HARMFUL ALGAL BLOOM MONITORING SYSTEM
Southwest Florida Intensification Forecast
The Southwest Florida Intensification Forecast provides an early warning of red tide initiation or intensification for coastal managers and decision makers. Red tide, also known as the dinoflagellate Karenia brevis, is harmful to marine animals and can cause respiratory distress in humans. Due to this health concern, beach closures may be necessary when coastal waters contain high concentrations of Karenia brevis. The Southwest Florida Intensification Forecast alerts coastal managers to potential red tide (Karenia brevis) bloom initiation or intensification along the southwest Florida coast, which provides advanced warning of a potential bloom and helps to minimize impacts to public health and coastal economies.
Onshore Karenia brevis (red tide) bloom intensificiation is unlikely along the Southwest Florida coast, as suggested by model results. Observed cell counts are at background levels with an onshore excursion of 15km. For technical model details and output, please see figures and explanations below. Last Updated: 2023-12-10 EST
How the Forecast Works
During the early bloom period (typically each fall), Karenia brevis cells—which persist in the bottom waters offshore—can be moved onshore to the Southwest Florida coast by a process known as coastal upwelling. The graphics below demonstrate this process. Once near the coast, Karenia brevis cells can quickly reach levels that create a harmful algal bloom (HAB).
Image Caption: Downwelling - Southerly winds blowing along the Florida coast leads to downwelling. Offshore surface waters are moved onshore. Onshore bottom waters are moved offshore. Subsurface Karenia brevis cells are moved offshore resulting in low risk of bloom initiation.
Upwelling - Northerly winds blowing along the Florida coast leads to upwelling. Onshore surface waters are moved onshore. Subsurface Karenia brevis cells are moved onshore resulting in a high risk of bloom initiation.
Risk of HAB Initiation or Intensification
The likelihood of HAB initiation or intensification is greatest when Karenia brevis (red tide) cells are present (> 0 cells per mL) and there is a large onshore particle transport in the bottom waters (distance moved toward the coast or beach > 10 km). The greater the onshore transport in the bottom waters, the more likely HAB initiation or intensification will occur. K. brevis cell presence is estimated as the total of the top three observed
cell counts for the past 10-days.
Highly Likely - there is a high potential for HAB initiation or intensification to occur in the next 10 days due to large onshore movement at the bottom waters and elevated observed cell counts.
Likely - there is a likely potential of HAB initiation or intensification to occur due to the extent of onshore movement at the bottom and elevated observed cell counts.
Somewhat Likely - there is the potential for HAB initiation or intensification to occur due to onshore movement at the bottom and/or elevated observed cell counts.
Unlikely - HAB initiation or intensification is unlikely to occur due to low risk of onshore movement at depth and/or low observed cell counts.
Particle (Karenia brevis cell) Movement
The animation below shows the onshore and offshore movement of particles (representing Karenia brevis cells) along the southwest Florida coast from 7-days prior to the forecast date to 10-days after the forecast date. Particles start at 44 km (red), 31 km (dark blue), 18 km (light blue), and 6 km (green) offshore 7-days prior to the forecast date. The forecast uses a hydrodynamic model, which simulates water movement off the southwest Florida coast, using forecasts of wind speed and direction.