La Niña conditions end; 10th warmest March on record for the globe
Sea Surface Temperatures (SSTs) and deep water temperatures have warmed significantly in the equatorial Eastern Pacific over the first two weeks of April, and La Niña conditions are no longer present. While NOAA's Climate Prediction Center has not yet declared an end to this La Niña episode and dropped their La Niña advisory, it is very likely that the La Niña event that began in December 2008 is now over. The big question is whether an El Niño event will rapidly form in its place, in time for hurricane season. This did happen after the 1976 La Niña, which ended in April, with a weak El Niño beginning in September. However, it can take a few months for the atmosphere to adjust to the formation of a new El Niño, and there is no guarantee that a weak El Niño for the coming hurricane season would act to dramatically reduce Atlantic hurricane activity.The number of Atlantic hurricanes is typically reduced in an El Niño year, due to increased wind shear from strong high-level winds. Nearly all the model forecasts for the Niño 3.4 region predict neutral conditions for the August - October peak of hurricane season. Four out of 21 El Niño models are predicting an El Niño event for hurricane season; three are predicting a La Niña, and fourteen are predicting neutral conditions.
Figure 1. The difference of Sea Surface Temperature (SST) from average for the Niña 3.4 region of the equatorial Eastern Pacific (the area 5°N - 5°S, 120°W - 170°W). La Niña conditions are defined as occurring when the 1-month mean temperature anomaly in the Niña 3.4 region cools below -0.5°C. La Niña conditions began in December 2008 and ended in late March 2009. Image credit: NOAA Climate Prediction Center.
Tenth warmest March on record for the globe
Global temperatures remained about where they've been the past two years, with the planet recording its 10th warmest March on record, according to statistics released by the National Climatic Data Center. The period January - March was the eighth warmest such period on record.
An average March for the U.S.
For the contiguous U.S., March temperatures were the 51st warmest in the 115-year record, according to the National Climatic Data Center. The month had near-average precipitation, ranking as the 42nd wettest March. Three states (Delaware, Maryland, and New Jersey) experienced their driest year-to-date period ever. In neighboring states, Pennsylvania recorded its second driest year-to-date period and Massachusetts and West Virgnia experienced their fourth and fifth driest, respectively. The below-normal precipitation averages led to the driest ever start to the year for the Northeast region. Record amounts of snow fell in North Dakota during March. Fargo received 28.1 inches, which was nearly 2 more inches than the previous March record set in 1997. Fargo also recorded 4.62 inches of precipitation which set a new monthly record. Runoff from the record precipitation led to the highest flood levels ever observed on the Red River in North Dakota. The river crested in Fargo at a record level of 12.4 m (40.8 feet), shattering the previous record of 12.2 m (40.1 feet) set in 1897.
Through March, the U.S. has only seen about 50% of normal tornado activity for the year, according to NOAA's Storm Prediction Center. There were just 9 tornado deaths through March, compared to 70 deaths through March of 2008, and the 3-year average of 44 deaths.
On April 14, 2009, 17% of the contiguous United States was in moderate-to-exceptional drought. This is a drop from the 21% figure observed January through March.
Bahamas 2009 Weather Conference
This week, many of the world's hurricane experts are gathered at the Bahamas Hurricane Conference. Check out their web site for short videos by some of the presenters. The 3-minute talk by NHC Director Bill Read and former NHC Director Max Mayfield on the inadequacy of our familiar Category 1-2-3-4-5 Saffir-Simpson scale is interesting. They make the point that no one scale will ever be able to capture the threats a hurricane poses, since these depend greatly on exactly what track the storm takes, and our forecasts will never be able to precisely pinpoint the track. Thus, introducing a new scale to quantify storm surge risk is not a complete solution to the inadequacies of the Saffir-Simpson scale. Coastal residents need to heed the detailed wind and storm surge forecasts for their area, regardless of what Category storm is approaching.