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000
NOUS41 KWBC 112110
PNSWSH

Service Change Notification 24-41
National Weather Service Headquarters Silver Spring MD
510 PM EDT Thu Apr 11 2024

To:  Subscribers
  -NOAA Weather Wire Service
  -Emergency Managers Weather Information Network
  -NOAAPORT
  Other NWS Partners, Users and Employees

From:  Geoff Manikin
  NWS Office of Science and Technology Integration
  Meteorological Development Laboratory

Subject:  Upgrade of National Blend of Models Guidance, Effective
  May 15, 2024

On or about Wednesday, May 15, 2024, beginning with the 1200
Universal
Time Coordinated (UTC) model run, the NWS Meteorological Development
Laboratory (MDL) will implement an update to the National Blend of
Models
(NBM) guidance over the Contiguous United States (CONUS) and OCONUS
(Alaska (AK), Hawaii (HI), Puerto Rico (PR), Guam (GU), and Oceanic
(OC))
National Digital Forecast Database (NDFD) domains.

In the event that the implementation date is declared a Critical
Weather
Day (CWD), an Enhanced Caution Event, or other significant weather is
occurring or is anticipated to occur, implementation of this change
will
take place at 1200 UTC on the next weekday not declared a CWD and
when no
significant weather is occurring.

1. Background

Comments/feedback on this upgrade were previously solicited publicly
from
November 20, 2023 through January 19, 2024:

https://www.weather.gov/media/notification/pdf_2023_24/pns23-
45_nbm_v4.2.pdf

NBM Version 4.2 will continue to fill existing product gaps requested
by
the Aviation, Water Resources, Marine, Winter, and Tropical NWS
Service
Programs. A listing of the new NBM v4.2 weather elements includes:
-10m instantaneous quantile mapped wind speed and wind gust guidance
in
the form of percentiles (1-99) and exceedance values (Wind speed:
7kts, 11
kts, 17 kts, 22 kts, 30 kts, 34 kts, 48 kts, and 64 kts; Wind gust:
17
kts, 22 kts, 30 kts, 34 kts, 41 kts, 48 kts, 56 kts, and 64 kts) for
the
CONUS domain

-10m instantaneous wind speed and wind gust mean and standard
deviation
derived from the quantile mapped forecasts

It is anticipated that these upgrades will benefit the NWS in its
goal
toward providing better Impact-Based Decision Support Services
(IDSS).

2. Summary of Product Enhancements

Several highlights associated with this upcoming release include the
following:

-New probabilistic Quantile Mapping-based (QM) 10m instantaneous wind
speed and wind gust percentiles and exceedance values (CONUS).
Varying
time windows of the analyzed cumulative distribution function are
used to
assist in removing daytime and nighttime biases.

-Mixing Height calculation is now dependent upon URMA surface terrain
height rather than the Rapid Refresh (RAP) model surface height
(CONUS).

-For QM Quantitative Precipitation Forecasts (QPF), smoothing is
introduced to the QM precipitation amount Cumulative Distribution
Functions (CDFs) to reduce the “lattice-like” features in the NBM
blended
snow amount for these inputs: European Centre for Medium-Range
Weather
Forecasts Ensemble (ECMWFE), Global Ensemble Forecast System (GEFS),
Global Forecast System (GFS), and Short-Range Ensemble Forecast
System
(SREF). Note that this modification was made for all regions where QM
QPF
is made (CONUS, Alaska, Hawaii, Puerto Rico, Oceanic).

-The Snow Liquid Ratio (SLR) calculation is modified by taking into
account the melting of snow where temperatures are at or above
freezing at
the surface, and the 25% reduction factor to each model input SLR
value is
removed (CONUS, Alaska).

-Usage of a downscaled wet bulb temperature for ECMWFE, GEFS, GFS,
and
SREF models for improvement in ice accumulations (CONUS, Alaska).

-Reduction of blocky precipitation type features in the winter
weather
suite by (1) omitting the parent 12km NAM as an input, (2) modifying
the
weights of the HiRes Window FV3, NAMNest, GFS, GEFS, and ECMWFE
inputs,
and (3) leveraging the downscaled the GFS (QPF) input.

-Modified usage of the HiRes Windows ARW and ARW2 in computation of
probability of precip types to remove inflated probabilities driven
by a
precipitation type computed in the output of those two models at a
much
lower precipitation rate threshold than used by other models.
Precipitation type information for those two inputs is now only used
in
the NBM when a minimum of 0.01” of precipitation falls during the
previous
hour.

-Removal of the consistency check between sky cover and ceiling
height for
CONUS and Alaska - Sky Cover percentage values can now be less than
57%
when a ceiling height is present.

