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HOME > Monitoring and Data > U.S. Climate Data > ENSO Impacts > Seasonal Impacts > ENSO Discussion: Virginia
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The 1997 El Niño: Potential Effects in Virginia
November 1997 to April 1998
Description Case Selection Comments
The specific temperature and precipitation graphs and statistics shown here are representative of those judged to be sufficiently reliable for display.

Updated 2 December 1997

We are currently in the midst of a strong El Niño (warm) episode, which is forecast to continue through February-April 1998. During this period the tropical ocean surface temperatures are forecast to remain comparable in magnitude and areal extent to that of 1982-83, which is considered to be the strongest warm episode of this century. In contrast to the 1982-83 El Niño, which caught the country by surprise, the present El Niño was predicted several months in advance. This improvement in climate prediction is the direct result of intensive research efforts by NOAA and its partners during the last 15 years. Part of this research effort, which is still ongoing, has been devoted to determining the effects of El Niño on temperature and precipitation patterns in the U. S. and globally. Some results of this research for your state are discussed below.

The information on state impacts is derived by looking at what has happened in those years during the past century that featured strong El Niño episodes. Four products are included for every period for which effects are highlighted. El Niño impacts vary with season. The first contrasts average conditions during El Nino episodes with what is expected in general. These figures for precipitation also include what took place in 1982/83 as a plausible scenario as to what might happen, because the present El Niño is at least as strong as any on record. These two estimates give a range of what might be expected. However, because of the probabilistic nature of the forecasts, the range could be greater. The second gives the change in probabilities for the respective variable and period. The Climate Prediction Center of NOAA makes seasonal forecasts for temperature (precipitation) probabilities in three categories: the warmest (wettest 1/3); the near normal 1/3; the coldest (driest) 1/3. The probability of getting any one of these three categories would be equally likely in the absence of El Niño. Probabilities of being wetter or drier or warmer or colder than normal can be dramatically changed by El Niño. The third and fourth products for each period are U.S.-wide maps of respectively (1) average temperature or precipitation rankings during El Niño episodes and (2) corresponding probabilities of the three categories. These maps place effects at the state level in a broader context.

Historically, strong El Niño episodes have featured below normal precipitation for Virginia and Washington, D. C. in the Fall (September through November) with deficits averaging two to three inches. This has most reliably been the case in central and northern Virginia (including Washington), but was not the case anywhere in the state in 1982-83. One reason for the latter is that the 1982-83 El Nino did not become strong until October. Pre-Winters (November and December) have reliably (eight out of ten instances) ranked among the warmest 1/3 of the 102-year record for strong El Ninos for almost the entire area, while late Winters/early Springs (February through April) have almost as reliably (five out of seven instances) ranked among the coldest 1/3 for all but northern Virginia and Washington.

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