A Deep Freeze in NYC

A massive arctic outbreak has sent most of the U.S. into a deep freeze.  From the Mid-West to the Gulf Coast and along the eastern seaboard, many cities are dealing with the coldest temperatures they have seen in nearly two decades.

Here in New York City, the mercury fell to 4°F in Central Park this morning – a new record low for the date.  The previous record of 6°F was set in 1896. Our normal low temperature for this time of year is 27°F.

While it certainly was bitterly cold today, it was not the coldest day the Big Apple has ever experienced. That dubious honor, according to the NWS, belongs to February 9, 1934, when the low was a brutal -15°F.

Our current frigid conditions are the product of a weakened polar vortex – the pattern of winds around the North Pole.  As it slowed down, arctic air pushed southward and caused a deep dip in the jet stream. This frosty air is not likely to stick around much longer, though.  As the jet stream retreats northward, temperatures are forecast to rebound to more seasonable, and even above average, levels by the end of week.

Image Credit: Mesonet

Image Credit: Mesonet

First Major Winter Storm of 2014

The first major winter storm of 2014 blasted a large area of the U.S. overnight. Packing heavy snow, high winds, and bitterly cold air, it impacted nearly twenty states from the Mid-West to New England.

Locally, the storm brought New York City 6.4 inches of powdery snow.  On average, the city usually receives 7 inches for the entire month of January. The storm also sent temperatures plummeting.  The high reading in the Central Park today was only 18°F.  Tonight, the temperature is expected to drop to a frigid 5°F.  When you factor in the wind chill, it will feel like -10°F.  Our normal high for this time of year is 39°F and our normal low is 28°F.

Bow Bridge

Central Park’s Bow Bridge in the snow.  Image Credit: The Weather Gamut.

Winter 2014

View of midtown Manhattan’s skyline from snow-covered Central Park.                                      Image Credit: The Weather Gamut.


Record Warm Weekend for NYC

What a difference a week can make!  Last weekend, New York City received five inches of snow.  This weekend, as winter officially arrived, the Big Apple experienced record-breaking warmth.

On Saturday, according to the NWS, the temperature in Central Park reached 65°F – a new record high for the date.  The previous record of 62°F was set in 1923 and tied in 2011.  On Sunday, the mercury continued to soar and the city’s temperature reached a balmy 71°F.  This shattered the old record of 63°F set in 1998. The average high for this time of year in NYC is 41°F.

These unseasonably high temperatures were the result of warm winds moving into the area from the south as the jet stream retreated to the north. The mild weather is not expected to last much longer, though. Colder – even below average – conditions are expected to return tomorrow as a cold front moves into the region.

Warmest November Ever Recorded for Planet Earth

This past November brought unseasonably cool conditions to most of the United States, including here in New York City.  The rest of the globe, however, experienced exceptional warmth.

According to the National Climatic Data Center, November 2013 was the warmest November ever recorded for the entire planet.  Earth’s combined average temperature for the month – over both land and sea surfaces – was 56.6°F.  That is 1.4°F above the 20th century average.  This November was also the 345th consecutive month that our global temperature was above its long-term norm.

While heat dominated most of the planet, Russia was particularly warm.  Some parts of the vast country, including the Urals, Siberia, and the Arctic Islands in the Kara Sea, posted temperatures of more than 14°F above the monthly average. As a whole, it was that nation’s warmest November since record keeping began in 1891.

Year to date, 2013 is now tied with 2002 as the planet’s 4th warmest year on record.

NCDC_Nov2013Image Credit: NOAA’s National Climatic Data Center

Public Display Thermometers

New York City, like most large cities, is a heat island.  With miles of paved surfaces, it is generally warmer than surrounding rural areas.

Within city limits, public display thermometers – on banks and gas stations – demonstrate this phenomenon on a micro scale. They are often positioned in the sun and over a concrete or asphalt surface that absorbs heat. As a result, they can read 5°F to 10°F higher than the city’s official air temperature taken in the more bucolic conditions of Central Park.

Gas station thermometer reads 104F, but the official high temeprature for the day was 92F.

The thermometer on this NYC gas station reads 104°F, but the official high temeprature for the day was 92°F.

Image Credit: The Weather Gamut

Heat Index

Temperature is one of the basic elements of weather.  Our perception of it, however, is often influenced by other factors.  In summer, this is usually humidity.

