MOS Expanded Change Logs (2001-2007)

June 05, 2007

GFS MOS Sky Cover Changes from Total to Opaque Sky

On June 5, 2007, 12Z, the Sky Cover (SKY) guidance in the short-range GFS MAV MOS was changed from Total Sky Coverage to Opaque Sky Coverage (this change will be made to the extended-range GFS MEX MOS at a later date). The MOS Sky Cover guidance predicts an estimate of the total percentage of the sky covered by clouds in terms of the five categories reported in the METAR observations: clear (CLR), few (FEW), scattered (SCT), broken (BKN), or overcast (OVR). The old Total Sky Cover guidance did not distinguish between opaque and translucent cloud cover. The new Opaque Sky Cover guidance produces an estimate of only clouds judged to be opaque. The anticipated effect of this change is to decrease the number of broken or overcast forecasts and to increase the number of clear or few forecasts when only cirrus clouds are expected.

This change will make the MOS guidance consistent with the NWS requirement for opaque sky cover information. Moreover, verifications of the two Sky Cover guidance systems indicate the new Opaque Sky Cover guidance is more skillful than the old Total Sky Cover guidance system.

Verification Charts:

Note: We do not have GOES Satellite Cloud Product (SCP) coverage over Alaska, so our new guidance for Alaska is not truly an opaque sky cover product, but rather a total sky cover.

Febuary 08, 2005

Effective with the 1200 UTC forecast cycle on February 8, 2005, MDL will be making a series of changes to the MOS products. These changes include new GFS BUFR products, new Eta BUFR products, increasing the frequency of issuance and stations available in the GFS-based coop MOS products, and new Eta marine text product. All of these changes are outlined below.

New GFS MOS BUFR products

We have redesigned the short-range GFS-based BUFR products to include updated elements and more stations. These products will contain GFS-based MOS forecasts for 6 to 84 hours from the 0000, 0600, 1200, and 1800 UTC model cycles. At some future date we will remove the current GFS-based BUFR products once customers have had a chance to modify their processes for the new products. The webpage http://www.nws.noaa.gov/mdl/synop/bufr.html has more details on our BUFR products, including WMO headers, and product content. Please see Technical Information Notice #04-53 for the official notification.

New Eta MOS BUFR products

We will begin issuing Eta-based MOS forecasts in BUFR format for 6 - 84 hours from the 0000 and 1200 UTC model cycles. The webpage http://www.nws.noaa.gov/mdl/synop/bufr.html has more details on our BUFR products, including WMO headers, and product content. Please see Technical Information Notice #04-52 for the official notification.

Changes to GFS-based MOS for cooperative observer stations

We will begin disseminating the short- and extended-range GFS MOS text products for cooperative observer stations over NOAAPORT and the SBN. We will be adding an extended-range text product at the 1200 UTC cycle, in addition to the current 0000 UTC product. A sample of the 12Z product is available here. The stations contained in all the coop text products will also change. We have added more sites to the message. A list of the 5656 sites available in the messages is available here. More details about the MOS guidance for cooperative observer sites is available at http://www.nws.noaa.gov/mdl/synop/coop.htm. Please see Technical Information Notice #04-54 for the official notification.

New Eta-based text product for marine sites

We will begin producing a text product containing temperature, dew point temperature, wind speed and direction guidance from the 0000 and 1200 UTC cycles of the Eta model. More details about the MOS marine guidance are available at http://www.nws.noaa.gov/mdl/synop/marinedesc.htm . Please see Technical Information Notice #04-51 for the official notification.

September 17, 2003

New Eta MOS Thunderstorm and Severe Thunderstorm Guidance

Effective with the 1200 UTC forecast cycle on September 17, 2002, guidance for the probability of thunderstorms and severe thunderstorms will be added to the Eta MOS messages. The probability of thunderstorm guidance provides forecasts of the probability of a thunderstorm in a 6-, 12- or 24-h period. Because the thunderstorm guidance was developed from lightning strike data extracted from the National Lightning Detection Network (NLDN), guidance is only provided for sites in the contiguous United States (CONUS). Both the thunderstorm and conditional severe storm probabilities are available year-round for stations in the CONUS. Forecast equations were developed for three seasons: Spring (March 16 - June 30), Summer (July 1 - October 15), and Cool (October 16 - March 15).

Sample Message 

KSAT   ETA MOS GUIDANCE    8/09/2002  0000 UTC
DT /AUG   9            /AUG  10                /AUG  11
HR   06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 03 06 09 12
.
.
.
T06      8/ 0  7/ 0 47/10 28/ 5  6/ 1  6/ 0 57/12 32/ 6 11/ 2
T12           15/ 0       57/12       14/ 2       61/13

The T06 line represents forecasts for the probability of thunderstorms (to the left of the diagonal) and the conditional probability of severe thunderstorms (to the right of the diagonal) during a 6-h period. The 6-h probability forecasts are valid for intervals of 6-12, 12-18, 18-24, 24-30, 30-36, 36-42, 42-48, 48-54, and 54-60 hours after the initial data times (0000 and 1200 UTC). In the message, the pair of forecast values is displayed under the ending time of the 6-h period. The thunderstorm probability is given to the nearest whole percent. Values range from 0 to 100%. A missing forecast value is indicated by 999. The conditional severe thunderstorm probability is given to the nearest whole percent. Values range from 0 to 98%. A missing forecast value is given by 99.

The T12 line represents forecasts for the probability of thunderstorms (to the left of the diagonal) and the conditional probability of severe thunderstorms (to the right of the diagonal) occurring during a 12-h period. The 12-h probability forecasts are valid for intervals of 6-18, 18-30, 30-42, and 42-54 hours after the initial data times (0000 and 1200 UTC). In the message, the pair of forecast values is displayed under the ending time of the 12-h period. The thunderstorm probability is given to the nearest whole percent. Values range from 0 to 100%. A missing forecast value is indicated by 999. The conditional severe thunderstorm probability is given to the nearest whole percent. Values range from 0 to 98%. A missing forecast value is given by 99.

