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Tropical Cyclone Formation Probability Guidance Product

Developed by the Regional and Mesoscale Meteorology Branch at CIRA
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Cooperative Research Program | Office of Research and Applications/Center for Satellite Applications and Research

Products Last Updated 2013 APR 23 06UTC

Combined image of all basins
Combined image of all basins
TD/TS Symbol Tropical Depression / Tropical Storm Hurricane Symbol Hurricane
Identifies regions of relatively-enhanced summation TC formation probability (see below). To dinstinguish between TC formation and non-formation cases, uses nearby TC formation (see below). Hence, provides a broad-scale "first guess" at areas with the potential for TC formation. The threshold summation probability values that define each potential category were chosen so that 100%/75%/25%/5% of dependent sample set cases meet or exceed the threshold values. Basins were treated independently, so corresponding dependent sample set occurrence frequencies may vary by basin.
Color bar TC Formation Area
of Interest Category
Occurrence Frequency
Dependent Cases
Possible (Blue) 4% 7% 5% 75%
Fair (Orange) 10% 26% 12% 25%
Good (Red) 20% 46% 18% 5%
Nearby TC Formation
Describes TC formation that occurs within 20° of a given point. This is less stringent than the 5° criterion used by the main TC Formation Probability product.
Summation TC Formation Probability
The sum of the TC formation probabilities at all grid points within a 20° lat by 20° lon subregion centered on that point.
Occurrence Frequency
For all points exceeding a given summation probabilty threshold, the percent of those cases that resulted in a "nearby" TC formation (as defined above).



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