National Weather Service Office of Meteorology

Technical Procedures Bulletin Series No. 408

NGM-BASED MOS GUIDANCE - THE FOUS14/FWC MESSAGE

by J. Paul Dallavalle, John S. Jensenius, Jr., and Stephen A. Gilbert

1. INTRODUCTION

In May 1987, the National Weather Service (NWS) implemented the first statistical guidance package (Jensenius et al., 1987) designed for application to the Nested Grid Model (NGM) (Phillips, 1979; Tuccillo and Phillips, 1986; Hoke et al., 1989). The equa tions used to produce the guidance were developed at the Techniques Development Laboratory (TDL) by using a modified perfect prog technique (Erickson, 1988). In July 1989, a new NGM-based Model Output Statistics (MOS) (Glahn and Lowry, 1972) package (Jac ks et al., 1990a; 1990b) replaced the perfect prog system; MOS forecasts were produced for maximum/minimum (max/min) temperature, probability of precipitation (PoP), cloudiness, and wind. This NGM-based MOS package is being enhanced to include forecasts for additional weather elements and for additional stations. For users external to the NWS, the NGM based MOS forecasts are issued with the bulletin heading FOUS14 KWBC (hereafter referred to as FOUS14). For NWS forecasters, the NGM-based MOS guidance p ackage is disseminated on the AFOS communications system under the FWC category (hereafter referred to as FWC).

This Technical Procedures Bulletin (TPB) describes the contents of the new, complete FOUS14/FWC message. Where appropriate, we refer the interested reader to other documents for details about the development of the equations used to produce the guidance. At the time this TPB was written, TDL had not finished developing all the required forecast equations. Thus, in some cases, technical documentation was not yet available. Documentation will be issued as new equations are developed and implemented.

The FOUS14 message (FWC) contains forecasts of max/min temperature; time-specific surface temperature and dew point; opaque cloud cover; surface wind direction and wind speed; PoP for 6-and 12-h periods; quantitative precipitation for 6- and 12-h periods; probability of thunderstorms and the conditional probability of severe thunderstorms for 6- and 12-h periods; conditional probability of precipitation type (freezing, snow, or liquid) and a corresponding category; snow amount; and categories of ceiling h eight, visibility, and obstruction to vision. Guidance is provided for projections of 6 to 60 hours for most weather elements. All messages are for stations in the contiguous United States. Note that some part-time stations do not have forecasts for al l weather elements and/or projections due to lack of developmental data. The FOUS14 product is prepared daily for dissemination at approximately 0400 and 1600 UTC for the 0000 and 1200 UTC forecast cycles, respectively.

Figure 1 gives an example of the FOUS14 issued for the 0000 UTC forecast cycle during the period of September 16 through May 15. Figure 2 gives an example of the message issued for the 1200 UTC forecast cycle during the period of May 16 through September 15. Note that the message does not contain forecasts of snow and precipitation type for the latter period. Note, too, that snow and precipitation type forecasts are never issued for certain stations in California and Florida.

2. MESSAGE FORMAT AND LINE-BY-LINE SAMPLE MESSAGE

The FOUS14 message shown in Figure 1 for Washington, D.C., is based on the 0000 UTC cycle on March 6. In the following sections, the various forecast elements are discussed in detail;; similar elements, such as temperature and dew point, have been grouped together for convenience. Each section begins with the portion of the message being discussed, preceded by the message heading to enhance readability.

A one-page summary of the FOUS1 4 message is given at the end of this TPB, and will also be available and distributed to TPB subscribers as a detached reference card.

a. Message Heading

NMCFWCDCA
FOUS 1 4 KWBC 060357
OCA ESC NGM MOS GUIDANCE 3/0&91 0000 UTC
DAY/MAR 6             /MAR 7                  /MAR 8
HOUR 06 09 12 15 18 21 00 03 08 09 12 15 18 21 00 03 06 09 12

The message heading shown above (see Figure 1 also) identifies the station for which the guidance is valid, the forecast cycle, and the day and hour for which the forecasts are valid. Note that the heading is transmitted with each station's message. In this example, the FOUS14 is for Washington, D.C. (DCA). All stations are identified by a three-character site identifier (see the Appendix for a complete list of stations). The characters adjacent to the site location identifier (in this instance, ESC) identify the NWS Regions to which the product is transmitted on the AFOS network. The characters of "E", "S", "C", and 'W' denote the Eastern, Southern, Central, and Western Regions, respectively. One or more of these letters may appear for any station since a message can be routed to more than one region.

