[Ncep.nhc.nco_contacts] HSU Shift Log -- Technical Edition -- Sun Aug 06, 2017

Mark DeMaria - NOAA Federal mark.demaria at noaa.gov
Sun Aug 6 14:32:50 UTC 2017

The ECMWF SHIPS and related models (TAB, LGEM, RII) still use the 2016
configuration. For the TAB model the averaging radius for the steering flow
is 450 k. The GFS TAB uses a smaller radius (350 km), which is the 2017
configuration. Based on a study by Dave with several seasons of forecasts,
the 350 km radius version gives slightly lower track  forecast errors.
However, as we have found out this year, the 350 km version leaves in too
much of the GFS vortex, so it is more suspectible to being influenced by
that. That sometimes introduces some pretty significant wobbles in the TAB
track. If the TAB model starts off a litttle slow for a westward moving TC,
that introduces a northward bias due to GFS representation of the TC that
was not removed properly.

Another difference is that the EC TAB uses the EC fields, while the GFS TAB
uses the GFS fields. If the represenation of the TC or the steering is
different in the two models, TAB wll also be different.

Matt Onderlinde and  I working on changing the radius of the GFS TAB back
to 450 km to reduce the vortex influence. We hope to have code to submit to
NCO by the end of this week.


On Sun, Aug 6, 2017 at 4:16 AM, HSU Shift Log <nhc.tsbadmin at noaa.gov> wrote:

> *HSU Shift Log for Sun Aug 06 2017 04:16:32 GMT-0400 (EDT)*
> *Shift:* A
> *Forecaster:* S R Stewart
> *Technical Issues Summary:*
> *ATCF issues:* None.
> *N-AWIPS issues:* None.
> *AWIPS-2/NCP issues:* None.
> *Other Techincal issues:* Significant differences exist between GFS-TABM
> and ECMWF-TABM forecast tracks; TABM-EC is closer to the ECMWF
> deterministic positions than TABM-GFS is to the GFS sfc positions. Why?
> This affects other SHIPS output parameters besides track.
> *Miscellaneous issues:* None.
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