Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) AC 00-45F, CHG 2 Section 8: Forecast Charts Page 8-33
Figure 8-45. High-Level SIGWX Chart - ICAO Area J Example
Figure 8-46. High-Level SIGWX Chart - ICAO Area M Example
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) 9 SUPPLEMENTARY PRODUCTS
9.1 Collaborative Convective Forecast Product (CCFP) The Collaborative Convective Forecast Product (CCFP) is a graphical representation of forecast convective occurrence verifying at 2-, 4 -, and 6-hours after issuance time (Figure 9-1).
Convection, for the purposes of the CCFP forecast, is defined as a polygon of at least 3,000 square miles containing all of the following threshold criteria:
• A coverage of at least 25 percent of echoes with at least 40 dBZ composite reflectivity,
• A coverage of at least 25 percent of echoes with echo tops of FL250 or greater, and
• A forecaster confidence of at least 25 percent.
All three threshold criteria must be met for any area of convection 3,000 square miles or greater to be included in a CCFP forecast. This is defined as the minimum CCFP criteria. Any area of convection, which is forecasted to NOT meet all three of these criteria, is NOT included in a CCFP forecast.
The CCFP is intended to be used as a strategic planning tool for air traffic flow management. It aids in the reduction of air traffic delays, reroutes and cancellations due to significant convection. It is not intended to be used for tactical air traffic flow decisions, in the airport terminal environment, or for pilot weather briefing purposes. The graphical representation is subject to annual revision.
Figure 9-1. CCFP Example
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-1
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
9.1.1 Issuance The CCFP is issued by the Aviation Weather Center (AWC) from March through October for the 48-contiguous states. Canadian forecasts are included on the product are available for southern Ontario and Quebec between April through September. This area is roughly from north of Wisconsin extending eastward to north of Maine.
The CCFP is issued every two hours, eleven times per day. Issuance times are from 08Z to 04Z during standard time and from 07Z to 03Z during daylight savings time. The product can be found on the AWC web page at http://aviationweather.gov/products/ccfp/.
9.1.2 Collaboration The CCFP is produced from a collaborative effort between public and private meteorologists.
The collaboration occurs between meteorologists from the Aviation Weather Center (AWC), Center Weather Service Units (CWSU), Meteorological Services of Canada (MSC), commercial airlines offices, and other private weather companies.
9.1.3 Content Data graphically displayed on the CCFP consist of coverage of convection within a defined polygon, forecaster confidence of convective occurrence, and forecast movement of the convective areas. A data block also displays text information about coverage and confidence as well as forecast echo tops and convective growth information.
9.1.3.1 Coverage The convective coverage within the forecast polygon is represented by the amount of fill within the polygon (Figure 9-2).
y Solid coverage, depicted by solid fill, means 75 to 100 percent of the polygon is forecast to contain convection.
y Medium coverage, defined by medium fill, indicates 50-74 percent of the polygon is forecast to contain convection.
y Sparse coverage, represented by sparse fill, means 25-49 percent of the polygon is forecast to contain convection.
A line of forecast convection, either within a forecast area or alone, is depicted by a solid purple line. For a line of convection to be forecast, it must meet the flowing criteria:
y Its length must be at least 100 miles long,
y The width of the line must be 40NM wide, and
y 75 percent of the line must be expected to contain convection.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-2
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-3
Figure 9-2. CCFP Forecast Convective Coverage
9.1.3.2 Confidence Confidence represents the subjective opinion of the forecasters that the polygon will meet the minimum CCFP threshold criteria. The forecaster’s confidence is represented by the color used to depict the polygon (Figure 9-3).
y A blue color represents high forecaster confidence (50-100 percent) the forecast convection will meet the minimum criteria.
y A gray color indicates low forecaster confidence (25-49 percent) the forecast convection will meet the minimum criteria.
Confidence is not to be associated with probability of occurrence.
Figure 9-3. CCFP Forecast Confidence
9.1.3.3 Movement Forecast movement for each polygon or line is indicated with a gray or blue arrow (Figure 9-4).
The arrow points in the direction of forecast movement. A number at the tip of the arrow represents the speed in knots.
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 9-4. CCFP Forecast Convective Movement
9.1.3.4 Data Block A data block is located adjacent to every polygon forecast (Figure 9-5 and Figure 9-6). A thin line connects the data block to the associated forecast area. Each data block contains information about forecast maximum echo tops (TOPS), convective growth rates (GWTH), forecaster confidence (CONF), and convection coverage (CRVG).
Figure 9-5. CCFP Data Block
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-4
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