Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 9-6. CCFP Data Block Example
9.1.3.4.1 Tops The word, TOPS, is used to depict the forecast maximum echo tops, in thousands of feet MSL, specified by three selected layers listed in Table 9-1. The heights of the forecast echo tops must cover at least 25 percent of the polygon. The exact location of the highest echo top within the polygon cannot be determined.
Table 9-1. CCFP Tops FL250 – FL310 Flight level 250 to flight level 310 FL310 – FL370 Flight level 310 to flight level 370 370+ Above flight level 370
9.1.3.4.2 Growth The contraction, GWTH, is used to depict the forecast average growth rate of the convection.
The growth rate applies to both the height and areal coverage of the echoes (Table 9-2).
Table 9-2. CCFP Growth ++ Fast positive growth + Moderate positive growth NC No change in the growth
- Negative Growth
9.1.3.4.3 Confidence The contraction, CONF, depicted on the chart is the confidence the depicted polygon will meet the minimum CCFP criteria (Table 9-3).
Table 9-3. CCFP Confidence LOW 25 to 49 percent HIGH 50 to 100 percent
9.1.3.4.4 Coverage The contraction, CVRG, is used to depict the forecast convective coverage within the polygon (Table 9-4). The coverage represents the percentage of the area forecast to be covered by convection.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-5
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Table 9-4. CCFP Coverage 25 – 49% Sparse 50 – 74% Medium 75 –100% Solid
9.1.4 Strengths and Limitations The primary strength of the CCFP is it relies on the vital collaborative efforts between several meteorological units in the private and public sector. The process helps produce the best possible convective forecast to assist in strategic air traffic decision-making.
The limitation of the CCFP is it does not include a forecast for all convection. If the convection does not meet the threshold criteria, it is not included in the CCFP. It is not intended to be used as a tactical short-term decision tool.
9.1.5 Use The CCFP is to be used as a strategic planning tool for air traffic flow management in the 2- to 6-hour forecast period.
The product is not intended to be used as a pilot weather briefing tool.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-6
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
9.2 National Convective Weather Forecast (NCWF) The National Convective Weather Forecast (NCWF) is a near real-time, high resolution display of current and one-hour extrapolated forecasts of selected hazardous convective conditions for the conterminous United States. The NCWF is a supplement to, but does not substitute for, the report and forecast information contained within Convective SIGMETs. The NCWF is intended for use by general aviation, airline dispatchers, and Traffic Management Units.
9.2.1 Issuance The NCWF is issued by the Aviation Weather Center (AWC) and is updated every five minutes.
The product is available on the Aviation Digital Data Service (ADDS) web page at:
http://adds.aviationweather.noaa.gov/convection/java/ and the AWC web site at:
http://aviationweather.gov/products/ncwf/
9.2.2 Content The NCWF displays current convective hazard fields, one-hour extrapolated forecast polygons, forecast speed and directions, and echo tops. Previous performance polygons can also be selected for display (Figure 9-7).
Figure 9-7. NCWF Example AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-7
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
9.2.2.1 Current Convective Hazard Fields The current convective hazard field is a high-resolution display that identifies selected hazards associated with convective precipitation. The field is created from WSR-88D national reflectivity and echo-top mosaics and cloud-to-ground lightning data.
WSR-88D radar reflectivity data are filtered to identify locations having significant convective precipitation. Reflectivity data with echo tops of less than 17,000 feet MSL are eliminated from the data. This process removes ground clutter and anomalous propagation as well as significantly reduces the amount of stratiform (non-convective) precipitation from the data. Most stratiform precipitation tops are below 17,000 feet. The filter also removes shallow convection with tops below 17,000 feet. Shallow convection is often short-lived but can contain conditions hazardous to aviation and may be embedded in stratiform convection.
Frequencies of cloud-to-ground lightning are added to the filtered radar data to provide a more accurate picture of current hazardous convective conditions.
