Test dive with waypoint straight west

RU29 is 125 nautical miles directly south of Galle, Sri Lanka.  We objective is to continue moving Ru29 north towards Galle but to stay offshore of the 40 nautical mile wide (magenta line) shipping lanes.  We have about 85 nautical miles (about 150 km) to go until we reach the southern side of the shipping lanes.

Ru29 has flown 50 km north in about 4 days.  If we can keep up this speed, we can cover the next 150 km in 12 days, and be at the edge of the shipping lanes ready for pick up.  So give us two weeks.

Today is Saturday, Oct 13.  Two weeks from now is Saturday, Oct 27. So we would like to recover soon after Oct 27.

This plan depends on no major changes in the currents between our present location and our target location 150 km north.  The last blog entry indicates that the models do not agree.

To determine which model is more likely to be correct, we did a test dive with the waypoint straight to the west. The compass heading rose shows the result. The red arrow shows the commanded heading.  The light blue bars is a histogram in 30 degree increments of the direction RU29 actually flew. The dark blue arrow is the average heading, indicating we flew 120 degrees to the right of the waypoint, or towards 30 degrees east of north.

Here we zoom in to the location of RU29 and overlay the Copernicus currents.  The glider moved to the northeast, and Copernicus says the currents by the glider are very low.

Now we remove the Copernicus currents and overlay the Hycom currents.  HYCOM says the currents are strong and to the west.  But the glider flew northeast.

Looks like the Copernicus model is giving us a better result more consistent with the observed glider behavior.   Zooming even closer in on copernicus, there is an eddy just to the south of the shipping lanes.  The distance from RU29 to the center of the eddy is about 140 km, so again, less than 2 weeks away.  If we park there, the distance from Galle to Ru29 will be 66 nautical miles.

Hope is to bring RU29 a bit farther north than that, and sit at the outer edge of the shipping lanes, only 40 nautical miles from Galle.

Last 5 posts by Scott Glenn

• Early Season in the Mid Atlantic - June 17th, 2021
• Disturbance in the Gulf - June 16th, 2021
• Hurricane Gliders 2021 - May 3rd, 2021
• Hurricane Iota - November 16th, 2020
• Hurricane Eta - Low Wind Shear, High SST - November 2nd, 2020