NOUS41 KWBC 251122 AAC


Technical Implementation Notice 13-13, Amended

National Weather Service Headquarters Washington DC

719 AM EDT Thu Jul 25 2013

To:†††††† Subscribers:

††††††††† -Family of Services

††††††††† -NOAA Weather Wire Service

††††††††† -Emergency Managers Weather Information Network

††††††††† -NOAAPORT

††††††††† Other NWS Partners, Users and Employees

From:†††† Timothy McClung

††††††††† Science Plans Branch Chief

††††††††† Office of Science and Technology

Subject:Amended Hurricane Weather and Research Forecast

††††††††† (HWRF) Model Changes: Effective July 25, 2013


Amended to reschedule the effective date from July 30 to

Thursday, July 25, 2013

Effective on or about Thursday, July 25, 2013, beginning with the

1200 Coordinated Universal Time (UTC) run, the National Centers

for Environmental Prediction (NCEP) will upgrade the HWRF

Princeton Ocean Model (POM) coupled system.

The FY2013 HWRF model will be implemented on NCEPís new Weather

and Climate Operational Supercomputing System (WCOSS), scheduled

to become the operational machine on or about July 25, 2013.A

separate TIN will be issued announcing the operational switch to

the WCOSS system. In the event that switch date is changed, this

TIN will be modified to reflect that change in implementation


Forecasts from the upgraded FY2013 HWRF model will be made

available through a parallel feed from WCOSS starting June 15,

2013. The HWRF GRIB products from WCOSS are disseminated via the

NCEP Parallel FTP server:


and the products will be displayed through NCEPís parallel Model

Analysis and Guidance (MAG) website:


The 2012 version of operational HWRF model will continue

providing forecasts through NCEP Central Computing System (CCS)

until the WCOSS machine goes live on July 25, 2013.The HWRF

GRIB products are not available on NOAAPORT or AWIPS but they are

disseminated via the NCEP production FTP server:


The scientific enhancements include the following:

-- Implement HWRF GSI V3.7 one-way hybrid EnKF-3DVAR data

assimilation with GDAS forecasts as first guess and 80-member GFS

EnKF forecasts for ensemble covariances, assimilation of all

conventional data and provision to assimilate real-time inner-

core TDR/FL/SFMR/Dropsonde recon datasets

-- Improve storm size correction in the vortex initialization,

modified filter domain and use GFS vortex when the storm is

weaker than 16 m/s

-- Upgrade the nest movement algorithm using 9 parameters based

on NCEP tracker

-- Redesign nest-parent interpolations for improved treatment of

nest boundaries

-- Increase frequency of physics calls from 180 sec. to 30 sec.

and increase size of the third domain from 5-deg x 5.5-deg to

6-deg x 6.5-deg

-- Modify GFS PBL to include variable critical Richardson number

-- Fix bug for GFDL radiation

-- Remove flux truncation from HWRF to POM

-- Improve HWRF Unified Post Processor to reduce domain

discontinuities in the simulated satellite imagery products

The model has been extensively tested with a combination of all

the upgrades listed above for a 3-year sample of cases. The

results showed impressive and remarkable results. For Atlantic

basin track, the HWRF is improved by ~5-15% and now appears

competitive with the GFS. For intensity, the model reduces errors

by ~15%, has demonstrated skill greater than that of the NHC

official forecast and greater than that of the statistical

models. Similar improvements are noted for the Eastern North

Pacific basin as well.

There are no changes to existing products or their contents.

There will be an increase of roughly 1GB in product size due to

expanded size of the third domain. The grid is not changing, but

additional points will now have non-missing values.

More details about the HWRF-POM are available at:


NCEP encourages users to ensure their decoders are flexible and

are able to adequately handle changes in content order, changes

in the scaling factor component within the product definition

section (PDS) of the GRIB files, and any volume changes which

may be forthcoming. These elements may change with future NCEP

model implementations. NCEP will make every attempt to alert

users to these changes prior to any implementations.

For questions regarding these model changes, please contact:

Dr. Vijay Tallapragada

NOAA/NCEP/Environmental Modeling Center

Hurricane Forecast Project

National Centers for Weather and Climate Prediction

College Park, Maryland, 20740.



NWS National Technical Implementation Notices are online at: