Wind Chill…What Does It Mean?

Wind Chill With all the recent cold weather, the term “Wind Chill” has been extensively used to describe just how cold it FEELS outside.  But what does that mean?  How is it computed?  What is the basis behind this seemingly subjective measure of “temperature”?  I hope to answer some of this along with a brief history of the term “wind chill”. History Prior to 1945 everyone knew that it felt colder under windy conditions but there was no objective measure to report to the public.  It was in 1945 that Paul Siple and Charles Passel published a paper quantifying the impact of wind on apparent temperature.  They used a pretty simple experiment to test come up with their numbers.  A vessel of near freezing water was set in various temperatures and wind conditions and was timed to observe how long it took to freeze.  Of course, when you think about it, there are several problems with this original wind-chill methodology including, but not limited to, that they were measuring energy loss, not temperature.  So you would not get wind chill temperature, you would instead receive a number representing the amount of energy lost in an hour over 1 square meter. It was not until 1998 that Robert Quayle and Robert Steadman released a paper titled “The Steadman Wind Chill: An Improvement over Present Scales”.  What Steadman did was expand on the work done by Siple and Passel but took into consideration the natural heating of the human body by its own metabolism.  Steadman had experience with how heat is lost and gained in the human body and used this...
Boom Goes the Dynamite

Boom Goes the Dynamite

A new day is upon us and still nothing positive to report on the progress of Sandy AKA Frankenstorm.  As of the 8am advisory, sandy has sustained winds at 80 mph and is moving to the NW at 10mph.  She has weakened in a  tropical sense but that means very little to the impact on the east coast. Powder Keg Although Sandy is weakening, she still threatens to pack a huge punch as she approaches the Eastern Seaboard.  Media outlets have correctly been billing this storm as a hybrid storm because Sandy will lose her tropical characteristics in the next few days as a trough approaches the area.  Upper level energy will move in from the west (see image) and provide a spark for Sandy to explode into a quickly deepening area of low pressure.  Pressure gradients will be very steep which means that a very large area can expect tropical storm force winds with area along the coast experiencing hurricane force gusts.   Where and When Everyone wants to know exactly where and when this event will take place.  Unfortunately there is still a bit of disagreement among the models as to where the storm will be strongest.  American models (GFS, NAM) suggest that the storm will make the greatest impact in Long Island and may even have the storm follow down the Long Island Sound, which would be devastating for some communities along the waterway, especially on the southern half where the sound funnels into New York City.  The every consistent Euro continues to strike Delmarva which could push water up the Delaware River into Philadelphia.  This...

The Fine Print

I would not be doing my job if I failed to mention the possibility of this storm missing the region completely.  There is evidence that the storm will veer off into the Atlantic and miss the chance at phasing with the frontal system approaching from the west.  Although the overwhelming majority or meteorologists are in agreement that a portion of the Northeast US will be heavily impacted by the system, it is not unheard of for all the atmospheric models being wrong, especially in such a transition time of year.  Sometimes you can choose red or black on the roulette wheel…and green hits. At times we as scientists like to get caught up in the extreme and fail to acknowledge the mundane, and this storm is no different.  Communicating information to the public is dicey at times because people have a tendency to latch on to certain words or phrases.  If I say strong winds will cause massive power outages, and you don’t lose power, suddenly I was wrong; even if half of your state is without power.  Educating a large population on something as fickle as the movement of a tropical cyclone is a monumental task, and it takes on a new level of importance when there is the risk of property damage and harm to a number of humans. I take the “apologize for overstating a storm” rather than “apologize for you being...