Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
5.6.2.3 Sky Cover The sky cover symbol is plotted at the station location and is filled according to the summation total of the sky condition element from the METAR report. For example, if the METAR sky condition element was SCT030 BKN060 OVC090, the sky cover would be overcast. Sky cover symbols are listed in Figure 5-41.
5.6.2.4 Station Identifier (STNID) The four-letter ICAO station identifier is entered to the upper right of the station.
5.6.2.5 Wind Wind is plotted in increments of 5 knots (kts). The wind direction is referenced to “true” north and is depicted by a stem (line) pointed in the direction from which the wind is blowing. Wind speed is determined by adding the values of the flags (50 kts), barbs (10kts), and half barbs (5 kts) found on the stem.
A single circle over the station with no wind symbol indicates a calm wind.
Some sample wind symbols are shown on Figure 5-46.
Figure 5-43. AAWU Alaska Weather Depiction Chart Wind Symbols
5.6.2.6 Temperature (TMP deg F) Temperature in degrees Fahrenheit is plotted to the upper left of the sky cover symbol.
5.6.2.7 Visibility (VIS) Visibility in statute miles is plotted to the left of the sky cover symbol. Decimals are used to represent tenths of miles when necessary.
AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-47
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
5.6.2.8 Dew Point Temperature (DEWPT deg F) Dew point temperature in degrees Fahrenheit is plotted to the lower left of the sky cover symbol.
5.6.2.9 Ceiling (CIG) Ceiling is the height from the base of the lowest layer aloft covering more than one-half the sky.
Additionally, vertical visibility into a total surface-based obscuration is defined as a ceiling. For a METAR report, the first broken (BKN) or overcast (OVC) layer is the ceiling. For example, if the METAR sky condition element is SCT030 BKN060 OVC090, the ceiling is 6,000 feet.
For a total surface-based obscuration, no ceiling is plotted and the METAR must be consulted.
If the sky cover is clear, few, or scattered, no ceiling is plotted.
The ceiling is plotted to the lower right of the station circle. Ceilings are reported as hundreds of feet above ground level (AGL). If no ceiling is present, the code 999 will be plotted.
5.6.2.10 Present Weather (WX) Present weather symbols are entered to the left of the station. Note that the older Surface Aviation Observation (SAO) code is used instead Surface Analysis Chart symbols or the modern METAR code.
Table 5-16 Alaska Weather Depiction Charts Precipitation Symbols Table 5-17 Alaska Weather Depiction Charts Obstruction to Visibility Symbols Symbol Meaning Symbol Meaning T Thunderstorm BD Blowing Dust R Rain BN Blowing Sand RW Rain Shower BS Blowing Snow L Drizzle BY Blowing Spray ZR Freezing Rain D Dust ZL Freezing Drizzle F Fog A Hail GF Ground Fog IP Ice Pellets H Haze IPW Ice Pellet Showers IF Ice Fog S Snow K Smoke SW Snow Showers SP Snow Pellets SG Snow Grains IC Ice Crystals Table 5-18 Alaska Weather Depiction Charts Precipitation Intensity Symbols Symbol Meaning
- Light (No symbol) Moderate + Heavy
AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-48
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
5.6.3 Use The Alaska Weather Depiction Charts provide an overview of weather flying categories and other adverse weather conditions for the chart valid time. The chart often does not completely represent the en route conditions because of terrain variations and the possibility of weather occurring between reporting stations. These charts should be used in addition to the latest METAR/SPECIs, pilot weather reports, and radar and satellite imagery for a complete look at the latest flying conditions.
33 43 PLERZ 45 PAFK 3QФ 999 A PACK 45 _PASW 36 PAZk 43 40 48 PAAG PAER 19 PS BABY 999 PASY 27 SMCAZ PALV |44 SORT _PAWR PAEN 10• 60 RUFAZ 38
45. PAL. *KNTUS 36®50 NABAZ 19945 42 PAIL ILI SURFACE OBSERVATIONS PAHO? IMP(devISOWX ISTNID 182 05/04/2005 IFR_MVFR VFR DEWPT(deg F) _ CIG Figure 5-44. AAWU Alaska Weather Depiction Chart - South Central Alaska Example AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-49
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
5.7 Radar Summary Chart The Radar Summary Chart (Figure 5-49) is a computer-generated mosaic of radar echo intensity contours based on Radar Weather Reports (Section 2.3) over the contiguous U.S.
Possible precipitation types, cell movements, maximum tops, locations of line echoes, and remarks are plotted on this chart. Much of this information is often truncated due to space limitations. Severe thunderstorm and tornado watches are plotted if they are in effect when the chart is valid. The Radar Summary Chart is available on the National Weather Service (NWS) Fax Charts web site at: http://weather.noaa.gov/pub/fax/QAUA00.TIF 0920Z MON 13 JUN 2005 RADAR SUMMARY SD095- 220 NE 220
NE NE NE 28 RW NE ¿ NE NE
• NE
NE NE R 190 NEVA NE NE 260 NE NA NET 137 NE NE NE NE -NE.
