The Geostationary Lightning Mapper (GLM) has been providing unprecedented observations of total lightning since becoming operational in 2017. The potential for GLM observations to be used for forecasting and analyzing tropical cyclone (TC) structure and intensity has been complicated by inconsistencies in the GLM data from a number of artifacts. The algorithm that processes raw GLM data has improved with time; however, the need for a consistent long-term dataset has motivated the development of quality control (QC) techniques to help remove clear artifacts such as blooming events, spurious false lightning, ‘bar’ effects, and sun glint. Simple QC methods are applied that include scaled maximum energy thresholds and minima in the variance of lightning group area and group energy. QC and anomaly detection methods based on machine learning (ML) are also explored. Each QC method is successfully able to remove artifacts in the GLM observations while maintaining the fidelity of the GLM observations within TCs. As the GLM processing algorithm has improved with time, the amount of QC flagged lightning within 100 km of Atlantic TCs is reduced, from 70% during 2017, to 10% in 2018, to 2% during 2021. These QC methods are relevant to the design of ML-based forecasting techniques which could pick up on artifacts rather than the signal of interest in TCs if QC wasn’t applied beforehand.
Are Forecasts of the Tropical Cyclone Radius of Maximum Wind Skillful?
Benjamin C. Trabing, Andrew B. Penny, Jonathan Martinez, and 1 more author
The radius of maximum wind (RMW) defines the location of the maximum winds in a tropical cyclone and is critical to understanding intensity change as well as hazard impacts. A comparison between the Hurricane Analysis and Forecast System (HAFS) models and two statistical models based off the National Hurricane Center official forecast is conducted relative to a new baseline climatology to better understand whether models have skill in forecasting the RMW of North Atlantic tropical cyclones. On average, the HAFS models are less skillful than the climatology and persistence baseline and two statistically derived RMW estimates. The performance of the HAFS models is dependent on intensity with better skill for stronger tropical cyclones compared to weaker tropical cyclones. To further improve guidance of tropical cyclone hazards, more work needs to be done to improve forecasts of tropical cyclone structure.
2023
The Development and Evaluation of a Tropical Cyclone Probabilistic Landfall Forecast Product
Benjamin C. Trabing, Kate D. Musgrave, Mark DeMaria, and 3 more authors
The sensitivity of tropical cyclone secondary eyewall formation (SEF) and subsequent eyewall replacement cycles (ERCs) to shortwave radiation is examined in this study by varying the solar constant and diurnal cycle at different times prior to an ERC using idealized simulations from the Weather Research and Forecasting model. The magnitude of shortwave radiation plays an important role in modifying the timing of the SEF with nonlinear interactions amplifying the SEF formation differences at longer lead-times. Shortwave radiation has a delaying effect on the SEF and ERC primarily through its modifications of the distribution of convective and stratiform heating profiles in the rainbands. Shortwave radiation reduces both the area and diabatic heating of convection in the model domain, while increasing the amount of stratiform precipitation that has weaker low-level cooling and upper-level heating rates. The primary mechanism by which shortwave radiation reduces the diabatic heating profile and frequency of convection in the rainbands is through heating of the mid-upper troposphere which stabilizes the region and reduces convective available potential energy.
Observations of Diurnal Variability under the Cirrus Canopy of Typhoon Kong-rey (2018)