The FAA Communication's Software Upgrade of the FAA's two message switching centers in Atlanta and Salt Lake City originally scheduled for December 1996 have been rescheduled for January 8, 1997.
The Software upgrade at the at the FAA's Atlanta message center will begin at 0515Z on January 8. The message center will shut down at this time. During the upgrade, customers should expect some delay in data distribution and multiple service interruptions as well as complete outages of individual circuits of up to 30 minutes.
The Software upgrade of the FAA's Salt Lake message center will commence at 0615Z on January 8 after resumption of service at the Atlanta Center. Similar interruptions and delays will occur with the shut down of the Slat Lake Center for up to 30 minutes.
The Climate Bulletin--published monthly by the National Centers for Environmental Prediction's Climate Prediction Center--will end hardcopy distribution with the February 1997 issue. However, the Climate Bulletin will continue to be available on the Internet at:
Recently the ASOS Program Office received several inquires concerning the automated reporting of rain at temperatures less than 20F/-5.6C. In the current version of ASOS software (V2.40), the ASOS present weather algorithm may report rain (RA), which is usually light, at temperatures down to 0F/-17.8C. This software change was made to permit the proper handling of freezing rain (FZRA) events that occur at temperatures below 20F. For ASOS to report FZRA, a positive indication from the freezing rain sensor must be confirmed by detection of rain through the present weather sensor (i.e., Light Emitting Diode Weather Identifier (LEDWI)). Unfortunately, other present weather (e.g., ice pellets (PE)) and obscurations (e.g., blowing snow (BLSN)) may be reported as rain when they are detected by the LEDWI. At sites with observer oversight, these erroneous reports of rain may be changed through backup and augmentation.
Below are two cases which illustrate the problems encountered when blowing snow is occurring. The first case illustrates an event from Aberdeen, SD (ABR) where observer oversight was provided. Included are the 5-Minute Observations, 1-Minute Archive data from the sensors, and the METAR/SPECI reports transmitted from the site. The second case compares two sites reporting the occurrences of similar events. A site without observer oversight (Watertown, SD - ATY) is compared to a site with an observer providing oversight (ABR). These sites are about 75 miles apart, but they are experiencing very similar meteorological conditions.
Case 1: Five-Minute Observations, the 1-Minute Data from the sensors, and the METAR/SPECI reports transmitted from the site are provided. This data set shows that the automated sensor detected rain (R), snow (S), and unknown precipitation (P). These reports were changed by the observer to blowing snow (BLSN).
12/18/96 02:55:31 5-MIN KABR 180855Z 34023G29KT 1 1/2SM BLSN FEW015 BKN027
OVC038 M19/M22 A3013 1110 79 -2800 330/23G29 RMK AO2 PK WND 33030/0836
SLP235 T11891217 55001 $
UTC WX T PRECIP SUN SNOW ZR PRESS1 PRESS2 PRESS3 TEMP DEWPT
0856 P 0.00 28.733 28.735 28.742 -2 -7
12/18/96 02:58:33 METAR KABR 180856Z 34024G29KT 1 1/2SM BLSN FEW015 BKN027
