USS Salt Lake City: 1941

Here’s a first look at the navigation and temperature data from 1941 you’ve transcribed from the logbooks of the USS Salt Lake City (CA-25), a heavy cruiser commissioned in 1929. The Salt Lake City was 585 feet long and capable of making 33 knots on four steam turbines (107,000 horsepower).

The processing code used to convert Zooniverse classifications into transcription-verified and quality-controlled data was written by science team member Praveen Teleti. There are 8,760 hourly marine weather records (WRs) in this series, the first installment on roughly 832,000 WRs (~580,000 are ready for processing as of August 2021) transcribed from only our 19 ships. This is more than the total number of U.S. Navy WRs from the WWII era currently available in the global standard dataset – ICOADS (the International Comprehensive Ocean Atmosphere Data Set).

The track of the Salt Lake City for 1941 is shown in Figure 1. The first two months of the year were taken up by an extended overhaul in the Mare Island Naval Shipyard. In March the ship moved to Pearl Harbor and spent considerable time in training exercises in the area of the Hawaiian Islands. One cruise was made to Midway Island on March 17. In July and August Salt Lake City and USS Northampton (CA-26) made a voyage to Brisbane, Australia, for training and likely intelligence gathering around New Guinea. In early December Salt Lake City was part of Task Force 8 with the aircraft carrier Enterprise (CV-6), two other cruisers and nine destroyers assigned to deliver a squadron of fighter planes to Wake Island. On the way back on December 5-6 the task force was delayed by stiff easterly winds and rough seas and so was still at sea on December 7¹.

Figure 1. The track of the USS Salt Lake City for 1941. (Map: P. Teleti)

Figure 2 shows the plots of the air (blue) and seawater (orange) temperatures from the ship’s deck log, before and after initial quality control checks. The periods the ship was in port are indicated by the grey broken line. These data are nearly all from the neutrality period prior to the U.S. entry into World War II, in December 1941. Nevertheless, the logbooks show that the Salt Lake City was frequently operating in ways consistent with a wartime footing, including ‘darkened ship’ that may affect how some weather readings were made.

The most obvious difference between the uncorrected data (top) and quality-controlled data (bottom) is the frequency of large departures in the former. These seem to be associated most often with various typewriter key miss-strikes, especially the key next door (like 1 or 3 instead of 2). These have been corrected, but other characteristics of the data will need further examination, particularly relating to the seawater temperatures measured in the main engine room cooling water injection.

Figure 2. Air (blue) and seawater (orange) temperatures recorded in the USS Salt Lake City deck logs, January though December 1941. The top panel shows the data prior to initial quality checks, and the lower panel after one round of adjustment.

Also notable, but not surprising, is the difference between ‘at sea’ and ‘in port’ air temperatures. The higher values in port are likely the result of low air circulation in the thermoscreen, combined with a multitude of heating factors on the ship itself, and heat island effects within urbanized ports. The low values, seen for example during the September period in Pearl Harbor, are more puzzling. The period the ship was in Brisbane is marked by an especially wide daily temperature range (between ~45° and 69°), but this is well within cool season climatology for this location. A photo of the Salt Lake City alongside in New Farm, Brisbane, during this visit is shown in Figure 3.

Figure 3. The USS Salt Lake City alongside in New Farm, Brisbane, August 5-10, 1941. The ship is painted with a false bow wave, a form of camouflage. Two of four Curtis SOC Seagull scout planes are visible amidships. (Photo: Naval History and Heritage Command NH 80837)

There is a curious historical event along the ship’s track on the return voyage from Brisbane. After sailing the ship made two brief stops, possibly clandestine, to reconnoiter Port Moresby and Rabaul, in New Guinea. At the latter, Salt Lake City came to anchor on 16 August, somewhere near the port (the place names and bearing marks were left intentionally blank in the typed logbook). Three Seagull scout planes were launched, missions undeclared in the log. These places would become incredibly important to the defense of Australia and other Allies with the outbreak of war just three months later. A new analysis of pre-war planning by the Navy suggests some officers were well attuned to the dangerous situation in the Pacific that summer but were unheeded by policy makers².

1. Historical information from Naval History and Heritage Command (NHHC), Dictionary of American Naval Fighting Ships, available online at https://www.history.navy.mil/research/histories/ship-histories/danfs.html
2. NHHC (2021): Richmond Kelly Turner, Planning the Pacific War. U.S. Navy Operations in World War II. OPNAV Support Section, Histories Branch. Retrieved 16 August 2021.