Tina at the Wheel
I just returned from a great visit to the Naval Research Lab at Stennis Space Center in Mississippi. i flew down Sunday and returned very early thursday morning. So Tina has been at the wheel. Balancing the educational aspects of letting the students fly and the judgement of an experienced pilot is often difficult, but Tina did great. She has been easing Scarlet down and around the bottom of the "U" shaped trough and is now bringing us up the eastern side. It was pretty scary heading down into this, since the currents kept going south as the trough deepended and deepened. We kept wondering if we had been pulled through the bottom and were heading south into very difficult territory - warm temps and westerly currents - a bad combination for a glider trying to stay clean and head east. But this morning we found that all was fine, and that the currents had turned to the east. With that, Tina turned the glider at noon and set it on a new path to the east. The objective is to keep crossing east into the streamlines that had north and east rather than continuing to circle th low (dark blue just to our northwest). With the students, they also mapped out two routes to Faial, a northern route shown in red and a southern route shown in yellow. The students noticed that the northern route was becoming more and more viable as the clockwise eddy it circles gets more and more round. The southern route has persisted for many days, and is pretty much found in both the altimeter-derived geostrophic currents (black arrows) or the Naval Research Lab's HYCOM forecast model (white arrows).
We are not sure which route we'll take, but its nice to have options. You don't always get to choose the option with a glider, so you sometimes have to just live with whatever the ocean gives you. In this case, it looks like we have two good options. The big uncertainty remains near 40-42 N, 33W, where the different products have a different location for the clockwise rotating eddy. This difference was inspiration for the Great Eddy Hunt NRL just conducted to help us out. It is a typical operational scenario - the Navy has a glider in one location, they want to send it to another location, but there is an eddy in the way. Is there a way you can tell if the eddy is real from the data? The prize was an R.U.COOL baseball cap - I always carry spares. I think I owe them a whole box. I'll write up the story over the weekend.