During the development, the lightning data were placed on a 48 km grid, and all of the strikes that occurred anywhere in the 48 km grid box were assigned to the center point of the grid box. This is an areal forecast covering the grid box, and the forecast verifies when a thunderstorm occurs anywhere in the grid box.

For the text messages, a nearest neighbor approach was used to match each CONUS MOS site to the closest thunderstorm grid point. For the GRIB and graphics products, the forecasts have been analyzed to a 40 km Lambert Conformal grid covering the CONUS and about 150 km beyond.

May 6, 2003

AWIPS CHANGE NOTICE NO AB370

TENTATIVE EFFECTIVE DATE MAY 06 2003

[AB370] ON THE ABOVE EFFECTIVE DATE THE ADDITION OF GFS MOS MARINE WIND SPEED AND DIRECTION ALPHANUMERIC GUIDANCE PRODUCTS WILL BE ADDED TO THE SATELLITE BROADCAST NETWORK. GUIDANCE WILL BE PROVIDED FOR FORECAST PROJECTIONS OF 6 THROUGH 84 HOURS FOR WIND SPEED AND DIRECTION.

CHRISTOPHER MCALOON [301] 713-0023 EXTENSION 141 IS THE COGNIZANT TECHNICAL INDIVIDUAL. ANTHONY ROBINSON [301] 713-1373 EXTENSION 165 IS THE DRG FOCAL POINT FOR THIS ITEM.

THE FOLLOWING PRODUCTS WILL BE ADDED TO THE SATELLITE BROADCAST NETWORK:

AWIPS ID  WMO HEADINGS
--------  ------------
MMGHI1    FQPA20 KWNO
MMGNE1    FQUS21 KWNO
MMGSE1    FQUS22 KWNO
MMGGL1    FQUS23 KWNO
MMGGF1    FQUS24 KWNO
MMGNW1    FQUS25 KWNO
MMGSW1    FQUS26 KWNO
MMGAK1    FQAK37 KWNO

LLOYD E. IRVIN CHIEF GRAPHICS & DISPLAY SECTION

October 1, 2002

Improved AVN MOS Probability of Precipitation (PoP) and Quantitative Precipitation Forecast (QPF) guidance for Hawaii

Effective with the 0000 UTC cycle on October 1, 2002, MDL will implement a new system of AVN MOS Probability of Precipitation (PoP) and Quantitative Precipitation Forecast (QPF) guidance for Hawaii. Equations in this new forecast system have been developed to enhance the representation of local climatic effects in the MOS forecasts and to improve apparent shortcomings in the forecasts at Lihue (PHLI) and Kona (PHKO). In order to accomplish this, stations in the new PoP/QPF system were grouped so as to develop two sets of regionalized operator equations in place of the original single set of equations valid for all of Hawaii. The new forecast regions were chosen to differentiate among stations which have a high climatic relative frequency of precipitation and those stations which are drier due to their locations with respect to high terrain and the prevailing winds. We also have enlarged the developmental data sample by including data which were not yet available at the time the original AVN MOS system was developed, namely observations from three additional sites and a complete complement of model and predictand data from the 2001-2002 cool season.
For a complete summary of the AVN MOS products, including graphical displays of the probabilities, please view the: MOS Forecast Products Page

September 18, 2002

Wind Guidance added to the MRF MOS Messages

Effective on or about September 18, 2002, guidance for maximum sustained surface wind speed (WND) during a 12-h period will be added to the MRF MOS alphanumeric and BUFR messages produced from the 0000 UTC run of the NWS Global Forecast System (GFS). Guidance for the wind speed will be available in the alphanumeric message for forecast projections valid every 12 hours ending 24 to 192 hours after 0000 UTC. The forecasts are valid for the 1200-0000 and 0000-1200 UTC periods. In the development of the equations used to produce this guidance, the record observations at all hours between 1200 and 0000 UTC (or between 0000 and 1200 UTC) were examined, and the maximum sustained wind speed was extracted. The equations were derived for individual stations.

Since the wind speed is continuous, a full range of forecast values is possible and will be displayed in the message in units of knots. Likewise, because equations were developed for individual stations, missing forecasts are possible if the station was not open full-time during the period of record used for development. A missing forecast is denoted by 999. Finally, please note that the wind speed forecasts are inflated before dissemination to the users, as is done with MOS wind speed forecasts valid at specific hours. In AWIPS, the MRF MOS alphanumeric messages are available as the MEXxxx product where xxx denotes the station identifier (3 characters). See Technical Procedures Bulletin No. 460 at TPB 460 for further details about the MEX product. Note, however, that the description of the WND guidance is incorrect in the TPB. A modified TPB will be forthcoming soon.

In addition to the guidance for sustained wind speed, the BUFR messages contain probabilistic forecasts of four categories of wind speed, namely, speeds less than 13 knots, 13 to 21 knots, 22 to 33 knots, and 34 knots or greater. Guidance is valid for projections every 12 hours from 24 to 192 hours after 0000 UTC.

September 17, 2002

0600 and 1800 UTC Visibility and Obstruction to Vision Forecasts

Effective on or about September 18, 2002, guidance for visibility (VIS) and obstruction to vision (OBV) will be added to the AVN MOS alphanumeric and BUFR messages produced from the 0600 and 1800 UTC runs of the NWS Global Forecast System (GFS). Guidance for VIS and OBV will be available in the alphanumeric message for forecast projections valid every 3 hours from 6 to 60 hours after 0600/1800 UTC, as well as 66 and 72 hours after 0600 and 1800 UTC. Categorical forecasts in the message denote predicted conditions of visibility (1 = < 1/4 mi; 2 = > 1/4 mi to 1/2 mi; 3 = > 1/2 mi to < 1 mi; 4 = 1 to < 3 mi; 5 = 3 to 5 mi; 6 = 6 mi; 7 = > 6 mi) and expected non-precipitating obstructions to vision (N = none; HZ = haze, smoke, dust; BR = mist (fog with visibility > 5/8 mi); FG = fog or ground fog (visibility < 5/8 mi); BL = blowing dust, sand, snow) at specific locations. In AWIPS, the alphanumeric messages are available as the MAVxxx product where xxx denotes the station identifier (3 characters). See Technical Procedures Bulletin No. 481 for further details.

