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).
Figure 1: Surface forecast valid at 7:00 on Wednesday, November 27, 2019.
The risk of high winds was recognized early on Wednesday morning and the Hazardous Weather Outlook (HWO) issued at 4:31 am by the National Weather Service office in Cleveland included a High Wind Warning for the counties along the lakeshore. The HWO also included a Gale Warning (sustained winds from 34 to 47 knots) for all of Lake Erie through 4:00 am on Thursday morning.
The marine forecast for Lake Erie’s western basin predicted exceptionally nautical conditions, including the potential for 18 foot waves:
Wednesday: South winds to 30 knots becoming southwest and increasing to 40 knot gales this afternoon. Showers this morning, then a chance of showers this afternoon. Waves 3 to 6 feet building to 10 to 14 feet. Waves occasionally around 18 feet.
Wednesday Night: Southwest gales to 40 knots becoming northwest and diminishing to 30 knots after midnight. A chance of rain showers through the early overnight. Waves 10 to 14 feet subsiding to 7 to 11 feet. Waves occasionally around 18 feet.
Hurricane Force Gusts
As expected, the winds in the western basin veered from southerly to west-southwesterly with the passage of the cold front. At South Bass Island, the wind veered from 200 degrees to 250 degrees between 10:00 am and 11:00 am (click here for observations). The winds remained westerly through early morning on Thursday before veering to northwesterly. Located 30 miles east of South Bass Island, the cold front passed the Lorain harbor lighthouse at approximately 11:30 am, and in response the wind veered to westerly. The westerly winds at Lorain harbor persisted overnight and veered to northwesterly around 5:00 am on Thursday (click here for observations).
Sustained wind speeds and gusts increased rapidly across Lake Erie’s western basin following passage of the cold front. The sustained winds at South Bass Island reached gale force between 10:00 am and 11:00 am on Wednesday morning and remained above 34 knots until 7:00 am on Thursday morning (Figure 2). During Wednesday afternoon, four gusts exceeded 60 knots – 63.3 knots at 1:53 pm, 62.2 knots at 2:21 pm, 64.4 knots at 3:03 pm, and 61.1 knots at 4:05 pm. These four near hurricane-force blasts were not isolated instances – nearly 20% of the gusts at South Bass Island from noon on Wednesday to 7:00 am on Thursday morning exceeded 50 knots (click here for a graph). The strong gusts were not associated with thunderstorm activity, instead they were the result of the large-scale weather pattern moving across the lower Great Lakes.
Figure 2: Sustained wind speed and gusts at South Bass Island.
Gale force winds reached Lorain harbor at 11:00 am on Wednesday and quickly increased to storm force (48 to 63 knots) at 11:40 am as sustained winds reached 51.9 knots. Consistent with the observations at South Bass Island, the sustained winds at Lorain remained at gale or storm force through 7:00 am on Thursday morning (Figure 3). The highest gust observed at Lorain harbor was 70.2 knots at 2:30 pm on Wednesday. Far from an anomaly, this hurricane-force blast was among thirteen gusts that exceeded 60 knots (click here for a list). A remarkable 45% of the gusts from noon on Wednesday until 7:00 am on Thursday exceeded 50 knots (click here for graph).
Figure 3: Sustained wind speed and gusts at Lorain harbor.
Wave Heights
Unfortunately, the weather buoy in Lake Erie’s western basin (NDBC 45005) was retrieved for the season and the observation stations at South Bass Island and Lorain harbor do not observe wave heights. For these reasons, in situ measurements of the wave heights are not available for this event. However, the computer-derived analysis of wave heights from the Great Lakes Coastal Forecasting System (GLCFS) indicates that at 7:00 pm on Wednesday evening, wave heights were nearly 10 feet in the western basin, approximately 15 feet in the central basin, and a whopping 17 feet near Buffalo (Figure 4).
Figure 4: GLCFS wave height analysis at 7:00 pm on Wednesday, November 27, 2019.
Strong Winds Modify Lake Levels
The Hazardous Weather Outlook on Wednesday morning also included a Low Water Advisory for Lake Erie’s western basin from early Wednesday morning through Thursday morning. When strong winds persist for several hours, the force of the wind pushes the water from the windward side of Lake Erie toward the leeward shore. The lowering of water levels near the windward shore and resulting increase in water levels along the leeward shore is known as a displacement in the Great Lakes region.
The most significant displacements on the Great Lakes occur when strong winds are aligned with the long axis of the lake. In the case of Lake Erie, strong southwesterly or northeasterly winds produce the highest displacements. It is not uncommon for the water level across the Lake to vary by several feet during such an event – such was the case on November 27, 2019.
At 12:00 am on Wednesday morning (prior to the high winds), the Lake Erie water level measured 573.51 feet at Toledo, Ohio and 572.63 feet at Buffalo. As the westerly winds increased across the western basin, the force of the wind steadily pushed the water toward the east end of Lake Erie. The water level at Toledo reached a minimum of 567.62 feet at 8:42 pm on Wednesday – a drop of 5.71 feet in just 21 hours! Approximately an hour earlier at 7:54 pm, a maximum height of 578.79 feet was reach at Buffalo – a storm-related increase of 5.64 feet (Figure 5). The decrease in water level extended well east of Toledo, as evidenced by the 2.09 foot drop at Cleveland.
Figure 5: Lake Erie displacement on November 27, 2019.
Seiche
As the speed of the wind dropped, its ability to maintain the unnatural distribution of water faltered and the steady force of gravity stepped in to restore order. However, gravity doesn’t immediately return the level of the lake to equilibrium. Instead, the lake sloshes back and forth – a seiche – while gravity slowly dampens the oscillations. The graph of water levels at Toledo and Buffalo shows the oscillations in water level – alternating between rising and falling — that occurred during the two days following the high wind event.
Figure 6: Lake Erie seiche on November 28 to November 30, 2019.
Water Level Hazards
Low water levels present obvious hazards to boaters, particularly in areas such as Lake Erie’s western basin where the Lake is relatively shallow. Channels may become unnavigable and dangerous areas such as reefs become even challenging as the water level drops. When conditions are favorable for the development of a displacement/seiche, prudent mariners check the Water Level Displacement forecast from the Great Lakes Coastal Forecasting System (click here for GLCFS forecast products).