The 1997 El Niño: Potential effects in Minnesota - November 1997 to April 1998
Climate Prediction Center (CPC), NWS/NOAA
Updated 17 November 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 moderate to strong El Niño episodes. Three types of products are
included. The first consists of U.S.-wide maps of average precipitation rankings during El Niño
episodes for the November-December and January-March periods. El Niño impacts vary with
season. Although El Niño may have an impact on Minnesota precipitation, historically there has not
been a consistent response. Similar U.S.-wide maps of average temperature rankings during El Niño
episodes for the December-February and February-April periods follow. The second product type
gives the change in temperature probabilities by season. The Climate Prediction Center of NOAA
makes seasonal forecasts for temperature probabilities in three categories: the warmest 1/3; the near
normal 1/3; the coldest 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 warmer or colder than normal can
be dramatically changed by El Niño. The third type of figure converts the average rankings shown
earlier to average temperatures and a departure from average. This estimate gives a temperature that
might be expected based on historical data. However, because of the probabilistic nature of the
forecasts, the range of the average temperature could be significantly warmer or colder.
Historically, moderate to strong El Niño episodes have featured an increased frequency of occurrence
of above normal temperatures over the state during December-February. During nine moderate to
strong El Niño episodes temperatures averaged 3-4 degrees Fahrenheit above normal, and for about
six of these cases December-February temperatures were among the warmest third of the years in the
102 years of record.