Marine Forecasts

Marine Products Special Marine Warning BULLETIN - IMMEDIATE BROADCAST REQUESTED SPECIAL MARINE WARNING NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 155 PM EDT FRI OCT THE NATIONAL WEATHER SERVICE IN DETROIT/PONTIAC HAS ISSUED A * SPECIAL MARINE WARNING FOR... LAKE ST CLAIR * UNTIL 430 PM EDT * AT 153 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A LINE OF STRONG THUNDERSTORMS FROM 12 MILES WEST OF NEW BALTIMORE TO 7 MILES WEST OF DOWNTOWN DETROIT…MOVING EAST AT 30 MPH. * THE THUNDERSTORMS WILL BE NEAR... MOUNT CLEMENS AT 223 PM EDT GROSSE POINTE PARK AT 231 PM EDT HARSENS ISLAND AT 245 PM EDT THESE STORMS WILL PRODUCE WIND GUSTS OVER 35 KNOTS...BRIEFLY HIGHER WAVES...HEAVY RAIN...SMALL HAIL...AND DANGEROUS LIGHTNING STRIKES.

Marine Weather Observations and Forecasts

How we obtain observations of current conditions. How we develop forecasts of future conditions.

Observational Tools Remote Measurement

Observational Tools Direct Measurements We obtain observations of current conditions on and near the lakes from several sources – Buoys These are usually positioned near mid-lake – Ship reports From the main shipping lanes, also usually near mid-lake – Coast Guard stations On land, along the shoreline – Land observing stations that are near the water On land, along or near the shoreline

NOAA Marine Observations Infrastructure National Data Buoy Center

Forecasting Tools The role of observations Observing tools allow us to measure the air and better understand what is happening now and why. Build a picture of the atmosphere in its current state.

Forecasting Tools Computer Simulations A computer simulation of the atmosphere is started on the current picture obtained from observations. –applies rules of atmospheric physics to the picture of the current atmosphere… –to produce a series of new pictures showing future conditions of the atmosphere…

Marine Meteorology Weather elements that most impact marine conditions. –Wind speed and direction –Air temperature –Water temperature –Precipitation systems

Marine Meteorology Wind

Marine Meteorology Waves Waves on the Great Lakes are primarily wind driven. Three factors determine wave height... Wind speed –Primary factor –Greater wind speed >> larger waves, but with an upper limit. Wind duration –For a given wind speed, waves grow larger as duration increases. Wind direction/distance (fetch) –Distance wind travels over water. Waves increase with larger fetch over the water.

Marine Meteorology Wind-Stability Often the most important element in determining wind speed and wave height... –Temperature Water > Air atmosphere will be unstable. –In turn, this will create mixing between vertical layers of atmosphere. –Higher winds aloft are brought to the water surface quickly. –Air interacts more efficiently with water surface.

Marine Meteorology Wind-Stability

Great Lakes Marine Weather Services Forecasts of High Impact Events  Storm Watch (24-72hrs) / Warning (<24 hours)  Gale Watch (24-72hrs) / Warning (<24 hours)  Hurricane Force Wind Watch/Warning  Small Craft Advisories (of all kinds)  Brisk Wind Advisory (for ice covered nearshore areas)  Low Water Advisory  Heavy Freezing Spray Watch/Warning  Freezing Spray Advisory  Dense Fog Advisory  Special Marine Warnings – high winds (34 knots+) and waves from thunderstorms, waterspouts, seiche.  Coastal Flood Warning  Rip Current Threats

Marine Hazards Definitions SMALL CRAFT ADVISORY: Issued only for the near shore waters and Lake St. Clair when sustained wind speeds within the range of knots or wave heights of 3-5 feet. GALE WARNING: A warning of sustained surface winds, or frequent gusts, in the range of knots. STORM WARNING: A warning of sustained surface winds, or frequent gusts, in the range of knots. SPECIAL MARINE WARNING: Issued for a brief/sudden occurrence of sustained wind or frequent gusts > 34 knots and/or waterspouts, usually associated with thunderstorms. MARINE WEATHER STATEMENT: Issued to provide details on significant or potentially hazardous conditions, including updates to Special Marine Warnings.

NOAA Weather Radio All Hazards NOAA Weather Radio –7 transmitters serving southeast Michigan marine areas. Available 24/7 Public and Marine Forecasts Interrupt Broadcast with the issuance of watches and warnings

NWS Detroit/Pontiac Other Things We Do Upper Air Balloon –Launched twice daily (6AM/PM EST, 7AM/PM EDT Internet – Public Service Telephone –(248) , 8 AM to 4 PM, business days

NWS Detroit/Pontiac Forecast and Warning Responsibility for Land Areas Public Forecast and Severe Weather Warning Responsibility for: –17 Counties in Southeast Michigan Aviation Forecast Responsibility for: –Detroit Metro Airport –Detroit City Airport –Oakland County International (Pontiac) –Flint Bishop Airport –Tri Cities Airport (Saginaw)

Forecasting Tools Computer Simulations However, since these simulations are designed to cover the whole USA......they tend to have difficulty resolving small scale, local weather features......many of which are important to marine interests! –Lake and land breezes –Effects of land and water topography on wind patterns –Associated impacts on wave patterns.

Forecasting Tools Computer Simulations To help forecast these small, local, features... …NWS Detroit/Pontiac runs a simulation… –covers a much smaller area, and has the computing power to resolve important weather details. –This local model uses wind conditions tuned by a meteorologist to produce more accurate wave forecasts for the lakes.

Forecasting Tools Computer Simulations  A NWS supercomputer center near Washington DC runs a series of simulations: –They cover North America and extend from 1 hour to 14 days. –They form the basis of weather forecasting in the United States. –NWS Meteorologists evaluate and use the output to create forecasts for home area (recall the service area map).