Black and white photograph of the aerology crew in the weather office aboard USS YORKTOWN during Korea.
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Captain Jocko Clark and his Favorite Weather-Guesser

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Most of us have experienced the frustration of ruined plans due to a faulty weather forecast. While weather inaccuracies are a minor annoyance for many, they represent a much heavier burden for the meteorologists who make them. Now, imagine the stakes aboard the USS Yorktown, where a single bad forecast from the aerology department could delay a mission—or even risk lives. The pressure wasn’t just intense—it was mission-critical. For an aircraft carrier, poor weather could ground an entire attack and stall the Navy’s plans until conditions improved. Likewise, launching an air group into clear skies that soon turned rough threatened the safety of pilots and their crews. Accurate weather predictions were essential for both successful missions and pilots’ safety.

Black and white snapshot of a member of the crew of USS YORKTOWN plotting the winds aloft during Korea.

Black and white snapshot of a member of the crew of the USS Yorktown plotting the winds aloft during Korea.


Enter Lieutenant James Vonk, head of the Yorktown’s aerology department during WWII and the man responsible for briefing the ship’s first captain, Joseph “Jocko” Clark. Vonk held a master’s degree in meteorology from Columbia University and, according to the crew, was the most accurate weather-guesser the Yorktown had ever seen. Officers on the bridge recalled that whenever Vonk wanted to reassure everyone of his forecast, he’d stick a finger in his mouth, hold it up to check the wind, pause dramatically, and then declare his prediction spot-on. Many sailors scoffed at this ritual, but Vonk was rarely wrong. More importantly, he was one of the few aboard CV-10 who could stand his ground when Jocko’s temper turned stormy.


The bridge of the Yorktown was sometimes a chaotic place, where Jocko was known to chew out any officer who failed to meet his high standards. While he had a soft spot for the average enlisted man, he pushed his officers to nearly unattainable levels of perfection. Vonk was the only officer who could go blow for blow with Jocko in a shouting match. Air Operations Officer Cooper Bright recalled a moment when Jocko and Vonk stood over a chart, arguing about where the weather would break—determining the perfect window for the Yorktown to launch its air groups. The two men shouted back and forth, gesturing wildly over the chart. Jocko bellowed, “+#$%*@ I know the weather! It’ll clear up over here!” as he jabbed at one spot. Vonk shot back, “You’re crazy as hell! It’s over here!” pointing to another. It was the first time Bright had seen anyone yell at the captain. Minutes later, the weather broke exactly where Vonk had predicted. He turned to Jocko and yelled, “Didn’t I tell you so?!” Jocko thundered back, “Yeah, you did!” With that, the head weather-guesser stormed out of the bridge.

Caricature by John Furlow of "Jocko" Clark in his pajamas, holding his head and profanely demanding "ORDERLY ! Where's My Milk??". The flustered orderly salutes and responds "Y-Y-YESSIR! GETTING IT RIGHT AWAY S-SIR!!" .

Caricature by John Furlow of "Jocko" Clark in his pajamas, holding his head and profanely demanding "ORDERLY ! Where's My Milk??". The flustered orderly salutes and responds "Y-Y-YESSIR! GETTING IT RIGHT AWAY S-SIR!!" .


Both men understood the importance of their weather predictions; getting it wrong not only set back strategic goals but endangered pilots’ lives. Vonk and the other officers understood why Jocko pushed them so hard, even if they never got used to his temper. Earning his trust and appreciation was seen as a mark of excellence aboard the Yorktown. Most of the Fighting Lady’s crew believed wholeheartedly that they had both the best captain and the most scrupulous weather-guesser. Despite their animated arguments, Jocko respected Vonk immensely and personally ensured he was rewarded for his accuracy. As Vonk’s roommate and Yorktown ace Smokey Stover wrote in his diary, “I doubt if there are a half-dozen officers in the Navy, even, who have had as much liberty as [Vonk].”


Jocko’s appreciation for his officers went beyond granting liberty—he credited many of his personal successes to them. When Jocko was promoted to rear admiral, he quickly began maneuvering to bring his most trusted officers with him, rewarding those who had earned his confidence. James Vonk was among those he wished to keep in his command, but Admiral Marc Mitscher had already claimed the top weather-guesser. After leaving CV-10, Vonk went on to serve as meteorologist for the admiral of Task Force 58. Vonk was one of the few who could outshout Jocko and still earn his unwavering trust—a testament to why the admiral always kept him close.