11/14/16 Aviation Weather Services AC 00-45H 5-44 OTHER WATCH INFORMATION...CONTINUE...WW 646...
DISCUSSION...THUNDERSTORMS WILL CONTINUE TO INCREASE ACROSS WATCH AREA WHERE AIR MASS HAS BECOME STRONGLY UNSTABLE AND UNCAPPED.
VEERING SHEAR PROFILE SUPPORT STORMS EVOLVING INTO SHORT LINE
SEGMENTS ENHANCING WIND DAMAGE POTENTIAL AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM MOTION VECTOR 33025.
... NAME
5.6.2.4 Public Tornado Watch Notification Message.
The SPC issues a Public Tornado Watch Notification Message when forecasting two or more tornadoes or any tornado that could produce EF2 or greater damage. The forecast event minimum thresholds are at least 2 hours over an area at least 8,000 mi2. Below these thresholds, the SPC, in collaboration with affected NWS offices, may issue for smaller areas and for shorter periods of time when conditions warrant, and for Convective watches along coastlines, near the Canadian border, and near the Mexican border.
A Public Tornado Watch Notification Message contains the area description and axis, watch expiration time, the term “damaging tornadoes,” a description of the largest hail size and strongest thunderstorm wind gusts expected, the definition of the watch, a call-to-action statement, a list of other valid watches, a brief discussion of meteorological reasoning, and technical information for the aviation community.
The SPC may enhance a Public Tornado Watch Notification Message by using the words “THIS IS A PARTICULARLY DANGEROUS SITUATION” when there is a likelihood of multiple strong (damage of EF2 or EF3) or violent (damage of EF4 or EF5) tornadoes.
The SPC includes the term “adjacent coastal waters” when the watch affects coastal waters adjacent to the Pacific/Atlantic coast or the Gulf of Mexico.
Adjacent coastal waters refers to a WFO’s near-shore responsibility (out to 20 NM for oceans), which include portions of the Great Lakes.
The SPC issues a watch cancellation message whenever it cancels a watch prior to the expiration time. The text of the message will specify the number and area of the canceled watch.
5.6.2.4.1 Format of a Public Tornado Watch Notification Message.
The format for a Public Tornado Watch Notification Message is the same as the Public Severe Thunderstorm Watch Notification Message.
11/14/16 Aviation Weather Services AC 00-45H 5-45
5.6.2.4.2 Example of a Public Tornado Watch Notification Message.
A Public Tornado Watch Notification Message contains three bulleted blocks of information:
• The geographic area of the watch,
• The valid time of the watch, and
• A description of the primary threats anticipated within the watch.
A plain text summary is included beneath the bulleted information.
(Note this is a fictitious example) WWUS20 KWNS 050550 (communication header) SEL2 SPC WW 051750
URGENT - IMMEDIATE BROADCAST REQUESTED TORNADO WATCH NUMBER 243
NWS STORM PREDICTION CENTER NORMAN OK 1250 AM CDT MON MAY 5 2011
THE NWS STORM PREDICTION CENTER HAS ISSUED A * TORNADO WATCH FOR PORTIONS OF
WESTERN AND CENTRAL ARKANSAS
SOUTHERN MISSOURI
FAR EASTERN OKLAHOMA * EFFECTIVE THIS MONDAY MORNING FROM 1250 AM UNTIL 600 AM CDT.
...THIS IS A PARTICULARLY DANGEROUS SITUATION...
* PRIMARY THREATS INCLUDE
NUMEROUS INTENSE TORNADOES LIKELY NUMEROUS SIGNIFICANT DAMAGING WIND GUSTS TO 80 MPH LIKELY NUMEROUS VERY LARGE HAIL TO 4 INCHES IN DIAMETER LIKELY THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 100 STATUTE MILES EAST AND WEST OF A LINE FROM 15 MILES WEST NORTHWEST OF FORT LEONARD WOOD MISSOURI TO 45 MILES SOUTHWEST OF HOT SPRINGS ARKANSAS. FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU2).
REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA.
PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING
WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE WARNINGS.
OTHER WATCH INFORMATION...THIS TORNADO WATCH REPLACES TORNADO WATCH NUMBER 237. WATCH NUMBER 237 WILL NOT BE IN EFFECT AFTER 1250 AM CDT. CONTINUE...WW 239...WW 240...WW 241...WW 242...
11/14/16 Aviation Weather Services AC 00-45H 5-46 DISCUSSION...SRN MO SQUALL LINE EXPECTED TO CONTINUE EWD...WHERE
LONG/HOOKED HODOGRAPHS SUGGEST THREAT FOR EMBEDDED SUPERCELLS/POSSIBLE TORNADOES. FARTHER S...MORE WIDELY SCATTERED
SUPERCELLS WITH A THREAT FOR TORNADOES WILL PERSIST IN VERY STRONGLY DEEP SHEARED/LCL ENVIRONMENT IN AR.
AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT TO 4 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM MOTION VECTOR 26045.
