ONBOARD CARD 06 — Gulf Stream Exit
Phase: Approaching and crossing the south wall of the Gulf Stream. Typical elapsed time: Race start +36–55 h
TL;DR
- Stay in Stream sail until water temp + wave state confirm you're out (20–30 nm into Sargasso).
- Decision quality is degraded at hour 40+ — Navigator + Skipper own tactical calls.
- WCE routing is a 20–30 min Navigator task — protect their time at the chart table.
- Meander exit (T-ME): if bearing change to Bermuda >15° from pre-planned → exit now.
- WCE check mandatory at exit using pre-loaded SST + altimetry.
- Wake Navigator at south wall confirmation; Skipper if WCE routing change needed.
DATA TO CHECK
At south wall approach: - Water temp: watch for sharp drop (Gulf Stream 79–86°F; Sargasso 75–79°F post-wall) - GPS/log current vector: should be diminishing as you exit the core - Wind: post-Stream wind matching pre-race forecast? - Are you exiting at planned latitude or has Stream set you east/west?
At confirmed exit: - Record: exit latitude, exit UTC time, peak current observed, SST at exit - Compare to pre-race plan: faster/slower/different than planned? - Execute post-Stream routing plan.
POST-STREAM TRANSITION
Check immediately at exit: - Is there a warm-core eddy between current position and Bermuda? (pre-loaded plan) - What is the wind angle for the Sargasso leg — reaching, running, or upwind? - What sail does this demand?
TRIM / SAIL
Post-Stream winds often shift slightly or lighten. Common transitions: - SW reaching in Stream → lighter SE or E fetch to Bermuda - NW running in Stream → NW or W reaching to Bermuda (can be fast) - Post-frontal NW → may stay consistent through to Bermuda
| Conditions | Sail |
|---|---|
| 10–18 kts reaching | Code 67 / A3 |
| 8–14 kts light reaching | Code 67 / A1-1 |
| 18–25 kts reaching | A3 / J3 |
| Upwind to Bermuda | J1 or J3 |
RED FLAGS
- Water temp drops then RISES again: may be entering a warm-core eddy — check GPS/log current immediately
- Post-Stream wind is 30° different from forecast: update routing picture; call Navigator
- Crew severely fatigued after the Stream: simplify sail plan for the next 12 h
DECISION THRESHOLD
Meander exit check (if T-ME was the pre-race strategy): 1. Confirm current position vs pre-planned exit latitude (from T-1 brief) 2. Calculate VMG to Bermuda from current position — is it deteriorating? 3. Bearing to Bermuda has rotated >15° from the pre-planned meander-exit bearing (written on the route card at T-1 — not the rhumb heading, not the entry bearing) → exit now 4. Significantly east of rhumb and Bermuda is now upwind → exit now 5. "Stay in the current a little longer" temptation = how boats lose the final 100 nm
2024 reference: boats that stayed in the meander too long were set east and finished upwind to Bermuda.
Warm Core Eddy check (mandatory at exit): Using pre-loaded SST and altimetry, confirm exit latitude vs any identified WCE. If heading toward the adverse (western or southern) limb: adjust heading now. Every hour in adverse eddy current costs 1–2 nm effective loss. If pre-loaded SST/altimetry is unavailable: infer a WCE from (a) the GPS-vs-log current vector (a clockwise set = WCE), (b) the SST trend on the instruments, and (c) any Bermuda-heading change >10° from plan. If uncertain, route per T-WCE — usually pass west of the suspected eddy's center.