NOUS41 KWBC 231057 AAA



Technical Implementation Notice 13-23, Amended

National Weather Service Headquarters Washington DC

658 AM EDT Mon Sep 23 2013


To:       Subscribers:

          -Family of Services

          -NOAA Weather Wire Service

          -Emergency Managers Weather Information Network


          Other NWS Partners, Users and Employees


From:     Timothy McClung

          Science Plans Branch Chief

          Office of Science and Technology


Subject:  Amended: Temporary Change to Preemption of HIRESW:

          Effective August 13, 2013, updated September 19, 2013.


Amended to temporarily suspend all preemption of the High-

Resolution Window Forecast System (HIRESW) system for the 2013

hurricane season 


With the increased size and power of the Weather and Climate

Operational Supercomputing System (WCOSS), the preemption of the

HIRESW runs will be suspended and NWS will run HIRESW and the

hurricane models concurrently. This change will allow HIRESW to

provide heavy precipitation (e.g., Colorado floods) and severe

weather guidance without affecting the Hurricane Center requests

for runs of hurricane models.  This change will ensure there will

be no breaks in the Hurricane Weather Research and Forecast

System data assimilation cycle that was introduced this season. 

Previously on August 13, 2013, NCEP relaxed the preemption of the

HIRES to only preempt for four or more storms, but effective

immediately no HIRESW runs will be preempted for the remainder of

the 2013 hurricane season. Below is the text from the original

TIN. Preemption is expected to return for the 2014 hurricane



Effective on or about Tuesday, August 13, 2013, beginning with

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

Centers for Environmental Prediction (NCEP) will modify the

preemption of the High-Resolution Window Forecast System



Due to resource limitations, NWS has had to cancel select HIRESW

runs during hurricane season depending on the number of hurricane

models running during that cycle. Currently, the HIRESW runs are

preempted when there are 3 or more tropical storms being run.


Because of the increased size and power of the new WCOSS

supercomputers, beginning August 13, the HIRESW runs will not be

preempted until 4 or more tropical storms are being run. This

rule will apply for the remainder of the 2013 hurricane season

only. Once the HIRESW suite is upgraded late this year or early

next year, the preemption limit likely will return to a smaller

number of storms. With a subsequent upgrade to either the

Hurricane Weather and Research Forecast (HWRF) or the HIRESW, the

preemption could begin with just 1 storm. A new Technical

Implementation Notice would alert users to such a change.


Long term, the HIRESW functionality will be covered by the High

Resolution Rapid Refresh ENSEMBLE (HRRRE), which will provide 

18-24 hour guidance updated hourly, and by the Short Range

Ensemble Forecast (SREF), which will provide longer range

ensemble guidance by extending the HRRRE members to 48-60 hours,

4 times per day.  This configuration (roughly 2018) will

alleviate the need for any preemption.


For questions regarding these model changes, please contact:


  Geoff Dimego

  NCEP/EMC, Mesoscale Modeling Branch

  College Park, Maryland, 20740



NWS National Technical Implementation Notices are online at: