Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
9.3.2.10 Icing Severity plus Supercooled Large Droplets (SLD) - Maximum The Icing Severity plus Supercooled Large Droplets (SLD) product (Figure 9-21) depicts at all altitudes, between 1,000 feet MSL and FL300, 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 (FAR Part 25 Appendix C), can be particularly hazardous to some aircraft.
By FAA policy CIP is a Supplementary Weather Product for enhanced situational awareness only and must bea used with one or more primary products (safety decision) such as an AIRMET or SIGMET (see AIM 7-1-3).
Maximum icing severity (1000 ft. MSL to FL300) Analysis valid 1500 UTC Mon 27 Nov 2006 SLD threat None Trace Light Moderate Heavy If Trace-Light I Light-Moderate I Moderate-Severe Icing PIREP Symbale W Trace Yul Light y Moderate fl Severe Figure 9-21. CIP Icing Severity plus Supercooled Large Droplets (SLD) - 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 AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-23
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) where no probability of icing exists and, therefore, no intensity is necessary. Locations where a threat for SLD exists are depicted with red hatching.
9.3.3 Strengths and Limitations
9.3.3.1 Strengths The CIP product suite is updated hourly and provides a diagnostic tool to assist in determining the probability for icing, the intensity of icing and the threat for SLD.
9.3.3.2 Limitations Actual icing severity may be different than what is depicted on the CIP graphics and plotted PIREPS because:
• Different aircraft types experience different severities of icing in the same atmospheric environments. Severity definitions are currently pilot-based and thus are a function of the aircraft type, flight phase (takeoff/landing, cruise, etc.), aircraft configuration, as well as the pilot’s experience and perception of the icing hazard.
• Assessing the amount and drop size of supercooled liquid water (SLW) in the atmosphere is difficult.
• The Icing Severity products depict the seve rity of the meteorological icing environment and not the resultant icing that may occur on the aircraft.
9.3.4 Uses The CIP Icing Probability product can be used to identify the current three-dimensional probability of icing.
The CIP Icing Severity product can be used to determine the intensity of icing. The CIP Icing Severity – Probability > 25% or Probability > 50% depicts the probability of a given intensity of icing occurring.
Finally the Icing Severity plus SLD product can help in determining the threat of SLD which is particularly hazardous to some aircraft.
Icing PIREPs are plotted on single altitude graphics if the PIREP is within 1,000 feet of the graphic’s altitude and has been observed within 75 minutes of the chart’s valid time. On CIP Max product, 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 product in an effort to reduce clutter.
The PIREP legend is located on the bottom of each graphic.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-24
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
9.4 Forecast Icing Potential (FIP) The Forecast Icing Potential (FIP) provides a three-dimensional forecast of icing potential (or likelihood) using numerical weather prediction model output (Figure 9-17). The FIP product suite is automatically generated with no human modifications. It may be used as a higher resolution supplement to AIRMETs and SIGMETs but is not a substitute for them. It is authorized for operational use only by meteorologists and dispatchers. The forecast area covers the 48-contiguous states, much of Canada and Mexico and their respective coastal waters.
9.4.1 Issuance The FIP is issued every hour and generates hourly forecast for 3 hours into the future. For example, forecasts issued at 1300Z would be valid for 1400Z, 1500Z and 1600Z. Six-, 9-, and 12-hour forecasts are issued every three hours beginning at 00Z. For example, a forecast suite issued at 0300Z would have valid times at 0900Z, 1200Z and 1500Z respectively. The product is issued by the Aviation Weather Center (AWC) and is available through the Aviation Digital Data Service (ADDS) web site at: http://adds.aviationweather.noaa.gov/icing/icing_nav.php.
9.4.2 Content The FIP forecasts the likelihood of icing from super-cooled liquid water droplets. The likelihood field ranges from 0 (no icing) to 100 (icing likely). The scale depicts likelihood of icing using “cool” and “warm” colors, with warmer colors indicating a higher likelihood of icing. Regions depicted in white indicate zero icing potential according to the CIP. Brown regions indicate areas of terrain.
The scale is not calibrated as a true probability value. It does, however, have value in pointing out differences in the likelihood of encountering icing at a given location. For example, a value of 70 does not indicate there is a 70 percent chance of encountering icing. However, when comparing it to other higher or lower values will indicate if there is a greater or lesser likelihood of encountering icing. No information is provided as to the severity of icing and none should be inferred. FIP output is available for 1,000 foot vertical intervals. ADDS displays every third level except on the Flight Path Tool which provides access to all levels.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-25
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 9-22. FIP Example
9.4.3 Strengths and Limitations
Strengths
y The FIP can be used to help determine the forecast for potential for icing through the entire vertical depth of the atmosphere.
y The product is updated hourly.
Limitations
y The product does not display any information about the severity of icing.
y The product only displays the forecast potential for icing, not the absolute probability.
y It is only approved for use by meteorologists and dispatchers.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-26
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
y The product is generated without human modification. Therefore, the forecasts are only as accurate the computer model output used to create them.
9.4.4 Use The FIP is primarily used to help determine the likelihood of icing at the specified forecast valid times.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-27
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
9.5 Graphical Turbulence Guidance (GTG) The Graphical Turbulence Guidance (GTG) product suite provides a three-dimensional diagnosis and forecast of Clear Air Turbulence (CAT) potential. The GTG is created using a combination of computer model output and turbulence observations. The GTG product suite, which consists of the GTG analysis and forecast and Composite analysis and forecast, is automatically generated with no human modifications. It may be used as a supplement to AIRMETs and SIGMETs but is not a substitute for them. It is authorized for operational use only by meteorologist and dispatchers. The GTG is available for the 48-contiguous states, much of Canada and Mexico and their respective coastal waters.
9.5.1 Issuance The GTG analysis is issued hourly. The 3-, 6-, 9-, and 12-hour forecasts are issued every three hours beginning at 00Z. For example, a forecast suite issued at 0600Z would have valid times at 0900Z, 1200Z, 1500Z, and 1800Z respectively. The GTG Analysis and Forecasts, along with the Composite products, are issued by the Aviation Weather Center (AWC) and are available through the Aviation Digital Data Service (ADDS) web site at:
http://adds.aviationweather.noaa.gov/turbulence/turb_nav.php.
9.5.2 Content
9.5.2.1 GTG Analysis and Forecast The GTG Analysis and Forecast graphics depict the location and intensity of potential Clear Air Turbulence (CAT) (Figure 9-18). Standard intensity terminology is used. The GTG output is available for 1,000 foot vertical intervals between FL200 and FL450. ADDS turbulence page displays every third level starting at FL210 level, while the ADDS Flight Path Tool provides access to all levels.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-28
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 9-23. GTG Example
9.5.2.2 GTG Composite Analysis and Forecast The GTG Composite products display the maximum intensity of potential turbulence between FL200 and FL450 (Figure 9-19). In other words, at any given location, the displayed value represents the maximum potential turbulence between FL200 and FL450. Single altitude graphics must be examined to determine the altitude of the potential turbulence.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-29
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
Figure 9-24. GTG Composite Example
9.5.3 Strengths and Limitations The GTG provides an hourly, high resolution analysis and forecast of clear-air turbulence potential at and above FL200. However, the product is only for turbulence associated with upper level fronts and jet streams while other known causes of turbulence are not forecasted.
Strengths
y The product is issued hourly
y Turbulence is plotted to a high resolution.
Limitations
y The accuracy of the analysis is dependent on the number of PIREPs available.
Typically at night fewer pilot reports are received, so the accuracy decreases.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-30
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) y For the GTG forecast, the product is only as accurate the computer model output used to create them.
y The product only displays clear air turbulence (CAT) for upper-level fronts and the jet stream. Other known causes of turbulence are not included in the product.
y Data and forecast are only available for FL200 and above.
y It is only approved for use by meteorologists and dispatchers.
9.5.4 Use The Composite product can provide a quick method to determine what the greatest potential of current or forecast turbulence is at a given location. However, to determine the turbulence potential at any given altitude, the individual altitude products must be viewed.
The ADDS web site allows users to overlay turbulence PIREPS on the single altitude graphics.
For the PIREP to be plotted on the single altitude product, it must be located within 1,000 feet vertically of the altitude and have been reported within 90 minutes of the chart time. For example, if a user viewed the FL240 GTG product with a valid time of 1400Z the displayed PIREPS could be located between FL230 and FL250 and reported between 1230Z and 1400Z.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-31
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
9.6 Meteorological Impact Statement (MIS) A Meteorological Impact Statement (MIS) is an unscheduled flow control and flight operations planning forecast issued by Center Weather Service Units (CWSUs) (Figures 9-21 and 9-22). It is a forecast and briefing product for personnel at Air Route Traffic Control Centers (ARTCCs), Air Traffic Control System Command Center (ATCSCC), Terminal Radar Approach Control Facilities (TRACONS) and Airport Traffic Control Towers (ATCTs) responsible for making flow control-type decisions.
A MIS may be tailored to meet the unique requirements of the host ARTCC. These special requirements will be coordinated between the host ARTCC and the CWSU.
MISs are available on the Aviation Weather Center (AWC) web site at:
http://aviationweather.gov/products/cwsu/.
9.6.1 Valid Period A MIS is valid up to 12 hours after issuance time and details weather conditions expected to adversely impact air traffic flow in the CWSU area of responsibility. The MIS can be immediately effective for existing conditions when CWSU operations begin or for rapidly deteriorating conditions or be effective up to two hours in advance of expected conditions.
