VOLUME 31 JOURNAL OF CLIMATE 1JUNE 2018 Reanalysis of the 1954–63 Atlantic Hurricane Seasons a SANDY DELGADO Florida International University, Miami, Florida CHRISTOPHER W. LANDSEA NOAA/NWS/NCEP/National Hurricane Center, Miami, Florida HUGH WILLOUGHBY Florida International University, Miami, Florida (Manuscript received 3 August 2015, in final form 29 November 2017) ABSTRACT The National Hurricane Center (NHC) ‘‘best track’’ hurricane database (HURDAT2) is the main historical archive of all tropical storms, subtropical storms, and hurricanes from 1851 to the present in the North Atlantic basin, which includes the Caribbean Sea and Gulf of Mexico. The Atlantic Hurricane Reanalysis Project is an ongoing effort to maintain HURDAT2 and to provide the most accurate database possible based upon on all available data. The work reported here covers hurricane seasons from 1954 to 1963, during the early years of aircraft reconnaissance, but before satellite imagery became available routinely. All available original obser- vations were analyzed from aircraft reconnaissance, ships, land stations, land-based radars, and satellite images. The track and intensity of each existing tropical cyclone have been reassessed, and previously unrecognized tropical cyclones have been discovered, analyzed, and recommended to the Best Track Change Committee for inclusion into HURDAT2. Changes were recommended for every storm analyzed in this 10-yr period. 1. Introduction intensity, seasonal forecasting, and climatic change studies’’ The goal for this project is to reanalyze the National (Landsea and Franklin 2013,p.3576;seealsoLandsea et al. Hurricane Center (NHC) ‘‘best-track’’ North Atlantic 2008). The challenge is that HURDAT2 was not developed hurricane database (HURDAT2; Landsea and Franklin with these purposes in mind. Thus, the focus of the Atlantic 2013) for the period 1954–63. Since the database was ini- Hurricane Reanalysis Project is to improve the accuracy tially developed in the 1960s, HURDAT2 has been utilized and completeness of HURDAT2 through the correction of for such purposes as ‘‘setting appropriate building codes for random errors and biases, by revisions where necessary, to the time of genesis or dissipation, positions, intensities,1 coastal zones, risk assessment for emergency managers, 2 analysis of potential losses for insurance and business in- central pressures, and status (Office of the Federal terests, development of intensity forecasting techniques, 1 verification of official and model projections of track and The highest 1-min average wind (at an elevation on 10 m with an unobstructed exposure) at a particular point in time. 2 Status in this era is restricted to the following categories: tropical Denotes content that is immediately available upon publica- cyclone, extratropical cyclone, and tropical disturbance. A tropical tion as open access. cyclone is a warm-core nonfrontal synoptic-scale cyclone, originat- ing over tropical or subtropical waters, with organized deep con- vection and a closed surface wind circulation about a well-defined Supplemental information related to this paper is available at the center. A tropical disturbance is a discrete tropical weather system of Journals Online website: https://doi.org/10.1175/JCLI-D-15-0537.s1. apparently organized convection, generally 100 to 300 mi in di- ameter, originating in the tropics or subtropics, having a nonfrontal aCurrent affiliation: Key West Weather Forecast Office, NOAA/ migratory character, and maintaining its identity for 24 h or more. It National Weather Service, Key West, Florida. may or may not be associated with a detectable perturbation of the wind field. An extratropical cyclone is a cyclone (of any intensity) for Corresponding author: Sandy Delgado, sandy.delgado@ which the primary energy source is baroclinic (i.e., results from the noaa.gov temperature contrast between warm and cold air masses). DOI: 10.1175/JCLI-D-15-0537.1 Ó 2018 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses). 