The "NGM MOS GUIDANCE" on the same line as the site location identifier indicates the contents of the message. The date of the forecast cycle for which the message is issued follows this information. The form of mm/dd/yy is used, where mm is the month ( 1 through 12), dd is the day (1 through 31), and yy is the last two digits of the year. The forecast cycle is identified by 0000 or 1200 UTC. ln the above example, the MOS guidance for DCA is based on the 0000 UTC forecast cycle of the NGM on March 6, 19 91.

The DAY and HOUR lines denote the date and hour (UTC) at which the forecasts are valid. The DAY line indicates both the month and day of month. Note that the month is denoted by the standard three or four letter abbreviation, as necessary. For temperat ure, dew point, clouds, wind direction and speed, precipitation type, ceiling height, visibility, and obstruction to vision, the date and hour denote the specific time that the forecasts are valid. For PoP, quantitative precipitation, snow amount, thunde rstorms, and severe thunderstorms, the time indicates the end of the period over which the forecasts are valid. For max/min temperature, the date group gives only the approximate ending time of the daytime and nighttime periods for which the max and min temperature guidance, respectively, are valid.

b. MX/MN - Maximum/Minimum Temperature Forecasts

NMCFWCDCA
FOUS14 KW13C M=7
DCA ESC NGM MOS GUIDANCS 3/OSMI 0000 LFTC
DAY/MAR 6             /MAR 7                  /MAR 8
HOUR 06 09 12 15 IS 21 00 03 06 09 12 15 18 21 00 03 06 09 12
MX/MN                  59          39          54          24

The max/min surface temperature forecasts are displayed for projections of 24, 36, 48, and 60 hours after the initial data time (0000 or 1200 UTC). Although the MX/MN forecasts are presented at consecutive 12-h intervals, each forecast is actually valid for a daytime or nighttime period. For the NGM-based MOS guidance, daytime is defined as 7 a.m. to 7 p.m. Local Standard Time (LST). Nighttime is defined as 7 p.m. to 8 a.m. LST. Note that the extra hour in the nighttime definition is intended to captu re the minimum temperatures observed near sunrise during the winter. Thus, the valid date in the appropriate column of the DAY and HOUR lines must be converted by the forecaster to his/her local date. This local date then denotes the appropriate daytime or nighttime for the max or min temperature forecast. For the 0000 UTC forecast cycle, the temperatures are shown in MX/MN order and are valid for todays max, tonight's min, tomorrow's max, and tomorrow night's min. For the 1200 UTC cycle, the tempera tures are shown in MN/MX order and are valid for tonight's min, tomorrow's max, tomorrow night's min, and the day after tomorrow's max. Each temperature forecast is presented in whole degrees Fahrenheit and three characters are allowed. A missing foreca st is indicated by 999. For further information on the max/min guidance, see TPB No. 406 (Jacks and Dallavalle, 1992).

c. TEMP - Surface Temperature and DEWPT- Surface Dew Point Forecasts

NMCFWCDCA
FOUS14 KWBC 060357
DCA ESC NGM MOS GUIDANCE 3/06/91 0000 UTC
DAY /MAR 8            /MAR 7                  /MAR 8
HOUR 06 00 12 15 18 21 00 03 08 09 12 15 18 21 00 03 06 09 12
                       ...
TEMP 37 34 33 38 45 53 52 49 46 43 40 42 47 51 42 39 35 30 24
DEWPT27 28 28 30 32 36 40 38 41 41 37 33 28 27 25 21 20 19 19

Time-specific surface temperature and dew point forecasts are valid every 3 hours from 6 to 60 hours after 0000 and 1200 UTC. These forecasts are valid at 0600, 0900,..., 21 00, 0000 UTC, and so forth. Each temperature and dew point forecast is presente d in whole degrees Fahrenheit; a missing forecast is indicated by 999. Note that only three characters are available for the temperature and dew point forecasts, so that two consecutive forecasts of 100 degrees or more (or -10 degrees or less) will appea r with no spaces between them. TPB No. 406 contains more details regarding the 3-h surface temperature and dew point guidance.

