Forensic Meteorological Investigation of Damaging Wind and Rainfall Conditions in Long Beach, California Between January 1 and January 31, 2017
Total Page：16
File Type：pdf, Size：1020Kb
Forensic meteorological investigation of damaging wind and rainfall conditions in Long Beach, California between January 1 and January 31, 2017 Radar image of southern Los Angeles County at 2:35pm PST, 22 January 2017. Prepared by: Dr. Ryan Truchelut Prepared for: Wilson Phillips Prepared on: September 21, 2017 Document reference number: WT20170905 WeatherTiger, LLC P.O. Box 894 Tallahassee, FL 32302 (850) 733-8431 http://www.weathertiger.com/ WT20170905: Page 1 Table of Contents Background …...........................................…......... 3 Meteorological overview ….................................. 3 National Weather Service warning products …... 4 Observed meteorological data …........................ 6 Storm damage reports …............................................. 9 Analysis ….................................................................. 10 Conclusions …....................................................... 12 Appendix: Detailed data …................................... 13 WT20170905: Page 2 I. Background WeatherTiger, LLC has been contracted by Wilson Phillips of Long Beach, California to investigate the meteorological conditions during the month of January 2017 relevant to an ongoing insurance claim. The street address of the house is 2004 Ocean Avenue, Long Beach, California, which is located in coastal Los Angeles County at approximately 33.724 degrees north latitude, and 118.283 degrees west longitude. This coordinate is used to determine the distance between the claim site and the historical weather observations referenced in this report. In accordance with best practices in the feld of forensic meteorology, all historical data and forecast products used to prepare this report originate from the National Weather Service (NWS) and National Oceanic and Atmospheric Administration (NOAA), a division of the United States Department of Commerce. This report was authored by Dr. Ryan Truchelut, in coordination with WeatherTiger research staf. My professional background in both operational forecasting and research meteorology is extensive. I am co-founder and President of WeatherTiger, a meteorological consulting frm ofering customized short- and long-range weather forecasts and full-spectrum decision support for commodity, risk, public safety, and retail markets. I have an undergraduate degree in Geosciences from Princeton University and master's and doctoral degrees in Meteorology from Florida State University, have authored papers for both peer-reviewed scientifc press and national media outlets, and served as the ofcial hurricane expert for the USA Today Network during the 2017 hurricane season. My academic credentials and professional experience qualify me to assess the weather conditions relevant to this case, and I will ofer my professional opinion on the probable meteorological causes of the damage to 2004 Ocean Avenue and an assessment of the use of weather data in the American Engineers engineering report in the Analysis section. II. Meteorological overview January of 2017 was a notably active period of weather in southern California, with multiple strong storms moving into the region from the southwest due to an active subtropical jet stream triggered by a La Nina event. This type of event is known as an “atmospheric river,” in which a steady fux of oceanic moisture moves into a single region repeatedly. After several years of much drier than normal conditions between 2013 and 2016, dry soil and repeated storm systems impacting the state led to widespread fooding issues and wind damage. These conditions were refected by the declaration of a State of Emergency by Governor of California Jerry Brown and the subsequent declaration of a Major Disaster area by the Federal Emergency Management Agency, both including all of Los Angeles County, as a result of the January storms. To put the atmospheric river event of January 2017 into historical perspective, Figure 1 plots the percentage of normal rainfall received in the state of California, relative to the 30-year climate normal observed during 1981-2010. Los Angeles County, including Long Beach, received between 200 and 300% of average precipitation for January. More broadly, January 2017 ranked as the seventh-wettest January since 1895 for the entire state of California. WT20170905: Page 3 Figure 1: Accumulated precipitation as a percentage of normal across California over January 2017. The claim site is marked with a red star on this fgure. III. National Weather Service warning products The NWS Local Forecast Ofce (LFO) responsible for issuing routine weather forecasts and severe weather warnings for Los Angeles County is NWS Oxnard. As with all 122 