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
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) Weather Unit Г1580
AL AL A 200 WINDS A CONTOURS VAL 11160/2005 1ЭV 11760S - 140 Figure 5-52. Alaskan Initial Geopotential Heights and Winds Chart - 200MB Winds and Contours Chart Example A f 412 8g817 Alaska Aviation 1182
- 8940
- I Am 29O90M -90§
- 175 8820- SOONE MINDS AND CONTOURS VALID 122 5/4/2005 - 140 / -135 9120-150 Figure 5-53. Alaskan Initial Geopotential Heights and Winds Chart - 300MB Winds and Contours Chart Example AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-59
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) W0 114 - 522967 5280 Weather Unit
- 1ź5 500HB WINDS AND CONTOURS VALID 122 5/4/2005 5580- 140 Figure 5-54. Alaskan Initial Geopotential Heights and Winds Chart - 500MB Winds and Contours Chart Example
- 2820.
eather Unit T 3000 ·[_→ -1Ý52760. 700MB WINDS AND CONTOURS VALID 12Z 5/4/2005 140 -135 - 130 Figure 5-55. Alaskan Initial Geopotential Heights and Winds Chart - 700MB Winds and Contours Chart Example AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-60
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) AC 00-45F, CHG 2 Section 5: Graphical Observations and Derived Products Page 5-61
Figure 5-56. Alaskan Initial Geopotential Heights and Winds Chart - 850MB Winds and Contours Chart Example
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) 6 PRODUCTS FOR AVIATION HAZARDS
6.1 Significant Meteorological Information (SIGMET) A SIGMET is a concise description of the occurrence or expected occurrence of specified en route weather phenomena which may affect the safety of aircraft operations. SIGMETs are intended for dissemination to all pilots in flight to enhance safety. SIGMETs are issued by the responsible MWO as soon as practical to give notice to operators and aircrews of potentially hazardous en-route conditions.
• SIGMETs are available on the Aviation Digital Data Service (ADDS) web site at:
http://adds.aviationweather.noaa.gov/airmet/
o Alaska SIGMETs are also available on the Alaska Aviation Weather Unit (AAWU) web site at: http://aawu.arh.noaa.gov/
o Hawaii SIGMETs are also available on the NWS WFO Honolulu web site at:
http://www.prh.noaa.gov/hnl/pages/aviation.php
6.1.1 SIGMET Issuance SIGMETs are issued from Meteorological Watch Offices (MWO). The U.S. has three MWOs:
the Aviation Weather Center (AWC), the Alaska Aviation Weather Unit (AAWU), and the Weather Forecast Office (WFO) in Honolulu. Their areas of responsibility are as follows:
• The AWC:
o Twenty (20) domestic Air Route Traffic Control Center (ARTCC) Flight Information Regions (FIRs) covering the conterminous U.S. (CONUS) and adjacent coastal waters (Figure 6-1).
o The New York, Houston, Miami, and San Juan Oceanic FIRs (Figure 6-2).
o The Oakland Oceanic FIR north of 30 north latitude, and the portion east of 140 west longitude which is between the equator and 30 north latitude (Figure 6-3).
• The AAWU is responsible for the Anchorage Continental FIR and Anchorage Oceanic FIR (Figure 6-3).
• WFO Honolulu is responsible for the Oakland Oceanic FIR south of 30 north latitude and between 140 west and 130 east longitude (Figure 6-3).
AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-1
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) San Francisco Chicago Boston Salt Lake City Dallas/Fort Worth Miami Figure 6-1. AWC SIGMET Areas of Responsibility - Conterminous U.S.
NEW YORK OCEANIC FIR
• 130
HOUSTON MIAMI
OCEANIC OCEANIC Q MIAMI FIR FIR OCEANIÇ SER SAN JUAN ı20 → FIR
- 90 - 80 <øБ0 -50 -40 Figure 6-2. AWC SIGMET Areas of Responsibility - Atlantic Basin AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-2
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 6-3. SIGMET Areas of Responsibility – Pacific Basin
6.1.1.1 SIGMET Identification When a SIGMET is issued, it is assigned a unique series identifier:
• AWC for CONUS o NOVEMBER through YANKEE, excluding SIERRA and TANGO
• AWC for Oakland Oceanic FIR o ALFA through HOTEL
• Honolulu MWO for Oakland Oceanic FIR o NOVEMBER through ZULU
• AAWU for Anchorage FIR o INDIA through MIKE AC 00-45F, CHG 2 Section 6: Products for Aviation Hazards Page 6-3