-Gridded LAMP (GLMP) ceiling height is used as NBM ceiling height
over
coastal waters through hour 16 in the operational NBM, with the Rapid
Refresh (RAP) ceiling height used thereafter. In this upgrade, the
GLMP is
used through forecast hour 24 with the usage of the RAP ceiling
height
starting at forecast hour 25.

-Runtime of the tropical cyclone feature matching technique is
optimized
to preserve the National Hurricane Center’s Gridded Tropical
Cyclone
forecast advisory Message (wTCM) wind field while also ensuring a
meteorologically consistent wind field along the periphery and
outside
edges of the wTCM (CONUS, Hawaii, Puerto Rico, Guam, Oceanic).

3. NBM Product Changes

With NBM v4.2 continuing to move towards probabilistic guidance, we
have
replaced the current methodology employed to generate deterministic
wind
speed and wind gust guidance with the mean of the distribution
calculated
from the QM technique. As noted above in Section 2, the new wind
product
will be updated four times daily with no changes to the number of
available projections and hourly issuance cadence. We do note however
that
the wind direction is calculated from a separate but similar set of
model
inputs and remains unchanged from the methodology calculated in NBM
v4.1.
The following hyperlink provides a comprehensive listing of all the
multi-
model inputs used to generate the new 10m probabilistic wind speed
and
wind gust product.

NBM v4.2 10m probabilistic wind speed and wind gust multi-model
inputs:
https://www.weather.gov/media/mdl/nbm/docs_v42/NBM_v4.2_Quantile_Mapp
ed_Mo
del_Inputs_for_Probabilistic_10m_Wind_Speeds_and_Wind_Gusts.pdf

NBM v4.2 10m probabilistic wind speed and wind gust multi-model
inputs as
a function of NBM cycle issuance:
https://www.weather.gov/media/mdl/nbm/docs_v42/QMD_Run_Availability_i
n_NBM
_Model_Availability_V4.2.pdf

4. NBM Text Product Changes

A comprehensive list of stations for which deterministic-based Hourly
(NBH), Short-term (NBS), Extended (NBE), Super Extended (NBX), and
probabilistic Extended (NBP) station text bulletin guidance can be
found
at: https://vlab.noaa.gov/web/mdl/nbm-stations-v4.2

A description of all NBM text file products can be found here:
https://vlab.noaa.gov/web/mdl/nbm-textcard-v4.2

Changes to the deterministic wind speed and wind gust product:

Please note that the values in the deterministic wind speed and wind
gust
text messages are the mean of the distribution of the QM solution
noted in
section 2. The associated standard deviation values are also derived
from
the QM solution space.No changes have been made to the
probabilistic
text message to incorporate the new QM 10m wind speed and wind gust
guidance.  That update will be made with the next upgrade to NBM
v5.0.

As a reminder, the file names of the five types of NBM text messages
are:

a. blend_nbhtx.t[hh]z  [where hh=00,01,02,...,23]
b. blend_nbstx.t[hh]z  [where hh=00,01,02,...,23]
c. blend_nbetx.t[hh]z  [where hh=00,01,02,...,23]
d. blend_nbxtx.t[hh]z  [where hh=00,01,02,...,23]
e. blend_nbptx.t[hh]z  [where hh=00,01,02,...,23]

For a comprehensive document fully describing changes to the text
products, please refer to Section 7 - “NCEP Web Services
(NOMADS/FTPPRD)
Dissemination”.

5. NBM Runtime Changes

With the implementation of v4.2, dissemination delays can be expected
for
many of the quantile mapped products with shorter delays for a
majority of
the NBM core products. In some instances, however, users can expect
earlier arrival times of the data. For specific timing information
please
see the following link:
https://www.weather.gov/media/mdl/nbm/docs_v42/Dissemination_Timing_D
iffer
ences.pdf

6. Changes to SBN/NOAAPORT Dissemination

While the NBM runs hourly and produces output to 264 hours for each
cycle,
as with NBM v4.1, only a subset will be disseminated across the
Satellite
Broadcast Network (SBN) and NOAAPORT due to bandwidth limitations.
NBM
v4.2 data will be disseminated in GRIB2 format and will contain
grouped
WMO headers, as is done in NBM v4.1.