The BUFR messages contain probabilistic forecasts of the categories of visibility and obstruction to vision as well as the categorical guidance. Guidance is valid for projections every 3 hours from 6 to 78 hours after 0600/1800 UTC.

Finally, note that when this change is made, the MOS equations used to predict visibility and obstruction to vision during the 0000 and 1200 UTC forecast cycles will also be revised; additional model and observational data were used to redevelop the forecast equations.

New Probability of Precipitation Occurrence Forecasts

Effective on or about September 18, 2002, the probability of precipitation occurrence (PoPO) at a specific hour and the probability of precipitation occurrence over a 3-h period (PoPO3) will be added to the AVN MOS BUFR messages produced from all four runs of the NWS Global Forecast System (GFS). Guidance for PoPO and PoPO3 will be available for forecast projections valid every 3 hours from 6 to 78 hours after 0000, 0600, 1200, and 1800 UTC.

The BUFR messages are used primarily to support the Interactive Forecast Preparation System (IFPS). The PoPO denotes the likelihood of precipitation in any form occurring at a specific time. The PoPO3 indicates the likelihood of precipitation in any form occurring within a 3-h period ending at the specified hour. In both instances, the definition of the event differs from that used for the probability of precipitation (PoP). For PoPO, the event is defined as occurring if the METAR record observation at the hour reports precipitation. For the PoPO3, the event is defined as occurring if any one of the four METAR record observations for the 3-h period ending at the specified time reports precipitation. For example, the PoPO3 forecast for a period ending at 1200 UTC indicates whether precipitation is expected in any of the record observations taken at 0900, 1000, 1100, or 1200 UTC. Unlike PoP which predicts measurable precipitation over some interval of time, PoPO predicts precipitation occurrence at specific hours.

September 17, 2002

New Eta MOS Thunderstorm and Severe Thunderstorm Guidance

Effective with the 1200 UTC forecast cycle on September 17, 2002, guidance for the probability of thunderstorms and severe thunderstorms will be added to the Eta MOS messages. The probability of thunderstorm guidance provides forecasts of the probability of a thunderstorm in a 6-, 12- or 24-h period. Because the thunderstorm guidance was developed from lightning strike data extracted from the National Lightning Detection Network (NLDN), guidance is only provided for sites in the contiguous United States (CONUS). Both the thunderstorm and conditional severe storm probabilities are available year-round for stations in the CONUS. Forecast equations were developed for three seasons: Spring (March 16 - June 30), Summer (July 1 - October 15), and Cool (October 16 - March 15).

Sample Message 

KSAT   ETA MOS GUIDANCE    8/09/2002  0000 UTC
DT /AUG   9            /AUG  10                /AUG  11
HR   06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 03 06 09 12
.
.
.
T06      8/ 0  7/ 0 47/10 28/ 5  6/ 1  6/ 0 57/12 32/ 6 11/ 2
T12           15/ 0       57/12       14/ 2       61/13

The T06 line represents forecasts for the probability of thunderstorms (to the left of the diagonal) and the conditional probability of severe thunderstorms (to the right of the diagonal) during a 6-h period. The 6-h probability forecasts are valid for intervals of 6-12, 12-18, 18-24, 24-30, 30-36, 36-42, 42-48, 48-54, and 54-60 hours after the initial data times (0000 and 1200 UTC). In the message, the pair of forecast values is displayed under the ending time of the 6-h period. The thunderstorm probability is given to the nearest whole percent. Values range from 0 to 100%. A missing forecast value is indicated by 999. The conditional severe thunderstorm probability is given to the nearest whole percent. Values range from 0 to 98%. A missing forecast value is given by 99.

The T12 line represents forecasts for the probability of thunderstorms (to the left of the diagonal) and the conditional probability of severe thunderstorms (to the right of the diagonal) occurring during a 12-h period. The 12-h probability forecasts are valid for intervals of 6-18, 18-30, 30-42, and 42-54 hours after the initial data times (0000 and 1200 UTC). In the message, the pair of forecast values is displayed under the ending time of the 12-h period. The thunderstorm probability is given to the nearest whole percent. Values range from 0 to 100%. A missing forecast value is indicated by 999. The conditional severe thunderstorm probability is given to the nearest whole percent. Values range from 0 to 98%. A missing forecast value is given by 99.

During the development, the lightning data were placed on a 48 km grid, and all of the strikes that occurred anywhere in the 48 km grid box were assigned to the center point of the grid box. This is an areal forecast covering the grid box, and the forecast verifies when a thunderstorm occurs anywhere in the grid box.

For the text messages, a nearest neighbor approach was used to match each CONUS MOS site to the closest thunderstorm grid point. For the GRIB and graphics products, the forecasts have been analyzed to a 40 km Lambert Conformal grid covering the CONUS and about 150 km beyond.

September 16, 2002

Changes to Text Message by Station List - Form Method

On Monday, September 16, 2002 we made some changes to our web pages. We have had several requests asking us to change the method used to post the requests of MOS bulletins by station names. These changes will allow users more flexibility in automatically retrieving desired station text bulletins. In addition, if a user is interested in requesting the same set of stations everyday, he/she will be able to bookmark the link to request those stations without going through the selection form each time.

We have also added a new link which will allow users to select a station id, or group of ids, and get back multiple versions of the MOS guidance. Our One-Stop MOS link will return the MOS text products from the AVN-, MRF- and Eta-based MOS messages for the desired stations in one request. We hope to add the NGM stations soon, but the NGM uses an older form of the station list which will require a little more time and thought on our end to fit into the script.

