Diurnal Pulsing of Tropical Cyclones: An Overlooked Yet Fundamental TC Process?

New GOES infrared satellite imagery has been developed to continuously monitor changes in the cloud top convective and cirrus canopy structure of tropical cyclones. This satellite imagery has also revealed a curious diurnal pulsing pattern that may represent an unrealized, yet fundamental process of mature tropical cyclones. “Cool rings” can be tracked in the infrared that begin forming in the storm's inner core at sunset each day. Similar to ripples that form after a pebble is thrown into a pond, the “cool ring”, or pulse, continues to move away from the storm overnight, reaching areas several hundred kilometers from the storm center by the following afternoon. There appear to be marked structural changes and disruptions to a storm as this pulse evolves and moves out from the inner core each day. The timing and propagation of these "cool rings" also appears to be linked to the diurnal cycle, making them remarkably predictable. Discussion will include: • Examples of recent and historical tropical cyclones exhibiting diurnal pulsing; • Diurnal pulse characteristics, hypothesized triggers, and potential predictability; • Preliminary findings from a NOAA G-IV jet that sampled diurnal pulsing in 2011 Hurricane Katia; • Results from an axisymmetric hurricane model based on Rotunno and Emanuel (1987) to assess how radiative adjustments to the model field can produce pulse-like features in simulations. Possible mechanisms that generate this pulsing will also be examined; • Results from a 1km tropical cyclone nature run of the WRF/ARW model that has been found to exhibit the tropical cyclone pulsing. Possible mechanisms producing this simulated pulsing will also be examined; • Tropical cyclone diurnal pulsing sampling strategies for the 2012 Atlantic Hurricane season;