An anomalous warming of the central and eastern Pacific along the equator is part of a well known climate event--El Niño. The current El Niño began back in the Spring of 2006 and reached its peak in November and December. El Niño has far reaching effects. The anomalous warming of sea surface temperations in the eastern Pacific also shifts the focus for deep to that region. This in turn effects the general circulation pattern, which impacts both temperature and precipitation patterns well into middle latitudes. Deviations to the rainfall pattern across the US due to El Niño are well established based on past events. Most notably the northern Gulf Coast experiences above average rainfall as does California and the Southwest due to a stronger-than-average subtropical jet stream, while the Ohio Valley and the Northwest see below normal rainfall.

The TRMM-based, near-real time Multi-satellite Precipitation Analysis (MPA) at the NASA Goddard Space Flight Center is used to monitor rainfall over the global tropics. MPA rainfall anomalies are shown here for the period 25 December 2006 to 25 January 2007 across the US. The anomalies are obtained by subtracting climatological values from the current values for the period. The climatology is based on data collected since TRMM's launch back in November of 1997. Several of the notable features associated with El Niño are evident. The northern Gulf Coast west of Florida is wetter than average as is southern California. The four-corners region is also very moist, which is typical for El Niño. Drier than normal conditions are evident over the Ohio Valley. There are some exceptions, however. Montana for example is usually drier than average but appears relatively moist, and Florida is usually wetter than average but shows below normal rainfall for the period. Also, the dry anomaly in the Northwest is concentrated over northern California.

TRMM is a joint mission between NASA and the Japanese space agency JAXA.

Images produced by Hal Pierce (SSAI/NASA GSFC) and caption by Steve Lang (SSAI/NASA GSFC).