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...

Quick NYC Update

The exerts below speaks loudly as to what the impact of this storm could be.  Please if you have the moment read the entire post, http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2278   the destructive potential of the storm surge was exceptionally high: 5.7 on a scale of 0 to 6. This is a higher destructive potential than any hurricane observed between 1969 – 2005, including Category 5 storms like Katrina, Rita, Wilma, Camille, and Andrew.   That is pretty impressive!  But what doe this mean to property in NYC?  Sandy’s storm surge will be capable of overtopping the flood walls in Manhattan, which are only five feet above mean sea level. On August 28, 2011, Tropical Storm Irene brought a storm surge of 4.13′ to Battery Park on the south side of Manhattan. The waters poured over the flood walls into Lower Manhattan, but came 8 – 12″ shy of being able to flood the New York City subway system. According to the latest storm surge forecast for NYC from NHC, Sandy’s storm surge is expected to be several feet higher than Irene’s. Several FEET higher, not inches.  This would be catastrophic to the NYC subway system.  Definitely something worth keeping an eye on as we head into this week.  I do hope that the water does not make it to the subway system, but it can not be ignored.  ...
Maybe the Mayans Were on to Something

Maybe the Mayans Were on to Something

What a night last night with Tsunami warnings being issued for Hawaii after a massive earthquake off the Western Canadian coast!  I’m starting to think the Myans are on to something with the whole world ending in December. So it begins. The effects of Sandy are already being felt in the Lehigh Valley and Suburbs of Philadelphia.  Light rain has been falling since roughly 7am in Allentown while the wind has been steadily increasing through the morning and has been consistent out of the NE.  Expect deteriorating conditions through Sunday, Monday and into the early morning hours of Tuesday with the worst of the storm expected to strike the area in the evening hours Monday. Current Conditions Sandy is beginning to show signs of strengthening, with pressure down to 951mb (Normal Sea Level pressure is 1013mb) and dropping!   Winds are still assumed to be at hurricane force on the south western quadrant but these are satellite estimates, hurricane hunter aircraft have not measured any hurricane force winds in the areas surrounding the eye.  Much of the strengthening is now becoming more due to baroclinic (temperature gradient) processes rather than tropical, what this means is that the storm is starting to transition into a hybrid monster. Jet energy is currently located in the lower Mississippi valley and is continuing to propagate towards Sandy. Forecast Sandy is still forecast to make landfall somewhere on the New Jersey coast late Monday night.  It must continually be noted however, that for communities inland, landfall should not be the focus of attention; this storm is enormous and will have a large impact regardless of where the...
The Calm Before the Storm

The Calm Before the Storm

Communities up and down the east coast of the United States have been watching Sandy and the computer models closely over the past few days hoping for any sign that the storm would not be as bad as forecast.   Unfortunately, I do not bring good news on this Saturday morning, Sandy is still forecast to phase with an upper level trough and move inland somewhere on the Jersey Coast. Current Conditions   Sandy is a weak category 1 hurricane but the rain surrounding the storm is easily seen on Radar along the east coast.  One thing that must be noted is how large Sandy is; clouds associated with the system stretch from just north of Miami to almost Boston!  Some other features on the visible sat image are the cold front and some, what I assume are, foggy conditions in Iowa. Rainy conditions located in the region around Lake Erie are associated with an upper level jet entrance region; this is NOT the upper level energy which will cause Sandy to transform into the hybrid system we expect to see over the next few days.  Jet winds currently located over the Panhandle/ Mountain West are the final ingredient that will make this storm the monster it will be.  This energy will continue to propagate eastward and will “absorb” Sandy in the next 36-50 hours.     Forecast Unlike in some systems we will be forecasting this winter which seem to change each and every forecast cycle, this has been a pretty “easy” forecast.  The low pressure center should pass somewhere over New Jersey (likely along the North Jersey Shore) and bring...
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 Storm of the Century of 2012

The Storm of the Century of 2012

As time progresses as does my confidence in the track of the storm that is currently Sandy.  24 hours of model runs have come in since my last update and most have kept the same path as was shown yesterday. The storm has been named “Frankenstorm” by a clever forecaster at HPC and is now trending on Twitter. Past 24 hours Sandy has already caused extensive damage to Jamaica, Cuba, and Haiti with several deaths reported in the region.  The storm, unexpectedly, remained quite strong after passing over Hispaniola, remaining a strong cat 1 hurricane.   As of the 2pm NHC advisory, the storm has sustained winds of 105 mph which is a strong category 2 hurricane on the verge of reaching major hurricane status (>110 mph). Forecast As each model run is processed, meteorologists everywhere get chills thinking about the unprecedented results of a “landfalling” major hybrid hurricane.  Sandy will continue to move northward for the next 2-3 days before making a shift west or even southwestward as the negatively tilted trough from the west approaches. Major cities along the east coast will be impacted but the degree of damage very much depends on the location of the low pressure center.  The operational GFS has Sandy making a hard left turn when it is about even with New York City and bringing what would be a very large surge of water directly down the Long Island Sound.  The end result would be flooding through lower Manhattan and into Brooklyn.  For Philadelphia, the worst case would be the European solution which has the center coming up the mouth of the...