882
NOUS41 KWBC 242110 AAB
PNSWSH

Service Change Notice 24-80 Updated
National Weather Service Headquarters Silver Spring MD
510 PM EDT Tue Sep 24 2024

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

From:  Judy Ghirardelli
       NWS Office of Science and Technology Integration
       Meteorological Development Laboratory

Subject: Updated: Changes and Additions to LAMP Station-based
and Gridded Guidance: Effective on or about September 30, 2024

Updated to postpone the implementation date to on or about
September 30, 2024, due to a Critical Weather Day (CWD) being
declared.

In addition to the below changes, an additional bug discovered
during NCEP stability testing will be fixed with this upgrade.
Rapid Refresh (RAP) visibility forecasts used as a first guess
in the GLMP visibility observational analysis for areas outside
the CONUS had incorrect decimal scaling, causing slightly
degraded analysis output over the affected areas of the grid.
This fix restores the intended scaling of the RAP visibility
data used as a first guess and thus will improve the visibility
analysis output over areas outside the CONUS.

The original notice follows:

On or about September 26, 2024, beginning with the 1630
Coordinated Universal Time (UTC) model run, the NWS
Meteorological Development Laboratory (MDL) will implement
changes to the Localized Aviation Model Output Statistics
Program (LAMP) station-based and Gridded LAMP (GLMP) guidance.
Comments/feedback on this upgrade were previously solicited
publicly from February 23, 2024 through March 25, 2024 via this
Public Information Statement:
https://www.weather.gov/media/notification/pdf_2023_24/pns24-
11_lamp_glmp_v2.6.pdf

In the event that the implementation date is declared a Critical
Weather Day (CWD), an Enhanced Caution Event (ECE), or other
significant weather is occurring or is anticipated to occur,
implementation of this change will take place at 1630 UTC on the
next weekday not declared a CWD and when no significant weather
is occurring.

LAMP/GLMP v2.6 will include the following enhancements/changes
in support of the National Blend of Models (NBM) and other NWS
initiatives:

1) Addition of station-based LAMP guidance for ceiling height
and visibility valid for 15-minute periods out to six hours,
updated every 15 minutes (96 cycles per day). This will include
guidance for the lowest category ceiling height and lowest
category visibility condition that is forecast to occur during
each 15-minute period. The guidance will be produced in a text
bulletin format that displays ceiling height and visibility
categories valid for 15-minute periods out to six hours for 1818
contiguous U.S. (CONUS) stations. [Note that with this upgrade,
there will be a new station bulletin for the 15-minute lowest
ceiling and visibility LAMP guidance for the new station KSMB.
Station "KSMB" in the 15-minute bulletin is a Federal Aviation
Administration (FAA)-owned Automated Weather Observing System
(AWOS) station located near the San Mateo Bridge near San
Francisco, California. The use of this designator in the LAMP
15-minute bulletin is intended to be temporary until an official
designator is approved by the FAA]. There are 19 CONUS LAMP
stations for which a 15-minute bulletin will not be produced due
to missing MOS predictor data for many projections.  A list of
the 19 LAMP stations that will not have a 15-minute bulletin can
be viewed here:
https://vlab.noaa.gov/documents/6609493/7858387/Stations_without
_a_15-min_text_bulletin_v2.6.pdf

Please note that this 15-minute LAMP guidance is in addition to
the current hourly LAMP ceiling and visibility guidance which is
valid at the top of the hour in the forecast period.  The
current hourly LAMP ceiling and visibility guidance valid at the
top of the hour is not impacted by this.

2) Addition of GLMP guidance for ceiling height and visibility
valid for 15-minute periods out to six hours, updated every 15
minutes (96 cycles per day). This will include probabilistic and
deterministic guidance for the lowest ceiling height and lowest
visibility condition that is forecast to occur during each 15-
minute period. The guidance will be produced in gridded binary
version two (GRIB2) format on the NBM CONUS domain for the
following variables:

 1. Deterministic ceiling height (m)
 2. Probability of ceiling < 500 ft (%)
 3. Probability of ceiling < 1,000 ft (%)
 4. Probability of ceiling <= 3,000 ft (%)
 5. Deterministic visibility (m)
 6. Probability of visibility < 1 mi (%)
 7. Probability of visibility < 3 mi (%)
 8. Probability of visibility <= 5 mi (%)

Please note that the spatial extent of this new guidance will be
limited to the part of the domain covered by the HRRR, and will
contain missing values outside of this area.  Also please note
that this 15-minute GLMP guidance is in addition to the current
hourly GLMP ceiling and visibility guidance which is valid at
the top of the hour in the forecast period.  The current hourly
GLMP ceiling and visibility guidance valid at the top of the
hour and which supports the NBM is not impacted by this.

3) Minor bug fixes to currently operational products that
include: A) Addition of a post-processing check for GLMP wind
gusts to prevent negative values from occurring on the grid, B)
An adjustment to the LAMP advection model to prevent large
visibility values from advecting over the station in rare cases
of high winds for stations in Hawaii, and C) Removal of a
problematic mesonet station (TRJHS - Troy, OH) from the GLMP
temperature/dewpoint analysis.

