NOUS41 KWBC 201100



Service Change Notice 17-33

National Weather Service Headquarters Silver Spring, MD

700 AM EDT Mon Mar 20 2017


To: Subscribers:

-NOAA Weather Wire Service

-Emergency Managers Weather Information Network


Other NWS Partners and NWS Employees


From: Allison Allen

Chief, Marine, Tropical and Tsunami Services Branch


Subject: Expansion of the CPHC Tropical Weather Outlook to

5 Days and Introduction of a 5-Day Companion Graphic

to Match Products Issued by the NHC

Beginning on or around June 1, 2017, the Central Pacific

Hurricane Center (CPHC) will expand its 2-Day Tropical Weather

Outlook (TWO) to 5 days. CPHC will also introduce a 5-Day

Graphical Tropical Weather Outlook (GTWO) graphic in addition to

2-Day graphic already available. These changes will allow all

NWS TWO and GTWO products to have the same valid times and



The 5-Day TWO from CPHC will provide a current assessment in

plain language of areas of disturbed weather and their potential

for tropical formation over the next 120 hours for the central

Pacific basin. Like the 2-Day TWO, the new 5-Day TWO will

provide probabilistic information, in 10-percent increments,

about a system's potential for developing into a tropical

cyclone. The forecast and discussion will be provided on a

disturbance-by-disturbance basis for both the 2-day and 5-day

periods for the central Pacific basin.


The 5-Day GTWO from CPHC will be a visual companion to the 5-Day

forecast and discussion in the TWO text product and will be

produced four times daily by the CPHC for the central Pacific

basin. These changes will make CPHCs TWO and GTWO products

consistent with those issued by the National Hurricane Center

(NHC) for the Atlantic and east Pacific basins and will include

the recently approved changes to the NHC GTWO for potential

tropical cyclones as noted in Service Change Notice 17-30

Updated: Changes to the Graphical Tropical Weather Outlook

(GTWO) issued by the NHC effective on or around May 15, 2017:


The GTWO is a web-based set of graphics that identify the

locations of disturbed weather and the areas where these

disturbances could develop into tropical cyclones. Disturbance

locations, when they exist, are indicated by Xs and the

potential formation areas are shown as shaded or hatched areas.

The areas are color-coded based upon the forecast likelihood of

tropical cyclone formation in the next 2 days on the 2-Day GTWO

and 5 days on the 5-Day GTWO:

-Yellow, 30 percent or less chance

-Orange, 40-60 percent chance

-Red, 70 percent or greater chance

When a user moves the computer mouse pointer over a disturbance

in the graphic, the associated text for that disturbance pops

up. Clicking on a disturbance will display a version of the

graphic showing only that particular disturbance. Each of the

single-disturbance graphics displays the quantitative genesis

probability, given in 10 percent increments, and a

disturbance number (i.e., Disturbance 1, Disturbance 2), with

the text for each numbered disturbance given beneath the



CPHC will issue both the TWO and GTWO four times daily during

the hurricane season at 0000, 0600, 1200, and 1800 Coordinated

Universal Time (UTC). CPHC will issue special TWOs and updates

to the GTWO any time important changes have occurred that need

to be conveyed before the next scheduled issuance or outside of

hurricane season when the TWO and GTWO are not routinely issued.

The TWO and GTWO will be found on CPHC's website at:

For questions regarding this notice, please contact:


Jessica Schauer

NWS Tropical Service Program Lead

NWS Marine, Tropical and Tsunami Services Branch

Miami, FL 33165

Telephone: 305-229-4476



Wayne Presnell

NWS Marine, Tropical and Tsunami Services Branch

Silver Spring, MD 20910

Telephone: 301-427-9390



National Service Change Notices are online at: