MSEAS Forecast EM-APEX Float Forward Flowmaps for 06 Jun 0000Z to 20 Jun 0000Z 2025, Issued 07 Jun 2025

Shown are our MIT-MSEAS forecasts of forward float flowmaps for three EM-APEX floats in the Gulf region during the period June 6–20, 2025.

We first compute the 3D forward float flowmaps for different time windows (spanning June 6–20) for the whole Gulf domain. Float forward flowmaps link the initial location of a float to its final position as it is advected over a specified time window by the currents and its vertical profiling motions. To mimic these motions of EM-APEX floats, the vertical velocity from the MIT MSEAS PE is replaced with an analytic float behavior model that either has the float parked at 1500 m or makes a profile from 1500 m to 0 m and back down to 1500 m over an 8.5 hour period.

In the table of panels below, we show float flowmap forecasts for two types of EM-APEX behaviors, first for floats doing one profile per day and then for floats doing two profiles per day. For each type, two floats aim to start in LC frontal eddies (LCFEs) and remain in these LCFEs, while a third float aims to start and remain in the main LC. In all cases, forecasts start on June 6, 2025.

We selected the initial float regions (two floats in LCFEs and one float in the main LC lobe) based on watermass analyses (T, S, σ_T) at several depths, velocity and vorticity fields at several depths, and Lagrangian feature analysis (coherent structures, FTLE, etc.). Once these initial regions are defined, we then highlight the forward float flowmaps at the initial time and color their forecast positions at the different intermediate times of the forward float flowmap in two different ways. The first coloring scheme is a solid color for each region surrounding each float: 1 (dark blue), 2 (green), and 3 (maroon). This scheme simply highlights where the material in the region is going over time. The second scheme colors floats in each region by their initial distance from the centroid of the region. This scheme highlights how each region is being distorted, especially how its edges can be affected by shear and turbulence.

Floats starting in the northern Loop Current (LC) Frontal Eddy (FE) region (green) on June 06 are forecast to advect eastward along the LC and largely split in two parts by June 11. Even floats from the centroid are strongly sheared and split between two new smaller LCFEs. By June 20, floats released in this northern LCFE are forecast to be on along the LC or on the edges of newly formed smaller LCFEs west of Tampa, off the west Florida shelf.

Floats from the eastern Tortugas LCFE region (maroon) mostly remain coherent and within the region they started until June 9. Later, float locations mostly on the edges are strained into filaments forming from the edges of the LCFE by June 20, see solid and distance color maps.

Floats starting in the LC core region (dark blue) are forecast to remain inside the LC but are advected to the southeast with some distortion but less filamentation than the other LCFE regions. By June 20, they have partly spread into a cluster of three and have remained within the meandering LC core, see solid and distance color maps.

The results for the twice-a-day sampling are very similar to the once-a-day sampling (e.g. compare for example once-a-day to twice-a-day on June 20) indicating that the extra sampling should not increase the risk of the float leaving the initial watermass in which it was placed by June 20.