.
.. NAME To see a dynamic representation of this, please go to the following Web site:
http://www.spc.noaa.gov/products/watch/ww0020.html.
5.6.3 Collaborative Decision Making (CDM) Collaborative Convective Forecast Planning (CCFP) Guidance.
For years, CCFP was the acronym for the Collaborative Convective Forecast Product.
Beginning late 2014 the product’s name changed as well as its production and some of its content. CCFP is now the acronym for Collaborative Decision Making (CDM) Convective Forecast Planning (CCFP) guidance.
Whereas forecasters produced the old CCFP, the new CCFP is a fully automated product produced by computer model algorithms with an appearance similar to the human-produced CCFP.
The new CCFP is issued year round compared to the old CCFP, which was issued during spring, summer, and fall.
The CCFP is a graphical representation of Convective forecasts at 2, 4, 6, and 8 hours after issuance time (see Figure 5-25, CDM Convective Forecast Planning (CCFP) Guidance—Example). Convection, for the purposes of the CCFP forecast, is defined as a polygon of at least 5,000 mi2 containing all of the following threshold criteria:
• An aerial coverage of at least 25 percent;
• At least 25 percent of the tops to be FL250 or greater; and
• A confidence of at least 25 percent that the event will meet minimum CCFP criteria.
All three criteria above must also occur over an area of 5,000 mi2 or greater to be included in a CCFP forecast. This is defined as the minimum CCFP criteria. Any area of convection that does not meet 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.
11/14/16 Aviation Weather Services AC 00-45H Figure 5-25. CDM Collaborative Convective Forecast Planning (CCFP) Guidance-Example 340
- 340 Моп Tue 22Z O0Z 2 hour forecast 4 hour forecast 34D Tue Tue 02Z 04Z 6 hour forecast 8 hour forecast CONFIDENCE:
HEIGHT 25-49% 50-100% HIGH TOPS: 100'S OF FEET MSL SPARSE 25000 - 29000 290 CONVECTIVE 25-39% 30000 - 34000 340 COVERAGE: MEDIUM+ 35000 - 39000 40000+ >400 390 40-100% 5-47
11/14/16 Aviation Weather Services AC 00-45H 5-48 Figure 5-26. CDM Collaborative Convective Forecast Planning (CCFP) Guidance—Example
5.6.3.1 Issuance.
The CCFP is issued by the AWC.
The CCFP is issued every 2 hours. The CCFP product issuance time is approximately the bottom of the hour preceding the FAA’s air traffic control system command center’s (ATCSCC) strategic planning telecom (i.e., the 1600 UTC issuance would be available at ~1530 UTC for the 1615 UTC strategic planning telecom). The product can be found on http://www.aviationweather.gov.
5.6.3.2 Content.
Data graphically displayed on the CCFP consist of coverage of convection within a defined polygon, maximum tops, and confidence of Convective occurrence meeting the CCFP minimum criteria.
Additional information on the CCFP product is available on the CFFP Web page form on the INFO tab, on http://www.aviationweather.gov.
5.6.3.3 Coverage.
The Convective coverage within the forecast polygon is represented by the amount of fill within the polygon (see Figure 5-27, CCFP Product Legend).
The polygon is then assigned as a sparse or medium coverage.
11/14/16 Aviation Weather Services AC 00-45H 5-49
• Medium coverage, defined by medium fill, indicates 40 to 100 percent of the polygon is forecast to contain convection.
• Sparse coverage, represented by sparse fill, means 25–39 percent of the polygon is forecast to contain convection.
Figure 5-27. CCFP Product Legend
5.6.3.3.1 Confidence.
Confidence represents the model algorithm’s prediction that the polygon will meet the minimum CCFP threshold criteria. The confidence is represented by the color used to depict the polygon (see Figure 5-27).
• A blue color represents high confidence (50–100 percent) that the forecast convection will meet the minimum criteria.
• A gray color indicates low confidence (25–49 percent) that the forecast convection will meet the minimum criteria.
Confidence is not to be associated with probability of occurrence.
5.6.3.3.2 TOPS.
The word “TOPS” is used to depict the forecast maximum echo tops, in thousands of feet MSL, specified by four selected layers listed in Figure 5-27.
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.
5.6.3.4 Use.
The CCFP is a strategic planning tool for air traffic flow management in the 2- to 8-hour forecast period.
The CCFP does not include a forecast for all convection. If the convection does not meet the threshold criteria, it is not included in the CCFP. The CCFP is not intended to be used as a tactical short-term decision product.
The product is not intended to be used as a pilot weather-briefing product;
however, CCFP is available to pilots and aircraft dispatchers as an additional product for strategic planning.
11/14/16 Aviation Weather Services AC 00-45H 5-50
5.6.4 Extended Convective Forecast Product (ECFP).
The ECFP Planning Tool (see Figure 5-28, ECFP Example) is a graphical representation of the forecast probability of thunderstorms and is also intended to support the long-range planning for Convective constraints in the National Airspace System (NAS). The product identifies graphically where thunderstorms are expected through the next 72 hours over the CONUS. Although the ECFP uses CCFP-style graphics to facilitate ease of interpretation, the ECFP does not forecast CCFP criteria.
