11/14/16 Aviation Weather Services AC 00-45H Figure 5-80. NDFD Sky Cover Graphic Product-Example 40 50 60 70 80 90 94 hortland lo 100- 39 Concore 98% 100 -100- syracuse 075 Albany: ₩ 9800 Bostop Baffalo 100 Te 00 -100 _Elmira Hartford TOU 98 100F ity
• 13 Pittsburgh 72 _Philadelphi 95 86 68
• Hashime 1% 96* Richnork
• 19 Roanoke Sky Cover (%) For Sat Mar 28 2015 8AM EDT (Sat Mar 28 2015 12Z) National Digital Forecast Database 11z issuance Graphic created-Mar 28 7:19AM EDT
5.20.2.2.2 Weather.
The Weather Graphic Product (see Figure 5-81, NDFD Weather Graphic Product-Example, Figure 5-82, NDFD Weather Graphic Product-Example, Figure 5-84, NDFD Weather Graphic Product-Example, Figure 5-85, NDFD Weather Graphic Product-Example, and Figure 5-86, NDFD Weather Graphic Product-Example) is the forecast predominate weather (precipitating or non-precipitating) valid at the indicated hour. The weather element includes type, intensity, and probability (see Figure 5-83, Legend for NDFD Weather Graphic). Darker shades of precipitation represent probabilities for 55 percent or greater.
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11/14/16 Aviation Weather Services AC 00-45H 5-153 Note: The NDFD graphical products are directed to all users
(e.g., public) and not specifically directed at aviation users. These graphics use weather symbology that differs from that used in Significant Weather (SIGWX) forecasts and METARs.
Figure 5-81. NDFD Weather Graphic Product—Example
The product’s legend will change depending on the forecast weather, e.g., the legend box will have fog only when fog is forecast on the graphic.
11/14/16 Aviation Weather Services AC 00-45H Figure 5-82. NDFD Weather Graphic Product-Example None Rain Snou Portland
- SH SH- SH- concors -SH- Syracuse Hibany 05-5 - Boston 1SH-/F Buffalo SH- Elnira Hartfol → SH- S- SH THeu YI SHE Pittsburgh SH- _Phi delphi • SH- SH- Hashinetor SH- sy- Richmonde Roanoke Predominant Weather For Sat Mar 28 2015 8AM EDT (Sat Mar 28 2015 12Z) National Digital Forecast Database 11z issuance Graphic created-Mar 28 7:09AM EDT Forecast valid for day 1 at 8 a.m. EDT (i.e., 12Z or 1200 UTC). Snow showers are forecast to extend from Virginia up to and across New England. Mixed precipitation (combination of rain and snow, rain and sleet, or snow and sleet) is forecast over portions or North Carolina and southern Virginia as well as off the coast of New England. Darker shades indicate 55 percent or greater probability.
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11/14/16 Aviation Weather Services AC 00-45H Figure 5-83. Legend for NDFD Weather Graphic National Digital Forecast Database Graphical Forecast Weather Legend None Rain L, R, FW, T Drizzle, Rain, Rain Showers, Thunderstorms Severe T+ Severe Thunderstorms Wintry Mix RIS Rain / Snow Mix Ice IP, ZL, ZR Sleet, Freezing Drizzle, Freezing Rain Snow SW, S Snow Showers, Snow Obstructions To Vision F Fog H Haze K Smoke BS, BD Blowing Snow, Blowing Dust Weather Intensity: - Light + Heavy Weather Probability: Darker shades indicate higher probability 5-155
11/14/16 Aviation Weather Services AC 00-45H Figure 5-84. NDFD Weather Graphic Product-Example None Rain Fog Poplar bluff Tulsa Nashville Jonesbora RH- Little Rock Temphis • T/RH Huntsville Tupelo ° RH/T Texal Tana - Birningham
• T/RH- T/RH- © RH - RH/T Shreveport Jackson TARH øȚ/RH—¢ Lufkin PREP Nobile.
Lake Charles a New Orie Housto Predominant Weather For Mon Mar 30 2015 8AM EDT (Mon Mar 30 2015 12Z) National Digital Forecast Database 17z issuance Graphic created-Mar 28 1:10PM EDT Forecast valid for day 3 at 8 a.m. EDT (i.e., 12Z or 1200 UTC). Thunderstorms and light rain showers are forecast from Texas and Oklahoma to across the southeastern United States. Darker shades indicate 55 percent or greater probability. Fog is forecast across southern Mississippi and eastern Louisiana.
