Summer Oscillations in Tropical Thunderstorm Activity: Potential Sources of Predictability

  • 21 July 2015
  • Number of views: 1824

During the summer, the Indian Ocean and the West Pacific Ocean regions tend to undergo oscillations between periods of active and inactive thunderstorm activity over a period of weeks to months. These oscillations in tropical thunderstorm activity are associated with a phenomenon known as the Boreal Summer Intraseasonal Oscillation (BSISO).

A new Climate Program Office-sponsored study published in the journal Climate Dynamics and led by Drs. Sun-Seon Leon and Bin Wang from the University of Hawaii has identified the characteristic wind and cloud variations associated with the two main areas of thunderstorm activity over the Indian Ocean and West Pacific that make up the BSISO.

In addition, using a novel model prediction dataset called the Intraseasonal Variability Hindcast Experiment, a dataset also funded in part by the Climate Program Office, the authors have examined the predictability and model prediction skill of the thunderstorm activity areas. They find that the Indian Ocean part of the BSISO is potentially predictable by global models 40-45 days in advance, whereas the West Pacific part is potentially predictable 33-37 days in advance. The study further reveals that the prediction skill of the BSISO itself is much higher than usual when the regional thunderstorm activity centers comprising the BSISO are unusually active or unusually inactive.

This study advances knowledge of how tropical phenomena can serve as sources of predictability -- information that NOAA may eventually be able to translate into improved seasonal predictions of weather conditions over the U.S. 

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