Aviation Weather Services, Advisory Circular 00-45G Change 2 (October 2014) certification envelopes (14 CFR part 25 Appendix C), can be particularly hazardous to some aircraft.
Figure 9-21. CIP/FIP 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 where no probability of icing exists and, therefore, no intensity is necessary. Locations where a threat for SLD exists are depicted with red hatching.
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Aviation Weather Services, Advisory Circular 00-45G Change 2 (October 2014) Strengths and Limitations 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.
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 severity of the meteorological icing environment and not the resultant icing that may occur on the aircraft.
Uses The CIP/FIP Icing Probability product can be used to identify the current and forecast three-dimensional probability of icing. The CIP/FIP should be used in conjunction with the report and forecast information contained in an AIRMET and SIGMET.
The CIP/FIP Icing Severity product can be used to determine the intensity of icing. The CIP/FIP Icing Severity – Probability > 25 percent or Probability > 50 percent 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/FIP 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/FIP Max product in an effort to reduce clutter. The PIREP legend is located on the bottom of each graphic.
Section 9: New Generation Weather Products Page 9-25
Aviation Weather Services, Advisory Circular 00-45G Change 2 (October 2014) Graphical Turbulence Guidance (GTG2) 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 should be used in conjunction with the report and forecast information contained in an AIRMET and SIGMET. The GTG is available for the 48 contiguous states, much of Canada and Mexico and their respective coastal waters.
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.
Content GTG Analysis and Forecast The GTG Analysis and Forecast graphics depict the location and intensity of potential Clear Air Turbulence (CAT) (Figure 9-22). Standard intensity terminology is used. The GTG output is available for 1,000-foot vertical intervals between 10,000 feet MSL and FL450. ADDS turbulence page displays every second level starting at 10,000 feet MSL, while the ADDS Flight Path Tool provides access to all levels.
Section 9: New Generation Weather Products Page 9-26
Aviation Weather Services, Advisory Circular 00-45G Change 2 (October 2014)
Figure 9-22. GTG Example GTG Composite Analysis and Forecast The GTG Composite products display the maximum intensity of potential turbulence between 10,000 feet MSL and FL450 (Figure 9-23). In other words, at any given location, the displayed value represents the maximum potential turbulence between 10,000 feet MSL and FL450.
Single altitude graphics must be examined to determine the altitude of the potential turbulence.
Section 9: New Generation Weather Products Page 9-27
Aviation Weather Services, Advisory Circular 00-45G Change 2 (October 2014) GTG2 - Maximum turbulence intensity (10000 ft. MSL to FL450) Valid 1200 UTC Fri 18 Oct 2013 00-hr forecast from 1200 VTC 18 Oct ADDE None Light Moderate or greater Turb PIREP Symbols 1 Smooth A Light A Moderate A Savera Smooth-Light - A Light-Moderate / Moderate-Severe A Extreme Figure 9-23. GTG Composite Example
9.5.3 Strengths and Limitations The GTG provides an hourly, high resolution analysis and forecast of clear-air eddy dissipation rate (EDR) at and above 10,000 feet MSL. However, the product is only for turbulence associated with upper level fronts and jet streams while other known causes of turbulence are not forecasted.
9.5.3.1 Strengths
• The product is issued hourly
• Turbulence is plotted to a high resolution.
Section 9: New Generation Weather Products Page 9-28
Aviation Weather Services, Advisory Circular 00-45G Change 2 (October 2014) Limitations
• T he accuracy of the analysis is dependent on the number of PIREPs available.
Typically at night fewer pilot reports are received, so the accuracy decreases.
• For the GTG forecast, the product is only as accurate the computer model output used to create them.
• 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.
• Data and forecast are only available for 11,000 feet MSL and above.
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.
Section 9: New Generation Weather Products Page 9-29
Aviation Weather Services, Advisory Circular 00-45G, Change 2 (October 2014)
Meteorological Impact Statement (MIS) An MIS is an unscheduled flow control and flight operations planning forecast issued by Center Weather Service Units (CWSUs) (Figures 9-24 and 9-25 and Table 9-5). 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.
An 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.
Valid Period An 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.
