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National Weather Service Forecasters Use GPS Precipitable Water Vapor For Enhanced Situational Awareness During The Southern California Summer Monsoon

Abstract

During the North American Monsoon, low-to-mid level moisture is transported in surges from the Gulf of California and Eastern Pacific Ocean into Mexico and the American Southwest. As rising levels of precipitable water interact with the mountainous terrain, severe thunderstorms can develop, resulting in flash floods that threaten life and property. The rapid evolution of these storms, coupled with the relative lack of upper-air and surface weather observations in the region, make them difficult to predict and monitor, and guidance from numerical weather prediction models can vary greatly under these conditions. Precipitable water vapor (PW) estimates derived from continuously operating ground-based GPS receivers have been available for some time from NOAA’s GPS-Met program, but these observations have been of limited utility to operational forecasters in part due to poor spatial resolution. Under a NASA Advanced Information Systems Technology project, 37 real-time stations were added to NOAA’s GPS-Met analysis providing 30-minute PW estimates, reducing station spacing from approximately 150 km to 30 km in southern California. An 18-22 July 2013 North American Monsoon event provided an opportunity to evaluate the utility of the additional upper-air moisture observations to enhance National Weather Service (NWS) forecaster situational awareness during the rapidly developing event. NWS forecasters used these additional data to detect rapid moisture increases at intervals between the available 1-6 hour model updates and approximately twice daily radiosonde observations, and these contributed tangibly to the issuance of timely flood watch and warnings in advance of flash floods, debris flows, and related road closures.

Article / Publication Data
Active/Online
YES
Volume
96
Available Metadata
DOI ↗
Fiscal Year
NOAA IR URL ↗
Publication Name
Bulletin of The American Meteorological Society
Published On
November 01, 2015
Publisher Name
American Meteorological Society
Print Volume
96
Print Number
11
Page Range
1867–1877
Issue
11
URL ↗

Authors

Authors who have authored or contributed to this publication.