d. CLDS - Opaque Cloud Amount Categorical Forecasts

NMCFWCDCA
FOUS14 KWBC 060357
DCA ESC NGM MOS GUIDANCE 3/06/91 0000 UTC
DAY /MAR 8            /MAR 7                  /MAR 8
HOUR 06 00 12 15 18 21 00 03 08 09 12 15 18 21 00 03 06 09 12
                       ...
CLDS OV OV OV OV OV OV OV OV OV OV BK BK BK SC SC SC CL CL CL

Forecast categories of opaque cloud cover (see the following table) are available in plain language for projections at 3-h intervals from 6 to 60 hours after the initial data times (0000 and 1200 UTC). All forecasts are valid for specific times (i.e., 06 00, 0900, 1200 UTC, and so forth). Two characters identify the category (CL - clear; SC - scattered; BK - broken; OV - overcast); a missing forecast is denoted by XX. TPB No. 387 gives information about the NGM-based MOS cloud forecasts. Note that the cloud forecasts for the 9-, 15-, 21 -, 27-,33-,39-,45-,51-, and 57-h projections will not be available until the spring of 1993.

Opaque Cloud Cover Categories
CL - 0 tenths of opaque clouds;
SC - 1 to 5 tenths of opaque clouds;
BK - 6 to 9 tenths of opaque clouds;
OV - 10 tenths of opaque clouds or totally obscured;
XX - missing.

e. WDIR - Surface Wind Direction and WSPD - Surface Wind Speed Forecasts

NMCFWCDCA
FOUS14 KWBC 060357
DCA ESC NGM MOS GUIDANCE 3/06/91 0000 UTC
DAY /MAR 8            /MAR 7                  /MAR 8
HOUR 06 00 12 15 18 21 00 03 08 09 12 15 18 21 00 03 06 09 12
                       ...
WDIR 26 18 08 12 14 14 15 18 24 27 28 29 29 29 29 33 01 02 00
WSPD 01 04 08 10 11 12 16 IS 13 15 12 20 24 22 14 12 14 08 00

Surface wind direction and speed forecasts are given at 3-h intervals for projections of 6 to 60 hours after the initial data times (0000 and 1200 UTC). These are forecasts of 1-minute average winds at specific times throughout each day (i.e., 0600, 0900 , 1200 UTC, and so forth). The wind direction is given in tens of degrees and varies from 01 (10 degrees) to 36 (360 degrees). The wind speed is given in knots; the maximum speed allowed in the message is 98 knots. A calm wind is denoted with both dire ction and speed of 00 (0000). Missing forecasts are denoted by 99 for both direction and speed. TPB No. 399 (Miller, 1992) gives more details on the wind forecasts.

f. POP06 - Probability of Precipitation (PoP) in a 6-h period and POP12 - Probability of Precipitation in a 12-h period

NMCFWCDCA
FOUS14 KWBC 060357
DCA ESC NGM MOS GUIDANCE 3/06/91 0000 UTC
DAY /MAR 8            /MAR 7                  /MAR 8
HOUR 06 00 12 15 18 21 00 03 08 09 12 15 18 21 00 03 06 09 12
                       ...
POP06	       4	     9	    46    85    	62	3	7    12	8
POP12			           49	          91		8	     19

The POP06 and POP12 forecasts are for the probability of 0.01 inches or more of liquid equivalent precipitation occurring during a 6-h and 12-h period, respectively. The 6-h PoP's 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). The 12-h PoP's are valid for intervals of 12-24, 24-36, 36-48, and 48-60 hours after the initial data times (0000 and 1200 UTC). In the message, the forecast values are displayed under the ending time of the period. The probability is given to the nearest percent. Values range from 0 to 1 00%. A missing forecast is indicated by 999. The TPB describing the PoP system is currently in preparation.

g. OPF - Quantitative Precipitation Forecasts

NMCFWCDCA
FOUS14 KWBC 060357
DCA ESC NGM MOS GUIDANCE 3/06/91 0000 UTC
DAY /MAR 8            /MAR 7                  /MAR 8
HOUR 06 00 12 15 18 21 00 03 08 09 12 15 18 21 00 03 06 09 12
                       ...
QPF        O/    O/   1/1    3/    2/4   O/    0/0   O/    0/0

