Jonathan R. Moskaitis

Adjoint Sensitivity and Predictability of Tropical Cyclogenesis

AbstractThe sensitivity of tropical cyclogenesis and subsequent intensification is explored by applying small perturbations to the initial state in the presence of organized mesoscale convection and synoptic-scale forcing using the adjoint and tangent linear models for the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS). The forward, adjoint, and tangent linear models are used to compare and contrast predictability characteristics for the disturbance that became Typhoon Nuri and a nondeveloping organized convective cluster in the western Pacific during The Observing System Research and Predictability Experiment (THORPEX) Pacific Asian Regional Campaign (T-PARC) and the Tropical Cyclone Structure-2008 (TCS-08) experiments.The adjoint diagnostics indicate that the intensity (e.g., maximum surface wind speed, minimum surface pressure) of a tropical disturbance is very sensitive to perturbations in the moisture and temperature fields and to a lesser degree the wind fields. The highest-resolution...

A View of Tropical Cyclones from Above: The Tropical Cyclone Intensity Experiment

AbstractTropical cyclone (TC) outflow and its relationship to TC intensity change and structure were investigated in the Office of Naval Research Tropical Cyclone Intensity (TCI) field program during 2015 using dropsondes deployed from the innovative new High-Definition Sounding System (HDSS) and remotely sensed observations from the Hurricane Imaging Radiometer (HIRAD), both on board the NASA WB-57 that flew in the lower stratosphere. Three noteworthy hurricanes were intensively observed with unprecedented horizontal resolution: Joaquin in the Atlantic and Marty and Patricia in the eastern North Pacific. Nearly 800 dropsondes were deployed from the WB-57 flight level of ∼60,000 ft (∼18 km), recording atmospheric conditions from the lower stratosphere to the surface, while HIRAD measured the surface winds in a 50-km-wide swath with a horizontal resolution of 2 km. Dropsonde transects with 4–10-km spacing through the inner cores of Hurricanes Patricia, Joaquin, and Marty depict the large horizontal and ver...

A Case Study of Deterministic Forecast Verification: Tropical Cyclone Intensity

Deterministic predictions of tropical cyclone (TC) intensity from operational forecast systems traditionally have been verified with a summary accuracy measure (e.g., mean absolute error). Since the forecast system development process is coupled to the verification procedure, it follows that TC intensity forecast systems have been developed with the goal of producing predictions that optimize the chosen summary accuracy measure. Here, the consequences of this development process for the quality of the resultant forecasts are diagnosed through a distributions-oriented (DO) verification of operational TC intensity forecasts. DO verification techniques examine the full relationship between a set of forecasts and the corresponding set of observations (i.e., forecast quality), rather than just the accuracy attribute of that relationship. The DO verification results reveal similar first-order characteristics in the quality of predictions from four TC intensity forecast systems. These characteristics are shown to be consistent with the theoretical response of a forecast system to the imposed goal of summary accuracy measure optimization: production of forecasts that asymptote with lead time to the central tendency of the observed distribution. While such forecasts perform well with respect to the accuracy, unconditional bias, and type I conditional bias attributes of forecast quality, they perform poorly with respect to type II conditional bias. Thus, it is clear that optimization of forecast accuracy is not equivalent to optimization of forecast quality. Ultimately, developers of deterministic forecast systems must take care to employ a verification procedure that promotes good performance with respect to the most desired attributes of forecast quality.

Numerical Simulations of Typhoon Morakot (2009) Using a Multiply Nested Tropical Cyclone Prediction Model

AbstractHigh-impact Typhoon Morakot (2009) was investigated using a multiply nested regional tropical cyclone prediction model. In the numerical simulations, the horizontal grid spacing, cumulus parameterizations, and microphysical parameterizations were varied, and the sensitivity of the track, intensity, and quantitative precipitation forecasts (QPFs) was examined. With regard to horizontal grid spacing, it is found that convective-permitting (5 km) resolution is necessary for a reasonably accurate QPF, while little benefit is gained through the use of a fourth domain at 1.67-km horizontal resolution. Significant sensitivity of the track forecast was found to the cumulus parameterization, which impacted the model QPFs. In particular, the simplified Arakawa–Schubert parameterization tended to erroneously regenerate the remnants of Tropical Storm Goni to the southwest of Morakot, affecting the large-scale steering flow and the track of Morakot. Strong sensitivity of the QPFs to the microphysical parameter...

On the Impact of Unmanned Aerial System Observations on Numerical Weather Prediction in the Coastal Zone

AbstractThe Trident Warrior observational field campaign conducted off the U.S. mid-Atlantic coast in July 2013 included the deployment of an unmanned aerial system (UAS) with several payloads on board for atmospheric and oceanic observation. These UAS observations, spanning seven flights over 5 days in the lowest 1550 m above mean sea level, were assimilated into a three-dimensional variational data assimilation (DA) system [the Naval Research Laboratory Atmospheric Variational Data Assimilation System (NAVDAS)] used to generate analyses for a numerical weather prediction model [the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS)] with a coupled ocean model [the Naval Research Laboratory Navy Coastal Ocean Model (NCOM)]. The impact of the assimilated UAS observations on short-term atmospheric prediction performance is evaluated and quantified. Observations collected from 50 radiosonde launches during the campaign adjacent to the UAS flight paths serve as model forecast verification. Experim...