to get on-the-spot weather data. That way, when you see your meteorologist doing a live report, screaming above the roar of a hurricane, “I’m standing in 70 MPH winds” , they can whip out their Kestrel to prove it!

Thanks to our friends at local ABC affiliate WPVI-TV, for pointing out the Kestrel cameo. Their weather team is top notch.

Who is your fave local weather team or meteorologist?

Send me your picks and why. I’ll feature the top 5 submissions on our page, Twitter and Facebook. Plus you’ll win a Kestrel Weather Prize pack!

I’m going to give a shout out to one of my fave meteorologists. She’s a former Philly weather girl who is currently a Chief Meteorologist in Chicago. She LOVES everything weather and covers some of the coldest games in the NFL. Plus her name is Amy Freeze. Seriously. Doesn’t get better.

Learn more about Amy and download some DIY forecasting tips from her Freeze Front website . It’s pretty “cool”. Pardon the weather humor, you knew it was coming.

Amy Freeze & her Kestrel 2500 at Chicago Bears game

Your Kestrel Weather Girl,

Monica Devlin

mdevlin@nkhome.com

twitter.com/KestrelChick

Facebook.com/KestrelMeters