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STAR Satellite Rainfall Estimates
Self-Calibrating Multivariate Precipitation Retrieval (SCaMPR)

Hurricane Iselle approaching the Big Island of Hawaii, 24 hours beginning 00 UTC 8 August 2014

Hurricane Iselle approaching the Big Island of Hawaii, 24 hours beginning 00 UTC 8 August 2014

Ensemble Tropical Rainfall Potential (eTRaP)

Tropical cyclones are usually best known for strong winds, but they also produce heavy rainfall and inland flooding that frequently accounts for the majority of the damage-notable examples include Hurricane Agnes (1972), Hurricane Floyd (1999), Tropical Storm Allison (2001), and Tropical Storm Lee, which in 2011 broke many of the record flood crests set by Agnes.

Tropical Rainfall Potential (TRaP; Kidder et al. 2005) is a 0-24 hour forecast of rainfall for a tropical system produced by extrapolating the current rainfall for a tropical system (derived using rain rates from microwave-frequency satellite-based sensors) along the official forecast storm track. TRaP became operational at NESDIS in 2003 and was followed by ensemble TRaP (eTRaP; Ebert et al. 2011), which is an ensemble of TRaPs for different satellite instruments, lead times, and forecast tracks. The ensemble provides information about forecast uncertainty, which is shown in the form of maps of the probability that the rainfall will exceed specific thresholds during the next 24 hours in 6-hour intervals. Real-eTRaP forecasts can be accessed from OSPO in real time at

Efforts to improve eTRaP are ongoing. Rainfall rates from new instruments are being added to the ensemble to replace retired instruments and ensure continuity, and recently the exceedance probabilities were calibrated to remove bias. Upcoming improvements include adding a climatology-persistence forecast called R-CLIPER to the ensemble and accounting for the influence of orography on rainfall.


Kidder, S. Q., S. J. Kusselson, J. A. Knaff, R. R. Ferraro, R. J. Kuligowski, and M. Turk, 2005: The Tropical Rainfall Potential (TRaP) technique, Part I: Description and examples. Wea. Forecasting, 20, 456- 464. DOI: 10.1175/WAF860.1

Ebert, E. E., M. Turk, S. J. Kusselson, J. Yang, M. Seybold, P. R. Keehn, and R. J. Kuligowski, 2011: Ensemble Tropical Rainfall Potential (eTRaP) forecasts. Wea. Forecasting, 26, 213-224. DOI: 10.1175/2010WAF2222443.1