For those users who like the programming details, we changed the FORM METHOD from "POST" to "GET" and changed our cgi scripting language from Fortran to Perl. If you want to get to the desired stations without going through the form, the stations can be entered on the URL line following the question marks at the end of the address. For an example, try https://weather.gov/cgi-bin/mos/getmet.pl?sta=KDCA

August 21, 2002

On Wednesday, August 21, 2002, MDL's data on tgsv1.nws.noaa.gov will be transitioned to the new NWS FTP server, TGFTP, at tgftp.nws.noaa.gov . The new server has increased capacity and should provide more robust service. TGFTP will have 24x7 technical support provided by the Tech Control Center, which can be reached at (301) 713-0902. For those of you who subscribe to Family of Services (FOS), this data can also be accessed at ptgftp.nws.noaa.gov .In addition to moving the data to the new server, the NWS is adopting a set Directory and File Naming Standard for their ftp servers. A description of this new standard can be found at http://www.nws.noaa.gov/datamgmt/filstnd.html . All of MDL's files have been placed in locations according to this directory standard. To help our users, we have prepared a cross-reference that contains the current name and location on TGSV1 and the new name and location on TGFTP of all files. This document also lists several files that will be permanently removed from the server, in addition to new Eta MOS files that will be available.

To reach TGFTP, type ftp://tgftp.nws.noaa.gov if you are using a web browser, or ftp tgftp.nws.noaa.gov if you are ftp'ing from the command line. In general, our text products can be found in SL.us008001/DF.anf, our GRIB products in SL.us008001/DF.gr1, and our BUFR products in SL.us008001/DF.bf . Please see the cross reference for specific file locations.( Cross-reference in HTML format )

As of Wednesday, July 24th, most of the files are being posted on both the old and new servers. We encourage our users to modify their processes to access the data on the new server as soon as possible. Please contact us if you have any problems accessing the new data. We want to help make this transition as smooth as possible for our users. We will also have to make slight modifications to our webpage to accomodate these changes in the FTP server. We will be updating all of the "Full Text Message" links on our products page in the next few weeks.

July 30, 2002

Addition of Climatology to MOS MEX Messages

After 1200 UTC on July 30, 2002, climatic normals for the max/min and PoP will be included in the MEX messages. These values are the same climatic normals included in the obsolete MRF MOS FOX messages and are not available for all stations. Under the column labeled "CLIMO", the "X/N", "P12", and "P24" lines for some stations will now contain climatic normals valid during the 96 - 120 h period, which is approximately the mid-point of the projections included in the MEX message. The normal min and max temperatures are based on 30-year normals (1961 - 1990) provided by the National Climatic Data Center. The normal observed relative frequencies of 0.01 inches or more of precipitation were computed from 13 years of data (October 1972 to September 1985), and are documented in NOAA Technical Report NWS 39. A sample MEX message which includes the climatic normals is available for July 24, 2002. Please note that no date separator (|) is placed between the last forecast date and the "CLIMO" columns, and that each climatic normal can be up to 3 digits wide. Missing values are indicated by 999, and if both max/min or both 12-h PoP values are missing, the CLIMO column will contain 999999. For further information see the Extended-range GFS MOS Technical Procedures Bulletin 05-07 (PDF) .

June 11, 2002

Dissemination of New Eta MOS

Effective with the 1200 UTC forecast cycle on June 11, 2002, MDL will begin disseminating new Eta MOS(MET) guidance. Guidance is available for 1258 sites in the continental US. They are listed at www.nws.noaa.gov/mdl/synop/stadrg.htm. The Eta MOS guidance will be produced at the 0000 and 1200 UTC model cycles. At this time, forecasts are available for maximum/minimum temperature, surface temperature, dewpoint, wind speed and direction, PoP and QPF, and total sky cover. In the coming months, we will be adding thunderstorm and severe weather forecasts, and precipitation type guidance to the messages. In addition to the alphanumeric text messages, we have some GEMPAK images of the forecasts on our website.
The alphanumeric messages will be available on the AWIPS/NOAAPORT datastream with the following headers:

AWIPS ID	WMO HEADER
----------------------------
METNE1		FOUS44 KWNO
METSE1		FOUS45 KWNO
METNC1		FOUS46 KWNO
METSC1		FOUS47 KWNO
METRM1		FOUS48 KWNO
METWC1		FOUS49 KWNO

On or around June 25th, the alphanumeric text messages and GRIB files will be available for anonymous ftp on the NWS ftp server, tgftp.nws.noaa.gov. We will send more details about the location of these files as the date approaches. In the future, we will produce files containing the Eta MOS forecasts in BUFR format. Technical Procedures Bulletin 486 describes the format for the Eta MOS MET message.

April 24, 2002

Impact of Changes to the NCEP Global Forecast System on the MOS Guidance

On March 6, 2002, NCEP changed the configuration of the Global Forecast System (GFS) to provide four runs of the Global Spectral Model for forecast projections out to 384 hours. These runs of the GFS are generated during the 0000, 0600, 1200, and 1800 UTC forecast cycles, and are initialized with data available by approximately 2 hours and 45 minutes after the nominal initial time (that is, a data cut-off of 2+45 after 0000, 0600, 1200, and 1800 UTC). Prior to this enhancement, these runs of the Global Spectral Model comprised the AVN. Before the reconfiguration of the GFS, the Global Spectral Model, run during the 0000 UTC forecast cycle with a data cut-off of approximately 6 hours, produced the primary model guidance for projections to 384 hours. This particular configuration of the GFS comprised the MRF. Since the changes made on March 6 provide four extended runs of the GFS, NCEP is terminating the MRF, effective April 24, 2002.