4) The following issues were discovered during or after the 30-
day user comment period and will be fixed with this
implementation:

A) Correcting the metadata for a mis-located station (KGVW -
Galveston, TX oil platform) that was being used in the LAMP
advection model analysis. Due to the mis-location, this station
was being tossed from the analysis most of the time and had
little impact on the advection output. This change is expected
to improve the advection output in the vicinity of the old
location and in the vicinity of the correct location.

B) Correcting a setting in the analysis software that controls
augmentation of LAMP station forecasts with observations and
MOS, which was impacting the currently operational GLMP wind
gust grids beyond 35 hours. The fix restores the original
intended weighting of observations and MOS in the wind gust
analysis for the 36-38 hour projections, resulting in increased
magnitudes in areas where there are few or no LAMP stations.

C) Rapid Refresh (RAP) visibility forecasts used as a first
guess in the GLMP visibility observational analysis for areas
outside the CONUS had incorrect decimal scaling, causing
slightly degraded analysis output over the affected areas of the
grid. This fix restores the intended scaling of the RAP
visibility data used as a first guess and thus will improve the
visibility analysis output over areas outside the CONUS.

Expected benefits of this LAMP/GLMP v2.6 upgrade include:

1) The addition of station-based and gridded guidance for
ceiling and visibility valid for 15-minute periods out to six
hours, updating every 15 minutes (96 cycles per day), will
provide higher temporal resolution guidance for ceiling height
and visibility to aviation users.

2) Addressing the various bugs listed above will improve the
quality of the currently operational station-based and gridded
guidance for users, including the gridded guidance used by the
NBM.

More details about LAMP/GLMP products and this implementation
can be found online at the LAMP Documentation web site:
https://vlab.noaa.gov/web/mdl/lamp-documentation

Changes to dissemination:

1) On the change date, the new text bulletins that display
ceiling height and visibility categories valid for 15-minute
periods out to six hours for 1818 CONUS stations, updating every
15 minutes (96 cycles per day), will be made available on NCEP
Web Services at:

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

with file name "lmp.tHHMMz.subhbull.f0015-f0600.txt" (where HH
is the LAMP cycle hour and MM is the LAMP cycle minute).

2) On the change date, new GRIB2 files containing probabilistic
and deterministic guidance for the lowest ceiling height and
lowest visibility condition that is forecast to occur during
each 15-minute period out to six hours on the NBM CONUS domain
will be made available on NCEP Web Services at:

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

with file names "glmp.tHHMMz.subh.fhhmm.co.grib2" (where HH is
the nominal GLMP cycle hour, MM is the nominal GLMP cycle
minute, hh is the forecast projection hour, and mm is the
forecast projection minute).

3) On the change date, the following currently operational GLMP
GRIB2 files for CONUS and Alaska NBM domains residing on NCEP
Web Services will have a change in file name:

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

Old file names:
glmp.tHH30z.master.fPPP.ak.grib2
glmp.tHH30z.master.fPPP.co.grib2
New file names:
glmp.tHH30z.hourly.fPPP.ak.grib2
glmp.tHH30z.hourly.fPPP.co.grib2
(where HH is the GLMP cycle hour and PPP is the forecast
projection 000-038).

There are no changes to LAMP or GLMP WMO headers or Satellite
Broadcast Network routing with this implementation. Complete
lists of LAMP and GLMP WMO headers can be found here:
https://vlab.noaa.gov/documents/6609493/7858387/lampheaders_2024
_v2.6.docx.pdf
https://vlab.noaa.gov/documents/6609493/7858387/glmpheaders_2024
_v2.6.docx.pdf

A consistent parallel feed of data will be available on the NCEP
parallel NOMADS site beginning at least 30 days prior to
implementation at the following locations:

https://nomads.ncep.noaa.gov/pub/data/nccf/com/lmp/para
https://nomads.ncep.noaa.gov/pub/data/nccf/com/glmp/para
https://ftpprd.ncep.noaa.gov/data/nccf/com/lmp/para
https://ftpprd.ncep.noaa.gov/data/nccf/com/glmp/para
ftp://ftpprd.ncep.noaa.gov/pub/data/nccf/com/lmp/para
ftp://ftpprd.ncep.noaa.gov/pub/data/nccf/com/glmp/para

Questions concerning parallel data should be directed to the
NCEP HPC Dataflow team at ncep.pmb.dataflow@noaa.gov.

NCEP encourages users to ensure their decoders are flexible and
are able to adequately handle changes in content format
(including format and order of variables) 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.

Questions, comments or requests regarding this change should be
directed to the contacts below.

Judy Ghirardelli
Email: judy.ghirardelli@noaa.gov
Meteorological Development Laboratory
Decision Support Division Chief
Silver Spring, MD

and/or

Phil Shafer
Email: phil.shafer@noaa.gov
Meteorological Development Laboratory
Decision Support Division
LAMP Team Lead
Silver Spring, MD

For questions relating to dataflow, please contact:

Margaret Curtis
NCEP Central Operations Acting HPC Dataflow Team Lead
ncep.pmb.dataflow@noaa.gov

Links to the LAMP products and descriptions can be found at:

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

NWS Service Change Notices are online at:

https://www.weather.gov/notification/