Baja Bash Weather Window Forecast
The Baja Bash has one master: the North Pacific High. When it builds strong and far enough north, you motor 800 miles up the Pacific coast of Baja California in glassy conditions. When it falters, you're beating into 25-knot headwinds and square seas from Cabo San Lucas to San Diego.
Experienced Bash sailors spend hours poring over GFS runs, pressure charts, and ensemble models to answer one question. We answer it with a single number.
What is the North Pacific High Window Score?
The PHWS measures the quality of North Pacific High positioning for northbound flow — nothing more, nothing less. A high score means the synoptic setup is favorable. It does not mean flat water.
From 21 years of ERA5 data (2005–2025): even at a perfect score of 100, only ~11% of Baja Bash days are all-green at every station. The route is structurally hard. The score tells you when the atmosphere is on your side — the Sea State Modifier tells you whether the ocean has caught up.
NPH Index — Synoptic Setup
| Score | Tier | What it means | Historical all-green rate |
|---|
| 80–100 | NPH Open | Pacific High fully positioned. Departure gate is the remaining check. | ~11% |
| 65–79 | NPH Transitional | Pacific High improving — window often opens within 24 h. | ~9% |
| 50–64 | NPH Building | Pacific High not ready. Headwinds likely at compression zones. | ~7% |
| 0–49 | NPH Adverse | Strong gradient or high banked against coast. Hard conditions. | ~3% |
Two-Axis Verdict
The verdict is built from two independent axes that are allowed to disagree. Captains often depart in tactically clean but strategically imperfect windows on shorter Baja hops, and the system shows both signals so you can do the synthesis yourself.
Axis 1 — Tactical Verdict (GO / NO GO / WAIT). Driven purely by segment-level gates: can the boat physically make this passage right now?
- NO GO — Departure gate fails on BOTH the Cabo → Punta Tosca cape stretch AND the Punta Tosca → Mag Bay post-cape leg. NW wind > 15 kt sustained, peak NW too high, steep seas (> 6 ft @ < 8 s), or BI > 1.8 on the post-cape leg are hard stops. A bad cape alone with a clean post-cape leg is NOT a NO GO — boaters will endure the funnel for a good window past Tosca.
- WAIT — Departure is safe but a downstream segment fails the route gate (BI > 1.8 or sustained NW > 22 kt). Leaving means walking into a known problem.
- GO — Departure and all route segments pass. The reason text adapts to the synoptic axis (e.g. "Segments clean — pattern marginal" when the synoptic context is mid-tier). When the NPH score is in the marginal "Building" tier (50–64), the GO badge is striped green/amber — a "short hops only" caution — without changing the verdict.
Axis 2 — Pattern Confidence. A separate chip rendered alongside the verdict, derived from the NPH Index + 48h trend. Answers: how favorable / stable is the larger pattern?
- Stable — gradient_score ≥ 80, neutral trend. Synoptic setup fully favorable.
- Improving — trend Window Opening. Pattern weakening in the user's favor.
- Marginal — gradient_score 65–79, neutral trend. Transitional — segments may be sailable but synoptic confidence is moderate.
- Unstable — gradient_score < 65, neutral trend. Pacific High building — pattern hostile to bash.
- Deteriorating — trend Window Closing. Pattern strengthening against you.
Closing-window flag. When today is GO but tomorrow's departure gate fails, a yellow ⚠ closing window chip fires alongside the verdict — that's the "go now" signal that experienced cruisers read on their own.
Bash Index (BI) per segment
Wind and swell are scored from the dawn window (5–9 am local) — actual departure time. BI = 0.35·wind + 0.27·swell + 0.25·chop + 0.13·period + heading/steep/gust penalties. If afternoon NW wind is forecast ≥ 8 kt above dawn levels, a "Depart early" warning fires.
| BI | Rating |
|---|
| ≤ 1.3 | Manageable |
| 1.3–1.8 | Difficult |
| > 1.8 | Dangerous — triggers NO GO or Problem Ahead |
Window Map — Segment Status
The window map shows each route segment (rows) across the 7-day forecast (columns). Each cell reflects conditions at the dawn window (5–9 am local) — actual departure time for that leg.
| Status | What it means |
|---|
| OPTIMAL | BI ≤0.7 and wind ≤10kt. Light air, low swell — ideal motoring conditions. |
| OPEN | BI ≤1.3. Manageable bash — uncomfortable but passable for a prepared crew. |
| TIGHT | BI 1.3–1.8. Difficult — significant headwind or swell. Staging stop worth considering. |
| SHUT | BI >1.8, NW wind >18kt at departure, or steep seas >6ft/@<8s. Hard stop for that leg. |
The You Are Here selector highlights your current position. Rows above your position are dimmed (already sailed). The best departure date shown is the earliest day where all remaining legs are OPEN or better.
Window Map — interactive elements
- Route projection (weather-gated). A blue outline + ✈ glyph traces where your boat would be if it departs each leg only on a green (OPTIMAL/OPEN) day, holding through marginal (TIGHT) or closed (SHUT) days until a window opens. Transit still uses real segment distances and your saved boat speed (or 6 kt for guests), so long legs consume extra days (a 5 kt boat skips a day on the long Mag Bay → Turtle Bay leg). A faint grey ✈ on the "you are here" row marks days spent waiting for the first green window.
- Click any cell to open a detail modal with the gate-by-gate breakdown for that segment-day: sustained vs peak wind (with cape amplifier shown for the departure cell), period vs minimum, steep-seas check, and Bash Index against the Manageable / Difficult / Dangerous boundaries. The modal includes a "Show this segment in detail table" button that scrolls to and highlights the matching row in the Route Segment Sea State table at the bottom.
- Hover any cell for a tooltip explaining its status from the underlying numbers.
- Live-nowcast badges on today's column compare the current model analysis to the dawn forecast: ✓ live match, ≈ live drift (3–7 kt or 0.5–1.5 ft off), ≠ live divergent. Tooltip is explicit: this is a model nowcast that aggregates obs into the analysis where available — not a raw buoy reading. Use as a freshness check, not as ground truth.
- Dawn → afternoon line on today's departure cell when the wind ramp is ≥ 4 kt — surfaces the pattern for non-dawn departures.
Decision Output
GO / NO GO / WAIT on the tactical axis, with a colored Pattern chip on the synoptic axis. "CAUTION" is intentionally absent — it caused indecision; the two axes carry the nuance instead. NO GO is departure-truth: if the boat can't safely leave right now, nothing else matters.
Why all-green days are rare by design
Even with perfect gradient score, the compression zones at Punta Eugenia / Cedros and Cabo San Lázaro almost always produce elevated BIs due to cape geometry and swell exposure. An all-green Baja Bash is a genuine weather gift — not a reasonable expectation.
Updated every 6 hours. Forecast numbers come from ECMWF IFS 0.25° — the authoritative model for this tool. Seven days of forecast.
Built for the cruiser sitting in a marina in La Paz, Cabo San Lucas, or Puerto Vallarta asking the question every northbound sailor asks: Is this the week?
