Hello All,

Our report for May 20 follows.  We are poised to begin the second
tracer release tommorow (Saturday).

Cheers,

Dennis



May 20
------

VPR survey continued; expected completion at 0400 May 21.  Rain and fog 
during the day, and 20-30 knt NW wind blows up during the night.  Email
system operational again.

Forecasting Activities:
-----------------------

UNC forecast products were not received, so the central forecast
EN324_FC.28 had to proceed without TDBC forcing, using winds
extracted from NMFS source.

The May 20 central forecast, its two predecessors and associated
sensitivity experiments were evaluated against the available drifter
data set described in the May 19 narrative.  The results for deep
and shallow drifters are presented in tabular form below:


                                         Mean Forecast Error (km)

                                             Surface  Deep
EN324_FC.23  May 17 central [FC.13 rerun]     13.5     3.4
EN324_FC.20  May 18 central [FC.16 rerun]     11.9     4.0
EN324_FC.24  (20) + EL9905 Mass Fields        12.3     3.0
EN324_FC.28  May 20 central                   12.7     4.0

It appears that we have finally hit the point of diminishing returns
with respect to "more data (and commensurately longer runs) are 
better."  The May 17 central forecast
has a lower forecast error than both the May 18 and May 20 central
runs.  This is a welcome result, as the longer simulations (up to 18 
days from cold start to finish) were taking several hours to run.
Also, it is interesting to note the improvment in forecast skill when
the mass fields were updated with the EL9905 bongo data (run 24).  This
is consistent with the results reported by the Edwin Link team.


Operational Products:
---------------------

During the VPR survey, a remnant from the tracer release was found in a
small patch in the pycnocline of one of the survey legs.  When this came
to light, the chief scientist requested a forecast of where that patch
would be the following day so it could be resampled.  At that time, the
central forecast had yet to be run due to delays in the delivery of
emailed forecast inputs.  Instead, the central forecast from May 18 was
rerun as EN324_FC26 with a numerical drifter inserted at the observed
and place.  A time annotated plot of the forecast drifter trajectory
was provided to the chief scientist.  That forecast simulation ended
at 0800 the following morning, approximately one hour after the search
for the patch was to begin.  The same run was extended one day under
the assumption of constant forcing (Figure 0520.1).  Knowing that 
there had been a dramatic change in the weather, the May 20 central 
forecast was launched with the products that were available at
the time; this included NMFS wind stress and heat flux. 
The strong northwest wind caused the simulated drifter to move much
farther southwest, as to be expected with a strong northwest wind
(Figure 0520.2).