RAMM/CIRA 1st Quarter Report
Interaction with Naval Research Laboratory: Work with the Naval Research Laboratory on the development of a Consensus (5 members)/Ensemble (5 members) (or Consemble) tropical cyclone intensity prediction system continues. Forecasts for tropical cyclone intensity change are created using the Statistical Typhoon Intensity Prediction Scheme in the Northern and Southern Hemisphere. Forecasts are provided to the Joint Typhoon Warning Center so that they can be utilized in their forecasting activities. Results in the Northern Hemisphere suggest that the consemble significantly improves forecasts in the 48-72 hour forecast time period. In the Southern Hemisphere these forecast are the first to produce skillful intensity forecasts in this region of the world. (J. Knaff)
Publication Contributions: A note discussing the pitfalls of selective consensus forecasting in tropical cyclone track forecasting has been prepared for publication with personnel from the Naval Research Laboratory in Monterey. Selective consensus forecasting refers to the process of a forecaster removing a member or members from a consensus of global tropical cyclone tracks to form a new consensus forecast. The selective consensus was compared to a consensus created from the global models. The overall results for the 2000 through 2005 seasons show that the use of selective consensus produces slightly less skillful forecasts and that as the use of selective consensus increases forecast skill decreases, suggesting over use will deteriorate the final forecasts.
A technical comment discussing issues contained in the recent Webster et al, 2005, Science article entitled “Comments on “Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment” was prepared. Comments will be submitted for publication next quarter. (J. Knaff)
AMSU Transition: Transitioning the AMSU-based tropical cyclone intensity and structure to NCEP operations continue. This quarter, NOAA-18 data and retrievals were added to the algorithm with help from A. Krautkramer at TPC. Now that these changes have been implemented, the processing algorithms have been handed to NCO for transition to NCEP operations before the next Atlantic tropical cyclone season. (J. Knaff, M. DeMaria)
Hurricane Intensity Information Provided to Admiral Lautenbacher. Information on the impact of ocean heat content on hurricane intensity was provided in response to a request from the office of Admiral Lautenbacher. The question concerned how fast a category 1 hurricane can intensify into a category 5 storm, and how well air-sea interaction processes are understood. Analysis of historical data showed that a category 1 storm can intensify to a category 5 storm in as little as 24 hours, and this time is comparable to the time it takes to cross an oceanic eddy in the Gulf of Mexico. With regard to air sea interactions, the basic processes are understood from a qualitative point of view, but there are still large uncertainties in the surface exchange coefficients at high wind speed, and the impact of the sea state on the fluxes. This information was in preparation for the Admiral's upcoming trip to the European Space Agency meeting where Envisat will be discussed. (M. DeMaria)