NOUS41 KWBC 191830



Technical Implementation Notice 13-42

National Weather Service Headquarters Washington DC

130 PM EST Tue Nov 19 2013


To: Subscribers:

-Family of Services (FOS)

-NOAA Weather Wire Service

-Emergency Managers Weather Information Network


Other NWS Users and Employees


From: Mark Tew

Chief, Marine and Coastal Weather Services Branch


Subject: Temporal Resolution of Forecasts for Hazards,

Significant Wave Heights, Wind Direction, Speed and

Gusts on the Oceanic Domain in the Experimental

National Digital Forecast Database (NDFD) Will Increase

Effective December 18, 2013


Effective Wednesday December 18, 2013 at 1400 Coordinated

Universal Time (UTC), NDFD hazards, significant wave height, wind

direction, speed and gusts provided on the oceanic domain will

become available in experimental status at 3-hour resolution

through Day 3 instead of the current 6 hour resolution. Days 4-6

will remain at 6-hour temporal resolution.


This change will enable NDFD oceanic users to access finer

resolution forecasts from the Ocean Prediction Center and most

Weather Forecast Offices. The effective resolution from the

Tropical Analysis and Forecast Branch (TAFB) and Honolulu

Forecast Office (HFO) will not increase at this time.


The significant wave height grid is the average wave height,

trough to crest, of the one-third highest waves valid for the top

of the designated hour.


-Significant wave height is the combination of wind waves and


-Wind Direction is the 10-meter wind direction using 36 points

of a compass valid at the top of the indicated hour.

-Wind Speed is defined as the sustained 10-meter wind speed, in

knots, valid at the top of the indicated hour.

-Wind gust is the maximum 3-second wind speed, in knots, forecast

to occur within a 2-minute interval at a height of 10 meters.


This change primarily affects users who pull NDFD elements in the

Gridded Binary 2 (grib2) format from the NWS file transfer

protocol (FTP) server, either via the internet or the FOS server

access service, and users who pull HTML files from the NWS

hypertext transfer protocol (http) server. Those users will now

be able to access oceanic forecasts for Day 1-3 at a finer

temporal resolution.

These grids will continue to be available from the NDFD in

grib2 files via http and ftp, and in graphics via a map viewer at

the experimental site below:


Information on accessing and using NDFD elements is online at:


If December 18, 2013, is a critical weather day, this

implementation may be postponed. Users will be notified of that

decision via another Technical Implementation Notice (TIN) as far

in advance as possible.


For general questions regarding NDFD data, please email:


For technical questions regarding NDFD data, please contact:


David Ruth

Chief, Mesoscale Prediction Branch

National Weather Service

Office of Science and Technology

Silver Spring Maryland 20910


For questions regarding this notice, please contact:


David Soroka

Manager Marine and Coastal Weather Services Branch

National Weather Service

Office of Climate Water and Weather Services

Silver Spring Maryland 20910


TINs specifically related to the NDFD are online at:

National TINs are online at