Weather for Safety at Sea Stu Friedman
Follow Along Today… at www.colyc.org/weather Or email: Stufriedman1@gmail.com Always monitor and heed official warnings by the US Weather Service, Environment Canada and other governmental meteorological services
Topics for Today • Terminology and Dynamics • Sources of Information • Your Weather Strategy Safety at Sea Weather Presentation
Terminology and Dynamics
What Causes Wind - Pressure Gradients Safety at Sea Weather Presentation
Fronts Cold Front Warm Front • Cold air approaching • Cold air retreating • Wind shift to W/NW and • Wind shift to SW eventually N/NE • Often cloudy, wet • Source of lift, can lead to severe storms Occluded Front • Cold front caught up Stationary Front to warm front • Neither air mass moving • Signals beginning of • Light wind end of the Low • Fog? Stratus precipitation? • Heavy precipitation Safety at Sea Weather Presentation
Wind Around Fronts Safety at Sea Weather Presentation
Buys Ballot’s Law If a person stands with their back to the wind, the air pressure to the left is lower than the pressure to the right. Stu’s amendment – The center of low pressure is over your left shoulder. Safety at Sea Weather Presentation
2018 Mac – Day 1 2018 Mac – Friday Safety at Sea Weather Presentation
2018 Mac – Day 2 2018 Mac - Saturday Safety at Sea Weather Presentation
2018 Mac - Sunday 2018 Mac – Day 3 Safety at Sea Weather Presentation
Wind Measurement “Peak” = “Speed” = “Gust” = Maximum Average Instantaneous instantaneous over past 2 wind >10 kts over wind during the minutes wind speed. entire period (hr). must be >25kts Safety at Sea Weather Presentation
The Beaufort Scale Force Speed Specification (mph) (knots) Description (sea) (land) Sea like a mirror Smoke rises vertically Calm 0 0-1 0-1 Ripples, no crests Smoke drift, but wind vanes do not Light Air 1 1-3 1-3 move Small, short wavelets, Crests do not break, have Leaves rustle, felt on face, vanes Light Breeze 2 4-7 4-6 glassy appearance move Gentle Breeze Large wavelets, crests begin to break. Leaves and small twigs in constant 3 8-12 7-10 motion. Moderate Breeze Small waves, becoming larger. Frequent white Dust and loose paper moved, small 4 13-18 11-16 caps. branches moved. Fresh Breeze Moderate waves, many whitecaps. Small trees in leaf begin to sway. 5 19-24 17-21 Strong Breeze Large waves begin to form, extensive white foam Large branches in motion. Difficulty 6 25-31 22-27 crests. using umbrellas. Sea heaps up and white foam from breaking Whole trees in motion. Near Gale 7 32-38 28-33 waves blown in streaks. Inconvenience felt while walking. Gale Moderately high waves of greater length. Twigs broken off trees. 8 39-46 34-40 47-54 41-47 Severe Gale High waves. Crests of waves begin to topple, Slight structural damage may occur. 9 tumble, roll over. Spray may affect visibility. Roofing tiles blown off. Ground littered with many small twigs/broken branches. Very high waves with long overhanging crests. Small live trees uprooted, structural 55-63 48-55 Storm 10 Sea surface takes on white appearance. and vegetative damage. Exceptionally high waves. Small and medium Large live trees uprooted. Violent Storm 11 64-72 56-63 sized ships might be for a time lost to view Widespread structural damage. behind waves. Hurricane Air filled with foam and spray. Sea completely Severe and extensive damage. 12 72-83 64-71 white with driving spray. Windows broken. Roofs peeled off. Mobile homes overturned. Safety at Sea Weather Presentation
Representing Wind on a Map Safety at Sea Weather Presentation
Last Week’s 200+ Knot Jet Stream Safety at Sea Weather Presentation
ORD Winds During Summer Safety at Sea Weather Presentation
CGX Winds During Summer Safety at Sea Weather Presentation
Measuring Waves Max aximum Wav ave Height A wave twice the height of f a sig ignificant wave is is lik likely to occur 3 tim imes in in 24 hours (1 (1 in in every 3,0 ,000) Sig ignificant Wave Height average of f la largest 1/3 /3 of f all ll waves Safety at Sea Weather Presentation
3 Requirements for Convection Element Impact How to Anticipate Moisture Enables cloud formation. Warm and humid surface Surface dry air has more conditions. difficulty rising and forming clouds. Surface Causes air parcels to rise Everything from fronts, Lifting and possibly condense geography, outflow from storms, into clouds. etc. Instability Cold air aloft makes CAPE – Convective Available rising parcels more Potential Energy. buoyant and cloud tops higher. Safety at Sea Weather Presentation