NE NA NE NE NE NE NA NE NE NE LEGEND. NE ECHO AREAS INTENSITIES 1-3-5 NE NE
WEATHER WAT START END S ¡ PRECIPITATION SPEED NOAA/NUS/NCEP WASHINGTỔN IS DEPT OF COMMERCE NCEP + 09202 MON 13 JUN 2005 RADAR SUMMARY SD09 Figure 5-45. Radar Summary Chart Example
5.7.1 Issuance The chart is issued hourly. Figure 5-50 depicts the WSR-88D weather radar network from which the chart is produced.
5.7.2 Format The Radar Summary Chart depicts precipitation type, intensity, coverage, movement, echoes, and maximum tops.
5.7.2.1 Precipitation Type The precipitation type, determined by a computer model, is indicated on the chart by symbols located adjacent to the precipitation areas. These symbols (Table 5-20) are not in METAR AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-50
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) format. Freezing precipitation is not reported in Radar Weather Reports and, thus, not plotted on the Radar Summary Chart.
Table 5-19. Radar Summary Chart Precipitation Type Symbols
SYMBOL MEANING R Rain RW Rain shower S Snow SW Snow shower T Thunderstorms
5.7.2.2 Precipitation Intensity The six precipitation intensity levels coded in the Radar Weather Report are consolidated into three contour intervals for the Radar Summary Chart (Figure 5-47). Precipitation intensity is correlated only for liquid precipitation, not solid precipitation (e.g., snow).
KOT· KMSX KGGW * KMBX O KNVY KULI OKIEX ÖKBIS KELA KABR O КМРУ KCEB :
КМАХ KUDK KF SDO KARY KHKX KBCI
KDYN A KLOT KOLEO ALŘx KCTS курх FOAK O KIWx TO KUX KDAX KFTCO O KELD KIWXO CKLEX KIL O in St KIND OKIN
OKIE KPUX O KODCO OESGF OKHPE KEYXO OEVIX кРУх KAEX. KUND KIN
• CECAF OKNEX YO KIWA KYDS OKIBB IDE CRAMA CATLE KIZK ксио квих KYUX KHỐX КИАГ OKFYS OKSHV КРОЕ EJAN KFOXO O EVA KGEK O PAPD POTA C Figure 5-46. WSR-88D Weather Radar Network AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-51
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 5-47. Radar Summary Chart Precipitation Intensity
5.7.2.3 Echo Coverage All of the shaded areas within the contours are assumed to contain precipitation. However, actual precipitation coverage is less. This is because only a fraction of a grid box needs to be covered with echoes for the entire grid box to be plotted as precipitation on the chart.
5.7.2.4 Line Echoes When precipitation echoes are reported as a LINE, a line will be drawn through them on the chart (see Table 5-21). Where there is 8/10ths or more coverage, the line is labeled as solid (SLD) at both ends.
Table 5-20. Radar Summary Chart Echo Configuration Symbols
SYMBOL MEANING
8/10ths or greater coverage in a line.
Line of echoes.
Solid line of thunderstorms with intense to extreme precipitation.
5.7.2.5 Cell Movement Cell movement is the average motion of all cells within a configuration. An arrow indicates direction of cell movement. Speed in knots is entered near the arrowhead. LM identifies little AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-52
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) movement. Movement of areas and lines can be significantly different from the motion of the individual cells that comprise these configurations.
Table 5-21. Radar Summary Chart Cell Movement Examples
SYMBOL MEANING
Cell movement to the northeast at 35 knots Cell movement to the east at 24 knots
Cell movement to the south at 18 knots
Cell movement to the southwest at 12 knots LM Little cell movement
5.7.2.6 Maximum Top
Figure 5-48. Radar Summary Chart Maximum Top Example
A maximum top is the altitude of the highest precipitation echo as coded on a Weather Radar Report (Section 2.3). Altitudes are sometimes augmented by satellite data. Individual Radar Weather Reports should be used to determine if satellite data was used for precipitation echo tops.
Tops are plotted in 3-digit groups representing height in hundreds of feet MSL and are underlined. Where it is necessary to offset a top for reasons of insufficient space, a line is drawn from one end of the underline to a small black square which represents the location of the top.
Maximum echo top does not equal maximum cloud top. The maximum echo top is the altitude of the highest light precipitation echo, not highest cloud top. Also, all radar heights are approximations due to radar wave propagation variations depending on atmosphere conditions.
AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-53
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
5.7.2.7 Weather Watch Areas Heavy dashed lines outline Tornado (WT) (Section 5.5.2) and Severe Thunderstorm (WS) Watch (Section 5.4.2) areas. The type of watch and the watch number are enclosed in a rectangle and positioned as closely as possible to the northeast corner of the watch. If there is no room at the northeast corner of the watch, the watch information is offset and connected to the watch by a thin line. The watch number is also printed at the bottom of the chart (in Mexico) together with the issuance time and expiration time under a label reading “WEATHER WATCH AREAS”. In case no weather watch is in effect, “NONE” is printed at the bottom of the chart.
Table 5-22. Radar Summary Chart Weather Watch Area Examples
SYMBOL MEANING
Severe Thunderstorm Watch number 210
Tornado Thunderstorm Watch number 457
5.7.2.8 Operational Contractions Radar sites which report PPINA, PPINE, and PPIOM in their Weather Radar Reports (Section
2.3.1.10) are abbreviated to NA, NE, and OM respectively and plotted over the radar sites on the chart.
Table 5-23. Radar Summary Chart Operational Contractions
SYMBOL MEANING NA Not available NE No echoes OM Out for maintenance
5.7.3 Use The Radar Summary Chart aids in preflight planning by identifying areas of precipitation and highlighting its characteristics. This chart displays precipitation only; it does not display clouds, fog, fronts, or other boundaries. Therefore, the absence of echoes does not equal clear AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-54
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) weather. Cloud tops will be somewhat higher than precipitation tops detected by radar. The chart must be used in conjunction with other charts, reports, and forecasts.
The radar summary chart is for preflight planning only and should always be cross-checked and updated by current WSR-88D images. Once airborne, the pilot must evade individual storms by in-flight observations. This can be done by using visual sighting or airborne radar as well as by requesting weather radar information from En route Flight Advisory Service "Flight Watch" briefers at Automated Flight Service Station (AFSS). AFSS Flight Watch briefers have access to current weather radar imagery.
• 1119Z TUE 28 SEP 2004 RADAR SUMMARY SD115 NE
NE NE NE
NE NE NE NE NE NE NE NE €NE NE NE NE NE RU -180 NA O230 NE NE NE 200 P NE NE NE NEVE SLEI NE NE
NENE NE 'NE NE NE NE NE NE NE NE WE NE
WE NA NE NA NA NA NE 340 280
WEATHER WATCH AREAS ' AREA END AREA OF PRECIPITATION SPEED NONE NOAA/NUS/NCEP WASHINGTON ПСЕР 1119Z TOE 28 SEP 2004 RADAR SUMMARY SD11 Figure 5-49. Radar Summary Chart Example AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-55
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
5.8 Alaska Initial Geopotential Heights and Winds Charts The Alaska Initial Geopotential Heights and Winds Charts (Figure 5-54) display an analysis of the observed height contours and winds at selected constant pressure surfaces (flight levels).
Figure 5-50. Alaskan Initial Geopotential Heights and Winds Chart Example
Table 5-24. Pressure Altitudes of Alaska Initial Geopotential Heights and Winds Charts
CHART PRESSURE ALTITUDE (Feet, MSL)
PRESSURE ALTITUDE (Meters, MSL) 200 MB 39,000 ft 12,000 m 300 MB 30,000 ft 9,000 m 500 MB 18,000 ft 5,500 m 700 MB 10,000 ft 3,000 m 850 MB 5,000 ft 1,500 m
5.8.1 Issuance The charts are issued twice daily with valid times of 00z and 12z and can be found on the Alaska Aviation Weather Unit (AAWU) web site at: http://aawu.arh.noaa.gov/upperwinds.php.
AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-56
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
5.8.2 Analysis The analysis of both height contours and winds are based on output from the North American Mesoscale (NAM) computer forecast model.
5.8.2.1 Height Contours Height contours are lines of constant height referenced to MSL and are used to map the height variations of constant pressure surfaces. They identify and characterize pressure systems on constant pressure charts.
Contours are drawn as solid lines and labeled in meters. The intervals at which the contours are drawn are 60 meters on all of the charts.
5.8.2.2 Winds Wind is plotted in increments of 5 knots (kts). The wind direction is referenced to “true” north and is depicted by a stem (line) pointed in the direction from which the wind is blowing. Wind speed is determined by adding the values of the flags (50 kts), barbs (10kts), and half barbs (5 kts) found on the stem.
A single circle over the station with no wind symbol indicates a calm wind.
Figure 5-55 contains some examples wind symbols.
Figure 5-51. Alaskan Initial Geopotential Heights and Winds Chart Wind Plotting Model
5.8.3 Use The Alaska Initial Geopotential Heights and Winds Charts are used to provide an overview of heights, pressure patterns and winds at specified pressure altitudes. Pressure patterns cause AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-57
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) and characterize much of the weather. Typically, lows and troughs are associated with bad weather, clouds and precipitation, while highs and ridges are associated with good weather.
AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-58