The National Oceanic and Atmospheric Administration (NOAA) says La Nina weakened in March and is expected to continue its transition to ENSO-neutral conditions during April. It says while all the Nino indices have warmed "considerably" during the last two months, conditions are consistent with La Nina.
"A majority of models predict ENSO-neutral conditions for March-May 2012, continuing through the Northern Hemisphere summer 2012," says NOAA. "Based on the continued weakening of the negative sea surface temperatures (SST) anomalies during March 2012, and on the historical tendency for La Nina to dissipate during the Northern Hemisphere spring, we continue to expect La Nina to dissipate during April 2012. ENSO-neutral conditions are then expected to persist through the summer. Thereafter, there is considerable uncertainty in the forecast, which slightly favors ENSO-neutral or developing El Nino conditions over a return to La Nina conditions during the remainder of 2012."
NOAA says La Nina has the following weak influences on the climate outlook: There is an increased chance of above-average temperatures in the south-central U.S., and below-average temperatures in the Northwest. Also, drier-than-average conditions are more likely across Utah and Colorado, and along the western Gulf of Mexico.
Juli says: NOAA said there is "considerable uncertainty" once La Nina is gone, whether El Nino will build -- which is associated with above-trend yields in the Midwest. But the transition to neutral-ENSO conditions this summer diminishes the chance of below-trend yields.