OVC038 M19/M22 A3013 RMK AO2 PK WND 33030/0836 SLP236 T11891217 55001 $
(RS)
0857 S- 0.00 28.733 28.735 28.742 -2 -7
0858 P 0.00 28.732 28.734 28.741 -2 -6
0859 S- 0.00 28.733 28.736 28.742 -2 -7
0900 S- 0.00 28.733 28.736 28.743 -2 -7
12/18/96 03:00:31 5-MIN KABR 180900Z 34020G28KT 1 3/4SM BLSN SCT027 OVC038
M19/M22 A3013 1110 79 -2800 330/20G28 RMK AO2 $
0901 S- 0.00 28.733 28.736 28.742 -2 -7
0902 S- 0.00 28.734 28.736 28.743 -2 -7
12/18/96 03:04:32 SPECI KABR 180902Z 34022G28KT 2SM BLSN SCT027 OVC036
M19/M22 A3013 RMK AO2 PK WND 33027/0901 $ (RS)
UTC WX T PRECIP SUN SNOW ZR PRESS1 PRESS2 PRESS3 TEMP DEWPT
0903 P 0.00 28.731 28.734 28.741 -2 -7
0904 P 0.00 28.728 28.731 28.738 -2 -7
0905 P 0.00 28.729 28.732 28.739 -2 -7
12/18/96 03:05:31 5-MIN KABR 180905Z 34022G27KT 2SM BLSN SCT027 OVC036
M19/M22 A3013 1110 79 -2800 330/22G27 RMK AO2 PK WND 33027/0901 $
0906 P 0.00 28.728 28.731 28.738 -2 -7
0907 R- 0.00 28.728 28.731 28.738 -2 -7
0908 P 0.00 28.728 28.730 28.737 -2 -7
0909 P 0.00 28.728 28.731 28.738 -2 -7
0910 P 0.00 28.728 28.731 28.737 -2 -7
12/18/96 03:10:31 5-MIN KABR 180910Z 34022G27KT 1 3/4SM BLSN SCT027 BKN036
OVC044 M19/M22 A3012 1120 79 -2800 330/22G27 RMK AO2 PK WND 33027/0901 $
0911 P 0.00 28.729 28.731 28.738 -2 -7
0912 P 0.00 28.728 28.731 28.738 -2 -7
12/18/96 03:14:33 SPECI KABR 180912Z 34021G27KT 1 3/4SM BLSN SCT027 BKN036
OVC044 M19/M22 A3012 RMK AO2 PK WND 33027/0901 $ (RS)
0913 S- 0.00 28.729 28.731 28.738 -2 -7
0914 P 0.00 28.728 28.730 28.737 -2 -7
0915 P 0.00 28.729 28.731 28.738 -2 -7
12/18/96 03:15:31 5-MIN KABR 180915Z 34018G27KT 2SM BLSN SCT027 BKN036
OVC044 M19/M22 A3013 1110 79 -2800 330/18G27 RMK AO2 PK WND 33027/0901 $
0916 P 0.00 28.727 28.730 28.737 -2 -7
0917 P 0.00 28.727 28.730 28.737 -2 -7
0918 P 0.00 28.727 28.730 28.737 -2 -7
0919 P 0.00 28.726 28.729 28.736 -2 -7
0920 P 0.00 28.726 28.728 28.735 -2 -7
12/18/96 03:20:31 5-MIN KABR 180920Z 34024G27KT 2 1/2SM BLSN SCT027 BKN036
OVC046 M19/M22 A3012 1120 79 -2800 330/24G27 RMK AO2 PK WND 33027/0901 $
12/18/96 03:22:33 SPECI KABR 180920Z 34024G27KT 2 1/2SM BLSN SCT027 BKN036
OVC046 M19/M22 A3012 RMK AO2 PK WND 33027/0901 $ (RS)
0921 R- 0.00 28.726 28.728 28.735 -2 -7
0922 R- 0.00 28.725 28.728 28.735 -2 -7
0923 R- 0.00 28.724 28.727 28.734 -2 -7
0924 R- 0.00 28.725 28.728 28.735 -1 -7
0925 R- 0.00 28.725 28.728 28.734 -1 -6
12/18/96 03:25:31 5-MIN KABR 180925Z 34022G27KT 2SM BLSN SCT027 BKN036
OVC046 M19/M22 A3012 1120 79 -2800 330/22G27 RMK AO2 PK WND 33027/0901 $
0926 R- 0.00 28.726 28.729 28.735 -2 -6
0927 R- 0.00 28.726 28.729 28.735 -1 -7
0928 P 0.00 28.726 28.728 28.734 -1 -7
0929 P 0.00 28.726 28.729 28.736 -2 -7
0930 P 0.00 28.727 28.729 28.736 -1 -7
12/18/96 03:30:31 5-MIN KABR 180930Z 34024G27KT 2SM BLSN BKN027 BKN036
OVC046 M18/M22 A3012 1120 75 -2800 330/24G27 RMK AO2 PK WND 33027/0901 $
Case 2: Watertown, SD (ATY) is an ASOS site without observer oversight. Meanwhile, at Aberdeen, SD (ABR) an observer is providing oversight. ABR is reporting blowing snow and ATY is reporting rain, snow, and unknown precipitation during this time period. Begin and end times for these events are encoded in remarks of the reports (e.g., RAB1455E36UPB07E20B36SNB12E19B20E22B42E52) transmitted from ATY.
