Data & Method
Every number, sourcedThe crossing score
Each hour of the next seven days gets a color. Wind sets it: 8 knots and under reads go, 9–13 reads caution, 14 and up reads rough. The crossing takes the worse of your two selected ends each hour, because a passage is only as calm as its roughest stretch. Swell then works as a knockdown only: a steep set (4 ft at 8 seconds or less) or a big one (6 ft at any period) drops the hour one level, marked with a tick. Small, long-period swell is left alone — it rolls gently under a hull. A sizable swell out of the south (135–225°) also knocks down hours at the south-facing backside spots, because hurricane-season souths make those shores sketchy. Any two spots pair as a run — mainland to island, island to island, or harbor to harbor along the coast. Backside spots are routed around the nearer end of their island, and the longest open-water leg carries the swell reading.
Two watch flags read the synoptic picture: a south swell watch when directional swell shows hurricane-season energy from Mexico, and a Santa Ana watch when sustained NE wind appears in the next 48 hours — upgraded to a cold Santa Ana warning when the freezing level sits low during the event, because cold events blow hardest.
Live data sources
Forecast wind & freezing level
Open-Meteo weather forecast API, sampled at both ends of your selected run, hourly, 7 days, refreshed about every 30 minutes. Wind at 10 m in knots; freezing level height feeds the cold–Santa Ana check; hourly visibility (worst of the two ends) drives the fog hatch and marine-layer watch.
Forecast waves & directional swell
Open-Meteo marine API, sampled at the midpoint of the exposed leg of your run: significant wave height and period, plus swell height, period, and direction for the south-swell logic.
Observed conditions
NOAA National Data Buoy Center — the latest real observation from the channel’s buoy (San Pedro 46222 for the Catalina chart, East Santa Barbara Channel 46053 for Chart 002), shown under the chart so you can compare forecast against what the water is actually doing, including water temperature.
Tides
NOAA CO-OPS tide predictions — the next ~36 hours of highs and lows for the channel’s reference station (Los Angeles Harbor / Santa Barbara), in feet above MLLW.
Marine warnings
National Weather Service active alerts for the channel’s coastal-waters zone (PZZ655 for the Catalina chart, PZZ645 for the Santa Barbara Channel). A Small Craft Advisory or Gale Warning shows as a banner above the chart — the NWS is the authority; this site is a planning aid.
The chart itself
The basemap is NOAA’s live Chart Display Service — the real electronic navigational charts (ENC) rendered in traditional paper-chart symbology, with actual soundings, buoys, shipping lanes, and restricted areas, warmed to sit with the site’s 1960s C&GS palette (see About the Charts). Our route, spots, wind, and pen reading are drawn as a layer on top. This page is a planning aid, not an ECDIS — navigate with official NOAA charts and current Notices to Mariners.
Live vessels (AIS layer)
When the AIS chip is on, vessel positions come from aisstream.io — crowd-received AIS broadcasts, refreshed about every 45 seconds. Coverage depends on volunteer shore receivers and boats actually transmitting; positions can be minutes old. Never use this layer for collision avoidance — that’s what radar, eyes, and your own AIS are for.
Sunrise & sunset
Computed on the page from standard NOAA solar equations for the midpoint of your run — the daylight band on the ship’s log follows the actual day. Moon phase and illumination are computed the same way — the “Tonight” strip says whether you’ll have moonlight on the water before first light.
Honest limits
Forecasts are reliable roughly 7–10 days out; past that, lean on the seasonal pattern. The hourly engine samples a handful of points — it cannot see every wind line or lee. Conditions are a planning aid, not a safety guarantee: check the current NOAA marine forecast, file a float plan, and use your own judgment before any crossing.