Guidance for liquid-equivalent precipitation amount accumulated during a specified period is presented in categorical form. Forecasts for 6-h periods are displayed to the left of the diagonal. These forecasts are available for projections 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 time (0000 and 1200 UTC). Forecasts for 12-h periods are displayed to the right of the diagonal. The 12-h forecasts are available for projections of 12-24, 24-36, 36-48, and 48-60 hours after 0000 or 1200 UTC. In the message, the forecasts are displayed beneath the hour indicating the end of the period. The QPF guidance is a categorical forecast of liquid-equivalent precipitation equaling or exceeding certain specified amounts in the 6- or 12-h periods. The categories are as follows:

QPF Categories
0 = no precipitation expected;
1 = 0.01 - 0.09 inches;
2 = 0. 1 0 - 0.24 inches;
3 = 0.25 - 0.49 inches;
4 = 0.50 - 0.99 inches;
5 = > 1.00 inches for 6-h QPF;
1.00 - 1.99 inches for 12-h QPF;
6 = unavailable for 6-h QPF;
> 2.00 inches for the 12-h QPF;
9 = no forecast available.

At this time, a TPB is unavailable for the QPF.

h. TSVO6 - Thunderstorm and Severe Storm Probabilities for 6-h periods and TSV12 - Thunderstorm and Severe Storm Probabilities for 12-h periods

NMCFWCDCA
FOUS14 KWBC 060357
DCA ESC NGM MOS GUIDANCE 3/06/91 0000 UTC
DAY /MAR 8            /MAR 7                  /MAR 8
HOUR 06 00 12 15 18 21 00 03 08 09 12 15 18 21 00 03 06 09 12
                       ...
TSV06	  2/0   	3/0    4/1   5/1   6/2  16/3  11/1   8/0   0/0
TSVI2		   4/0		  8/1	     21/4	    9/1

Forecasts of the probability of a thunderstorm occurring during a 6-h (12-h period for TSV12) period are displayed to the left of the diagonal and the conditional probability of severe thunderstorms occurring during the same 6-h (12-h period for TSV12) pe riod is displayed to the right of the diagonal. As with POP06, both the 6-h thunderstorm and severe thunderstorm probabilities (TSVO6) are available for periods of 6-12, 12-18, 18-24, 24-30, 30-36, 36-42, 42-48, 48-54, and 54-60 hours after 0000 or 1200 LTC. Similarly, for TSVL 2, both the thunderstorm and severe thunderstorm probabilities are available for periods of 6-18, 18-30, 30-42, and 42-54 hours after 0000 or 1200 LTC. In the message, the forecasts are displayed beneath the ending hour of the a ppropriate period. The thunderstorm probability forecasts are given to the nearest whole percent and range from 0 to 1 00%; a missing forecast is denoted by 999. The conditional severe thunderstorm probabilities are given to the nearest whole percent an d range from 0 to 98%; a missing forecast is indicated by 99. Forecasts of both thunderstorms and severe thunderstorms are available year-round.

In developing the thunderstorm and severe storm probability equations, the occurrence of thunderstorms was defined by combining reports from surface hourly observations, radar echo intensity values from Manually Digitized Radar (MDR) data, and reports fro m spotter networks in the National Severe Storms Forecast Center (NSSFC) Severe Local Storms (SELS) logs. A radar echo at Video Integrator and Processor level 3 (VIP3) or greater was chosen to indicate the occurrence of a thunderstorm. Since MDR reports are for grid blocks approximately 47 km on a side and since a station seldom sits at the mid-point of a block, we defined the radar reporting area for a station as a 3 by 3 array of blocks with the station located in the interior block. Thus, a station report of a thunderstorm, an MDR report of VIP3 or greater within a station's area, or a SELS log report within a station's area indicated a thunderstorm occurrence. The reports were then accumulated over the appropriate 6-h (or 12-h for TSV12) period. Similarly, a severe thunderstorm (conditional, of course, upon a thunderstorm occurring) was defined by a station report in the hourly observation or a SELS log report within the station's area. TPB No. 407 (Bower, 1992) provides additional information a bout this product. Note that the thunderstorm probabilities indicate the likelihood of a thunderstorm within a station's area. The PoP indicates the likelihood of precipitation at a specific station site. Thus, for the same weather event, the thunderst orm probability can exceed the PoP.