The development of the ECFP planning tool was a response to FAA and industry needs in planning for weather hazards, specifically convection, 1 to 3 days in advance. To meet these planning needs, the ECFP provides traffic planners and collaborators a quick look at where the probability of convection is greatest. By utilizing CCFP-style graphics, users familiar with CCFP can easily determine where traffic constraints are most likely to occur over the next 3 days.
5.6.4.1 Issuance.
The ECFP is an automated forecast product issued by the AWC. It is issued 4 times a day at approximately 01:00, 07:00, 13:00, and 19:00 UTC.
Figure 5-28. ECFP Example
5.6.4.2 Content.
This automated graphical forecast is created from the Short Range Ensemble Forecast (SREF) Calibrated Thunderstorm guidance. Probability of Thunderstorm contours are depicted at 40, 60, and 80 percent probabilities, using CCFP-like shading. Hashed areas represent 40–59 percent probability,
11/14/16 Aviation Weather Services AC 00-45H 5-51 solid lined areas represent 60–79 percent probability, and solid blue-filled areas represent greater than 80 percent probability.
5.6.4.3 Use.
The ECFP is intended for FAA traffic managers at ARTCC, FAA ATCSCC, airline and aviation industry dispatch and flight planners, as well as commercial weather information providers supporting airlines and the FAA.
5.6.5 National Convective Weather Forecast (NCWF).
The NCWF is a near real-time, high-resolution display of current and 1-hour extrapolated forecasts of selected hazardous Convective conditions for the CONUS. The NCWF may be used in conjunction with the report and forecast information contained within Convective SIGMETs. The NCWF is available for use by General Aviation (GA), aircraft dispatchers, and Traffic Management Units (TMU).
5.6.5.1 Issuance.
The NCWF is issued by the AWC and is updated every 5 minutes. The product is available at the Convection Web page on http://www.aviationweather.gov.
5.6.5.2 Content.
The NCWF displays current Convective hazard fields (detection), 1-hour extrapolated forecast polygons (see Figure 5-29, NCWF Example), forecast speed and directions, and echo tops. Past performance polygons can also be selected for display.
11/14/16 Aviation Weather Services AC 00-45H 5-52 Figure 5-29. NCWF Example
5.6.5.2.1 NCWF Hazard Scale.
The Convective hazard scale uses six hazard levels (see Figure 5-30, NCWF Hazard Scale) to characterize hazardous convection conditions.
The six hazard levels are determined by two factors:
• Intensities and maximum tops of WSR-88D reflectivity data; and
• 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.
11/14/16 Aviation Weather Services AC 00-45H 5-53 Figure 5-30. NCWF Hazard Scale
5.6.5.2.2 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 1 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. In Figure 5-29, the light blue polygon denotes the location of the 1-hour forecast convective hazard field.
5.6.5.2.3 Forecast Speed and Direction.
Forecast speed and direction are assigned to current Convective hazard fields having a 1-hour extrapolated forecast. A line (or arrow on the AWC JavaScript product) is used to depict the direction of movement. 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) smooths erratic forecast velocities. In Figure 5-29, the forecast direction (depicted by an arrow) is pointing to the southeast, and the speed is 25 kts.
5.6.5.2.4 Echo Tops.
Echo tops are assigned to current Convective hazard fields having a 1-hour extrapolated forecast. Echo tops are depicted by a group of three numbers located near the current Convective hazard field and are plotted in hundreds of feet MSL. In Figure 5-31, NCWF One-Hour Extrapolated Forecast Polygon, Forecast Movement Velocity and Echo Tops—Example, the echo tops are 45,000 ft MSL.
11/14/16 Aviation Weather Services AC 00-45H 5-54 Figure 5-31. NCWF One-Hour Extrapolated Forecast Polygon, Forecast Movement Velocity and Echo Tops—Example
5.6.5.2.5 Past Performance Polygons.
Past performance polygons are magenta polygons displaying the past 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 past performance polygons allows the user to review the accuracy of the past hour’s forecast.
Figure 5-32, NCWF Past Performance Polygons—Example, depicts current Convective hazard fields and past performance polygons (magenta) valid at 1500Z. The past 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 past performance polygons. Extrapolated forecasts do not forecast developing hazardous Convective.
11/14/16 Aviation Weather Services AC 00-45H 5-55 Figure 5-32. NCWF Past Performance Polygons—Example
5.6.5.3 Strengths and Limitations.
5.6.5.3.1 Strengths.
Strengths of the NCWF include:
• Convective hazard fields that agree very well with radar and lightning data;
• Updates every five minutes;
• High-resolution forecasts of Convective hazards; and
• Well-forecasted long-lived Convective precipitation.
5.6.5.3.2 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;