A weather-savvy boater always begins their marine forecast with a review of the large-scale features. This strategy is a sound one because the weather we are concerned about – wind, waves, and thunderstorms – are associated with large-scale features such as highs, lows, and frontal boundaries. Continue reading
Category Archives: Marine Weather Forecasting
Decoding Meteorological Time
Introduction
Weather doesn’t recognize geographic or political borders. In a rare example of international cooperation, the majority of countries with a national weather forecasting agency readily share their observations and forecasts. In order to coordinate the timing of observations and forecasts, meteorologists adhere to a standard timekeeping system.
The original standard timekeeping system was Greenwich Mean Time (GMT), a 24-hour clock system based on the local time on the prime meridian in Greenwich, England. Since the local time in Greenwich is the same at GMT, 1:00 am is 0100 GMT, noon is 1200 GMT, and 6:00 pm is 18 GMT. Continue reading
Weather Forecast Model 101 — Forecasting A High Wind Event
Introduction
Several weeks ago, I published a summary of storm-force sustained winds, hurricane-force gusts, and a drop in water level approaching six feet across Lake Erie’s western basin, all courtesy of the passage of a deep low pressure system on November 27, 2019 (click here to read the summary). This article examines how the weather forecast models performed during the event. Continue reading
Weather 101 – Thunderstorm Resources
Seasoned boaters know first-hand that weather conditions on the Great Lakes can change from pleasant to terrifying very quickly. From dangerous lightning to high winds, thunderstorms can ruin an outing in many ways. However, reading the marine forecast before leaving the dock and regularly checking weather radar along the way will dramatically increase your chances of avoiding uncomfortable or dangerous conditions. Continue reading
Hurricane Force Winds on Lake Erie
Introduction
Wednesday, November 27, 2019 was a wild day on Lake Erie thanks to the passage of a deep low pressure system and its accompanying cold front. The surface forecasts issued by the Weather Prediction Center (WPC) suggested the powerful and fast-moving low and its cold front would reach Lake Erie’s western basin around sunrise on the 27th (Figure 1) and the eastern end of Lake Ontario by early evening (click here for forecast graphic). Continue reading
Lake Breeze Enhanced Thunderstorms
Introduction
Even when the atmosphere is supportive of thunderstorms, a source of lift is necessary to provide the upward motion required by a fledgling storm’s updraft. A reliable source of lift is often found near a cold, warm, or stationary front accompanying an approaching low pressure system (figure 1). Terrain or the leading edge of a downdraft from an existing thunderstorm (outflow boundary) can also provide a storm with this all-important ingredient. Continue reading
Clearing Up Clouds
Sailors have been watching clouds since the first boat was launched. As aficionados know, clouds come in an infinite variety of shapes and sizes. The overall shape of a cloud and the altitude where it forms help tell the story of current and short-term weather patterns.
A One-Two Weather Punch: The Sunday Morning Cold Front
Introduction
By any measure, the 2017 Chicago Yacht Club Race to Mackinac was no picnic. The Race started on Saturday under very pleasant southwesterly breezes and the fleet made good progress toward Mackinac Island. However, as the fleet worked north, two weather features delivered a one-two punch that prompted nearly a third of the competitors to withdraw from the Race. (Click here for Matt Gallagher’s thorough analysis of the reasons competitors gave for retiring.)
Tale Of Two Downbursts
Introduction
Lake Michigan sailors have had a challenging summer. In mid-July, competitors in the Chicago-Mac were treated to a rare type of downburst known as heat burst (or dry downburst) near Milwaukee late on Saturday night (click here for the summary). Three weeks later, sailors at the T-10 North American Championship near Chicago had an encounter with a different kind of downburst, one that blasted the fleet with hurricane-force winds. These downbursts, while similar in some ways, are very different in others. The downburst at the T-10 Nationals offers an opportunity to introduce a pair of relatively unknown Doppler weather radar products – storm heights (echo tops) and vertically integrated liquid (VIL) – that can help shed light on the evolution of an approaching thunderstorm.
A Rare Weather Event During The 2017 Chicago-Mac
Introduction
After a challenging 2016 Chicago Mac (click here for a summary), this year’s competitors were likely hoping for an easier trip to the island. But as is often the case, Mother Nature wasn’t inclined to cooperate. Although the race started in pleasant sailing conditions, a rare weather phenomenon known as a heat burst, or dry microburst, caused two separate and frightening incidents late on Saturday night. The one-two punch of Saturday’s heat burst, combined with brisk northerly winds following the passage of a cold front on Sunday, caused nearly 30% of the fleet to retire from the race. Continue reading