Current convective hazard fields are color coded according to the convective hazard scale for display on the NCWF (Figure 9-8).
Figure 9-8. NCWF Current Convective Hazard Fields Example
9.2.2.1.1 Convective Hazard Field Scale The convective hazard field scale uses six hazard levels (Figure 9-9) to characterize hazardous convection conditions.
The six hazard levels are determined by two factors:
y Intensities and maximum tops of WSR-88D reflectivity data, and
y Frequencies of cloud-to-ground lightning.
Higher hazard levels are associated with higher radar reflectivity intensities and higher frequencies of lightning strikes.
The six hazard levels are reduced to four-color codes for display on the NCWF. The relationships between the six hazard levels and four-color codes are summarized in Figure 9-9.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-8
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 9-9. NCWF Hazard Scale
9.2.2.2 One-Hour Extrapolated Forecast Polygons One-hour extrapolated forecast polygons are high-resolution polygons outlining areas expected to be filled by selected convective hazard fields in one hour. Extrapolated forecasts depict new locations for the convective hazard fields based on their past movements. Extrapolation forecasts do not forecast the development of new convective hazard conditions or the dissipation of existing conditions. Forecasts are provided only for convective hazard scale levels 3 or higher. The forecast polygons do not depict specific forecast hazard levels. On Figure 9-10, the light blue polygon denotes the location of the one-hour forecast convective hazard field.
9.2.2.3 Forecast Speed and Direction Forecast speed and direction are assigned to current convective hazard fields having a onehour extrapolated forecast. A line (or arrow on the AWC JavaScript product) is used to depict the direction of movement (Figure 9-10). The speed in knots is depicted by the first group of two numbers located near the current convective hazard field. The second group of three numbers identifies echo tops.
Forecast speed and direction is only updated every 10 minutes. The larger update time-interval (compared to five-minute updates for the NCWF) smoothes erratic forecast velocities. On Figure 9-10, the forecast direction (depicted by an arrow) is pointing to the southeast and the speed is 25 knots.
9.2.2.4 Echo Tops Echo tops are assigned to current convective hazard fields having a one-hour extrapolated forecast. Echo tops are depicted by a group of three numbers located near the current convective hazard field and is plotted in hundreds of feet MSL (Figure 9-10). The first number of the group identifies forecast speed of movement. On Figure 9-10, the echo tops are 45,000 feet MSL.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-9
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 9-10. NCWF One-Hour Extrapolated Forecast Polygon, Forecast Movement Velocity, and Echo Tops Example
9.2.2.5 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 one-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.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-10
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 9-11. NCWF Previous Performance Polygons Example
9.2.3 The ADDS and AWC JAVA display The ADDS web site allows for the display of all previously discussed attributes of the NCWF.
This site also allows many overlay options including METARs, TAFs, VORs, ARTCC boundaries, counties, highways and rivers. Product animation is also possible on the AWC JavaScript image.
9.2.4 Strengths and Limitations Strengths of the NCWF include:
y Convective hazard fields that agree very well with radar and lightning data,
y Updated every five minutes,
y High-resolution forecasts of convective hazards, and
y Long-lived convective precipitation is well forecast.
Limitations of the NCWF include:
y Initiation, growth, and decay of convective precipitation are not forecast,
y Short-lived or embedded convection may not be accurately displayed or forecast, AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-11
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
y Low-topped convection that contains little or no lightning may not be depicted,
y Erroneous motion vectors are occasionally assigned to storms, and
y Convective hazard field scales are not identified within the forecast polygons.
9.2.5 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, airline dispatchers, aviation meteorologists, and other interested aviation users in the general public. The NCWF is a supplement to, but does not substitute for, the report and forecast information contained in Convective SIGMETs.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-12
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
9.3 Current Icing Product (CIP) The Current Icing Product (CIP) product combines sensor and numerical data to provide a hourly three-dimensional diagnosis of the icing environment. This information is displayed on a suite of twelve graphics which are available for the 48 contiguous United States, much of Canada and Mexico, and their respective coastal waters.
