Tropical Storm Imelda Forms; Another Round of Heavy Rain and Potential Flooding in the Southwest

Tropical Storm Imelda has formed near the Bahamas Sunday afternoon, and continues to bring heavy rainfall. The risk of significant wind impacts from Imelda along the Southeast coast are decreasing. Another round of showers and storms with a heavy rain and flash flood threat will continue in the Southwest through Monday morning. Read More >

HFO’s Ua Net Real-Time Rain Gage Network

HFO’s Ua Net network of tipping bucket gages includes over 65 sites across the State of Hawaiʻi. The network is managed by HFO’s Hydrologist and maintained by Pacific Region Electronic Technicians. Most of the gages are telemetered via GOES (scheduled and random transmission channels), with a smaller number transmitting data via VHF radio using the ALERT protocol. Redundant workstations running the Datawise software provide forecasters with data alarms at 4 threshold levels. They are 0.25, 0.50, 0.75, and 1.00 in 15-minutes, which translates to 1, 2, 3, and 4 inch per hour rates.

Real-time rainfall data can be helpful with the flash flood warning and flood advisory decision making process, and can provide some lead time for the warnings depending on where the event is occurring. Typical flood advisory rain rates are in the range of 1 to 2 inches per hour. Rates of 3 to 4 inches per hour or more warrant consideration of a flash flood warning, especially if significant rainfall has recently occurred and the intense rain is expected to continue for 30 minutes or more.

In addition to providing forecasters with notifications of heavy rainfall, real-time gage data also serve as a ground truth verification data source for radar based rainfall estimates, and can be used to help adjust biases in the radar based estimates. The bias-adjusted estimates serve as the observational forcing for the National Water Model’s Hawaiʻi domain.

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Tropical Storm Imelda Forms; Another Round of Heavy Rain and Potential Flooding in the Southwest

Ua Net Automated Rain Gage Network