Archive for July 22nd, 2008

A bright & sunny day on Google Earth

Tuesday, July 22nd, 2008

RU17 is making rapid progress to the north, running up the eastern edge of the ring in the satellite Sea Surface temperature (image below).  The inertial waves are still visible in the last few days of its track.  Now we will be making the turn to the northeast.  The SST says the ring is open to the north, so we don't have to worry about being swept around.  But just in case, lets start flying northeast.


The below time series shows the effect of the inertial oscillations superimposed on the current to the north.  These inertial currents should start to fade away, just about the time Cristobal comes to bang on the ocean again.

Below are the great google earth series of images showing agreement between all of our data sources and models.  This is truly a great day.  First is another version of the Sea Surface temperature image showing us riding the currents to the north on the eastern side of a ring.

More altimetry must have come in because we see a definite change in the local altimetry Sea Surface Height product.  We are circling a low (blue) and heading north with the currents into a region that will soon start to turn us to the east. To aid the currents in that turn, we have asked RU17 to start flying to the northeast across this region where the current is turning.

Below is the NCOM forecast (yep, NCOM, not NLOM) that shows the ring in exactly the right place with its mouth open to the north, just like the satellite SSt and SSH.  Remarkable agreement.  So today we choose the NCOM model.

Below is the north-south component of the current.  Green is to the north. We are smack in the middle of the strong northward bright green currents.  This is what we need.  A ride to 41 N.

Below are the east,west currents. Red is to the east. Once we get to 41 N, we have a long series of eastward velocity segments running to 33 W.  Thats our target.



Now its Cristobal from the north

Tuesday, July 22nd, 2008

Now its Tropical Storm Cristobal that is heading for RU17.  Its due to arrive late thrusday to early friday. We are again forecast to be on the more severe right hand side of the storm track, but this time the approach is from the north. A great combination punch - Bertha from the south, Cristobal from the north. 

NOAA National Hurricane Center has Tropical Storm Cristobal north of the Gulf Stream, over the cold water, and undergoing the extratropical transition.  Extratropical transition often weakens the winds, but also often increases the area of high winds.  People living in the Middle Atlantic Bight often experience these Extratropical Transitions first hand, the most recent example being Tropical Storm Ernesto, which underwent the transition while over Pennsylvania, Maryland, Delaware and New Jersey. 

In the cloud/SST image below we don't see the nice eye wall structure in Critobal like we did in Bertha, but I really like the clear view of the ocean surface we get in the SST after each storm. The cold eddy RU17 is in right now is clearly visible in this image made possible by the passing of Bertha. 

So if we are looking for the silver lining in this one-two punch, this is about the best thing that can happen to us in terms of using the satellite Sea Surface Temperature for path planning.  Each passing storm wipes the slate clean of the summer surface warming, giving us a good view of the deep ocean structures that define our velocity field.  A couple of weeks after Crisobal we'll be into the intense summer surface heating of August, and we'll be hoping NOAA can send another tropical storm our way.