The CIP product suite is automatically produced with no human modifications. Information on the graphics is determined from observational data including WSR-88D radar, satellite, pilot weather reports, surface weather reports, lightning and computer model output.
FAA policy states the CIP is a supplementary weather product for enhanced situational awareness only and must be used with one or more primary products such as an AIRMET or SIGMET (see AIM 7-1-3).
9.3.1 Issuance The CIP product suite is issued hourly 15 minutes after the hour by the Aviation Weather Center (AWC). The products are available through the Aviation Digital Data Service (ADDS) web site at: http://adds.aviationweather.noaa.gov/icing/icing_nav.php.
.
9.3.2 Content The CIP product suite consists of 10 graphics including:
• Icing Probability,
• Icing Probability Maximum (Max),
• Icing Severity,
• Icing Severity Max,
• Icing Severity – Probability > 25%,
• Icing Severity – Probability > 25% Max,
• Icing Severity – Probability > 50%,
• Icing Severity – Probability > 50% Max,
• Icing Severity plus Supercooled Large Droplets (SLD), and
• Icing Severity plus Supercooled Large Droplets (SLD) Max.
The CIP products are generated for individual altitudes from 1,000 feet MSL to Flight Level (FL) 300 at intervals of 1,000 feet.
The CIP 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 the 1,000 AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-13
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) 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 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.
9.3.2.1 Icing Probability The Icing Probability product (Figure 9-12) displays, at a single altitude, the probability of icing.
Probabilities range from 0% (no icing expected) to 85% or greater (nearly certain icing.)
By FAA policy CIP is a Supplementary Weather Product for enhanced situational awareness only and must be used with one or more primary products (safety decision) such as an AIRMET or SIGMET (see AIM 7—1-3).
Probability of icing at 3000 ft. MSL Analysis valid 1500 UTC Mon 27 Nov 2006 terrain 5 15 25 35 45 55 65 75 g Negative LJ Trace-Light Wu Light-Moderate WI Moderate-Savera (percent) Icing PIREP Symbols LI Troce Lyl Light ' Moderate Y/ savera Figure 9-12. CIP Icing Probability (3,000 feet MSL) Example AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-14
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) "Cool" colors represent low probabilities and "warm" colors represent higher probabilities.
Probabilities do not reach 100% 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.
9.3.2.2 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% (no icing expected) to 85% or greater (nearly certain icing.)
dy FAA policy CIP is a Supplementary Weather Product for enhanced situational awareness only and must be used mith one or more primary products (safety decision) such as an AIRMET or SIGMET (see AIM 7-1-3).
Maximum icing probability (1000 ft. MSL to FL300) Analysis valid 1600 UTC Mon 27 Nov 2006 25 45 ₴5 75 If Trace-Light Vp Light-Maderate _I Moderate-Savera (percent) cing PIREP Symbals W Trace Ly Light ly/ Maderate Lyl Severa Figure 9-13. CIP Icing Probability - Max Example "Cool" colors represent low probabilities and "warm" colors represent higher probabilities.
Probabilities do not reach 100% because the data used to determine the probability of icing AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-15
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) cannot diagnose, with absolute certainty, the presence of icing conditions at any location and altitude. White regions indicate the probability of icing is zero.
9.3.2.3 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 standard icing intensity categories: trace, light, moderate and heavy.
By FAA policy CIP is a Supplementary Weather Product for enhanced situational awareness only and must be used with one or more primary products (safety decision) such as an AIRMET or SIGMET (see AIM 7—1-3).
Icing severity at 3000 ft. MSL Analysis valid 1500 UTC Mon 27 Nov 2006 terrain None Trace Light Moderate Heavy g Negative 4J Trace-Light W Light-Maderate I Moderate-Savare Icing PIREP Symbals W Trace l Light a maderate Ly severe Figure 9-14. CIP 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.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-16