With the implementation of NBM v4.2, the notable SBN/NOAAPORT
dissemination time changes can be summarized as follows:
-Fixed headers not matching the header scheme for the following
elements
(no net change in SBN bandwidth):
  - 6-h Probability of Thunder
  - Daytime Maximum and Nighttime Minimum Temperature
    Probabilities and Percentiles
  - 24-h, 48-h, and 72-h Ice and Snow Amounts
  - Solar Radiation
  - Maximum Hourly Reflectivity
  - Probability of Tornado, Severe Hail, and Severe Wind
  - Some elements at 2200 UTC and 2300 UTC not shifting day 1
    to day 0
    (i.e. ended in "Bxx" instead of "Axx")
  - All Global Domain Headers
New weather elements added:
 - Wind Speed and Wind Gust Percentiles (10th, 50th, and 90th) and
Wind
   Gust Standard Deviation in the CONUS domain
 - 6-h Probability of Precipitation in the Guam domain
 - Tropical Wind Speed in the Oceanic domain
Changes to SBN data as requested by various regions:
 - 12-h Probability of Precipitation now extends to 263 hours in the
   Alaska, Hawaii, and Guam domains
 - 2m Temperature, daily Maximum and Minimum Temperature, 6-h QPF,
Snow
   Level now extends to 263 hours in the CONUS and Alaska domains
 - 6-h and 12-h Probability of Thunder now extends to 191 hours in
the
   Alaska domain
 - Removal of "off-hour" Wind Speed, Direction, and Gust in CONUS to
   avoid duplication of data
A detailed listing of NBM v4.2 weather elements to be disseminated on
the
SBN/NOAAPORT as a function of cycle time and domains can be found in
the
following hyperlink:
https://vlab.noaa.gov/web/mdl/nbm-data-availability-v4.2

Unique originating center IDs have been assigned to each
geographic region.

List of originating center IDs (CCCC) for NBM products:

Geographic Region      Originating Center (CCCC)
-----------------      ------------------------
CONUS and Oceanic      KWEA, KWEB, KWEI, KWEO
Alaska       KWEC, KWED, KWEJ, KWEP
Hawaii       KWEE, KWEF, KWEK
Puerto Rico       KWEG, KWEH, KWEL
Guam       KWEM, KWEN, KWEQ
Global       KWER

The NBM text bulletin WMO header information for each of the five
bulletins to be disseminated every hour on the SBN is listed below.

WMO header information for NBM text products:

WMO Header     NBM Text Bulletin Description
----------     -----------------------------
FOUS15 KWNO    Hourly bulletin (1-24 hours)
FOUS16 KWNO    Short-range bulletin (6-66 hours)
FEUS16 KWNO    Extended bulletin (12-192 hours)
FEUS17 KWNO    Extra-extended bulletin (204-264 hours)
FEUS18 KWNO    Probabilistic extended bulletin (12-192 hours)

NBM v4.2 SBN/NOAAPORT Header Additions and Removals:

A detailed listing of NBM WMO headers (by NBM domain) to be added
over the
SBN/NOAAPORT can be found below:

CONUS Domain:
https://www.weather.gov/media/mdl/nbm/docs_v42/headers_additions_co.p
df
Alaska Domain:
https://www.weather.gov/media/mdl/nbm/docs_v42/headers_additions_ak.p
df
Hawaii Domain:
https://www.weather.gov/media/mdl/nbm/docs_v42/headers_additions_hi.p
df
Puerto Rico Domain:
https://www.weather.gov/media/mdl/nbm/docs_v42/headers_additions_pr.p
df
Guam Domain:
https://www.weather.gov/media/mdl/nbm/docs_v42/headers_additions_gu.p
df
Oceanic Domain:
https://www.weather.gov/media/mdl/nbm/docs_v42/headers_additions_oc.p
df
Global Domain:
https://www.weather.gov/media/mdl/nbm/docs_v42/headers_additions_glob
al.pd
f
A detailed listing of NBM WMO headers (by NBM domain) to be removed
from
the SBN/NOAAPORT can be found below:

CONUS Domain:
https://www.weather.gov/media/mdl/nbm/docs_v42/headers_removed_co.pdf
Alaska Domain:
https://www.weather.gov/media/mdl/nbm/docs_v42/headers_removed_ak.pdf
Hawaii Domain:
https://www.weather.gov/media/mdl/nbm/docs_v42/headers_removed_hi.pdf
Puerto Rico Domain:
https://www.weather.gov/media/mdl/nbm/docs_v42/headers_removed_pr.pdf
Guam Domain:
https://www.weather.gov/media/mdl/nbm/docs_v42/headers_removed_gu.pdf
Oceanic Domain:
https://www.weather.gov/media/mdl/nbm/docs_v42/headers_removed_oc.pdf

Global Domain:
https://www.weather.gov/media/mdl/nbm/docs_v42/headers_removed_global
.pdf

A. GRIB2 SBN/NOAAPORT output additions and removals:

https://www.weather.gov/media/mdl/nbm/docs_v42/NBM_v4.2_SBN_Product_A
dditi
ons_and_Removals.pdf

