Jon Gottschalck

Large-Scale Atmospheric and Oceanic Conditions during the 2011–12 DYNAMO Field Campaign

AbstractAn international field campaign, Dynamics of the Madden Julian Oscillation (DYNAMO), took place in the Indian Ocean during October 2011–March 2012 to collect observations for the Madden–Julian oscillation (MJO), especially its convective initiation processes. The large-scale atmospheric and oceanic conditions during the campaign are documented here. The ENSO and the Indian Ocean dipole (IOD) states, the monthly mean monsoon circulation and its associated precipitation, humidity, vertical and meridional/zonal overturning cells, and ocean surface currents are discussed. The evolution of MJO events is described using various fields and indices that have been used to subdivide the campaign into three periods. These periods were 1) 17 September–8 December 2011 (period 1), which featured two robust MJO events that circumnavigated the global tropics with a period of less than 45 days; 2) 9 December 2011–31 January 2012, which contained less coherent activity (period 2); and 3) 1 February–12 April 2012, a...

Observing and Predicting the 2015/16 El Niño

AbstractThe El Nino of 2015/16 was among the strongest El Nino events observed since 1950 and took place almost two decades after the previous major event in 1997/98. Here, perspectives of the event are shared by scientists from three national meteorological or climate services that issue regular operational updates on the status and prediction of El Nino–Southern Oscillation (ENSO). Public advisories on the unfolding El Nino were issued in the first half of 2015. This was followed by significant growth in sea surface temperature (SST) anomalies, a peak during November 2015–January 2016, subsequent decay, and its demise during May 2016. The life cycle and magnitude of the 2015/16 El Nino was well predicted by most models used by national meteorological services, in contrast to the generally overexuberant model predictions made the previous year. The evolution of multiple atmospheric and oceanic measures demonstrates the rich complexity of ENSO, as a coupled ocean–atmosphere phenomenon with pronounced glob...

Influence of the Madden–Julian Oscillation on Forecasts of Extreme Precipitation in the Contiguous United States

Abstract Extreme precipitation events are among the most devastating weather phenomena since they are frequently accompanied by loss of life and property. This study uses reforecasts of the NCEP Climate Forecast System (CFS.v1) to evaluate the skill of nonprobabilistic and probabilistic forecasts of extreme precipitation in the contiguous United States (CONUS) during boreal winter for lead times up to two weeks. The CFS model realistically simulates the spatial patterns of extreme precipitation events over the CONUS, although the magnitudes of the extremes in the model are much larger than in the observations. Heidke skill scores (HSS) for forecasts of extreme precipitation at the 75th and 90th percentiles showed that the CFS model has good skill at week 1 and modest skill at week 2. Forecast skill is usually higher when the Madden–Julian oscillation (MJO) is active and has enhanced convection occurring over the Western Hemisphere, Africa, and/or the western Indian Ocean than in quiescent periods. HSS gre...

The Madden–Julian Oscillation and the Relative Value of Deterministic Forecasts of Extreme Precipitation in the Contiguous United States

The Madden‐Julian oscillation (MJO) is the most prominent form of tropical intraseasonal variability that impacts weather and climate. Forecast skill of extreme precipitation in the contiguous United States (CONUS) during winter is higher when the MJO is active and has enhanced convection over the Western Hemisphere, Africa, and/or the western Indian Ocean. This study applies a simple decision model to examine the relationships between the MJO and the relative value of deterministic forecasts of extreme precipitation. Value in the forecasts is significantly higher and extends to longer leads (2 weeks) during active MJO.

An Evaluation of Precipitation Forecasts from Operational Models and Reanalyses Including Precipitation Variations Associated with MJO Activity

Abstract In this paper, the results of an examination of precipitation forecasts for 1–30-day leads from global models run at the European Centre for Medium-Range Weather Forecasts (ECMWF) and the National Centers for Environmental Prediction (NCEP) during November 2007–February 2008 are presented. The performance of the model precipitation forecasts are examined in global and regional contexts, and results of a case study of precipitation variations that are associated with a moderate to strong Madden–Julian oscillation (MJO) event are presented. The precipitation forecasts from the ECMWF and NCEP operational prediction models have nearly identical temporal correlation with observed precipitation at forecast leads from 2 to 9 days over the Northern Hemisphere during the cool season, despite the higher resolution of the ECMWF operational model, while the ECMWF operational model forecasts are slightly better in the tropics and the Southern Hemisphere during the warm season. The ECMWF Re-Analysis Interim (E...

Pentad Evolution of Wintertime Impacts of the Madden–Julian Oscillation over the Contiguous United States

AbstractLagged pentad composites of surface air temperature and precipitation are analyzed for the winter season (December–February) to assess the influence of the Madden–Julian oscillation (MJO) on the climate of the contiguous United States. Composites are based on the Wheeler and Hendon MJO index as well as an index developed and maintained at NOAA’s Climate Prediction Center (CPC), which is based on extended empirical orthogonal function analysis of upper-level velocity potential. Significant positive temperature anomalies develop in the eastern United States 5–20 days following Wheeler and Hendon MJO index phase 3, which corresponds to enhanced convection centered over the eastern Indian Ocean. At the same lag, positive precipitation anomalies are observed from the southern Plains to the Great Lakes region. Negative temperature anomalies appear in the central and eastern United States 10–20 days following Wheeler and Hendon MJO phase 7. These impacts are supported by an analysis of the evolution of 2...