The impact of these changes on the current suite of AVN and MRF MOS guidance is minimal as far as the forecaster is concerned. The bias characteristics of the AVN and MRF model runs used to develop the AVN and MRF MOS equations were essentially identical since the same Global Spectral Model was used in both model runs, but with different initial conditions. The different initial conditions imply, however, that forecast variables from the MRF model run might have different correlations with the observed weather than variables from the AVN model runs. Although the Meteorological Development Laboratory (MDL) developed different equations to generate the AVN and MRF MOS guidance, the output from the GFS can be used in either set of guidance equations.

During a 3-week period in March 2002, MDL tested the effects of the GFS change on the MOS guidance by using the new extended 0000 UTC GFS run initialized at 0245 UTC in the MRF MOS max/min temperature and PoP forecast equations. For max/min temperature, the mean absolute errors (MAE) of the test (or parallel) runs were nearly identical to those of the operational MRF MOS guidance at all projections, although some slight increase in the MAE of the parallel MRF MOS can be seen in the forecast projections of 120 to 180 hours. For PoP, the Brier scores (or mean square errors) of the parallel and operational guidance were also approximately identical; again, a very slight increase in the Brier score was evident in the test runs for projections of 120 to 144 hours. These minor differences in the operational and parallel MRF MOS guidance packages are not significant. Thus, when the MRF is discontinued, MDL will continue to produce extended- range guidance during the 0000 UTC forecast cycle by using GFS variables in the MRF MOS equations, and the forecaster should see little or no difference in forecast quality. No changes will occur in the AVN or MRF MOS guidance packages. In the short term, at least, the nomenclature of calling the latter package the "MRF MOS" guidance will be retained.

In the long term, however, these modifications to the GFS will require MDL to change the development approach used to generate the short- and extended-range guidance packages. MDL is planning to eliminate the two sets of forecast equations (one for the AVN run and one for the MRF run) used to produce max/min temperature and precipitation guidance during the 0000 UTC cycle. When the next MOS development is completed, only one set of GFS-based equations will be required to produce the guidance for these weather elements. Moreover, after a suitable sample of model data is gathered, MDL plans to develop an extended guidance package for the 1200 UTC forecast cycle. Other changes will include the extension of the short-range guidance to projections of 84 hours, and the increase in temporal resolution of the extended- range guidance. Of course, the terminology used to describe these MOS guidance packages will also evolve to reflect the short- and extended-range nature of the guidance, rather than emphasize the differences in model runs.

April 02, 2002

Changes to Webserver and Addition of Graphics

Webserver Changes:On April 2, 2002 at 9AM, our webpages are being moved to the newly upgraded NWS server. This server will provide better security and availability. For the most part this move will be transparent to users, but if you have bookmarked or linked to any pages that start out https://tgsv5.nws.noaa.gov or https://205.156.54.206, you will need to change the URLs to http://www.nws.noaa.gov 
New Graphics Pages:On April 2nd, at or around 1200 UTC, we will begin producing graphical images of the new AVN, MRF, and experimental Eta forecasts. As these graphics are new, there may be some kinks in the system that will need to be worked out.
Warm Season starts April 1st: Please note that on April 1st at 0000 UTC, the warm season equations take effect for most elements in the MOS system. One noteable exception is the thunderstorm and severe weather guidance, where the spring season equations went into effect on March 16th at 0000 UTC. (More details on the seasonal boundaries of the MOS equations can be found on the MOS FAQ page.

April 02, 2002

Addition of Temperature and Cloud Cover to Experimental Eta MOS

Effective with the 1200 UTC forecast cycle on April 2, 2002, MDL will begin producing experimental Eta MOS guidance for maximum/minimum temperature, surface temperature, dewpoint, and total sky cover. This is in addition to the wind and QPF guidance that has been available since March 21st.
Technical Procedures Bulletin 486 describes the format for the Eta MOS MET message. It includes a description of the total sky cover categories, and the projections for which forecasts will be available.

March 21, 2002

MDL is now producing test messages of their experimental MOS forecast guidance based on NCEP's Eta model, and is making these forecasts available on their webpage. At this time, the experimental Eta MOS bulletins contain guidance for wind direction, wind speed, probability of precipitation (PoP), and quantitative precipitation amount (QPF). In the near future, we will be adding guidance for maximum/minimum temperature, surface temperature, dewpoint temperature, and sky cover. The Eta MOS guidance will be produced during the 0000 and 1200 UTC forecast cycles. Guidance will be available for 1258 sites in the continental United States. The alphanumeric text messages will be disseminated under the WMO headers FOUS41 - 46. Follow the link for a complete list of available MOS sites and their associated WMO and AWIPS headers. For more details on the Eta MOS alphanumeric messages, please see Technical Procedures Bulletin 486

January 22, 2002

323 New Stations added to the AVN and MRF MOS guidance

Effective with the 1200 UTC cycle on January 22, 2002, MDL will produce MOS guidance for an additional 323 stations in the United States, Puerto Rico, and the Virgin Islands. AVN and MRF MOS forecast guidance for these additional stations will be available in the MAV and MEX alphanumeric text bulletins and BUFR format. For a complete list of the 1383 MOS stations, please see: www.nws.noaa.gov/tdl/synop/stadrg.htm

November 27, 2001

New Weather Elements added to 0600/1800 AVN MOS guidance

Effective with the 1800 UTC cycle on November 27, 2001, new weather element guidance will be added to the 0600/1800 UTC AVN MOS guidance packages. These packages, which were first implemented in October 2001, will contain guidance for maximum/minimum temperature, 2-m temperature and dew point, total sky cover, wind direction and speed, probability of precipitation (PoP), probability of thunderstorms, conditional probability of severe weather, conditional probability of precipitation types (freezing rain or snow), precipitation type, and ceiling height. The alphanumeric text messages are available on AWIPS under the MAV product identifier and on the Satellite Broadcast Network (SBN) and the Family of Services with the WMO headers FOPA20, FOUS21-26, and FOAK37-39. Note that these are the same product identifiers used for the 0000/1200 UTC AVN MOS packages. The 0600/1800 UTC guidance is available for the same sites and in the same format as the current 0000/1200 UTC packages.

