Realtime Analysis of Model ICs Wallace Hogsett, NHC 1

Introduction Part I: NHC diagnostics module – This diagnostics system inputs data from GFS/GFDL/HWRF and outputs figures of vortex structure. – Goal is to facilitate inter-model comparisons of initial vortex structure and gain insight into systematic characteristics of the various model initializations. Part II: A look toward 2011 – EMC/NHC collaboration. – More sophisticated and quantitative diagnostics. 2

Example 1 – Tomas Approaches Jamaica 3 Above: near-surface winds (shaded, kts), streamlines, and surface pressure (green dashed, hPa) from the GFS (left) and HWRF inner nest (center), and GFDL inner nest (right) ICs. GFS HWRF GFDL Approximate observed locations of RMW and 34kt radius (via P3 radar & SFMR). * GFDL is superior to HWRF in this case in terms of constraining initial storm size, which is key factor in the initial balance/imbalance issue. * Suggestion: Leverage GFDL size constraint methodology. RMW R 34kt RMW R 34kt

Example 2: Tomas’ Unexpected Weakening 4 On Halloween, Tomas weakened rapidly. HWRF predicted well the rapid weakening. GFDL predicted intensification prior to weakening. Was this HWRF success a lucky coincidence? Above: Time-series of minimum pressure (top) and maximum 10m winds (bottom) from HWRF (red) and GFDL (green) forecasts. Figure courtesy of Vijay and the HWRF team at EMC.

Example 2: Vertical Structure of Weakening Tomas 5 Vertical cross sections suggest that the HWRF handled well a northeasterly vortex tilt and the associated very dry layer directly above the vortex center. Why does HWRF capture this structure, but GFDL does not? Was a satellite dataset assimilated into HWRF? Above: South-north (top) and west-east (bottom) vertical cross sections of wind speed (shaded, kts), horizontal wind barbs (kts), and vertical vorticity (contoured, x s -1 ) taken through the center of the GFS (left), HWRF nest (middle), and GFDL nest (bottom) initial conditions. Dry layer eastward tilt GFS HWRF GFDL

Part I Summary NHC diagnostics module allows model-model comparisons in near realtime (Stream1). It has brought to light some strengths and weaknesses of the model initializations. As the Tomas example shows, initial vortex structure may be critical for short-term intensity forecast improvements. 6

Part II: Looking forward to 2011 Continue to produce realtime diagnostic products. – Possible expansion beyond initialization. – Include other HFIP models (stream 1.5)? Begin newly-formalized NHC-EMC collaboration, including assessment of upcoming 2011 size correction upgrades, and begin work on next-level diagnostics. 7 … example of next- level diagnostic product: Sfc convergence field, hodographs, Shear.

Part II: Looking forward to 2011 Goal: develop capability to calculate budget terms on native grids to diagnose source of systematic model biases. – feedback results to EMC 8 Upper level drying

Summary A diagnostics module developed at NHC has enabled realtime analysis of operational model ICs. Some 2010 results, including the HWRF vertical vortex structure and storm size, will hopefully aid EMC’s continuing development efforts. In 2011, we hope to take on some of the more difficult issues quantitatively (e.g., moisture budget). 9