The cyclone strengthened rapidly while it passed an area of high ocean heat content, as seen below (image courtesy of CIMMS and RSMAS). Although it has gained a lof of strength, reaching the Saffir-Simpson category 5 scale, it will likely not hold it for very long as it is leaving this area of high ocean heat toward one with cooler sea surface temperature.
As an additional sidenotem the cyclone is also dominating the upper-level divergence pattern in the form of velocity potential (divergence is the laplacian of velocity potential). In the plot below, yellow contours denote the velocity potential associated with large-scale upper level divergence, also associated with ascending motion. Green contours denote the opposite. Note the tight contours in the area where the storm lies. The filled contours denote the upper level streamfunction. Tropical cyclones do not tend to project strongly in the rotation in the upper levels. The contours in that area are likely due to Rossby waves.
In a couple of days, Sanba might become a threat to some land areas in this region.We should keep close attention as this situation unfolds.
