NOUS41 KWBC 061554

PNSWSH     

 

Public Information Statement, Comment Request

National Weather Service Headquarters Washington DC

1055 AM EST Wed Nov 6 2013

 

To:      Subscribers:

         -Family of Services

         -NOAA Weather Wire Service

         -Emergency Managers Weather Information Network

         -NOAAPORT

         Other NWS Partners and Employees

 

From:    Kathryn Gilbert

         Chief, Statistical Modeling Branch

         Meteorological Development Laboratory

 

Subject: Soliciting Comments on Proposed Additions to the

         Global Forecast System (GFS)-Based Gridded MOS

         Products over the CONUS and Alaska through

         December 6, 2013

 

The NWS Meteorological Development Laboratory (MDL) is

soliciting public comments by December 6, 2013, on the

proposed addition of several weather elements to the GFS-

Based Gridded Model Output Statistics (GMOS) Guidance over

the CONUS and Alaska.

 

1. Addition of precipitation type and PoPO

 

MDL is proposing to add the following precipitation type

guidance to the suite of GFS-based Gridded MOS over the CONUS

and Alaska:

 

  (1) Conditional probability of freezing precipitation

  (2) Conditional probability of frozen precipitation

  (3) Conditional probability of liquid precipitation

  (4) Conditional precipitation type best category

 

Equations for precipitation type probability are derived from

present weather observations at METAR sites and then

evaluated directly at each NDGD gridpoint to produce the

gridded forecasts. A gridded best category forecast is

generated by applying statistically-derived thresholds to the

probability forecasts at each gridpoint. Forecasts are

produced for valid times every 3 hours (on the hour) out to

192 hours in advance for the 0000 and 1200 UTC model cycles.

 

The precipitation type probability and best category

forecasts are conditional on some form of precipitation

occurring at the top of the valid hour. For users who wish to

calculate unconditional probabilities for precipitation type,

MDL is proposing to add the Probability of Precipitation

Occurrence on the hour (PoPO). Like precipitation type, PoPO

is derived from present weather observations at METAR sites,

and the resulting MOS equations are applied directly at each

grid point. The unconditional precipitation type probability

is the product of the conditional probability and the PoPO

value. Forecasts for PoPO are produced for the same valid

times as precipitation type, i.e., for every 3 hours out to

192 hours in advance for the 0000 and 1200 UTC cycles.  

 

Graphics, links to GRIB2 data for download, and more details

on the experimental GFS-based precipitation type products

over the CONUS and Alaska can be found at:

 

   http://www.mdl.nws.noaa.gov/~mos/gmos/ptype_conus2p5/

 

   http://www.mdl.nws.noaa.gov/~mos/gmos/ptype_alaska/

 

 

2. Addition of predominant weather and PPI

 

MDL is proposing to add grids of predominant weather and

Precipitation Potential Index (PPI) to the suite of GFS-based

gridded MOS guidance over the CONUS and Alaska. The

experimental MOS weather grid is the predominant weather

valid at the indicated hour, generated from a collection of

other gridded MOS elements. The gridded MOS weather element

provides type, probability, and intensity information valid

every 3 hours out to 192 hours in advance.

 

PPI supports the categorical information provided by the GMOS

weather grid. PPI values range from 0 to 100 and resemble

PoP12 values in magnitude. The PoP12 for any 12-hour period

can be derived by taking the maximum PPI value within the

desired period. PPI is not a probability forecast, which has

different statistical characteristics. For example, as

temporal resolution increases, probability should decrease

(i.e., 12-hour PoP forecasts will have a larger magnitude

than 6-h PoP forecasts). As temporal resolution increases,

the magnitude of PPI is unaffected. Forecasts for PPI are

produced for every 3 hours out to 192 hours in advance for

the 0000 and 1200 UTC cycles. 

 

Graphics, links to GRIB2 data for download, and more details

on the experimental weather grid and PPI over the CONUS and

Alaska can be found at the following link:

 

   http://www.mdl.nws.noaa.gov/~wxgrid/index.php

 

Users are encouraged to provide feedback on these

experimental products by using the brief survey and comment

form available at the following link:

 

   http://www.nws.noaa.gov/survey/nws-survey.php?code=GPTPW

 

General information on the gridded MOS file structure and

additional references is available at:

 

   http://www.weather.gov/mdl/synop/gmos.php

 

Comments and questions regarding the proposed addition of

precipitation type to the GFS-Based Gridded MOS suite over

the CONUS and Alaska should be submitted to:

 

  Phil Shafer

  NWS Meteorological Development Laboratory

  301 713-0023 x113

  Phil.Shafer@noaa.gov

 

Comments and questions regarding the proposed addition of

predominant weather and PPI to the GFS-Based Gridded MOS

suite over the CONUS and Alaska should be submitted to:

 

  Tabitha Huntemann

  NWS Meteorological Development Laboratory

  301 713-0224 x119

  Tabitha.Huntemann@noaa.gov

 

National Public Information Statements are online at:

 

   http://www.weather.gov/os/notif.htm

 

$$