Basis of Design Book 2 - City of St. Petersburg

4.3 BOUNDARY CONDITIONS
Boundary conditions for the baywide model include the tidal forcing at the mouth of Tampa Bay
as well as the wind field driving baywide and local circulation patterns.
The open boundary was based on the measured tides at Port Manatee (NOAA Gage 8726384).
Because the open boundary is near the inlet at the Gulf of Mexico, and the Port Manatee gage
is nearly 18 kilometers (km) to the east, it was necessary to adjust the amplitude and phase
(i.e., timing) of the boundary tidal signal. This 6-minute interval time series data was adjusted so
that the measured and simulated tides at Port Manatee are in good agreement. Figure 4-4
presents a comparison of the simulated and measured tides at Port Manatee. The boundary
was adjusted as follows:
• The astronomical tidal component was separated from the residual water levels
using the TTIDE analysis package.
• The astronomical tides were increased by a factor of 1.17 and then combined with
the residual water level component.
• The resulting signal was low-pass filtered (with a 1-hour filter) to remove highfrequency
noise in the signal.
• The time was shifted by 0.04 day.
Figure 4-5 presents a plot of the 30-day tides utilized for the model tidal forcing. Figure 4-6
presents a comparison of the tides at the boundary matching point (Port Manatee).
The wind boundary condition was taken directly from NOAA Station 8726520, for St.
Petersburg, FL. Figure 4-6 presents a plot of the wind speed and direction for the 30-day period
for the model wind forcing.
GNV/2012/122381A/8/8/2012
4-6