Posts

Miguel Pierre

Winter Forecast Update: Colder February, increased snow chances

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What a turn around this winter has been able to pull off over the past week or two. Record-breaking warmth in December gave way to arctic blasts and a historic, crippling blizzard this month. We also saw an atypical fantastic performance prior to the blizzard by the NAM model for this region. We warned the winter could return with a vengeance in a public article we wrote shortly after Christmas. Pattern signals and ensemble guidance were strongly hinting at opportunities for more cold and snow.

While many aspects of our Winter Forecast published in November have worked out, there have been setbacks and surprises as well. This post will serve as an update and stepping stone for the several weeks of winter still left to come.

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John Homenuk

Five things to expect during the upcoming winter

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Just about a month ago, we released our 2015-2016 Winter Forecast to the public. The forecast featured a tremendous amount of information, research, and data, most of it very technical in nature. With winter only a few weeks away, there is no better time than now for us to lay out the ideas we gathered in a more simplistic form. After all of our work to compile the forecast, there are five general things you should expect during this upcoming winter season.

1) The Winter of 2015-2016 will start off warm

Over the past few weeks, much has been made in regards to the warm pattern setting up for the month of December. Truth be told, confidence has never been higher that December will be a warmer than normal month with less snow than normal as well. Much of this can be attributed to the development and effects of a strong El Nino in the Equatorial Pacific. But some, also, has to do with the surrounding global circulations.

This month, the stratospheric polar vortex (way up there) tightened and strengthened over the North Pole. While this doesn’t totally eliminate any chance for our area to experience cold air, it does make it more difficult. A tighter and more consolidated stratospheric polar vortex means less atmospheric disruption in that region; i.e: Less high latitude blocking, or ridges, to displace the cold air farther south. This vortex is expected to weaken over the next 30 to 50 days, eventually moving and/or splitting and promoting high latitude blocking during the second half of the winter.

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John Homenuk

Winter Forecast 2015-2016

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You can view the entire 2015-2016 Winter Forecast in a PDF file by clicking here.

Primary Methodologies and Variables of Examination

  • El Nino Southern Oscillation (ENSO)
  • Arctic Oscillation (AO)
  • East Pacific Oscillation (EPO)
  • Pacific Decadal Oscillation (PDO)
  • North Atlantic Oscillation (NAO)
  • Siberian/Eurasian Snow cover and Stratospheric Warming
  • Solar Activity
  • Sea Surface Temperature Anomalies (SSTA)

Explanation of Variables

Over the past several months, our forecasters have monitored the above variables (plus others) and the trends in their behavior. We will be utilizing the above variables and indices, as well as their abbreviations, throughout the winter forecast. These variables reflect the atmospheric circulation patterns for certain geographical areas. For example, the AO refers to patterns within the Arctic Circle. The NAO refers to pattern characteristics in the North Atlantic, the PNA in the western part of North America, the PDO in the Pacific Ocean, and the EPO in the Northern and Eastern Pacific Ocean.

Typically, negative AO, NAO and EPO values correlate to enhanced high latitude blocking and high pressure to our north while lower pressure areas and troughs usually form underneath that high latitude ridging in the middle latitudes. In contrast, positive AO, NAO and EPO values generally yield lower pressure and less blocking to our north, while higher pressure and more ridging tends to build into the middle latitudes. There are exceptions to the rule, but generally the negative state of the above listed indices yields colder, more snowy weather in our area during the winter months.

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Doug Simonian

Winter 2014-2015 Review and Verification

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We made it! We can finally safely say that the winter season is over and, while the cold seems to want to endlessly stick around, Spring is strengthening its grasp. Now that the days of snow and bitter cold are over, we’ve compiled a detailed review of the brutal winter as well a verification for our winter forecast we issued back in early November.

Some highlights of this winter include:

1) The second coldest February on record, with widespread ice buildup on the Hudson River.

2) Winter storm “Juno” in late January which gave parts of eastern Long Island over two feet of snow.

3) A persistent cold and snowy pattern from late January through March, with an active assault of moderate snow events — somewhat reminiscent of last year’s winter.

4) Boston’s snowiest winter on record.

In our review, we break down the winter month-by-month and provide temperature departures and snowfall amounts for Central Park, as well as descriptors and verification statistics.

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