News
The 2025 Transpac will use Forecast-Time Correction Factor (F-TCF) scoring to account for varying weather conditions on start dates and how different types of boats use the same weather to sail different optimal courses to Honolulu. “Catalina Eddy” weather effects often make the first 200 miles of Transpac significantly different from one start day to another, and with three planned starts staggered over five days chances are high for different weather between the starts. Fortunately, “Catalina Eddies” are now well predicted by HRRR forecasts.
Further offshore, boats are expected to encounter reaching conditions in the synoptic breezes and steadier trade winds which change less rapidly and are well predicted by GFS forecasts. F-TCF scoring uses each boat’s predicted performance over a full spectrum of wind speeds and angles combined with the weather predicted immediately before the race to calculate each boat’s optimal route, predicted elapsed time, and then Time Correction Factor.
What is F-TCF and how does it work?
Each boat’s performance across the spectrum of wind speeds and angles is calculated by the ORR handicap system’s VPP.
Transpac will announce calculation details including the model times of the HRRR and GFS weather models that will be used to calculate the TCFs for each race day, the boundaries used between the HRRR and GFS, and the weather-routing settings used in Expedition routing software.
Hours before the start of the race, on each of the three start days, the predicted elapsed time to finish for every boat will be calculated with Expedition software using timely weather GRIB files and each boat’s polar file to determine their optimized route.
A forecast-time correction factor (F-TCF) will be calculated for each boat. The F-TCF is the ratio of each boat’s predicted elapsed time to complete the course to a scratch boat’s predicted elapsed time. The F-TCF for every boat will be communicated to the fleet the morning of each start.
The corrected finish time for any boat can be calculated by multiplying the F-TCF for a boat by the actual elapsed time (plus any penalties) for that boat.
A rank order of corrected finish times by division and overall will determine the order of finish for division and overall.
Comparing TCF to F-TCF
The mechanics of using a time correction factor remain generally the same, with differences in the weather, route, and when a boat’s F-TCF is calculated.
| TCF | F-TCF | |
| Weather used to calculate time correction factor | Average of historical weather patterns as Wind Matrix | Forecast weather for each start date |
| Route | Great Circle | Each boat's optimized route |
| When calculated | One time for the race | At each boat's start day |
US Sailing’s Offshore Office will use Expedition routing software to predict each boat’s elapsed time according to the rating rule’s polar performance data, and NOAA’s HRRR and GFS weather forecasts available shortly before the start. They calculate F-TCF from these predicted elapsed times.