SEMINAR: REMINDER - TODAY- AML IRR - 10:30a.m. - Kathryn Sellwood - NOAA/AOML/HRD's Hurricane Ensemble Data Assimilation System (HEDAS): Results of semi-operational implementation during the 2010 Atlantic hurricane season

["Aoml.Receptionist" <Aoml.Receptionist@noaa.gov>]

Informal Research Report

DATE:             Wednesday, January 19, 2011

TIME:              10:30a.m.– refreshments at 10:15 a.m.

Location:      AOML First Floor Conference Room

SPEAKER:       Kathryn Sellwood (CIMAS/HRD)

TITLE:            “NOAA/AOML/HRD's Hurricane Ensemble Data

     Assimilation, System (HEDAS): Results of

    semi-operational implementation during the

    2010 Atlantic hurricane season

ABSTRACT -- The Hurricane Ensemble Data Assimilation System (HEDAS) was developed at the Hurricane Research Division (HRD) of NOAA, in conjunction with an experimental version of the Hurricane Weather and Research Forecast model (HWRFx), in an effort to improve the initial representation of the hurricane vortex by utilizing high resolution in-situ data collected during NOAA’s Hurricane Field Program. HEDAS implements the “ensemble square root “ filter of Whitaker and Hamill (2002) using a 30-member ensemble obtained from NOAA/ESRL’s ensemble Kalman filter (EnKF) system and the assimilation is performed on a 3-km nest centered on the hurricane vortex.  As part of NOAA’s Hurricane Forecast Improvement Program (HFIP), HEDAS was run in a semi-operational mode for the first time during the 2010 Atlantic hurricane season assimilating airborne Doppler radar winds, dropwindsonde and flight level wind, temperature, pressure and relative humidity, and Stepped Frequency Microwave Radiometer surface wind observations as they were available.

 

The main focus of this talk will be to present a summary of HEDAS performance in the HWRFx model for the inaugural season.  The 19 HEDAS analyses and the resulting HWRFx forecasts are compared with HWRFx analyses and forecasts produced concurrently using the HRD modeling group’s vortex initialization that does not employ data assimilation. The initial vortex and subsequent forecasts are evaluated based on the thermodynamic structure, wind field, track and intensity. The results indicate that the assimilation of in-situ data produces a vortex that is consistent with the observed vortex structure. However the HEDAS analyses usually fail to capture the maximum observed winds, producing slightly weaker storms that those observed. Despite this tendency, the subsequent forecasts improve intensity forecasts on average without degrading the forecasts of the storm motion. There is also some indication of a positive temperature bias in the model that is only partially corrected by the observations. The 19 HEDAS cases from the 2010 Atlantic hurricane season illustrate the potential benefit of incorporating in-situ data in numerical model forecasts and provide further insight into the behavior of the model when inner core aircraft observations are assimilated.

 

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