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Figure 9-10. NCWF One-Hour Extrapolated Forecast Polygon, Forecast Movement Velocity, and Echo Tops Example Previous Performance Polygons Previous performance polygons are magenta polygons displaying the previous hour’s extrapolated forecast polygons with the current convective hazard fields. A perfect forecast would have the polygons filled with convective hazard scale levels 3 or higher data. Levels 1 and 2 would be outside the polygons. The display of previous performance polygons allows the user to review the accuracy of the previous hour’s forecast.
Figure 9-11 depicts current convective hazard fields and previous performance polygons (magenta) valid at 1500Z. The previous performance polygons are the 1-hour extrapolated forecasts made at 1400Z. Although the polygons do not perfectly match the current level 3 and higher hazard fields, the forecasts are still fairly accurate.
Newly developed convective hazard levels 3 and higher do not have previous performance polygons. Extrapolated forecasts do not forecast developing hazardous convective.
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Figure 9-11. NCWF Previous Performance Polygons Example Strengths and Limitations Strengths Strengths of the NCWF include:
• Convective hazard fields that agree very well with radar and lightning data,
• Updated every five minutes,
• High-resolution forecasts of convective hazards, and
• Long-lived convective precipitation is well forecast.
Limitations Limitations of the NCWF include:
• Initiation, growth, and decay of convective precipitation are not forecast,
• Short-lived or embedded convection may not be accurately displayed or forecast,
• Low-topped convection that contains little or no lightning may not be depicted, Section 9: New Generation Weather Products Page 9-12
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• Erroneous motion vectors are occasionally assigned to storms, and
• Convective hazard field scales are not identified within the forecast polygons.
Uses of the NCWF The purpose of the National Convective Weather Forecast (NCWF) is to produce a convective hazard field diagnostic and forecast product based on radar data, echo top mosaics, and lightning data. The target audience includes the FAA and other government agencies, pilots, aircraft dispatchers, aviation meteorologists, and other interested aviation users in the general public.
Current and Forecast Icing Products (CIP/FIP) The Current Icing Product (CIP) combines sensor and numerical weather prediction (NWP) model data to provide an hourly three-dimensional diagnosis of the icing environment. This information is displayed on a suite of graphics available for the 48 contiguous United States, much of Canada and Mexico, and their respective coastal waters. The Forecast Icing Product (FIP) provides the same suite of products describing the icing environment in the future and is solely NWP model-based.
The CIP/FIP product suites are automatically produced with no human modifications.
Information on the graphics is determined from NWP model output, observational data including WSR-88D radar, satellite, pilot weather reports, surface weather reports, and lightning network data.
Issuance The CIP and FIP product suites are issued hourly ~15 minutes after the hour by the Aviation Weather Center (AWC). The products are available through the Aviation Digital Data Service (ADDS) at http://www.aviationweather.gov/adds/icing/.
Content The CIP/FIP product suite consists of 10 graphics including:
• Icing Probability,
• Icing Probability Maximum (Max),
• Icing Severity,
• Icing Severity Max,
• Icing Severity – Probability > 25 percent,
• Icing Severity – Probability > 25 percent Max,
• Icing Severity – Probability > 50 percent,
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• Icing Severity – Probability > 50 percent Max,
• Icing Severity plus Supercooled Large Drop (SLD), and
• Icing Severity plus Supercooled Large Drop (SLD) Max.
The CIP/FIP products are generated for individual altitudes from 1,000 feet MSL to Flight Level (FL) 300 at intervals of 1,000 feet. Horizontal resolution is 20 km. FIP products are available at 1, 2, 3, 6, 9, and 12- h forecast lead times. With near-term NWP enhancements, these are planned to change to 500 ft. MSL horizontal and 13 km vertical resolution, and forecasts will be extended to 18 h with 1-h granularity.
The CIP/FIP Max products are a composite product which displays information about icing at all altitudes from 1,000 feet MSL to FL300. Single altitudes are referenced to MSL from 1,000 to 17,000 feet and Flight Levels above 17,000 feet. The ADDS Web site allows for access to every other altitude (1,000 FT, 3,000 FT, 5,000 FT, etc…). However, all altitudes can be accessed by use of the Flight Path Tool on the ADDS site.
Icing PIREPs are plotted on a single altitude graphic if the PIREP is within 1,000 feet of the selected altitude and has been observed within 75 minutes of the chart’s valid time. On the CIP/FIP Max graphics, PIREPs for all altitudes (i.e. 1,000 feet MSL to FL300) are displayed.
However, negative reports of icing are not plotted on the CIP Max products in an effort to reduce clutter. The PIREP legend is located on the bottom of each graphic.
Icing Probability The Icing Probability product (Figure 9-12) displays, at a single altitude, the probability of icing.
Probabilities range from 0 percent (no icing expected) to 85 percent or greater (nearly certain icing).
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Figure 9-12. CIP/FIP Icing Probability (3,000 Feet MSL) Example “Cool” colors represent low probabilities and “warm” colors represent higher probabilities.
Probabilities do not reach 100 percent because the data used to determine the probability of icing cannot diagnose, with absolute certainty, the presence of icing conditions at any location and altitude. White regions indicate that the probability of icing is zero. Brown regions indicate where higher-elevation terrain extends above the altitude of the particular graphic.
