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-------- Original Message --------
521
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@xxxxxxxx
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@xxxxxxxx
National Public Information Statements are online at:
http://www.weather.gov/os/notif.htm
$$
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