Sentinel-6B's sea level data waits five months for NOAA's hurricane heat algorithm

A radar altimeter fires thousands of pulses a second at the crests and troughs of waves, and what comes back is height, plus wave size and marine wind speed ^[13]. Height is useful because warm water expands, so a locally higher sea surface implies more heat in the column beneath it, and that inference is what helps forecast how fast a storm will grow ^[14]. NOAA's Satellite Ocean Heat Content Suite is the software that performs the conversion, and it has been running since 2012 ^[12].

Timing decides how much of this season the new satellite actually touches. Low-latency data has been flowing since mid-July, and the target for beginning to fold ocean height into the operational suite is the end of the year ^[7][16], which leaves roughly five and a half months in which the measurements exist but sit outside the algorithm that turns them into a forecaster's heat-content field ^[1]. NASA says the research models take longer still ^[8]. "Low latency" describes how fast the data arrives; trusting it operationally is a separate, slower process.

NASA's account gives the 30-second trail and the shared Continuity of Service mission ^[2][4] without saying, in this telling, what the tandem phase resolves. What matters is how the two instruments' height records are being tied to one another, which determines whether a sea level series now in its fourth decade ^[18] carries a step at the handover.

That series is why Josh Willis's comparison is checkable rather than impressionistic: it begins with TOPEX/Poseidon in 1992 ^[18], so both 1997 and 2015 fall inside it ^[2]. The operational tool has a shorter memory. A 2012 start puts the Ocean Heat Content Suite 15 years after the 1997 event and three years before 2015 ^[3], so the software doing the hurricane-relevant conversion has itself run through only one of the two analogues Willis names ^[5].

None of this establishes skill. Deirdre Byrne of NOAA calls the Sentinel-6 data quality unparalleled ^[17] and describes the goal as forecasting how much and how rapidly intensification will happen ^[11], but there is no figure here comparing forecasts made with the altimeter input against forecasts made without it. And because El Nino spreads warm water east and shifts hurricane activity from the Atlantic toward the Pacific ^[6], the basin where a heat-content improvement would be most visible this year is the Pacific. When the suite does start ingesting Sentinel-6 height, the number worth watching is intensification error inside the 48 hours before landfall ^[10].