4177 4178 JOURNAL OF CLIMATE VOLUME 31 Coordinator for Meteorology 2015). Some of the random This caused many errors, including a systematic but ar- errors include positions resulting from insufficient tificial apparent weakening before landfall. Another observations near the storm. Sparse observations also problem was that many tropical cyclones showed un- introduce biases in estimated intensity. For example, realistic accelerations or decelerations at the beginnings the intensity of hurricanes may have been significantly or the ends of their tracks when the original hand-drawn underestimated without ships passing close to or track maps were digitized in the 1960s. For example, the through the center and also without reconnaissance position in the track of tropical cyclones was assumed to aircraft observations (Landsea et al. 2004). Also, in be the point in the arrow at the end of the track and not the early 1960s, the first satellite images produced by the center position of the arrow, leading to unrealistic TIROS showed cloud masses that the forecasters were acceleration at the last point. In other cases, the analysis able to identify as tropical cyclones (United States did not follow storms until dissipation after extratropical Weather Bureau Topics 1960). However, without a transition (such as Carla in 1958, Anna in 1961, and technique to estimate intensity, the forecasters still Debbie in 1961). had to wait for reconnaissance aircraft or ship obser- vations to begin advisories operationally and to assess 2. Data sources and methodology the intensity in post analysis.3 New data sources, such as ship reports, land-based The primary objective is the reassessment of previous surface weather observations, and satellite and radar tracks, intensities, and classifications of tropical cyclones images, that were not available either operationally or as well as finding previously unknown tropical cyclones. during a postseason assessment (‘‘best track’’ analysis) Many of the data sources used in this paper are similar to have become available. The new data allow for a better those used in previous HURDAT2 reanalyses, as de- assessment of the track and intensity. One objective is scribed in Hagen et al. (2012). They include historical the correction of U.S. hurricane landfall characteristics, weather maps, microfilm of original hand-plotted sur- because many landfall intensities are inaccurate and face weather maps used by hurricane forecasters at the inconsistencies often exist between the last intensity Miami Weather Bureau Office (lead hurricane fore- record before landfall and the assigned Saffir–Simpson casting agency for the United States in the 1950s and category (Landsea et al. 2008). Moreover, some tropical early 1960s), the Comprehensive Ocean–Atmosphere cyclones that existed were not included in the original Dataset (COADS; Woodruff et al. 1987), Monthly HURDAT2 because of the lack of data over the open Weather Review, Connor (1956), Annual Tropical Storm Atlantic or because they were considered to have been Reports of the Navy Hurricane Hunter aircraft recon- extratropical. Also, advancements in the understanding naissance missions by the U.S. Fleet Weather Facility of tropical cyclones, such as the Brown et al. (2006) (1954–63), climatological data reports, and synoptic ob- pressure–wind relationship, and better analysis tech- servations from stations in the United States, Caribbean niques, such as the Franklin et al. (2003) flight level islands, Mexico, Bermuda, and Canada available from to surface wind methodology, support more accurate NOAA’s Environmental Document Access and Display interpretations. System, version 2 (EV2) website (https://www.ncdc. Systematic biases in the original HURDAT2 database noaa.gov/EdadsV2/). are typically easier to detect and quantify than are ran- Moreover, new data sources became available during dom errors. For example, when the original HURDAT2 the period of 1954–63. The Mariners Weather Log was developed, the position and intensity of the tropical (MWL), put out by the United States Weather Bureau, cyclones was estimated only once daily and then in- began publication in 1957. The MWL catalogs ship re- 2 terpolated to 6-hourly intervals (Landsea et al. 2008). ports of winds at least 35 kt (1 kt 5 0.51 m s 1) during each month, and also includes summaries of the tropical cyclones and other low pressure systems and their 3 Hurricane Esther in 1961 is an excellent example of this. The tracks. Data in the MWL sometimes reveal important satellite images showed a well-organized system over the eastern Atlantic, resembling a tropical storm, but it was not until re- observations that were not available from other sources, connaissance aircraft investigated the cyclone a couple days later including satellite images in the publications starting in that advisories started being issued. Without the data from ships or 1961. These data complement the information available reconnaissance aircrafts, there was not a method to estimate the from the other sources. organization state of disturbances and the intensities, or to know Figure 1 provides an example of the revolutionary their location in some cases, especially before satellite images. By the 1970s (outside of the scope of this paper), the methodology had advance for the reanalysis project provided by weather changed. Interpretation of satellite images allowed for estimate