Wednesday, April 10, 2019

Crewing to Annapolis: Wild Weather

We departed Sarasota at 10:30 AM on Monday morning with bright sunny skies and a slight north wind and preceded south on the ICW to Venice where we turned west out into the Gulf.

Once on the Gulf, we plugged in the Gulf Stream route to Miami and headed south toward Marathon and the Seven Mile Bridge. The weather forecast called for light northerly winds and seas of 2 to 3 feet with good conditions all the way to Miami, which we would reach early on Tuesday morning.

Brilliant sunset on Day 2 off the Florida Keys
Hard to believe but bad weather is ahead
However, after Miami, NOAA was forecasting northeasterly winds of 20 to 25 knots with gusts to 40 from mid-morning Wednesday all the way to Friday mid-day. Seas were predicted to run 10 to 17 feet during this period. The photo below shows us just south and east of Marathon. We had favorable conditions to Miami. Then conditions worsen dramatically.

What's going on? The answer is shown in the photos below. We had massive high pressure over the eastern seaboard running from northern Maine south and west to all the way to Alabama. Off the east coast, on essentially a parallel track, we had a massive low pressure area running from north of the Bahamas out into the Atlantic in a northeasterly direction.

A picture is worth a thousand words
Winds circulate clockwise around high pressure and counterclockwise around a low. In this case, the powerful high and low were creating a Venturi effect as described in Bernoulli's principle.

EXPLANATORY NOTE: Bernoulli's principle states that a region of fast flowing fluid (which includes air) exerts lower pressure on its surroundings than a region of slow flowing fluid. The principle applies to the motion of air over an airplane wing, to air flow through a carburetor, to a flag flapping in the breeze, and to the low pressure systems in hurricanes.

The result is shown in the photos above. The pressure constriction caused by the powerful pressure areas accelerated wind speeds between the high and low.

The text weather predictions for the area north of Miami to Fort Pierce showed that the winds would accelerate as noon approached on Wednesday. Hence, we decided to shoot for Fort Pierce and ride out the approaching wind storm at a marina. This proved to be a wise decision.

Approaching Fort Pierce as viewed on are navigation screens
Screens - Left: Chartplotter, Center: Night Vision, Right:Raday
We pulled into the Fort Pierce City Marina at 10;25 and within one hour the winds started to accelerate reaching 25 knots at the dock.  This continued for the next 36 hours at which point the winds began to slowly (i.e., very slowly) diminish.

By Friday morning the winds at the marina had diminished to around 10 knots from the north. Based on the forecast, we decided to run north on the ICW to Cape Canaveral and then at Canaveral turn hard right into the Canaveral Barge Canal which will take us via a lock to the Atlantic Ocean.

Winds were forecasted to be 10 knots out of the northeast with seas of 5 to 6 feet. This should produce favorable conditions for Guided Discovery as we run north around the cape. Conditions are predicted to slowly improve as we move north.

Bottom line. Taking a break for two days enabled us to avoid the high winds and heavy seas.

Written by Les.

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