i. PTYPE - Precipitation Type Forecasts (Conditional)

NMCFWCDCA
FOUS14 KWBC 060357
DCA ESC NGM MOS GUIDANCE 3/06/91 0000 UTC
DAY /MAR 8            /MAR 7                  /MAR 8
HOUR 06 00 12 15 18 21 00 03 08 09 12 15 18 21 00 03 06 09 12
                       ...
PTYPE S  S  S  S  S  R  R  R  R  R R      R     R     S     Z

The PTYPE guidance in the message gives the forecast precipitation type (H precipitation occurs) for specific times 6, 9,12,15,18, 21, 24, 27, 30, 33, 36, 42, 48, 54, and 60 hours after the initial hour of 0000 or 1200 UTC. The forecast is indicated by o ne character, where "Z" represents freezing precipitation (freezing rain, freezing drizzle, ice pellets (sleet), or any of these elements mixed with other precipitation types), IS" represents snow (snow, snow grains, snow pellets, or snow showers), and IR" represents liquid precipitation (rain, drizzle, or a mixture of rain or drizzle with snow). A missing forecast is denoted by "X. The precipitation type guidance is transmitted only during the period of September 16 May 15. The TPB describing this product is currently in preparation.

j. POZP - Probability of Freezing Precipitation (Conditional) and POSN - Probability of Snow (Conditional)

NMCFWCDCA
FOUS14 KWBC 060357
DCA ESC NGM MOS GUIDANCE 3/06/91 0000 UTC
DAY /MAR 8            /MAR 7                  /MAR 8
HOUR 06 00 12 15 18 21 00 03 08 09 12 15 18 21 00 03 06 09 12
                       ...
POZP  8 10 12  6  0  0  0  0  0  1  3	0	2    24    35
POSN 65 87 70 48 41 14 11 13 15 16 20	9    16   50   42

Conditional probability of freezing precipitation (given that precipitation is occurring) and conditional probability of snow (given that precipitation is occurring) forecasts are available for specific times 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 42, 48, 54, and 60 hours after 0000 and 1200 UTC. Freezing precipitation is defined as the occurrence of freezing rain or drizzle, ice pellets (sleet), or any mixture of freezing rain, drizzle, or ice pellets with other precipitation types. Snow is defined as the occurrence of a pure snow event, that is, snow, snow showers, snow grains, or snowy pellets or any combination of those elements. Snow mixed with rain is considered a liquid precipitation event. The probabilities are given to the nearest whole pe rcent, and values range from 0 to 100%. Missing values are indicated by 999. These probabilities are used in producing the categorical PTYPE forecast described in Section 2.i. The POZP and POSN guidance are transmitted only during the period of Septembe r 16 - May 15. The TPB describing this product is currently in preparation.

While that the conditional probability of liquid precipitation is not given in the message, note that the three conditional probabilities (freezing, frozen, and liquid), add to 100%.

k. SNOW - Snow Amount Categorical Forecasts

NMCFWCDCA
FOUS14 KWBC 060357
DCA ESC NGM MOS GUIDANCE 3/06/91 0000 UTC
DAY /MAR 8            /MAR 7                  /MAR 8
HOUR 06 00 12 15 18 21 00 03 08 09 12 15 18 21 00 03 06 09 12
                       ...
SNOW      O/    O/     0/1  O/    0/0   O/    0/0    O/   0/0
Categorical forecasts of snow amount are available in the message for both 6- and 12-h periods. The categorical forecasts of snow amount failing in 6-h periods are given to the left of the diagonal; forecasts are valid for 6-h periods ending 12, 18, 24, 30, 36, 42, 48, 54, and 60 hours after 0000 or 1200 UTC. The categorical forecasts for snow amount in 12-h periods are displayed to the right of the diagonal; forecasts are valid for 12-h periods ending 24,36,48, and 60 hours afterOO00 or 1200 UTC. The categories are denoted as follows:

Snow Amount Categories
0 = no snow expected;
1 = a trace to < 2 inches expected;
2 = 2 inches or more (6-h forecast);
2 to < 4 in. (1 2-h forecast);
4 = unavailable for 6-h forecast;
4 to < 6 in. (1 2-h forecast);
6 = unavailable for 6-h forecast;
6 inches or more (12-h forecast);
9 = no forecast available.

