It helps us to understand where we are heading during the winter ahead and how global circulation patterns may behave. This analog set matches quite closely with ongoing and expected conditions. Using a weighted analog set featuring mixed/variable La Nina events of at least moderate strength, we are able to compile an analog set of the SST anomalies in the Tropical Pacific. Using a weighted package of analog years, we can find a blend of years that featured similar ENSO conditions.
Central and east based La Nina’s behave quite differently, and factoring in “varied” conditions was challenging. ENSO can be a major pattern driver, and its location has major implications on the resultant global circulations. The regional bias of the Nina is therefore described as “varied”. This year, the coldest anomalies and subsurface cool areas are located between the central and east based Nina regions. The most frequently observed types of La Ninas are “central based”, when the coldest anomalies are in the central Tropical Pacific and “east based”, when the coldest anomalies lean eastward, closer to Central and South America in the eastern tropical Pacific. La Nina events can be broken down into subcategories separate from their strength, based on location. La Nina conditions are observed when colder than normal temperature anomalies exist in the aforementioned tropical regions of the Pacific Ocean. In a general sense, the more anomalous the positive sea surface temperature anomalies, the more convection that can then exert a stronger forcing mechanism on the adjacent regions of the atmosphere, reverberating throughout the globe.Īlmost all forecast model guidance now agree that we will experience a moderate or strong La Nina during the upcoming winter. The equatorial waters of the Pacific ocean that comprise the ENSO regions breed a great deal of convection, which then accordingly results in atmospheric ridging, and subsequently moves downstream, balancing the atmospheric regime. Forecast models agree that a moderate, or possibly strong La Nina will continue through this winter. This convection, most frequently observed in warm and moist climates, releases latent heat that then rises up into the atmosphere, forming ridges of higher atmospheric air pressure.
“Tropical forcing” refers to concentrated areas of showers and thunderstorms, otherwise referred to as convection, in meteorological regions of the tropics.
#NYC SNOW TOTALS DRIVERS#
The role of ENSOĪnticipated ENSO Conditions: Moderate or strong La NinaĮNSO conditions are one of they key drivers to the Winter pattern.
This will lead us to the conclusions which we believe will be the guiding forces for us during the seasons ahead. Instead of focusing on individual numerical indexes and values, we are going to try to paint a picture of the atmosphere and what it will be doing over the next few months – based on several global and hemispheric oscillations, conditions, and phenomena. We’ve been piecing together ideas for this upcoming winter since then, and we are excited to finally have a finished product. It is the product of several months of intensive research, which often begins in the prior Spring. We say it every year, but it’s worth repeating: Seasonal weather forecasting is one of the most challenging aspects of meteorology. NYC’s 30 year average annual snowfall is 28.9″, and we expect less than average snowfall during this upcoming winter season. The Winter of 2020-2021 is likely to feature warmer than normal temperatures in the NYC Area.
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