Technical Procedures Bulletin No. 481 describes the 0600/1800 UTC AVN MOS messages. Products containing all of the AVN MOS guidance in BUFR are also available. For the WMO headers of the BUFR products, please see: www.nws.noaa.gov/tdl/synop/stadrg.htm. Guidance for precipitation amount, visibility, and obstruction to vision will be added to the messages during the spring of 2002.

October 30, 2001

6/18Z AVN Guidance Additions

Upcoming Changes:
  • Effective with the 1800 UTC forecast cycle on October 30, 2001, guidance for the probability of 0.01 inches or more of liquid-equivalent precipitation (PoP) occurring during a 6-,12-, or 24-h period will be added to the
    0600/1800 UTC AVN MOS guidance. The 0600/1800 UTC guidance will be available in alphanumeric text bulletins (described in TPB 481) as well as in BUFR format (WMO headers JSMT20-29)
  • In the next four to six weeks, we expect to be adding maximum/minimum temperature, surface temperature, dewpoint, probability of thunderstorms, and conditional probability of severe thunderstorms to the
    0600/1800 UTC AVN MOS guidance.
Recent Changes:
  • We have added links to the new 0600/1800 UTC alphanumeric messages, in addition to links to our BUFR and GRIB files for all four cycles of the AVN MOS, and the 0000 UTC MRF MOS. 
  • Updated equations for AVN 0000/1200 UTC wind speed and direction were implemented on
    October 16, 2001.
  • Updated equations for MRF maximum/minimum temperature, surface temperature, and dewpoint were implemented October 1, 2001.
More details on the new guidance may be found at the following sites:

October 16, 2001

Announcement of 0600/1800 UTC AVN MOS Guidance

On or about October 16, 2001, we will be implementing new 0600/1800 UTC AVN MOS guidance packages for the same sites and in the same format as the current 0000/1200 UTC packages. The alphanumeric text messages will be available on AWIPS under the MAV product identifier and on the Satellite Broadcast Network (SBN) and the Family of Services with the WMO headeers FOPA20, FOUS21-26, and FOAK37-39. Please note that these are the same product identifiers used for the 0000/1200 UTC packages. Products containing all of the AVN MOS guidance in BUFR are also available. For the WMO headers of the BUFR products, please see: http://www.nws.noaa.gov/mdl/synop/stadrg.htm

Note that in this first implementation of the 0600/1800 UTC AVN MOS guidance products, guidance will not be available for all weather elements. In the October implementation, guidance will be available for wind speed and direction, total sky cover, ceiling height, and precipitation type. During implementations which are scheduled for later during the fall of 2001, we will add guidance for max/min temperature, surface temperature and dew point, probability of precipitation, precipitation amount, thunderstorms, and severe weather. Guidance for visibility and obstruction to vision will be added to the messages during the Spring of 2002.

The 0600/1800 UTC packages will be issued at approximately 1030/2230 UTC. Because we have used the same WMO headers, please note that these guidance packages will update the previous 0000/1200 UTC packages in the user's database. Users may want to ensure that they retain adequate previous 0000/1200 UTC products to maintain a complete set of weather element guidance. Further details regarding the AVN MOS (MAV) 0600/1800 UTC bulletins can be found in the Technical Procedures Bulletin (TPB) listed below.

Dallavalle, J.P., and M. C. Erickson, 2001: AVN-based MOS guidance - The 0600/1800 UTC alphanumeric messages. NWS Technical Procedures Bulletin No. 481, NOAA, U.S. Dept. of Commerce, 9pp.

October 10, 2001

Impact of October 10, 2001 backup test 1200 UTC AVN MOS WILL NOT BE AVAILABLE

The 1200 UTC AVN MOS guidance will NOT be available on Wednesday, October 10th due to the NCEP site outage backup test. More information on the backup test is included below:

This is a reminder that on Wednesday, 10 October 2001, NCEP will be exercising its site outage backup processing located at OPS in Silver Spring, MD. The exercise will occur during the 12 UTC model cycle and last approximately 6 hours. This exercise is now being performed on a quarterly basis and will be similar to a test performed earlier this year on June 19th. If we are unable to perform this exercise on the 10th we will try again the following day, Thursday 11 October 2001.

During this exercise a limited set of products will be distributed by the backup processing from NOGAPS, AFWA, FSL, and UKMET model guidance. Only limited NCEP model guidance will be available for 12 UTC this day. The models affected by this are the Eta, AVN, RUC2, RSAS, and NWW3 (wave) models. The 12 UTC AVN MOS products WLL NOT BE generated, but the 12 UTC NGM and NGM MOS products will be disseminated at the conclusion of this test, which will make them about 6 hours late.

Further information regarding NCEP's site outage backup processing can be found at the following link: https://www.ncep.noaa.gov/NCO/PMB/docs/ncep_backup.html . We apologize for any inconvenience this may create, however this exercise is needed to assure the continued flow of model guidance in case of a catastrophic site outage.

September 25, 2001

Air Force MOS Alphanumeric Bulletins

MDL will begin producing alphanumeric bulletins for the Air Force containing AVN (MAV) and MRF (MEX) MOS guidance on or about September 25, 2001. This guidance will be sent to the Air Force Weather Agency (AFWA) under new WMO Headings for dissemination on military communication circuits. Twenty-seven messages contain guidance for stations in the contiguous U.S., three contain guidance for Alaskan sites, one contains guidance for stations in Hawaii, and one contains guidance for Puerto Rico. The following two-line WMO headers are used:

AVN (MAV)
WMO Heading
MRF (MEX)
WMO Heading
Region
FOUS30 KWNO
MAVFxx,
where xx = 01 through 27
FEUS30 KWNO
MEXFxx,
where xx = 01 through 27
Contiguous United States
FOAK30 KWNO
MAVFxx,
where xx = 50, 51, or 52
FEAK30 KWNO
MEXFxx,
where xx = 50, 51, 52
Alaska
FOPA30 KWNO
MAVF70
FOPA30 KWNO
MEXF70
Pacific
FECA30 KWNO
MAVF80
FECA30 KWNO
MEXF80
Caribbean
 

The complete station list, organized by WMO Heading can be found on: www.weather.gov/mdl/mos_stations_afstadrg. Please note that we do not yet have guidance available for some of the stations requested by AFWA. Place holders (the message header) will appear in the bulletins for these stations. Further details regarding the AVN MOS (MAV) and MRF MOS (MEX) bulletins can be found in the Technical Procedures Bulletins (TPB's) listed below.

