JP3.43 Estimating local memory of tropical cyclones through MPI anomaly evolution (2008

JP3.43

Estimating local memory of tropical cyclones through MPI anomaly evolution

Robert Hart, Florida State University, Tallahassee, FL; and R. Maue and M. C. Watson

This study examines the local memory of atmospheric and oceanic changes

associated with a tropical cyclone (TC). The memory is quantified

through anomalous maximum potential intensity (MPI) evolution for 20 days

prior to the arrival of a TC through 60 days after the TC passage. The

MPI weakens and is not restored to the evolving climatology until weeks

after the TC has departed. Stabilization occurs through warming of the

atmosphere and cooling of the ocean surface on different timescales. The

timescale of MPI stabilization following TC passage is approximately 30-35

days for a tropical storm to 50-60 days for a category 3-5 hurricane, with

significant storm-specific and basin-specific variability. The

atmospheric stabilization begins with TC arrival and continues for

approximately 7-10 days after passage, when the troposphere cools below

normal. The rewarming of SST and the atmosphere to climatology occurs

within approximately 35 days for all intensities, despite a positive

(weakened) MPI anomaly through two months. This suggests that the

atmosphere warms beyond what can be attributable to sensible heating from

the rewarmed SST. The maintenance of a positive MPI anomaly beyond 35

days is thus attributed to a feedback on larger scales that requires

considerable further research.

A TC's passage through a region does not always lead to a weakening of the

MPI. In regions poleward of the sharp SST gradient, the MPI one month

after TC passage is often several millibars stronger than climatology.

There are also mesoscale regions of destabilization one month after TC

passage that may result partially from salinity changes driven by oceanic

mixing as well as changes in precipitation and evaporation.