The heat index, developed in the late 1970’s, is a measure of the apparent or “real feel” temperature when heat and humidity are combined.  Since the human body relies on the evaporation of its perspiration to cool itself, the moisture content of the air affects comfort levels. Basically, as humidity levels increase, the rate of evaporation decreases and the body can begin to feel overheated.  For example, an air temperature of 92°F combined with a relative humidity level of 60% will produce a heat index value of 105°F.

The National Weather Service issues heat advisories when the heat index is forecast to be at least 95°F for two consecutive days or 100°F for any length of time.  Extended exposure to high heat index values can lead to serious health hazards.

Heat-IndexImage Credit: NOAA

Temperature Influences Alligators

Temperature affects all living things in some way.  This is especially true of alligators.  While exploring the wetlands of South Carolina last week, I became much more aware of how ambient temperatures drive almost all aspects of their lives.

As cold-blooded reptiles, alligators are ectothermic.  They rely on external sources to regulate their body temperature.  For example, they lay out in the sun to warm up and float in water to cool down.  Temperature also affects an alligator’s ability to eat.  As temperatures decrease, so does its metabolism.  In fact, when temperatures fall below 70°F they stop feeding since they will not be able to digest what they consume.  If temperatures fall even further, into the 50°F range, alligators become inactive or dormant and ride out the colder weather in dens.

Environmental temperature also plays a critical role in determining the gender of baby alligators.  Through a process known as temperature-dependent sex determination (TSD), eggs that incubate at 93°F or higher all become males while temperatures below 86°F produce all females. Temperatures that hover in between create a mixture of both sexes. Scientists do not know exactly why this process developed, but they have found that it tends to produce more females than males.


An alligator basks in the sun along the edge of a swamp in South Carolina.

Image Credit: The Weather Gamut

Extreme Heat: Australia Adds New Colors to Weather Map

It is summer in Australia and it is hot!  Facing unprecedented heat, the Australian Bureau of Meteorology has added two new temperature categories – with corresponding colors – to their forecast map.

Previously capped at 50°C (122°F), the new map can represent readings up to 54°C  (129.2°F). Deep purple and hot pink will now indicate areas experiencing these new temperature ranges.

While Australia’s all time record high of 50.7°C (123.3°F), set on January 2,1960 in South Australia, currently still stands, this revised map anticipates a new record high.  For many, it also reflects a new climate reality.

Australian Bureau of Metereology temperature map with new colors to show extreme heat.  Image Credit: ABM

Australian Bureau of Metereology temperature map with new colors to show extreme heat.   Image Credit: ABM

Converting Fahrenheit and Celsius

There are many different scales by which temperature can be measured.  In weather, we most often use Fahrenheit or Celsius.

Gabriel Daniel, a German physicist, developed the Fahrenheit scale in 1714.  It marks water’s boiling point at 212°F and its freezing point at 32°F.  In 1742, Anders Celsius, a Swedish astronomer, formulated a new scale intended for scientific use.  It designates the melting point of ice at 0°C and the boiling point of water at 100°C.

Today, most of the world uses the Celsius scale.  In the U.S., however, Fahrenheit is still our official unit of measure for temperature.  To convert between the two scales, use the formulas below.

To convert from Fahrenheit into Celsius: Tc = (5/9)*(Tf-32)

To convert from Celsius into Fahrenheit: Tf = ((9/5)*Tc)+32

Image Credit: Gringer

Cricket as Thermometer

Snapple Real Fact #237, listed under the bottle cap, states, “The number of times a cricket chirps in 15 seconds, plus 37, will give you the current air temperature.”

Intuitively, this makes sense as all living things react to the weather in some way.  Crickets are cold-blooded insects and the ambient temperature directly affects their metabolic rate. As the temperature goes up, their energy level increases and they can produce more chirps.  As the temperature drops, the rate of chirping declines.

I have seen a few versions of the cricket-thermometer equation.  Most differ according to the species of cricket.  Others vary in time duration. The first person to study the correlation between air temperature and cricket chirps was  Amos Dolbear, a physics professor at Tufts University in the late 1800’s.  His equation measures the number of snowy-tree cricket chirps heard in one minute.

It states:  T= 50 + [(N-40)/4]   …where T= temperature and N= number of chirps per minute.  This is now known as Dolbear’s Law.

A simplified version, more akin to the Snapple fact, is: T= N14 + 40  … where T= temperature and  N14= number of chirps heard in 14 seconds.

These equations are for temperature readings in degrees Fahrenheit.

Snowy Tree CricketSnowy Tree Cricket  

Photo credit: Wikipedia