Public Information Statement
Issued by NWS National HQ
Issued by NWS National HQ
327 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 Centers 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