Tag Archives: cold

The Polar Vortex

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The Polar Vortex has been making headlines across most of the United States recently.  But, what exactly is it?

According to NOAA, the northern hemisphere polar vortex is a high altitude low-pressure system anchored over the Arctic.  More specifically, it is “the pattern of winds around the North Pole.”  It is always present, but tends to be stronger in the winter.

The configuration of the polar vortex – smooth or wavy – determines how much cold air escapes the region. Driven by the temperature difference between north and south, these winds typically circle the pole from west to east in a smooth pattern that bottles up the Arctic’s cold air.   When these winds weaken, the pattern becomes wavy and cold air pushes southward.

The connection between warming conditions in the Arctic (decreasing the temperature difference between north and south) and extreme weather events in the mid-latitudes is an active area of research. Some scientists suggest that increasing Arctic temperatures may be responsible for disrupting the pattern of the polar vortex.

The polar vortex is shown in purple. Image Credit: NOAA

Polar Vortex configuration: Smooth vs Wavy.  Image Credit: NOAA

A Deep Freeze in NYC

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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

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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.

 

NYC Monthly Summary: December 2013

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New York City experienced a wide array of temperatures this December.  We had highs that ranged from a chilly 30°F to a record warm 71°F.  These extremes balanced each other out in the end, though.  The city’s mean temperature for the month was 38.6°F, which is only 0.65°F above average.

On the precipitation side of things, NYC collected 4.85 inches of rain, which is 0.85 inches above normal.  This was the first time since June that we received above average rainfall. In terms of snow, the city saw 8.6 inches accumulate in Central Park, which is 3.8 inches above average for December.  Most of this fell during a widespread pre-season winter storm in the middle of the month.

Graph Credit: The Weather Gamut

Graph Credit: The Weather Gamut

Graph Credit: The Weather Gamut

Graph Credit: The Weather Gamut

The Chances for a White Christmas

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The holidays are here and many people are dreaming of a white Christmas.  The likelihood of seeing those dreams come true, however, are largely dependent on where you live.

According to NOAA, a white Christmas is defined as having at least one inch of snow on the ground on December 25th.  In the US, the climatological probability of having snow for Christmas is greatest across the northern tier of the country. Moving south, average temperatures increase and the chance of snow steadily decreases.

Here in New York City, the odds of having snow on Christmas Day are, on average, less than twenty-five percent. This low probability is largely due to the city’s proximity to the Atlantic Ocean and its moderating influence. This year, despite some significant snowfall earlier in the month and the possibility of a light snow shower tonight, NYC is not expecting a white Christmas.

Snow or no snow, the Weather Gamut wishes you a very Happy Holiday!

Image Credit: NOAA

Image Credit: NOAA

A Winter Preview for NYC

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It’s beginning to look a lot like winter in New York City.  Cold temperatures and snow have been dominating the weather for days.

On Sunday, 0.7 inches of snow dusted Central Park – the first measurable snowfall of the season. Yesterday, a second weather system brought the Big Apple a wintery mix that included 1.4 inches of snow. While this modest accumulation is nothing to write home about, it did set a new daily snowfall record for the date.  According to the NWS, the previous record of 1.3 inches was set in 1932.

The arctic air ushered in by this second system is expected to stick around for a while.  Temperatures are not likely to climb out of the 30s until early next week and more snow is possible over the weekend.

Winter officially begins on the solstice, December 21st.

NYC Monthly Summary: March 2013

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March roared like a lion in New York City this year, with cold and blustery conditions dominating the month. With all but ten days posting cooler than normal readings, the city’s average monthly temperature only reached 40.1°F.  That is 1.9°F below normal. In fact, this was the first March in twelve years that we did not have a single day break the 60°F mark. This was a huge departure from last March, which was the second warmest March on record for the Big Apple.

In terms of precipitation, snowfall was abundant.  March usually brings the city 3.6 inches of snow, but this year we saw 7.3 inches accumulate in Central Park.  Rainfall, however, was scarce.  The city only collected 2.90 inches, which is 1.46 inches below normal.

March2013Graph Credit: The Weather Gamut

Wind Chill

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Temperature is one of the basic elements of weather.  Our perception of it, however, is often influenced by other environmental conditions. Wind, for example, can make a cold day feel even colder.  This phenomenon is called the wind chill factor.

Wind chill is a measure of the apparent or “real feel” temperature.  It calculates the heat loss from exposed human skin through the combined effects of air temperature and wind speed. Essentially, the wind is carrying heat away from the body and allowing the skin to be exposed to cold air.  As the winds increase, heat is carried away at a faster rate and the colder the body feels.  For example, a temperature of 20°F and a wind speed of 5-mph will produce a wind chill index of 13°F.  At that same temperature, but with a wind speed of 10-mph, the wind chill index would be 9°F.

Extended exposure to low wind chill values can lead to frostbite, a serious winter health hazard.

windchillChart Credit: NOAA

Arctic Blast for NYC

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After a mild start to the season, winter has finally found New York City.

A deep dip in the jet stream has ushered in bitterly cold arctic air and brought the city its coldest temperatures of the season to date. While we are in the dead of winter and cold temperatures are expected, today’s high was only 20°F.  That is 18°F below average.  In fact, today was the coldest day NYC has experienced in two years.

These frigid conditions, according to the local forecast, are likely to stay in place for a while.  Temperatures are not expected to get above the freezing mark until early next week. Bundle up!

Jan_TempDrop

Graph Credit: The Weather Gamut

NYC Monthly Summary: November 2012

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November was unusually chilly in New York City this year.  In fact, we had 24 out of 30 days with below normal temperatures.  This extended stretch of cool weather helped lower the city’s average monthly temperature to 43.9°F, which is 4.2°F below normal.  

In terms of rainfall this November, NYC collected a meager 1.81 inches. That is 2.21 inches below average.  More significant precipitation, however, came in the form of snow.  A nor’easter blustered its way through the city on November 7th and brought the Big Apple its first snowfall of the season – 4.7 inches in Central Park. This accumulation not only set a new daily snowfall record, but also made November 2012 the 6th snowiest November on record.

Graph Credit: The Weather Gamut