MIS Criteria An 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, an MIS should be issued when:
• Any of the following conditions occur, are forecast to occur, and, if previously forecast, are no longer expected:
• Conditions meeting convective SIGMET criteria (Section 5.1.8)
• Icing - moderate or greater
• Turbulence - moderate or greater
• Heavy precipitation
• Freezing precipitation
• Conditions at or approaching Low Instrument Flight Rules (IFR)
• Surface winds/gusts >30 knots
• Low Level Wind Shear (surface - 2,000 feet)
• 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.
Section 9: New Generation Weather Products Page 9-30
Aviation Weather Services, Advisory Circular 00-45G, Change 2 (October 2014)
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 for internal use by ARTCC personnel, including Traffic Management Unit (TMU) and TRACON as needed. The MIS is not intended for use by pilots or dispatchers.
Format
Figure 9-24. Meteorological Impact Statement (MIS) Decoding Example
Table 9-5. Meteorological Impact Statement (MIS) – Decoding
LINE CONTENT DESCRIPTION 1 ZFW ARTCC Identification 1 MIS Product type 1 01 Issuance number 1 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 an 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.
Section 9: New Generation Weather Products Page 9-31
Aviation Weather Services, Advisory Circular 00-45G, Change 2 (October 2014)
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 2330 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 nautical miles south of Cleveland, Ohio to 20 nautical miles northeast of Beckley, West Virginia by 1900Z.
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Aviation Weather Services, Advisory Circular 00-45G, Change 2 (October 2014) Anchorage CWSU Seattle ChiS U Minneapolis CW/SU * Oakland Salt Lake Ca
- CWSU Denver CW/SU Chicago Cili's * Washingt , D.C.
Chis Los Angel CuV'S Uz Memphis CurSU Abuquerque Chi/SU * _ Fort worth Cries Honolulu CWSU * Houston CH/SU CựSU Figure 9-25. Center Weather Service Unit (CWSU) Areas of Responsibility - CONUS Figure 9-26. CWSU Anchorage, AK (PAZA) Area of Responsibility Section 9: New Generation Weather Products Page 9-33
Aviation Weather Services, Advisory Circular 00-45G, Change 2 (October 2014)
Ceiling and Visibility Analysis (CVA) The Ceiling and Visibility Analysis (CVA) product provides a real-time analysis of current observed and estimated C&V (ceiling and visibility) conditions across the continental United States. The product is primarily intended to help the general aviation pilot (particularly the Visual Flight Rules (VFR)-only pilot) avoid IFR conditions. However, CVA's overview of ceiling and visibility conditions can be useful to others involved in flight planning or weather briefing.
Issuance CVA is issued every five minutes and is available through the Aviation Weather Center’s (AWC) Aviation Digital Data Service (ADDS) Web site at: http://aviationweather.gov/add/cv.
Content CVA presents information via a full-CONUS graphic and 18 regional graphics. Each graphic is rendered on a horizontal grid of 5 km resolution and shows viewer-selectable representations of ceiling height above ground level (AGL), surface visibility in statute miles (sm) and FAA flight category designation.
Each regional display includes an overlay of station plots showing the current ceiling and visibility observations reported at selected METAR stations. To avoid overcrowding, the overlay shows only a subset of the total number of stations available.
CVA Ceiling Analysis The CVA Ceiling Analysis uses observed and estimated ceiling heights as follows:
At display points corresponding to METAR locations, CVA uses the ceiling values observed by the nearest METAR.
At display points between METAR locations (where there are no direct observations), CVA uses estimated ceiling values derived by adjusting the ceiling observation from the nearest METAR to take into account intervening changes in terrain height. When corresponding Geostationary Operational Environmental Satellite (GOES) satellite observations yield an unambiguous indication that no cloud is present, adjusted ceiling observations are reset to indicate clear conditions.
At display points where observed or estimated ceiling height is less than 200 ft. AGL, CVA reports “Possible Terrain Obstruction.”
The CVA Ceiling Analysis graphic is rendered as follows:
• Ceiling less than 1000 ft. AGL – pale yellow.
• Ceiling greater than or equal to 1000 ft. AGL – pale blue.
• Ceiling less than 200 ft. AGL and Possible Terrain Obstruction – orange.
Figure 9-27 shows a CONUS-scale CVA Ceiling Analysis. Figure 9-28 shows a regional-scale Ceiling Analysis.
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