AVN(MAV) 00/12Z:    mdl463.pdf
AVN(MAV) 06/18Z:    http://www.nws.noaa.gov/om/tpb/481body.htm
MRF(MEX) 00Z:    http://www.nws.noaa.gov/om/tpb/460.htm

July 24, 2001

Notice of Intent to Change AVN MOS Guidance

Effective with the 1200 UTC forecast cycle on or about July 24, 2001, guidance for categorical forecasts of precipitation amount (QPF) will be added to the new AVN MOS messages. These messages are identified with WMO headers FOPA20, FOUS21-FOUS26, and FOAK37-FOAK39, and are stored as MAV products in the AWIPS text data base. In addition, new forecast equations to predict the probability of precipitation (PoP) will be implemented. The PoP guidance provides forecasts of the probability of precipitation equaling or exceeding 0.01 inches of liquid-equivalent amount in a 6- or 12-h period. The 6-h probabilities for all sites are labeled as P06 and are valid 6-12, 12-18, 18-24, ..., and 66-72 hours after 0000 or 1200 UTC. Except for the stations in the FOPA20 message, the 12-h probabilities labeled as P12 are valid for periods of 12-24, 24-36, 36-48, 48-60, and 60-72 hours after either 0000 or 1200 UTC. For the FOPA20 sites, the 12-h probabilities are valid for periods of 6-18, 18-30, 30-42, 42-54, and 54-66 hours after 0000 or 1200 UTC. The QPF guidance labeled as Q06 and Q12, respectively, for the 6- and 12-h periods, provides categorical forecasts of precipitation amount for the same projections as the PoP. The categorical definitions are as follows:

0 = no precipitation;
1 = 0.01 to 0.09 inches;
2 = 0.10 to 0.24 inches;
3 = 0.25 to 0.49 inches;
4 = 0.50 to 0.99 inches;
5 = > 1.00 inches (Q06); 1.00 - 1.99 inches (Q12)
6 = > 2.00 inches (Q12 only)

More details on the new guidance may be found at the following sites:
http://www.nws.noaa.gov/tdl/synop/mos2000.htm
http://www.nws.noaa.gov/om/tpb/463.pdf

In addition to the new QPF guidance, we are updating the equations used to produce the visibility and obstruction to vision guidance available in the MAV message. This update eliminates spurious forecasts of low visibility conditions that had been noted by several forecasters.

June 25, 2001

MDL has begun producing test AVN MAV alphanumeric messages containing QPF guidance. These test messages are being produced in anticipation of a mid-July implementation. The QPF guidance will be available via the operational alphanumeric text bulletin, and the BUFR messages. You can view these test message via our Products page at: http://www.nws.noaa.gov/tdl/synop/products.htm in the AVN MOS (MAV) portion of the table. More information will be posted soon regarding the details of the guidance, and the scheduled date of implementation.

June 19, 2001

The 1200 UTC AVN MOS guidance will NOT be available on Tuesday, June 19th due to the NCEP site outage backup test. More information on the backup test is included below.

This is a reminder that on Tuesday, 19 June 2001, NCEP will be exercising its site outage backup processing located at OPS in Silver Spring, MD. The exercise will occur during the 12 UTC model cycle and last approximately 4 hours. This exercise is now being performed on a quarterly basis and will be similar to a test performed earlier this year on 06 February. If we are unable to perform this exercise on the 19th we will try again the following day, Wednesday 20 June 2001.

During this exercise a limited set of products will be distributed by the backup processing from NOGAPS, AFWA, FSL, and UKMET model guidance. Only limited NCEP model guidance will be available for 12 UTC this day. The models affected by this are the ETA, AVN, RUC2, RSAS, and NWW3 (wave) models. There will be no 12 UTC AVN MOS products generated, but the 12 UTC NGM and NGM MOS products will be disseminated at the conclusion of this test, which will make them about 4 hours late. All of these products will have NCEP identifying headers in them except for the global WAFS grids which will have a EGRR header instead of KWBC.

Further information regarding NCEP's site outage backup processing can be found at the following link: https://www.ncep.noaa.gov/NCO/PMB/docs/ncep_backup.htmln  We apologize for any inconvenience this may create, however this exercise is needed to assure the continued flow of model guidance in case of a catastrophic site outage.

May 15, 2001

Impact of May 15, 2001 changes to the AVN/MRF model on the MOS guidance

MDL worked with the EMC modelers in March and April to assess the impacts of the model changes on the MOS guidance. We (MDL) presented these results last week at a CAFTI meeting. Essentially, we found the following:

