Jun A Zhang
Hurricane Research Division, AOML, NOAA, Hurricane Research Division, AOML, NOAA, Hurricane Research Division, AOML, NOAA, Hurricane Research Division, AOML, NOAA
Author ProfileSundararaman Gopalakrishnan
Hurricane Research Division, AOML,NOAA, Hurricane Research Division, AOML,NOAA, Hurricane Research Division, AOML,NOAA, Hurricane Research Division, AOML,NOAA
Author ProfileAbstract
This study demonstrates a link between coastal downwelling and tropical
cyclone (TC) intensification. We show that coastal downwelling increases
air-sea enthalpy (heat, moisture) fluxes ahead of TCs as they approach
land, creating conditions conducive to intensification even in the
presence of typically inhibiting factors like strong vertical wind
shear. The study uses a coupled TC model (HWRF-B) and buoy observations
to demonstrate that coastal downwelling developed as three TCs in 2020
approached land. Results show downwelling maintained warmer sea-surface
temperatures over the ocean shelf, enhancing air-sea
temperature/humidity contrasts. We found that in such cases resulting
air-sea enthalpy fluxes can replenish the boundary-layer even when cool,
dry air intrudes, as in sheared storms and storms approaching
continental land-masses. The resulting warm, moist air is advected into
the TC inner core, enhancing convective development, thus providing
energy for TC intensification. These results indicate coastal
downwelling can be important in forecasting TC intensity change before
landfall.