Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Table 8-6. Mid-Level SIGWX Chart Issuance Schedule North Atlantic Ocean Region (NAT) Valid Times (UTC) Issued 0800 Issued 1400 Issued 2000 Issued 0200 0000 0600 1200 1800
8.3.3 Use The Mid-Level Significant Weather (SIGWX) Chart is used to determine an overview of selected flying weather conditions between 10,000 feet MSL and FL450. It can be used by airline dispatchers for flight planning and weather briefings before departure and by flight crew members during flight.
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Figure 8-29. Mid-Level SIGWX Chart Example AC 00-45F, CHG 2 Section 8: Forecast Charts Page 8-22
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
8.4 High-Level Significant Weather (SIGWX) Charts High-Level Significant Weather (SIGWX) Charts (Figure 8-30) provide a forecast of significant en route weather phenomena over a range of flight levels from FL250 to FL630, and associated surface weather features. Each chart depicts a “snap-shot” of weather expected at the specified valid time. They are available on the Aviation Weather Center (AWC) web site at:
http://aviationweather.gov/products/swh/.
Figure 8-30. High-level SIGWX Chart Example AC 00-45F, CHG 2 Section 8: Forecast Charts Page 8-23
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
8.4.1 Content
8.4.1.1 Thunderstorms and Cumulonimbus Clouds The abbreviation CB is only included where it refers to the expected occurrence of an area of widespread cumulonimbus clouds, cumulonimbus along a line with little or no space between individual clouds, cumulonimbus embedded in cloud layers, or cumulonimbus concealed by haze. It does not refer to isolated or scattered cumulonimbus not embedded in cloud layers or concealed by haze.
Each cumulonimbus area is identified with CB and characterized by coverage, bases and tops.
Coverage (Table 8-3) is identified as isolated (ISOL) meaning less than 1/8th, occasional (OCNL) meaning 1/8th to 4/8ths, and frequent (FRQ) meaning more than 4/8ths coverage.
Isolated and occasional CBs are further characterized as embedded (EMBD). The chart will not display isolated or scattered cumulonimbus clouds unless they are embedded in clouds, haze, or dust.
The vertical extent of cumulonimbus layer is specified by top and base heights. Bases that extend below FL250 (the lowest altitude limit of the chart) are encoded XXX.
Cumulonimbus clouds (CBs) are depicted by an enclosed (red) scalloped lines (Figure 8-31).
The identification and characterization of each cumulonimbus area will appear within or adjacent to the outlined area. If the identification and characterization is adjacent to an outlined area, an arrow will point to the associated cumulonimbus area.
On significant weather charts, the inclusion of CB or the thunderstorm symbol should be understood to include all weather phenomena normally associated with cumulonimbus or thunderstorm, namely, moderate or severe icing, moderate or severe turbulence, and hail.
Figure 8-31. High-Level SIGWX Chart Thunderstorm and Cumulonimbus Cloud Examples
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8.4.1.2 Moderate or Severe Turbulence Forecast areas of moderate or severe turbulence (Figure 8-32) associated with wind shear zones and/or mountain waves are enclosed by bold yellow dashed lines. Intensities are identified by standard symbols (Appendix J).
The vertical extent of turbulence layers is specified by top and base heights, separated by a horizontal line. Turbulence bases which extend below the layer of the chart are identified with XXX.
Thunderstorm turbulence is not identified.
Figure 8-32. High-Level SIGWX Chart Turbulence Examples
8.4.1.3 Moderate or Severe Icing Moderate and severe icing (outside of thunderstorms) above FL240 is rare and is not generally forecasted on High-Level Significant Weather Prog charts.
8.4.1.4 Jet Streams A jet stream axis with a wind speed of more than 80 knots is identified by a bold green line. An arrowhead is used to indicate wind direction. Wind change bars (double-hatched, light green lines) positioned along a jet stream axis identifies 20 knot wind speed changes (Figure 8-33).
Symbols and altitudes are used to further characterize a jet stream axis. A standard wind symbol (light green) is placed at each pertinent position to identify wind velocity. The flight level FL in hundreds of feet MSL is placed adjacent to each wind symbol to identify the altitude of the jet stream axis.
Jet stream vertical depth (jet depth) forecasts are included when the maximum speed is 120 knots or more. Jet depth is defined as the vertical depths to the 80 knot wind field above and below the jet stream axis using flight levels. Jet depth information is placed at the maximum speed point only, normally at one point on each jet stream. When the jet stream is very long and there are several wind maxima, then each maximum should include forecasts of the vertical depth.
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Figure 8-33. High-Level SIGWX Chart Jet stream Example Forecast maximum speeds of 100 knots at FL310 at one location and 120 knots at FL290 at another location.
At the latter location, the base of the 80 knot wind field it FL210, and the top of the 80 knot wind field is FL340.
8.4.1.5 Surface Fronts with Speed and Direction of Movement Surface fronts are depicted using the standard symbols found on the surface analysis chart.
