Extended Abstract (1.3M)7.1
Experiments in downscaled seasonal forecasting from the ENSO signal: extreme interseasonal and intraseasonal variability of Florida dry season storminess and rainfall and the role of the MJO, PNA, and NAO
Bartlett C. Hagemeyer, NOAA/NWS, Melbourne, FL; and R. J. Almeida
Since 1997 the authors have been investigating the ability to forecast the impact of the El Nino-Southern Oscillation (ENSO) on Florida dry season weather (1 November through 30 April). Most recently Hagemeyer (2000a-b) and Hagemeyer and Almeida (2002 and 2003) have focused on refining the definition of storminess and the storminess climatology and forecasting dry season storminess from the ENSO signal using multiple linear regression techniques. Their work has led to the development of an experimental web page that includes an experimental forecast of storminess and rainfall for the Florida dry season (http://www.srh.noaa.gov/mlb/enso/mlbnino.html).
Experimental predictions of storminess and rainfall were made for the 1999-00, 2000-01, and 2001-02 Florida Dry Seasons, but were not released to potential users. The successful verification of these forecasts was encouraging, but they were during a period of largely La Nina to neutral conditions. The 2002-2003 Dry Season forecast was the first issued well in advance on the WWW based on long-range predictions of the development of moderate El Nino conditions from the Climate Prediction Center. The forecast for accumulated storminess and rainfall from 1 November 2002 through 30 April 2003 was first released in January 2002 and updated monthly through March 2003 on the web page. The forecast was also communicated to the Emergency Management community of Florida during two workshops at the Florida State Department of Emergency Management in October 2002 just prior to the beginning of the Florida Dry Season.
The forecast of above normal storminess verified, but storminess was actually higher (11 storms) than might be expected from an El Nino of the magnitude of the 2002-03 event. The forecast of above normal rainfall did not verify as rainfall was near normal averaged over the entire state of Florida. Several interesting preliminary findings from the 2002-03 dry season will be expanded upon in the conference paper and presentation: 1) the role of the PNA, MJO, and NAO in interseasonal variability between the 2001-02 and 2002-03 dry seasons, 2) the regional differences in Florida rainfall over the season that suggest further downscaling of the seasonal forecast is necessary and of value to users, and 3) It has been noted that most El Nino’s produce above normal seasonal storminess, but the storms tend to come in waves with significant breaks in activity in between. The 2002-03 season displayed this interesting pattern in intraseasonal variability of storminess within the rise and fall of the El Nino regime that illustrates the potential value of forecasts of stormy periods with greater temporal resolution than a season to users.
Hagemeyer, B. C., 2000b: Development of a low pressure index as a proxy for dry season severe weather in Florida and its relationship with ENSO. Preprints, 20th Conference on Severe Local Storms. Orlando, FL, Amer. Meteor. Soc., 439-442.
Hagemeyer, B. C., and R. A. Almeida, 2002: Experimental Forecasting of Dry Season Storminess over Florida and the Southeast United States from the ENSO Signal using Multiple Linear Regression Techniques. Preprints, 13th Symposium on Global Change and Climate Variations joint with 16th Conference on Probability and Statistics in the Atmospheric Sciences. Orlando, FL, Amer. Meteor. Soc., J117-124.
Hagemeyer, B.C. and R.A. Almeida, 2003: Experimental forecasting of dry season storminess over Florida from the ENSO signal: latest results and advancements, Preprints, 14th Symposium on Global Change and Climate Variations. Long Beach, CA, Amer. Meteor. Soc., (on CD-ROM).
Supplementary URL: http://www.srh.noaa.gov/mlb/enso/mlbnino.html
Session 7, Seasonal prediction (Room 6C)
Wednesday, 14 January 2004, 8:30 AM-9:30 AM, Room 6C
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