The NGM forecast output bulletins are produced for groups of stations similar to the LFM forecast bulletins. However, the regional identification in the MANOP headers was changed. Table 4-3-6 lists the NGM forecast data regions, subregions, and stations available.

The arrangement of the data and the type of data, in some cases, is also slightly different from the LFM forecast bulletin. Table 4-3-7 is the first data block from a typical NGM forecast bulletin with the MANOP and identification lines. A second stations block of data would be printed to the right of this data block, so the actual bulletin would be formatted in two columns of station data, similar to the LFM bulletin. The MANOP and identification lines are similar to the LFM bulletin, which was described in the last section. Line 3 gives the coded format of the data columns, which is different from the LFM bulletin. Line 4, which begins with the three-letter station identifier, contains information from the analysis. Lines 5 through 12 are the forecast data. Each line begins with the number of hours after the analysis, in 6-hour increments, for which the forecast is valid, just as with the LFM format. In the following explanation, we will use line 7, the 18-hour forecast, as an example to clarify the breakdown of the information contained in the data columns and identified in line 3 by the coded format.

TT is the time in hours from the analysis time that the forecast is valid. In line 7, the 18 is 18 hours after 1200Z 4 December, or 0600Z 5 December.

R2 is the mean relative humidity in layers 2 through 9 of the NGM model. This equates to the layer from the boundary layer up to 480 millibars, or roughly 19,000 feet AGL. Example: 72 means the relative humidity in layers 2 through  

R3 is the mean relative humidity in layers 10 through 13 of the NGM model. This equates to the 480-millibar level through the 180-millibar level, or roughly 19,000 feet to 41,000 feet. Example: 23 is 23 percent.

VVV is the instantaneous vertical velocity in microbars per second at the 700-millibar level. Negative vertical velocities, or movement of air downward, are prefixed with a minus sign. Example: 009 in this case is 9 microbars per second (upward) vertical velocity.

LI is the Lifted Index in degrees Celsius. Negative LI values are subtracted from 100. Example: 15 is 15C, but a 95 would mean the Lifted Index is 05C.

DD is the wind direction in hundreds and tens of degrees at the boundary level, or about 986 feet above the surface. Example: 25 means the wind is from 250 true.

FF is the wind speed in knots at the boundary level, or about 986 feet above the surface. Example: 20 means the wind speed is 20 knots.

HH is the 1,000-to-500-millibar thickness in tens and units of decimeters. The hundreds digit (5) is omitted. Example: 34 means the meters.

T1 is the mean temperature in degrees Celsius through the boundary layer. In practice, this may be used as the forecast temperature for 17 millibars (roughly 480 feet) above the surface, which is usually rounded off to 500 feet AGL. Temperatures cooler than 0C are subtracted from 100. Example: 98 means that the 500 foot temperature is 2C.

T3 is the mean temperature through layer 3 of the NGM model in degrees Celsius. This layer extends from 78 to 138 millibars above the surface, or roughly from 2,240 feet to 3,925 feet AGL. In practice, this is used as an approximate temperature for the 3,000-foot AGL level. Temperatures below freezing are subtracted from 100. Example: 95 means the 3,000-foot temperature is 5C.

T5 is the mean temperature in degrees Celsius through layer 5 of the NGM, which extends from about 194 to 255 millibars above the surface, or essentially from about 5,836 to 7,906 feet AGL. In practice, the mean temperature of layer 5 (T5) is used as the temperature at 7,000 feet AGL. Temperatures below freezing are subtracted from 100. 95 means the 7,000 foot temperature is 5C.

Privacy Statement - Press Release - Copyright Information. - Contact Us - Support Integrated Publishing