NBM v4.2 GRIB2 header identifiers delineated by weather element and
domain
can be found here:

https://www.weather.gov/media/mdl/nbm/docs_v42/NBM_v4.2_Header_Scheme
.pdf

B. Text Bulletins on SBN/NOAAPORT:

NBH, NBS, NBE, NBX, and NBP will continue to be hosted on the
SBN/NOAAPORT
as in NBM v4.1. This station-based guidance covers 12-hour periods
for
projections 24-192 hours and has an identical format to the NBM v4.1
deterministic NBM extended ASCII text bulletins. Note that wind speed
percentile information found for all stations in the text bulletins
are
from the forecasts made in the Oceanic Domain, and not the Quantile
Mapping system. This is unchanged from the previous version.

Header information for the probabilistic and deterministic text
bulletin
files are identical to that of NBM v4.1. For reference, that header
information can be found here:

https://www.weather.gov/media/mdl/nbm/docs_v42/NBM_V4.2_Text_Product_
WMO_H
eader_Scheme.pdf

7. NCEP Web Services (NOMADS/FTPPRD) Dissemination

On implementation day, all GRIB2 master (Core and QMD) files, index
files,
and NBM text messages will continue to be hosted on NCEP web
services.
Please follow any one of the three subsequent hyperlinks to access
this
data:

https://nomads.ncep.noaa.gov/pub/data/nccf/com/blend/prod/
https://ftpprd.ncep.noaa.gov/data/nccf/com/blend/prod/
ftp://ftp.ncep.noaa.gov/pub/data/nccf/com/blend/prod/

Please note that the naming convention and directory structure for
the
Master GRIB2 files remain unchanged and delineate between the core
NBM
products and those derived from the QMD process.

File Naming Convention:
core/blend.tCCz.core.fHHH.rg.grib2 and
qmd/blend.tCCz.qmd.fHHH.rg.grib2,
where CC=NBM cycle time, HHH=forecast projection, and rg=NBM domain
that
includes: co, ak, hi, pr, oc, gu, global (core only)

On implementation day, forecasts from the “global” domain will
begin to
populate NCEP Web Services at the locations listed above at the 0000
UTC
and 1200 UTC cycles only. The ”global” domain is on a 50
kilometer
resolution grid, covering 85 degrees South to 85 degrees North
latitude
and 180 degrees West to 180 degrees East longitude. Elements include
Geopotential Height, Relative Humidity, Temperature, Wind Speed, and
Wind
Direction at the following pressure levels: 250, 500, 700, 850, and
925
millibars.

Changes to existing files on NOMADS/FTPPRD:

These links detail the elements added to or removed from output that
is
hosted on NOMADS/FTPPRD:

https://www.weather.gov/media/mdl/nbm/docs_v42/NBM_v4.2_NOMADS_Change
s-
Text.pdf
https://www.weather.gov/media/mdl/nbm/docs_v42/NBM_v4.2_NOMADS_Change
s-
Core.pdf
https://www.weather.gov/media/mdl/nbm/docs_v42/NBM_v4.2_NOMADS_Change
s-
QMD.pdf

Prior to implementation, users may find parallel NBM data for
download
here:
https://nomads.ncep.noaa.gov/pub/data/nccf/com/blend/para/
https://para.nomads.ncep.noaa.gov/pub/data/nccf/noaaport/blend/
https://vlab.noaa.gov/web/mdl/nbm-text-products

NCEP encourages users to ensure their decoders are flexible and are
able
to adequately handle changes in content order, changes in the scaling
factor component within the product definition section (PDS) of the
GRIB
files, and any volume changes that may be forthcoming. These elements
may
change with future NCEP model implementations. NCEP will make every
attempt to alert users to these changes prior to any implementations.

Any questions, comments or requests regarding this implementation
should
be directed to the contacts below. We will
review any feedback and decide whether to proceed.




For questions regarding the implementation of NBM guidance or data
available on Amazon Web Services, please contact:

Geoff Manikin
SMD Chief
MDL/Silver Spring, Maryland
geoffrey.manikin@noaa.gov

or

David Rudack
NBM Team Lead
MDL/Silver Spring, Maryland
david.rudack@noaa.gov

For questions regarding the data flow for NWS/NCEP services, please
contact:

Tony Salemi
NCEP Central Operations Acting Dataflow Team Lead
ncep.pmb.dataflow@noaa.gov

A web page describing the NBM can be found at:

https://vlab.noaa.gov/web/mdl/nbm

National Service Change Notices are online at:

http://www.weather.gov/notification