Posts

Doug Simonian

Winter 2014-2015 Review and Verification

/by

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.

Read more

John Homenuk

Winter Forecast 2014-2015

/2 Comments/by

View the entire 2014-2015 Winter Forecast in a PDF file by clicking here. 

You can also download it here. 

Primary Methodologies and Variables of Examination

  • El Nino Southern Oscillation (ENSO)
  • North Atlantic Oscillation (NAO)
  • Arctic Oscillation (AO)
  • East Pacific Oscillation (EPO)
  • Siberian/Eurasian Snow cover and Stratospheric Warming
  • October Greenland Blocking
  • Pacific Decadal Oscillation (PDO)
  • 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.

Seasonal Forecasting Brief

Seasonal forecasting is one of the most convoluted aspects of meteorology. Not only is it a difficult task for the meteorologists themselves, but it is difficult for readers and public viewers to understand the nature of the forecast at times. The root of the problem lies in the fact that seasonal forecasting is based on many different methods — all of which have tremendous variability and low percentage verification. Seasonal forecasting begins with an analysis of current conditions and atmospheric circulations, similar to any daily forecast. Beyond this point, forecasters use variables such as sea surface temperature anomalies, analogs, and comparative methodology.

Some forecasters have detailed the mentality very well when they have stated that long term forecasting is very much about “What can go wrong” as opposed to “How will my forecast be correct”. Our job as meteorologists is to detail the aspects that have formed the foundation for our forecast, express our concerns and confidence in all aspects, and try to deliver the ideas which we have formulated as a result of our research and work in attempting to understand the patterns evolution over the next several months.

We will begin by highlighting several variables which we have researched. Each variable will be listed with a conclusion and prediction on its state during the winter, as well as the methodology and reasoning behind that forecast.

Read more

John Homenuk

Plummeting AO could offer some winter hints

/0 Comments/by

As we’ve spoken about several times already this Autumn, our winter forecast doesn’t typically come out until the first week of November. Although some will bark at us for this — we’ve been hearing it already this Autumn — there are reasons for it. Mainly, our forecasters have recognized the importance of analyzing the pattern during October and the ideas moving into November. The recognition of the pattern during the next few weeks will be immensely important to understanding how things will shake down this winter. And our first “hint” could be offered during the next several days, as the AO — or Arctic Oscillation — is forecast to take a nose-dive.

The Arctic Oscillation is a large scale monitor of climate variability, also referred to as the Northern Hemisphere Annual mode. More simply, it’s a climate pattern characterized by winds circulating counterclockwise around the Arctic — typically at around 55°N latitude. In even more simple terms — the negative phase of the AO typically displaces cold air farther south in North America, while the positive phase keeps the colder air farther north, nearer to the poles and arctic regions. Forecast models are in good agreement that the AO will nosedive over the next several days — and not surprisingly, a major shot of below-normal temperatures is expected late this weekend into early next week. 

Read more