HFIP Workshop on Rapid Intensification of Tropical Cyclones:

A Brief Summary

Chris Davis

Topics and People

• Observations and Mechanisms• Current Prediction Capabilities• Future Directions

Speakers:Ed ZipserHaiyan JiangJon ZawislakRob RogerFalko JudtMark DeMaria

John KaplanVijay TallapragadaFuqing ZhangChris RozoffGopal

Panelists:Greg TripoliShuyi ChenJun ZhangJim DoyleJason SippelDave Nolan

The non-existence of RIas a distinct phenomenon?

Still, RI dominates the largest intensity forecast errors

Kaplan, DeMaria and Knaff, 2010

The nature of convection prior to RI• No evidence that intense “deep” convection precedes RI• Convection migrating to upshear side of vortex is observed

prior to RI

Haiyan Jiang

Where Convection Occurs

Schubert and Hack 1982

Rob Rogers

Inertial stability and the radial location of convection relative to the RMW

Knowledge of the spatial relation between convection and RMW is important => reconn data

Questions

• What is “deep” convection? Can microwave and aircraft data be consistent?

• Is the increase of area coverage a cause or a signal (vortex alignment)?

• Do we need to resolve enhanced inertial stability inside the RMW? requires 1-km resolution Rob Rogers

Current RI prediction• Dynamical models (HWRF) show some skill in W. Pac• Statistical models work well in E. Pac• Nothing works well in Atlantic• Are statistical methods and models better equipped

to handle favorable environments?• Are the sources of non-favorability so diverse that it

is tough to model them (or represent them statistically)?

• Why do models fail in the E. Pac? Resolution?

Perspective from Shuyi Chen, RSMAS/University of Miami

1. Modeling Issues: resolution and physics (biases)2. Deterministic vs. probabilistic forecasts3. Initial Condition Issues

Need accurate observation (not bogus) of vortex (outer and inner core winds)!

Judt et al. (2014)

168 h

Vortex Initialization

• Vortex/environment initialization:– Adjust the model initial state to a structure consistent with

model dynamics and environmental effects (shear)

• Poor RI prediction may result from spinup in the short range, and limited predictability beyond the first day or two.

• Vortex initialization perhaps most important for stronger storms that can still undergo RI

Predictability• Strong shear: high predictability, no RI• Moderate shear: low predictability, especially about timing• Weak shear: better predictability, perhaps still some

uncertainty to the extent that convective features are important

Fuqing Zhang

Moving Forward1 year; 3 years

1. RI is a probabilistic forecast, but NHC requires deterministic forecasts: how can ensembles inform these products?

– Develop products that define the most likely scenario (cluster) from the ensemble (if possible): reduce adverse effect of outliers

– Reduce model bias (see #3)2. Model initialization hampers RI prediction: What can be done?3. Can idealized simulations with HWRF be useful?

– reproduce PDF of RI– assess physics shortcomings: energy fluxes and dissipation

4. SHIPS-products using input from HWRF: Could this indicate an environmental or model error?5. Further test/implement updated statistical prediction methods (using microwave data); can reconn data be incorporated?