Flash Flood Forecasting over Complex Terrain : With an Assessment of the Sulphur Mountain NEXRAD in Southern California

by Committee to Assess NEXRAD Flash Flood Forecasting Capabilities at Sulphur Mountain, Claifornia; National Research Council (U. S.) Board on Atmospheric Sciences and Climate

• ISBN13: 9780309093163
• ISBN10: 0309093163
• Format: Paperback
• Copyright: 2005-01-28
• Publisher: Natl Academy Pr

Summary

The nation's network of more than 130 Next Generation Radars (NEXRADs) is used to detect wind and precipitation to help National Weather Service forecasters monitor and predict flash floods and other storms. This book assesses the performance of the Sulphur Mountain NEXRAD in Southern California, which has been scrutinized for its ability to detect precipitation in the atmosphere below 6000 feet. The book finds that the Sulphur Mountain NEXRAD provides crucial coverage of the lower atmosphere and is appropriately situated to assist the Los Angeles-Oxnard National Weather Service Forecast Office in successfully forecasting and warning of flash floods. The book concludes that, in general, NEXRAD technology is effective in mountainous terrain but can be improved.

Table of Contents

Executive Summary	1	(8)
Introduction	9	(3)
Flash Floods	12	(14)
The Physical Processes of Flash Floods	13	(13)
The National Weather Service and Flash Floods	26	(9)
The Modernization and Associated Restructuring of the National Weather Service	27	(2)
The Process of Issuing Flash Flood Forecasts, Watches, and Warnings	29	(6)
Nexrad	35	(24)
The NEXRAD Network	35	(5)
NEXRAD Scan Strategies	40	(1)
Precipitation Estimation	41	(8)
The Evolving NEXRAD System	49	(2)
Siting of the NEXRADs	51	(8)
Observational Challenges of Low-Level Radar Coverage in Complex Terrain and Coastal Areas	59	(15)
Beam Visibility	60	(1)
Propagation of Electromagnetic Radar Signals	61	(13)
Flash Flood Warning Process in Los Angeles and Ventura Counties	74	(17)
Rainfall Records for Los Angeles and Ventura Counties	77	(5)
The NWS Los Angeles-Oxnard Flash Flood Warning Process	82	(3)
Private Sector Role in Forecasts and Dissemination	85	(1)
Stakeholders	86	(2)
Need for Multigency and Public Collaboration	88	(3)
Evaluation of the Sulphur Mountain Radar and Flash Flood Warnings in Los Angeles and Ventura Counties	91	(26)
Radar Coverage	91	(9)
Availability of the Sulphur Mountain Radar	100	(1)
Flash Flood Warning Statistics	101	(16)
Potential Improvements in Flash Flood Warnings	117	(29)
Nexrad and Other Radar Sources	118	(17)
Modeling, Data Assimilation, and Decision Support Systems	135	(11)
Concluding Thoughts	146	(3)
REFERENCES	149
APPENDIXES
A Origin of the Study	169	(3)
B Characteristics of the NEXRAD Radar	172	(3)
C Chronology of the Siting of the Sulphur Mountain NEXRAD	175	(1)
D National Weather Service Flash Flood Verification Procedures	176	(4)
E Acronyms	180	(4)
F Community Participation	184	(2)
G Committee and Staff Biographies	186