  1. In March, we thought the temperature biases in the new MRF model (we'll call this the "parallel" from here on to distinguish it from the "operational" model {operational at that time}) were suspiciously bad. In fact, the modelers then found a mistake in the radiation package calculations over snowcover, and corrected the problem. This change invalidated our results comparing the operational and parallel versions of the model.
  2. We then did some MOS comparisons on retrospective model runs made for the month of February. We found that the temperature biases for the "parallel" MOS were colder than for the operational MOS. Since the operational MOS tended to be a little warm, this cooling in the MOS guidance actually had the net effect of improving the guidance! So for the February tests, the parallel MOS temperature guidance was actually slightly more accurate than the operational guidance. The parallel dewpoint guidance was slightly more accurate than the operational guidance, but the parallel seemed to have a distinct dry bias. The differences in the PoP and cloud guidance were slight. BOTTOM LINE: For the February test, we found no systematic degradation in the MOS guidance with the parallel MRF, except in Alaska, where a cold bias in the guidance was worsened. In the CONUS, the skill of the MOS guidance tended to stay the same, or, in some cases, actually increase.
  3. After the "bug" in the MRF model was fixed, we ran more tests for the period of April 14 to the present. We verified the first 14 days of that period. We continued to find that the parallel MOS guidance was cooler. For the min temperatures, the difference in skill between the parallel and operational MOS was minimal. However, the increase in the cold bias seemed to cause the parallel MOS max temperature guidance to deteriorate by as much as an average 0.5 degree F mean absolute error compared to the operational MOS max guidance. The skill of the parallel MOS PoPs also seemed to deteriorate slightly, but this was a very small, dry sample.
  4. Bottom Line: our samples were small, and we're reluctant to say that the MOS guidance will be less (or more) accurate after the AVN/MRF model is changed. However, we suspect that the temperature guidance, particularly during the warmer part of the day, will tend to be slightly cooler than last warm season. The dew point guidance will be slightly drier. If our test results hold up on a larger sample, the PoPs in the warm season will tend to be slightly less accurate, but may be better in the cool season.
  5. We're continuing to produce MOS packages from the parallel and operational versions of the MRF although our ability to compare the two MOS guidance packages will end Tuesday, May 15th. We're also looking at the model thermal fields to determine if we should redevelop the temperature and dewpoint guidance after eliminating certain model variables. We'll do additional experimentation as we can.

May 9, 2001

Notice of Intent to Change MRF MOS Guidance

Effective with the 0000 UTC forecast cycle on May 9, 2001, guidance for the probability of thunderstorms will be added to the MRF MOS messages. These messages are identified with WMO headers FEPA20, FEUS21-FEUS26, and FEAK37-FEAK39, and are stored as MEX products in the AWIPS text data base. The probability of thunderstorm guidance provides forecasts of the probability of a thunderstorm in a 12- or 24-h period. Because the thunderstorm guidance was developed from lightning strike data extracted from the National Lightning Detection Network, guidance is only provided for sites in the contiguous United States (CONUS). The 12-h probabilities labeled as T12 are valid for periods of 12-24, 24-36, 36-48, ..., and 180-192 hours after 0000 UTC. The 24-h probabilities are labeled as T24 and are valid 12-36, 36-60, 60-84, 84-108, 108-132, 132-156, and 156-180 hours after 0000 UTC. During the development, the lightning data were placed on a 48 km grid, and all of the strikes that occurred anywhere in the 48 km grid box were assigned to the center point of the grid box. This is an areal forecast covering the grid box, and the forecast verifies when a thunderstorm occurs anywhere in the grid box. For the text messages, a nearest neighbor approach was used to match each CONUS MOS site to the closest thunderstorm grid point. More details on the guidance may be found at the following web sites:

http://www.nws.noaa.gov/tdl/synop/mos2000.htm
http://www.nws.noaa.gov/tdl/synop/caftikkh/index.htm
http://www.nws.noaa.gov/tdl/synop/caftimay7

Please note that the techniques used in developing the MRF MOS thunderstorm guidance are analogous to those used in developing the thunderstorm guidance from the AVN model.

February 12, 2001

Change to AVN MOS Guidance

Enhancements have been made to the AVN MOS visibility, obstruction to vision, and conditional probabilities of severe thunderstorm guidance. These changes will be effective starting with the 1200 UTC model cycle on February 13, 2001. The visibility and obstruction to vision forecast equations for the 6-, 9- and 12-h projections have been redeveloped. The observed visibility predictor used in the development of these forecast equations was retooled to correspond one-to-one with the predictands. In other words, additional cutoffs were applied to compute more binary predictors of observed visibility. The conditional probability of severe thunderstorm forecasts have been modified for all projections. The conditional relative frequencies of severe thunderstorms have been smoothed. We suspect that the strong dependence on conditional relative frequencies in the severe thunderstorm equations led to the spikes we have been seeing in the forecasts. An example of an instance of these spikes is shown below.

KOZW   AVN MOS GUIDANCE    1/16/2001  1200 UTC                     
DT /JAN  16/JAN  17                /JAN  18                /JAN  19
HR   18 21 00 03 06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 06 12
N/X                    25          32          22          33    24
TMP  32 31 29 29 29 27 25 27 30 31 27 26 24 24 24 27 31 31 28 26 26
DPT  30 27 25 25 24 23 21 22 21 21 20 20 20 20 19 21 23 23 22 23 22
CLD  OV OV OV OV OV OV OV OV OV OV OV OV OV OV OV OV OV OV OV OV OV
WDR  27 27 26 26 26 27 27 29 28 24 18 19 19 19 18 18 18 18 00 00 01
WSP  08 06 04 03 04 04 02 01 02 02 01 02 04 03 03 03 04 03 00 00 03
P06         8     3     5     6     6     0     1     9     8 14 12
P12                    34          18           7          13    14
T06      0/ 0  0/86  0/ 0  0/ 0  1/ 0  0/79  0/ 0  0/ 0  0/ 0  1/ 0
T12            0/86        0/ 0        1/79        0/ 0     2/82   
POZ   0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  2  2
POS 100100100100100100100100100100100100100100100100100100100 94 86
TYP   S  S  S  S  S  S  S  S  S  S  S  S  S  S  S  S  S  S  S  S  S
CIG   4  4  4  4  4  4  4  4  4  5  5  5  4  4  4  5  4  4  4  4  2
VIS   7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  7  5  7  5 
OBV   N  N  N  N  N  N  N  N  N  N  N  N  N  N  N  N  N  N HZ  N BR