The damage potential of a hurricane is widely considered to depend more strongly on an integrated measure of the hurricane wind field, such as Integrated Kinetic Energy (IKE), than a point-based wind measure, such as maximum sustained wind speed (Vmax). Recent work has demonstrated that minimum sea level pressure (MSLP) is also an integrated measure of the wind field. This study investigates how well historical continental US hurricane damage is predicted by MSLP compared to both Vmax and IKE for continental United States hurricane landfalls for the period 1988–2020. We first show for the entire North Atlantic basin that MSLP is much better correlated with IKE (rrank = 0.50) than Vmax (rrank = 0.26). We then show that continental US hurricane normalized damage is better predicted by MSLP (rrank = 0.81) than either Vmax (rrank = 0.65) or IKE (rrank = 0.68). For Georgia to Maine hurricane landfalls specifically, MSLP and IKE show similar levels of skill at predicting damage, whereas Vmax provides effectively no predictive power. Conclusions for IKE extend to power dissipation as well, as the two quantities are highly correlated because wind radii closely follow a Modified Rankine vortex. The physical relationship of MSLP to IKE and power dissipation is discussed. In addition to better representing damage, MSLP is also much easier to measure via aircraft or surface observations than either Vmax or IKE, and it is already routinely estimated operationally. We conclude that MSLP is an ideal metric for characterizing hurricane damage risk.

This study investigates the contributions of incipient vortex circulation and mid-level moisture to tropical cyclone (TC) expansion within an idealized numerical modeling framework. We find that the incipient vortex circulation places the primary constraint on TC expansion. Increasing the mid-level moisture further promotes expansion but mostly expedites the intensification process. The expansion rate for initially large vortices exhibits a stronger response to increasing the mid-level moisture compared to initially small vortices. Previous studies have noted a proclivity for relatively small TCs to stay small and relatively large TCs to stay large; that is, TCs possess a sort of “memory” with respect to their incipient circulation. We reproduce this finding with an independent modeling framework and further demonstrate that an initially large vortex can expand more quickly than its relatively smaller counterpart; therefore, with all other factors contributing to expansion held constant, the contrast in size between the two vortices will increase with time. Varying the incipient vortex circulation is associated with subsequent variations in the amount and scale of outer-core convection. As the incipient vortex circulation decreases, outer-core convection is relatively scarce and characterized by small-scale, isolated convective elements. On the contrary, as the incipient vortex circulation increases, outer-core convection abounds and is characterized by relatively large rainbands and mesoscale convective systems. A combined increase in the amount and scale of outer-core convection permits an initially large vortex to converge a substantially larger amount of absolute angular momentum compared to its relatively smaller counterpart, resulting in distinct expansion rates.

The Madden-Julian oscillation (MJO) significantly impacts North Atlantic hurricanes, with more hurricane activity occurring when the MJO favors enhanced convection over Africa and the tropical Indian Ocean and suppressed hurricane activity occurring when the MJO favors enhanced convection over the tropical Pacific. Using data from 1905-2015, we find more hurricanes make landfall in the continental US when the MJO enhances convection over the tropical Indian Ocean. In addition, when the MJO enhances convection over the Western Hemisphere, tropical cyclones tend to form in the Gulf of Mexico or the Caribbean, leading to more Gulf Coast landfalls. As the MJO moves to the Indian Ocean, more storms form in the tropical Atlantic, increasing the number of Florida and East Coast landfalls. The MJO’s modulation of tropical cyclone steering winds appears to be secondary to its effects on genesis locations.

In this study, we used the potential vorticity (PV) diagnosis technique to investigate the key factors that affect the track forecasts of Hurricane Maria (2017) in the NCEP GFS v14, ECMWF IFS and GFDL SHiELD models. In Chen et al. (2019), it showed that a slow bias of Maria’s translation speed in the IFS 5-day forecasts was significantly improved by GFDL SHiELD with IFS initial conditions (SHiELD_IFS). Our results found that the slow moving bias in the IFS is mainly due to a strong, westerly steering flow contribution from a cutoff low from the northeast quadrant and another low system from the southwest quadrant of Maria. On the other hand, the SHiELD_IFS improves on the IFS by better simulating the strength of the Bermuda High, and low systems in the southwest, northwest, and northeast quadrants allowing for better track alignment with observations. We also found that the northward track bias of Maria in the legacy GFS and SHiELD with the GFS initial conditions (SHiELD_GFS) was associated with a weaker Continental High which contributed less northerly steering flow compared to that in the IFS and SHiELD_IFS. Furthermore, the Bermuda High was relatively weak in the SHiELD_GFS, while the two low systems in the northwest and northeast quadrants contributed steering flow opposing Maria’s moving direction, causing a slowdown of translation speed of Maria in the SHiELD_GFS. By performing this piecewise potential vorticity diagnosis on all of the storms in the 2017 North Atlantic Hurricane Season, we could possibly identify the key elements that generate the biases in TC track forecasts in these models.

This study investigates trends in global tropical cyclone (TC) activity from 1990–2020, a period where observational platforms are mostly consistent. Several global TC metrics have decreased during this period, with significant decreases in hurricanes and Accumulated Cyclone Energy (ACE). Most of this decrease has been driven by significant downward trends in the western North Pacific. Globally, short-lived named storms, 24-hr intensification periods of >=50 kt day-1 and TC-related damage have increased significantly. The increase in short-lived named storms is likely due to technological improvements, while rapidly intensifying TC increases may be fueled by higher potential intensity. Damage increases are largely due to increased coastal assets. The decreasing trends in hurricane numbers and global ACE are likely due to the trend towards a more La Niña-like base state from 1990–2020, favoring TC activity in the North Atlantic and suppressing TC activity in the eastern and western North Pacific.