Saturday, November 7, 2015

Snowbird Fall Migration: Transiting Cape Hatteras at Night

Cape Hatteras is a challenge for small pleasure boats, which is why most opt for the ICW between Norfolk and Morehead City.  That said, based on the number of wrecks, it also a challenge for ships.  

Hatteras presents several unique challenges. The Gulf Stream’s 2 to 3 knot warm water current turns northeast here and converges with the weaker cold water Labradore Current. Because of these currents, the Cape often sets up its own weather patterns and conditions can change rapidly (which we experienced last November).  It can also set up standing waves when winds and currents are in opposition.  Add the need to head 12 miles out to sea to round Hatteras’ uncrossable Diamond Shoal, and the fact the east bound weather fronts often converge here and you have a formula for rough unpredictable water.

I watch the weather at Hatteras almost every day trying to understand the factors that contribute to the consistently rough seas. My watch intensifies as the cruise south approaches. Hence, my decision, days earlier, that we had a weather window for the trip reflected my analysis of the predicted weather at the Cape.

This was still true on Saturday as shown in the photos below.  A weak high pressure system dominates the east coast and Siruis’ sea condition screen reflects calm seas on the east coast.

Late Monday, as we approached Hatteras, the forecast for Monday evening called for west winds of 10 to 15 knots with 3 to 5 foots seas and a period of 6 seconds.  NOAA's Tuesday prediction called for the winds to swing north and increase to 15 to 20 with 4 to 6 foot seas with a chance of showers in the morning. 

Actually, as early as Monday morning the winds had already swung northeast and continued to build as we proceeded south toward the cape. Northeast winds are favorable as they produce a push and a following sea (more push).  46 miles north of the Cape Hatteras Light at 10:00 PM we had 20 knot east northeast winds gusting to 25.  Seas, which we estimated at 3 to 4 feet, were off the port beam.  The boat was riding smoothly.  That said, this is Hatteras and conditions can get bad real fast. As a precaution, we followed our Standard Operating Procedure for preparing the boat for rough seas.  They never came.

At 2:00 AM on Tuesday we rounded the end of Diamond Shoal with northeast winds and a 3 to 4 foot following sea and continued on to Cape Lookout with essentially unchanged conditions.  In the 24 period starting at around 11:00 AM on Monday, we had rounded the dreaded Cape Hatteras and her somewhat nasty step sister, Cape Lookout, without difficulty. 

We also picked up speed and therefore time on the Cape Charles (Virginia Beach) to Morehead segment due to the following sea. At Block Island on Saturday night, we were averaging 8.6 knots. Then came the offshore crossing between the Hamptons and Cape May (NJ) where we dropped to 8.1 kts due to head winds and heavy seas.  Then Cape Hatteras segment got us up to 8.3 kts and within .1 knts of the boat's optimum cruising speed of 8.4.

At 12:30 PM on Tuesday we pulled into Morehead Yacht Basin.  Refueling was completed in 1 hour and 45 minutes by one very efficient crew.  We took on 849.1 gallons of diesel and by 2:15 PM we were on the water for the Morehead to Stuart Florida leg. Did I mention that we paid $2.26 for fuel?  That is the lowest price I’ve paid for diesel in years.  Below are statistics:

Hingham to Morehead City Data
> Engine Hours: 79 hours
> Time Enroute: 4 days and 3 nights
> Average Speed: 8.3 kts
> Diesel Fuel: 849.1 gallons
> Cost per gallon: $2.26

 Written by Les.









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