Severity of Convection Safety at Sea Weather Presentation
Single Cell (Pulse) Storms • Most common during summer • Sometimes seem “random” or “pop up” – not part of organized front or system • Typically last 30-60 mins • Minimal severe threat, except in “pulse storms” when instability is very high but shear is low. • KEY: Hard to track on radar! Safety at Sea Weather Presentation
Supercells • Can last for many hours • Threats include: - tornadoes - large hail - damaging winds • Often manifest a mesocyclone hook echo. • KEY: Not hard to track; produce gust front in advance Safety at Sea Weather Presentation
Squall Lines • Long line of thunderstorms • Can be broken or unbroken • “Bowing” of line often indicates strongest part of squall line - damaging straight-line winds • Gust front leading the line of storms on radar • Greatest danger for solid line is straight-line wind • Greatest danger for broken line is tornados Safety at Sea Weather Presentation
Downdrafts and Macro/Microbursts • Macro and microbursts caused by severe downdrafts associated with deep, moist, convection. • Microburst < 4km area; macroburst 4km – 10km • Not visible on standard doppler – need storm- relative velocity radar (RadarScope app). • Cause wind in excess of 60 knots. • Best predictor – “DCAPE” Safety at Sea Weather Presentation
Sources of Information
My Daily Forecasting Approach • Check current conditions • Check Skilling or your favorite forecaster – see general direction of things. • Check NOAA 48 hour marine forecast and/or 5 day offshore forecast. • Read NOAA Area Forecast Discussion. • Check hazards. • Assess underlying big picture data Safety at Sea Weather Presentation
Current Local Observations NWS Great Lakes Portal GLERL - Hazards, waves, winds, - Buoy observations weather - Special research products (e.g., Straits of Mackinac currents) Safety at Sea Weather Presentation
Local TV / Radio • Choose wisely • Focus on big picture trends – major changes in weather, fronts, convection. • Don’t believe the tombstones - considerably decreased confidence after each day forward. • POP – chance that any point in the forecast area will receive at least .01 inches of liquid precipitation. - Doesn’t indicate amount - Doesn’t necessarily indicate likelihood your location will receive precipation. Safety at Sea Weather Presentation
NOAA Marine Forecasts • Deliberately go out only 48 hours. • Offshore forecasts go out 5 days. • Fairly accurate. Reflect local factors such as sea breezes. • Do not reflect possibility or effect of convection, outflows, downbursts. Safety at Sea Weather Presentation
NOAA Area Forecast Discussion • Google it! • Updated several times daily. More often during unsettled weather periods. • Indicates confidence level – models in agreement? • Indicates favored/unfavored locations. • Lots of jargon and shorthand but still valuable to beginner. Safety at Sea Weather Presentation
Local Hazards NWS Hazardous Weather NWS Storm Prediction Outlook Center Safety at Sea Weather Presentation
Paid Weather Sources • Watch Rule 41 • Typically provide models and GRIBs • General, non-sailing specific: Accuweather Premium, Weatherbell • Repackagers of others’ models or obs ervations- SquidSailing, Windguru, others - Key is price and personal preference for interface • Run their own models - Predictwind, Sailflow, others - Core model data is based on government models – adjusted/extrapolated/interpolated. Safety at Sea Weather Presentation
Weather routers • Pre-race/Pre-passage strategy and routing • Customized for your boat, your weather conditions • However…..no help after the start - Rule 41 • Chris Bedford / Susan Gennett / Commanders Weather Safety at Sea Weather Presentation
NOAA Weather Radio • Great source of forecasts and hazards. • Available everywhere on the Lake • Know your zones • Know your channels • Know how to operate your radio Safety at Sea Weather Presentation
Using Your Cell Phone • Cellular coverage varies widely throughout the lakes - signal boosters available. • Most apps use HRRR data. Choose based on personal preference. • Weatherscope – most detailed data. Safety at Sea Weather Presentation
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