Icing Probability – Maximum The Icing Probability - Maximum graphic (Figure 9-13) displays the probability of icing at all altitudes from 1,000 feet MSL to FL300. Probabilities range from 0 percent (no icing expected) to 85 percent or greater (nearly certain icing).
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Figure 9-13. CIP/FIP Icing Probability – Max Example “Cool” colors represent low probabilities and “warm” colors represent higher probabilities.
Probabilities do not reach 100 percent because the data used to determine the probability of icing cannot diagnose, with absolute certainty, the presence of icing conditions at any location and altitude. White regions indicate the probability of icing is zero.
Icing Severity The Icing Severity product (Figure 9-14) depicts, at a single altitude, the intensity of icing expected at locations where the Icing Probability product depicts possible icing. Icing intensity is displayed using icing intensity categories: trace, light, moderate, and heavy.
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Figure 9-14. CIP/FIP Icing Severity (3,000 Feet MSL) Example The lightest blue color represents trace icing. As the blue-color shades become darker, the icing intensity increases. The darkest blue color represents heavy icing. White regions indicate where no probability of icing exists and, therefore, no intensity is necessary. Brown regions indicate where higher-elevation terrain extends above the altitude of the particular graphic.
Icing Severity – Maximum The Icing Severity - Maximum product (Figure 9-15) displays the intensity of icing at all altitudes from 1,000 feet MSL to FL300. Icing intensity is displayed using icing intensity categories: trace, light, moderate, and heavy.
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Figure 9-15. CIP/FIP Icing Severity – Max Example The lightest blue color represents trace icing. As the blue color shades become darker, the icing intensity increases. The darkest blue color represents heavy icing. White regions indicate where no probability of icing exists and, therefore, no intensity is necessary.
Icing Severity – Probability > 25 Percent The Icing Severity – Probability > 25 percent product (Figure 9-16) depicts, at a single altitude, where a 26 to 100 percent probability exists for the indicated icing intensity. Icing intensity is displayed using icing intensity categories: trace, light, moderate, and heavy.
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Figure 9-16. CIP/FIP Icing Severity Probability >25 Percent Example The lightest blue color represents trace icing. As the blue color shades become darker, the icing intensity increases. The darkest blue color represents heavy icing. White regions indicate where no probability of icing exists and, therefore, no intensity is necessary. Brown regions indicate higher-elevation terrain extending above the altitude of the particular graphic. A gray color is used to mask the intensity pixels where the probability of icing is 25 percent or less.
Icing Severity – Probability > 25 Percent – Maximum The Icing Severity – Probability > 25 percent - Maximum product (Figure 9-17) depicts, at all altitudes from 1,000 feet MSL to FL300, where the probability of the indicated icing intensity is 26 to 100 percent. Icing intensity is displayed using icing intensity categories: trace, light, moderate, heavy.
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Figure 9-17. CIP/FIP Icing Severity Probability >25 Percent Example The lightest blue color represents trace icing. As the blue color shades become darker, the icing intensity increases. The darkest blue color represents heavy icing. White regions indicate where no probability of icing exists and, therefore, no intensity is necessary. A gray color is used to mask the intensity pixels where the probability of icing is 25 percent or less.
Icing Severity – Probability > 50 Percent The Icing Severity – Probability > 50 percent product (Figure 9-18) depicts, at a single altitude, where the probability of the indicated icing intensity 51 to 100 percent. Icing intensity is displayed using icing intensity categories: trace, light, moderate, and heavy.
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Figure 9-18. CIP/FIP Icing Severity Probability > 50 Percent Example The lightest blue color represents trace icing. As the blue color shades become darker, the icing intensity increases. The darkest blue color represents heavy icing. White regions indicate where no probability of icing exists and, therefore, no intensity is necessary. Brown regions indicate where higher-elevation terrain extends above the altitude of the particular graphic. A gray color is used to mask the intensity pixels where the probability of icing is 50 percent or less.
Icing Severity – Probability > 50 Percent – Maximum The Icing Severity – Probability > 50 percent - Maximum product (Figure 9-19) depicts, at all altitudes from 1,000 feet MSL to FL300, where the probability of the indicated icing intensity is 51 to 100 percent. Icing intensity is displayed using icing intensity categories: trace, light, moderate, and heavy.
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Figure 9-19. CIP/FIP Icing Severity Probability > 50 Percent – Max Example The lightest blue color represents trace icing. As the blue color shades become darker, the icing intensity increases. The darkest blue color represents heavy icing. White regions indicate where no probability of icing exists and, therefore, no intensity is necessary. A gray color is used to mask the intensity pixels where the probability of icing is 50 percent or less.
Icing Severity Plus Supercooled Large Drops (SLD) The Icing Severity plus Supercooled Large Drops (SLD) product (Figure 9-20) depicts, at a single altitude, the intensity of icing expected as well as locations where a threat for SLD exists.
SLD is defined as supercooled water droplets larger than 50 micrometers in diameter. These size droplets include freezing drizzle and/or freezing rain aloft. SLD, which are outside the icing certification envelopes (14 CFR part 25 Appendix C), can be particularly hazardous to some aircraft.
Icing intensity is displayed using icing intensity categories: trace, light, moderate, and heavy.
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