Race IntelligenceTenby, Pembrokeshire, United Kingdom
Know your day before you race it.
Enter four numbers you already train with. You get a likely finish range, target paces and watts, and how I would race this course.
Published route evidence. Final 2027 route pending. Checked 15 Sept 2026.
01 Race Card
Your first range uses conservative assumptions. Add optional evidence to make it more specific. It is calculated in your browser and saved only on this device.
02 The course
You swim two loops from Tenby's famous North Beach, then run a genuine 1 km up the 'zig zag' ramp to transition, ride two loops through the rolling Pembrokeshire Coast National Park past castles and a Harry Potter filming location, then run four loops inside Tenby's medieval town walls and along its beachfront in front of tens of thousands of spectators. This course has a reputation as one of the hardest in the IRONMAN portfolio, and the rolling bike terrain, ridden twice, is where that reputation is earned.
Swim
3.8 km
A two-loop open-sea start from the famous North Beach, with a genuinely long 1 km run up the 'zig zag' ramp to transition, is loud, exposed and physically demanding before the bike even starts.
Source: 2027 current routeBike
180.2 km
A two-loop route through the genuinely undulating Pembrokeshire Coast National Park, ridden twice, makes pacing the rollers the whole bike variable, not just a single named climb.
Source: 2027 current routeRun
42.2 km
A four-loop course inside Tenby's medieval walls and along its beachfront, in front of tens of thousands of spectators, tests whatever the rolling bike left in the legs.
Source: 2027 current routeThese facts come from the organiser’s latest published material: swim, 2027 current route; bike, 2027 current route; run, 2027 current route. They describe the character of the course. They do not confirm the final 2027 route.
03 Race plan
One job for each part of this course. The distance markers tell you when the job changes. The course tells you why.
Swim
Two loops of open sea off the famous North Beach lead into a genuinely long 1 km run up the 'zig zag' ramp to transition. Settle into rhythm early and don't empty the tank before that run even starts.
Bike
The course moves through the genuinely undulating Pembrokeshire Coast National Park, past castles and landmarks easy to get distracted by. This lap repeats, so ride the rollers at a number you can hold twice.
As loop one closes, hold the same effort you plan for lap two rather than easing up early because the terrain briefly settles.
The second loop repeats the same rolling coastal terrain. Ride to the same power ceiling you set on lap one, especially on the rollers that felt manageable the first time.
Run
The run moves through Tenby's medieval town walls and beachfront in front of tens of thousands of spectators. Let the first loop feel genuinely easy after a demanding bike.
Passing the same walls and beachfront a second time gives a clear read on how loop one's pace is holding after a rolling bike course. Adjust deliberately here.
The third loop is where genuinely undulating bike terrain, ridden twice, starts to show up in the legs. Manage effort rather than chasing a pace that's slipping.
The final loop finishes among the biggest crowds of the day inside Tenby's walls. If both bike loops were paced evenly, this is where it pays off.
04 Race week
There is no useful 2027 forecast this far out. For now, past race dates give us a point of reference. Closer to the race, the forecast will tell us whether the plan needs changing.
A race-day forecast is not meaningful yet; check back closer to the event.
Historical baseline, 2019–2025 · Open-Meteo historical archive · Updated 2026-09-15.Historical comparison only. This is not a forecast for 2027.
05 Method
Your CSS, FTP, weight and run threshold create the first range. Open-water, bike, run and execution evidence can replace broad assumptions. Course data and the historical conditions baseline shape every simulation.
Confidence is built from four inputs
It starts with the targets in your Race Card, then samples the parts of a full distance that vary: open-water pace, transitions, bike speed at the planned power, and the drop in run performance after the swim and bike. Repeating that calculation produces a likely range rather than a single heroic number.
The current time calculation uses this race’s published distances, or standard full distance distances where none are published, with the available course headings, elevation and exposure evidence. Weather scenarios vary temperature, dew point, wind, gusts, rain and water conditions together. Unknown route detail stays visible as uncertainty rather than false precision.
It is not predicting your exact finishing time, placing, or race-day weather. It answers a narrower question: given the plan and the information we have, what range of day is plausible, and where is the uncertainty coming from?
Confidence is not a permanent “low”. It is recalculated across four separate inputs:
It starts low when those inputs are broad. It can become moderate or high as the evidence improves. A narrower range means better information, not a guarantee.
Evidence
Course status: Partially verified. The organiser’s descriptions and latest published route profiles are in use. The final 2027 route is not yet confirmed. Last checked 2026-09-15.