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NOAA > NWS > WFO Guam's Home > Probabilistic Winds >Probabilistic Winds Definitions
Definitions For Probabilistic Winds Forecasts
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Starting with the 2005 Tropical Cyclone season, the Central Pacific Hurricane Center will be producing experimental graphics products.

We welcome any and all feedback on these products. Please e-mail your comments to


  • Collaborative effort between Central Pacific Hurricane Center (CPHC) and National Hurricane Center (NHC)
  • Created when each tropical cyclone warning is issued by JTWC and is available on WFO Guam's website
  • Supplement to the current deterministic products to communicate risk to users/partners
  • Solicit feedback this typhoon season via the WFO Guam's webpage


  • Improved means of conveying forecast uncertainty using probability of wind speed exceeding particular thresholds
  • Accounts for uncertainty in track, intensity and size of the tropical cyclone
  • Focus on the size of the storm rather than only the center location and track forecast
  • Provides users with information that enhances their ability to make preparedness decisions specific to their own situations

Forecast Components

  • Incremental probabilities in 12 hour ranges (i.e., 0-12, 12-24, 24-36 etc) through 120 hours, or 5 days
    • Indicates the chance that winds at the specified level will start during or before the particular period
  • Specific sustained wind speed thresholds used:
    • 34 kts (39 mph) - Tropical Storm strength
    • 50 kts (58 mph)
    • 64 kts (74 mph) - Typhoon strength