9.6.2 MIS Criteria A MIS enables Air Traffic Control (ATC) facility personnel to include the impact of specific weather conditions in their flow control decision-making. At a minimum, a MIS should be issued when:
• Any of the following conditions occur, are forecast to occur, and, if previously forecast, are no longer expected:
o Conditions meeting convective SIGMET criteria (Section 5.1.8)
o Icing - moderate or greater
o Turbulence - moderate or greater
o Heavy precipitation
o Freezing precipitation
o Conditions at or approaching Low IFR
o Surface winds/gusts >30 knots
o Low Level Wind Shear (surface - 2,000 feet)
o Volcanic ash, dust storms, or sandstorms; and
• In the forecaster's judgment, the conditions listed above, or any others, will adversely impact the flow of air traffic within the ARTCC area of responsibility.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-32
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
9.6.3 MIS Issuance MIS phenomena forecasts use the location reference point identifiers depicted on the In-Flight Advisory Plotting Chart (Appendix F), and include the height, extent, and movement of the conditions. MIS product issuances are numbered sequentially beginning at Midnight local time each day. The MIS is disseminated and stored as a "replaceable" product. Therefore, each issuance will contain the details of all pertinent known conditions meeting MIS issuance criteria, including ongoing conditions described in previously issued MISs.
The MIS is distributed to ARTCC personnel, including Traffic Management Unit (TMU) personnel.
9.6.4 Format
Figure 9-25. Meteorological Impact Statement (MIS) Decoding Example
Table 9-5. Meteorological Impact Statement (MIS) – Decoding
LINE CONTENT DESCRIPTION 1 ZFW ARTCC Identification MIS Product type 01 Issuance number VALID 190200-191200 Valid period UTC date/time 2 …FOR ATC PLANNING PURPOSES ONLY… Product use statement 3 FROM OKC TO CDS TO GAG TO END TO OKC Phenomenon location 4 LLWS BLO 020 AGL DUE TO LLJ.
CONDS GRDLY IPVG AFT 10Z Phenomenon description
Any remarks such as “SEE CONVECTIVE SIGMET 8W"; "NO UPDATES AVBL AFT 0230Z";
and forecaster initials and/or facility identifier may be placed at the end of the MIS.
If the phenomenon described in a MIS is no longer expected, a cancellation MIS message may be issued. The FAA header does not contain an issuance number. If the phenomenon described in the MIS is expected to continue beyond the operating hours of the CWSU, then the remark "NO UPDATES AFT ttttZ" (where "ttttZ" is the UTC closing time of the CWSU) is added at the text end.
AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-33
Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009)
9.6.5 Examples
ZOA MIS 01 VALID 041415-041900 ...FOR ATC PLANNING PURPOSES ONLY...
FOR SFO BAY AREA BR/FG WITH CEILING BLW 005 AND VIS OCNL BLW 1SM.
ZOA CWSU
Meteorological Impact Statement issued by the Freemont, California CWSU. First MIS issuance of the day, valid from the 4th day of the month at 1415 UTC, to the 4th day of the month at 1900 UTC. For air traffic control planning purposes only. For the San Francisco Bay Area…mist and fog with ceilings below 500 feet MSL and visibility occasionally below 1 statute mile.
ZOA MIS 02 VALID 041650 ...FOR ATC PLANNING PURPOSES ONLY...
FOR SFO BAY AREA CNL ZOA MIS 01. CONDS HAVE IMPRD.
ZOA CWSU
Meteorological Impact Statement issued by the Freemont, California CWSU. The second MIS issuance of the day, valid the 4th day of the month at 1650 UTC. For air traffic control planning purposes only. For the San Francisco Bay Area. Cancel Freemont, California Meteorological Impact Statement number 1. Conditions have improved.
ZID MIS 03 VALID 041200-042330 ...FOR ATC PLANNING PURPOSES ONLY...
FROM IND TO 17WSW APE TO LOZ TO 13NE PXV TO IND TIL 21Z MOD TURB FL310-390 DUE TO JTST WS.
ZID W OF A LINE FM FWA TO BWG AFT 18Z OCNL SEV TSGR TOPS TO FL450. MOV FM 24035KT. MAX SFC WINDS 60KT.
ZID E OF A LINE FM FWA TO 35SE BKW MOD MXD ICE IN CLDS/PRECIPITATION 020-120. CONDS ENDING W OF A 40S CLE TO 20NE BKW LINE BY 19Z.
ZID CWSU
Meteorological Impact Statement issued by the Indianapolis, Indiana CWSU. The third MIS issuance of the day, valid from the 4th day of the month at 1200 UTC to the 4th day of the month at 2130 UTC. For air traffic control planning purposes only. From Indianapolis, Indiana to 17 nautical miles west-southwest of Appleton, Ohio to London, Kentucky to 13 nautical miles northeast of Pocket City, Indiana to Indianapolis, Indiana. Until 21Z, moderate turbulence between flight level 310 and flight level 390 due to jet stream wind shear.
For the Indianapolis ARTCC airspace west of a line from Fort Wayne, Indiana to Bowling Green, Kentucky. After 18Z, occasional severe thunderstorms, hail, tops to flight level 450. Moving from 240 degrees at 35 knots. Maximum surface winds 60 knots.
For the Indianapolis, Indiana ARTCC airspace east of a line from Fort Wayne, Indiana to 35 nautical miles southeast of Beckley, West Virginia. Moderate mixed icing in clouds and precipitation between 2,000 feet to 12,000 feet MSL. Conditions ending west of a line from 40 AC 00-45F, CHG 2 Section 9: Supplementary Products Page 9-34