####018005657#### NOUS41 KWBC 021830 PNSWSH Service Change Notice 24-47 National Weather Service Headquarters Silver Spring MD 230 PM EDT Thu May 2 2024 To: Subscribers: -NOAA Weather Wire Service -Emergency Managers Weather Information Network -NOAAPORT Other NWS partners and NWS employees From: Marina Timofeyeva Chief, Climate Services Branch Bruce Entwistle Chief, Aviation and Space Weather Services Branch Subject: Moving Downtown Los Angeles Weather Observations Site to the Frank Hotchkin Memorial Training Center on May 20, 2024 Effective Thursday, May 20, 2024 around 1500 Universal Coordinated Time (UTC) (8 AM PDT), the official Downtown Los Angeles weather observations site (KCQT) will be relocated to the Frank Hotchkin Memorial Training Center on the south side of Dodger Stadium. Observations collected at KCQT support NWS forecast activities, the climate record for Downtown Los Angeles, certain aviation operations, and needs of the meteorology, hydrology, and climatology research communities. Since 1999, the NWS has been collecting observations – temperature, precipitation, dew point, pressure and wind speed and direction – using an Automated Surface Observing System (ASOS) located on the campus of the University of Southern California (USC). This location is only about 10 miles from the Pacific Ocean, which has had a significant influence on temperature, humidity, and precipitation measurements. The site location is suboptimal in characterizing Downtown Los Angeles’s true weather and climate conditions. The core of Downtown Los Angeles is located farther inland from the coast and current site of KCQT. Gathering observations farther inland at the Frank Hotchkin Memorial Training Center is expected to better represent the weather and climate of Downtown Los Angeles. Downtown Los Angeles has one of the longest periods of record of weather observations in the West, dating back nearly 150 years to July 1877. The upcoming move to the Frank Hotchkin Memorial Training Center returns the Downtown Los Angeles observing site to a location near the previous Los Angeles Civic Center station, which was active from 1964 to 1999. The site relocation will help build on the climate records that are more representative of Downtown Los Angeles. Moreover, the move will provide better sampling of weather conditions conducive for the spread of brush fires closer to the foothills, and thus better assist NWS meteorologists in forecasting fire-weather conditions. The observing equipment will also change from an ASOS to different equipment that is also used for the Cooperative Observer Program (COOP). This change is necessary to align with infrastructure at Frank Hotchkin Memorial Training Center. The change in equipment type is not expected to significantly change measurements of meteorological or climatological variables. With the change of equipment from ASOS to COOP, there will no longer be a WMO Heading or AWIPS ID for real-time Downtown Los Angeles weather observations. Data collected from the Frank Hotchkin Memorial Training Center will still be available online via the NWS Weather and Hazards Data Viewer (https://www.wrh.noaa.gov/map/?wfo=lox) under the new equipment identification ‘FHMC1’. The data from the new site will also be provided in the Hourly Weather Roundup under ‘L.A. DOWNTOWN’ (https://www.weather.gov/wrh/TextProduct?product=loxrwrca) without the sky condition and visibility provided. Aside from real-time weather observations, WMO Headings and AWIPS IDs will switch from using ‘CQT’ to ‘FHM’ around or shortly after the completion of the observing site relocation. This applies to the daily Climate Report (CLICQT changing to CLIFHM), the Preliminary Local Climatological Data WS Form F-6 (CF6CQT changing to CF6FHM), and the monthly Climate Report (CLMCQT changing to CLMFHM). The National Weather Service thanks our partners at the Los Angeles City Fire Department for their collaboration and support of relocating the observation site. We also thank the USC for housing our weather observation site for the past 25 years. Observations gathered at USC have greatly contributed to the National Weather Service’s understanding of weather conditions to complete its mission of protecting life and property. The NWS will hold a news conference at the Frank Hotchkin Memorial Training Center to commemorate the Downtown Los Angeles observing site relocation and to discuss factors that lead to the move. For questions regarding the relocation of the official Downtown Los Angeles weather observation site or the news conference, please contact: Dr. Ariel Cohen, Meteorologist in Charge National Weather Service Los Angeles/Oxnard, California Oxnard, CA 805-988-6617 ariel.cohen@noaa.gov Resource: Downtown Los Angeles can experience large swings in meteorological observations, even across small distances. In 2000, David Bruno, Lead Meteorologist at NWS Los Angeles/Oxnard, published, “Climate of Los Angeles, California,” to identify and document this phenomenon. Data from this study was factored into the decision to relocate the site. You may access the publication using this link: https://www.weather.gov/media/wrh/online_publications/TMs/TM-261.pdf. National Service Change Notices are online at: http://www.weather.gov/notification ####018002346#### NOUS41 KWBC 021830 PNSWSH Service Change Notice 24-48 National Weather Service Headquarters Silver Spring MD 230 PM EDT Thu May 2 2024 TO: Subscribers: -NOAA Weather Wire Service -Emergency Managers Weather Information Network -NOAAPort Other NWS Partners and Employees FROM: Mike Hopkins, NOAA Director, Surface and Upper Air Division Office of Observations SUBJECT: Cooperative Hurricane Upper Air Stations (CHUAS) to Transition from the GRAW DFM09 to the GRAW DFM17 (Capless) Radiosonde and Supporting Software Version by July 27, 2024 All ten CHUAS sites will convert to an updated software version and new radiosonde through the next three months. The first part of this transition will be to start the implementation of the software upgrade the week of May 5, 2024. The quantity of legacy radiosondes that remain at each site will determine the order of the phased implementation. The anticipated completion date is estimated to be July 27, 2024, based on the radiosonde inventories at each of the CHUAS observing stations. The GRAW DFM17 (Capless) radiosonde will provide an exposed Relative Humidity sensor that will be more sensitive to changes in moisture concentrations encountered in the atmospheric sounding. The intention is to provide a better representation of relative humidity values than given by the legacy radiosonde. The required software upgrade (Version GRAWMET 5.16.04.22) to initialize the GRAW DFM17 (Capless) radiosonde will increase the number of Significant (SGL) levels in the World Meteorological Organization (WMO) Traditional Alphanumeric Codes (TAC) coded messages. This change of radiosonde models will align the CHUAS network’s radiosonde software version with the GRAW sites in the contiguous United States. This change will not have any impact on observing services because each site will remain operational during its transition. If you have questions or feedback, please contact: Hiram Escabi, Jr., NCE, CET Upper Air Program Manager NWS Program Management Branch Silver Spring, Maryland (301) 427-9195 hiram.escabi@noaa.gov National Service Change Notices are online at: https://www.weather.gov/notification/