Weather 2000 - FAQ Title Graphic

Q: There has been so much discussion over the last several years about El Niño and now La Niña. Does that really affect the weather for my town?
A: The ENSO phenomena (e.g. El Niño and La Niña), causes many atmospheric and oceanic circulation changes that can affect global weather patterns. Although ENSO might indirectly affect the weather in your region, it is only one of many atmospheric processes, from hemispheric to the micro-scale, that determine the weather for your town. The processes must be examined collectively before conclusions can be drawn.

Qualitative ENSO forecasts for geographic regions (ie, the Northeast) or climate divisions are often not representative of cities within that region. Large weather differences can occur from city to city, and even within a single metropolitan location. For example, for the winter of 1995-96, Central Park, NY recorded its 4th coldest winter in 32 years, while La Guardia Airport, right across the East River, experienced a much warmer 10th placed ranking.

Q: If the winter of 2002-03 was an El Niño winter, why was it not as warm as most seasonal forecasts predicted?
A: enso graphicThere really is no typical El Niño or La Niña weather, in that it does not behave the same way each time. With the exception of certain locations in the tropics, El Niño and La Niña weather is quite variable, so generalizations can often be misleading. For example, while on average, the upper mid-west of the United States is colder than normal during a La Niña winter and warmer than normal during an El Niño winter, the 1998-99 winter season displayed abundant warmth, while the 2002-03 winter season displayed widespread cold. There are really only a handful of well-documented ENSO events, and a sample size of dozens will be needed to draw any type of decisive conclusions. The intensity, timing, and interaction of the ENSO Event with many other ocean-atmosphere processes ultimately determines the weather. (Graphic source: CPC)
Q: Does El Niño and La Niña affect a location uniformly over the course of a season as indicated by analog forecasts?
A: Pittsburgh ExampleAs discussed above, many other atmospheric processes are involved in shaping seasonal weather. During the course of an entire season, the weather can be quite tumultuous, with enormous month to month fluctuations. For example, in 1999, Pittsburgh registered its 10th warmest February, only to be followed by the 7th coldest March in the last 47 years (see graphic on right). Generic qualitative forecasts for full seasons obviously mask these crucial mid-season pattern shifts. Our forecasts and reports have 30-day incremental resolution, allowing you to visualize the forecast of each month.