12/16/96 07:53:26 METAR KATY 161353Z AUTO 24017KT 5SM -SN BR SCT010 BKN016
OVC026 M02/M03 A2959 RMK AO2 SLP050 T10221028 FZRANO TSNO PNO $
12/16/96 07:58:43 METAR KABR 161356Z 30014KT 10SM SCT017 SCT022 BKN100
M01/M03 A2963 RMK AO2 PK WND 30028/1259 SLP053 P0000 T10111028 (RGB)
12/16/96 07:59:26 SPECI KATY 161359Z AUTO 25016KT 6SM -SN BR BKN008 BKN016
OVC026 M02/M03 A2959 RMK AO2 FZRANO TSNO PNO $
12/16/96 08:05:33 SPECI KABR 161403Z 31022G25KT 8SM SCT017 BKN022 OVC120
M01/M03 A2963 RMK AO2 PK WND 32026/1402 (KG)
12/16/96 08:20:26 SPECI KATY 161420Z AUTO 26018G24KT 9SM UP SCT009 BKN016
OVC021 M01/M02 A2959 RMK AO2 UPB04SNE04 FZRANO TSNO PNO $
12/16/96 08:34:26 SPECI KATY 161434Z AUTO 26020KT 5SM UP BR OVC013 M01/M02
A2959 RMK AO2 PK WND 26026/1425 UPB04SNE04 FZRANO TSNO PNO $
12/16/96 08:46:33 SPECI KABR 161444Z 31027G34KT 1 3/4SM -SN BLSN BKN019
OVC025 M02/M04 A2966 RMK AO2 PK WND 31034/1443 VIS 1 1/4V4 CIG 013V023
PRESRR P0000 (KG)
12/16/96 08:53:26 METAR KATY 161453Z AUTO 28020G28KT 4SM BR OVC013 M01/M03
A2960 RMK AO2 PK WND 28029/1440 UPB04E39RAB39E52SNE04 SLP053 6////
T10111028 55004 FZRANO TSNO PNO $
12/16/96 08:58:33 METAR KABR 161456Z 32022G35KT 1 1/2SM -SN BLSN FEW015
OVC025 M02/M04 A2967 RMK AO2 PK WND 30036/1446 PRESRR SLP070 P0000 60000
T10171039 53025 (KG)
12/16/96 09:03:32 SPECI KABR 161501Z 31020G30KT 3SM -SN BLSN FEW015 BKN023
OVC027 M02/M04 A2967 RMK AO2 PK WND 32028/1457 P0000 (KG)
12/16/96 09:02:26 SPECI KATY 161502Z AUTO 28022G31KT 4SM -RA BR BKN015
OVC028 M01/M03 A2960 RMK AO2 PK WND 28031/1455 RAB1455 FZRANO TSNO PNO $
12/16/96 09:13:33 SPECI KABR 161511Z 31023G33KT 1 3/4SM -SN BLSN BKN023
OVC028 M02/M04 A2967 RMK AO2 PK WND 31033/1506 P0000 (KG)
12/16/96 09:19:54 SPECI KABR 161517Z 30021G32KT 3SM -SN BLSN OVC025
M02/M04 A2968 RMK AO2 PK WND 31033/1506 P0000 (KG)
12/16/96 09:45:26 SPECI KATY 161545Z AUTO 28022G29KT 1 3/4SM -SN BR FEW010
BKN017 OVC027 M02/M03 A2964 RMK AO2 PK WND 28031/1455
RAB1455E36UPB07E20B36E42SNB12E19B20E22B42 FZRANO TSNO PNO $
12/16/96 09:53:26 METAR KATY 161553Z AUTO 28022G27KT 1 3/4SM UP BR FEW010
BKN017 OVC025 M02/M04 A2965 RMK AO2 PK WND 28031/1455
RAB1455E36UPB07E20B36SNB12E19B20E22B42E52 SLP069 T10221039 FZRANO TSNO PNO
$
12/16/96 09:58:40 METAR KABR 161556Z 30027G36KT 1 1/2SM BLSN OVC031
M03/M05 A2971 RMK AO2 PK WND 29036/1554 SNE20 SLP082 P0000 T10331050 (KG)
By analyzing the reports from ASOS sites with and without observer oversight, as well as other sources of data (e.g., satellite and radar), it is possible for the meteorologist to determine the weather occurring with a high degree of success. The ASOS Program Office is currently in the process of developing algorithms to report BLSN and PE. These algorithms are currently being examined as part of the 1996-1997 ASOS winter test activities. When software version 2.50 is implemented in mid 1997, either the BLSN/PE algorithms or a solution relieving this quality control workload will be implemented.