Forecasts are disseminated only for the period of September 16 - May 15. A TPB will be forthcoming when the guidance equations are completed.

l. CIG - Ceiling Height Categorical Forecasts

NMCFWCDCA
FOUS14 KWBC 060357
DCA ESC NGM MOS GUIDANCE 3/06/91 0000 UTC
DAY /MAR 8            /MAR 7                  /MAR 8
HOUR 06 00 12 15 18 21 00 03 08 09 12 15 18 21 00 03 06 09 12
                       ...
CIG   4  5  4  4  5  6  7  6  3  2  1     5     6

Forecasts of seven categories of ceiling height (see the following table) are available for specific times 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 42, and 48 hours after 0000 and 1200 UTC. The forecasts are displayed beneath the time of the day for whi ch they are valid. Values of 1 through 7 are allowed for the categorical guidance; a value of 9 denotes a missing forecast. The categories are as follows:

Ceiling Height Categories
1 = < 200 feet;
2 = 200 - 400 feet;
3 = 500 - 900 feet;
4 = 1000 - 3000 feet;
5 = 3100 - 6500 feet;
6 = 6600 - 12,000 feet;
7 = > 12,000 feet;
8 = no forecast available.

The categorical guidance is prepared by using probability forecasts of the same categories. The TPB describing the ceiling height guidance is currently in preparation.

m. VIS - Visibility Categorical Forecasts

NMCFWCDCA
FOUS14 KWBC 060357
DCA ESC NGM MOS GUIDANCE 3/06/91 0000 UTC
DAY /MAR 8            /MAR 7                  /MAR 8
HOUR 06 00 12 15 18 21 00 03 08 09 12 15 18 21 00 03 06 09 12
                       ...
VIS   3  4  3  5  5  5  5  4  2  2  1     3     4

Forecasts of five categories of visibility (see the following table) are available for specific times 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 42, and 48 hours after 0000 and 1200 UTC. The forecasts are displayed beneath the time of the day for which th ey are valid. Values of 1 through 5 are allowed for the categorical guidance; a value of 9 denotes a missing forecast. The categories are as follows:

Visibility Categories
1 = < 1/2 mile;
2 = 1/2 - 7/8 miles;
3 = 1 - 2 3/4 miles;
4 = 3 - 5 miles;
5 = > 5 miles;
9 = no forecast available.

The categorical guidance is prepared by using probability forecasts of the same categories. The TPB describing the visibility guidance will be prepared when the forecast equation development is completed.

n. OBVIS - Obstruction to Vision Categorical Forecasts

NMCFWCDCA
FOUS14 KWBC 060357
DCA ESC NGM MOS GUIDANCE 3/06/91 0000 UTC
DAY /MAR 8            /MAR 7                  /MAR 8
HOUR 06 00 12 15 18 21 00 03 08 09 12 15 18 21 00 03 06 09 12
                       ...
OBVIS H  H  H  N  N  N  N  F  F  F  F     H    N

Forecasts of three categories of obstruction to vision (see the following table) are available for specific times 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 42, and 48 hours after 0000 and 1200 UTC. The forecasts are displayed in plain language beneath th e time of the day for which they are valid. The categories are denoted by the letters F, H, and "N", a value of X denotes a missing forecast. The categories are as follows:

Obstruction to Vision Categories
F = fog or ground fog expected;
H = haze expected;
N = neither fog nor haze are expected;
X = no forecast available.

The categorical guidance is prepared by using probability forecasts of the same categories. The TPB describing the obstruction to vision guidance will be prepared when the forecast equation development is completed. Note that in the equation development , cases of fog were included in the sample whether or not precipitation occurred. Lower visibilities caused exclusively by precipitation occurrence are not predicted by this guidance.

University of North Dakota / School of Aerospace Sciences / Atmospheric Science Department

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