LFOs nationwide, NWS Oxnard is stafed continuously by trained meteorologists employed by the federal government to protect public safety. The Long Beach claim site is located in NWS forecast zone CAZ041, covering coastal Los Angeles County. All warnings referenced in this section cover CAZ041 and thus apply specifcally to Redondo Beach. Refective of the active weather pattern occurring during January 2017, an unusual number of WT20170905: Page 4 weather advisories and severe weather warnings were enacted during this time. Most relevant to this report are the three Wind Advisories and one Flash Flood Warning covering Redondo Beach. The NWS criteria for the issuance of a Wind Advisory are when sustained winds of 31 to 39 mph are expected to last for an hour or more, and/or wind gusts of 46 to 57 mph for any duration. Three Wind Advisories were issued during the study period for three separate storms: the frst for January 20th, the second for January 22nd extending into January 23rd, and the third for January 27th. The Wind Advisory for January 20th specifcally predicted, “gusts in excess of 55mph...possible across higher terrain such as the Palos Verdes peninsula,” located several miles south of Long Beach, as well as warned the public that “winds may down trees and power lines... with wet soils and strong gusty winds expected... there is a heightened potential for downed trees.” The full text of all the relevant NWS warnings and advisories may be found in the Appendix. Figure 2: Flash Flood Warning polygon (green outline) covering Long Beach, CA, issued at 2:39PM PST, 22 January 2017, with doppler radar imagery. The claim site is marked with a red star. The NWS' purpose for issuing a Flash Flood Warning Is to inform the public, emergency management, and other cooperating agencies that fash fooding is in progress, imminent, or highly likely. A Flash Flood Warning was issued at 2:39PM PST on January 22, 2017 by NWS Oxnard for a portion of southern Los Angeles County including Long Beach. This is shown graphically in Figure 2. The Warning was triggered by “widespread rainfall rates of around 0.75 inches per hour from Redondo Beach east through Long Beach and Lakewood,” and warned the public to take action due to the fact that “signifcant and serious urban fooding is expected on area roadways and freeways, especially on the 110 and 710 freeways.” It should be noted that Flash Flood Warnings cover only the area in which the fooding is occurring or expected, and are thus rare. Long Beach has only been placed under a Flash Flood Warning three times since 2005. WT20170905: Page 5 The archived NWS advisory and warning products show that these events were widely predicted ahead of their occurrence to cause widespread wind and water damage across Los Angeles County generally and Long Beach specifcally. Based on these products, our study of the historical weather data will focus on January 20t h and January 22n d as the most likely timing for wind and wind-driven rain damage to the 2004 Ocean Avenue property. IV. Observed meteorological data There are fve ofcial NOAA weather observation stations recording data each hour or more frequently within 12 miles of the claim site. Three of these observing stations are operated by the the National Weather Service and are located at Torrence Municipal (KTOA), Hawthorne Municipal (KHHR), and Los Angeles International (KLAX) Airports, respectively. The remaining two stations are marine weather stations operated by NOAA's National Ocean Service and located at the Port of Los Angeles Pier F (PFXC1) and Pier J (PRJC1), respectively. There are two other sources of meteorological data used in this report. NOAA operates co-operative observation stations across the country, which report a more limited set of weather data on a less regular schedule. The NOAA co-operative station in Redondo Beach (RDOC1) reports daily rainfall totals and is located about 3.5 miles northwest of the claim site, Finally, the NWS releases local storm report data highlighting the strongest wind gusts or other extreme observations from all available credible weather sources via Public Information Statements. Local storm report products can give a better sense of the maximum possible gusts that may have occurred at a given location. Figure 3: Daily and cumulative monthly rainfall totals for Redondo Beach (NOAA Co-op station RDOC1) for January 2017, with cumulative diference from January average conditions. As shown in Section II, January 2017 was a notably wet month for Los Angeles County overall. In the Long Beach area, the historical observations show this to be particularly true at the local level. Figure 3 shows the daily rainfall totals over the month for the Redondo Beach reporting station, RDOC1. Of particular note are the precipitation totals associated with the January 20th storm of just over 1”, and