(Figure 8-2). An arrow identifies the direction of frontal movement with the speed in knots plotted near the arrow head (Figure 8-34).
Figure 8-34. High Level SIGWX Chart Surface Front with Speed and Direction of Movement Example
8.4.1.6 Tropopause Heights Tropopause heights are plotted at selected locations on the chart. They are enclosed by rectangles and plotted in hundreds of feet MSL (Figure 8-35). Centers of high (H) and low (L) tropopause heights are enclosed by polygons and plotted in hundreds of feet MSL.
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Figure 8-35. High-Level SIGWX Chart Tropopause Height Examples
8.4.1.7 Tropical Cyclones Tropical cyclones are depicted by the appropriate symbol (Figure 8-36) with the storm’s name positioned adjacent to the symbol. Cumulonimbus clouds meeting chart criteria are identified and characterized relative to each storm.
Figure 8-36. High Level SIGWX Chart Tropical Cyclone Examples
8.4.1.8 Severe Squall Lines Severe squall lines are lines of CBs with 5/8 coverage or greater. They are identified by long dashed (white) lines with each dash separated by a V (Figure 8-37).Cumulonimbus clouds meeting chart criteria are identified and characterized with each squall line.
Figure 8-37. High-Level SIGWX Chart Severe Squall Line Example
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8.4.1.9 Volcanic Eruption Sites Volcanic eruption sites are identified by a trapezoidal symbol (Figure 8-38). The dot on the base of the trapezoid identifies the location of the volcano. The name of the volcano, its latitude, and its longitude are noted adjacent to the symbol.
Figure 8-38. High-Level SIGWX Chart Volcanic Eruption Site Example
8.4.1.10 Widespread Sandstorms and Dust storms Widespread sandstorms and dust storms are labeled with the appropriate symbol (Appendix I).
The vertical extent of sand or dust is specified by top and base heights, separated by a horizontal line. Sand or dust which extends below the lower limit of the chart (FL240) is identified with XXX (Figure 8-39).
Figure 8-39. High-Level SIGWX Chart Widespread Sandstorm and Dust Storm Example
8.4.2 Issuance In accordance with the World Meteorological Organization (WMO) and the World Area Forecast System (WAFS) of the International Civil Aviation Organization (ICAO), High-Level significant weather (SIGWX) forecasts are provided for the en-route portion of international flights. The National Weather Service (NWS) Aviation Weather Center (AWC) in Kansas City, MO provides a suite of SIGWX forecast products for the World Area Forecast Center (WAFC) in Washington, D.C. The charts are available for different ICAO areas around the world as defined in Table 8-7.
The charts are not amended.
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Table 8-7. High-Level SIGWX Chart Issuance Schedule – WAFC Washington ICAO Area Chart Type Chart Area Valid Times (UTC) Issued 0800 Issued 1400 Issued 2000 Issued 0200 A Americas Mercator 0000 0600 1200 1800 B1 Americas/ Africa Mercator 0000 0600 1200 1800 F Pacific Mercator 0000 0600 1200 1800 H N America/ Europe Polar Stereographic 0000 0600 1200 1800 I N Pacific Polar Stereographic 0000 0600 1200 1800 J S Pacific Polar Stereographic 0000 0600 1200 1800 M Pacific Mercator 0000 0600 1200 1800
The WAFC in London, England also issues High-Level Significant Weather (SIGWX) Charts for other geographical areas of the world. Both Washington and London WAFC charts are available online at: http://aviationweather.gov/iffdp/sgwx.shtml
8.4.3 Use High-Level Significant Weather (SIGWX) Charts are provided for the en route portion of international flights. These products are used directly by airline dispatchers for flight planning and weather briefings before departure and by flight crew members during flight.
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Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) PGEE07 KKCI 230000 FIXED PIC WASHINGTON "1270 340 340 ICAO TIME FORECAST CHART VALID 00 UTC 24 OCT 2006 SO ELE STORET • SERE TO CLEANE MENDA 340 340 340 [390] 300 [390 500 500 EMEL "PAUL" 530 530 530 530 530 INS 98-46 530 530 530 500 500 20 340 450 450 XXX 400 XXX 390 30/6: FL330 1270 390 340 Figure 8-40. High-Level SIGWX Chart - ICAO Area A Example AC 00-45F, CHG 2 Section 8: Forecast Charts Page 8-30
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Figure 8-41. High-Level SIGWX Chart - ICAO Area B1 Example
Figure 8-42. High-Level SIGWX Chart - ICAO Area F Example AC 00-45F, CHG 2 Section 8: Forecast Charts Page 8-31
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Figure 8-43. High-Level SIGWX Chart - ICAO Area H Example
Figure 8-44. High-Level SIGWX Chart - ICAO Area I Example AC 00-45F, CHG 2 Section 8: Forecast Charts Page 8-32