NOAA's Hydrometeorological Testbed (HMT) evolved from a community-wide recognition of the need to enhance and accelerate the transition of state of the art research and technology development into National Weather Service (NWS) operations: to bridge the so-called valley of death. As HMT enters its fourth full year in the American River Basin in California, is poised to embark on HMT-Southeast in North Carolina, and has begun to spin-off focused mini-testbeds, HMT's transition projects are reviewed.

HMT's five major activity areas –quantitative precipitation estimates (QPE) and forecasts (QPF), snow information, hydrologic applications, and verification and decision support tools (DSTs)– have led to transition projects which include: the installation of GPS-Met stations; soil moisture networks; snow-level radars; mesoscale modeling systems; a DST for extreme QPF; the Pacific Atmospheric River Threat Indicator (PARTI); normalized water vapor flux anomalies; ensemble QPF efforts (in connection with TIGGE); support of distributed hydrologic modeling through DMIP-II; establishing new performance measures for extreme QPF and the modeling and monitoring of snow level.