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11/14/16 Aviation Weather Services AC 00-45H Figure 5-85. NDFD Weather Graphic Product-Example None Rain Snou Fog TRH-
• RH- \Kalispel Havre © RH- Spokani Glasgow Minot o RH- Missoula Butte Bismarck Billings Yelloustone Rapid City Pierre Twin Falls Riverton Douglas Elko Predominant Weather For Sat Mar 28 2015 Salt Lake City North Platte SAM EDT (Sat Mar 28 2015 12Z) National Digital Forecast Database 11z issuance Graphic created-Mar 28 7:18AM EDT Forecast valid for day 1 at 8 a.m. EDT (i.e., 122 or 1200 UTC). Fog from North Dakota into South Dakota and light rain showers across the Northern Rockies. Darker shades indicate 55 percent or greater probability.
Figure 5-86. NDFD Weather Graphic Product-Example None Rain Snou Chicar South Bend Des Moines Fort Hayne Peoria Springfield Indianapolis
• 5- Cincinnati
- Columbia dusville R-/S- aducah R-/S- plar Bluffr Nashville Jonesbor a Little Rock temphis Huntsville TiDeln ° R-15- Predominant Weather For Sat Mar 28 2015 8AM EDT (Sat Mar 28 2015 12Z) National Digital Forecast Database 11z issuance Graphic created-Mar 28 7:18AM EDT Forecast valid for day 1 at 8 a.m. EDT (i.e., 12Z or 1200 UTC). Light snow is forecast from southern Iowa into central Missouri; a mix of precipitation (combination of rain and snow, rain and sleet, or snow and sleet) is forecast from western Missouri to northern Mississippi, along with light rain over most of Arkansas.
Darker shades indicate 55 percent or greater probability.
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5.20.2.2.3 Wind.
Wind is provided in two graphics, one for surface wind speed and direction (see Figure 5-87, NDFD Surface Wind Speed and Direction—Example) and one for wind gusts (see Figure 5-89, NDFD Surface Wind Gust Graphic—Example). Symbols for wind speed and direction (see Figure 5-88, NDFD Wind Speed and Direction Graphic Product Plot Model) are plotted on the graphic. Wind speed and gust speed are also depicted using a color.
Both wind speed and gusts are in knots.
Figure 5-87. NDFD Surface Wind Speed and Direction—Example
11/14/16 Aviation Weather Services AC 00-45H Figure 5-88. NDFD Wind Speed and Direction Graphic Product Plot Model Wind Speed & Direction Calm 5 knots Example Wind Barb 10 Knots 15 Knots Read as:
Horthwest Wind 20 Knots at 25 Knots 50 Knots 65 Knots Points to direction wind is coming from.
Small barbs indicate wind speed.
(1 Knot = 1.15 mph) Figure 5-89. NDFD Surface Wind Gust Graphic-Example tony ind
• 10 г Concor 610 racuse 7o 13 ffalo pittsbur Wind Gust(Kts) Sat Mar 28 2015 8AM EDT (Sat Mar 28 2015 12Z) National Digital Forecast Database 11z issuance Graphic created-Mar 28 7:13AM EDT 5-159
11/14/16 Aviation Weather Services AC 00-45H 5-160
5.20.2.3 Use.
Perhaps the adage “a picture is worth a thousand words” best describes the NDFD graphical products, which are one of the replacement products for the FA. The NDFD graphical products provide detailed forecasts of sky cover, weather, wind, and several other metrological elements, in a graphical Web-based format. Depending on the Web site, users can quickly scroll over or animate the products to view any changes in the forecast (e.g., movement, growth, or decay of areas of precipitation).
The NDFD graphical products complement the Short-Range Surface Prognostic Charts (see paragraph 5.16), which are also based on the NDFD, by providing more detail and additional weather elements.
The NDFD Sky Cover graphical product is a good situational awareness source for total cloud cover en route as well as at airports without a TAF.
Perhaps the best use of the NDFD Sky Cover graphical product is it provides forecasts of where the cloud cover is minimal, implying that VFR flight conditions are likely (except when smoke and haze exist or are expected). The NDFD Sky Cover graphical product does not provide cloud base height, cloud top height, or information on cloud layers.
The NDFD Weather graphical product is a good situational awareness source for weather (e.g., rain, snow, freezing rain, thunderstorm, fog, and surface wind) en route as well as at airports without a TAF. The NDFD Weather graphical product does not provide visibility forecasts associated with the forecast weather; thus, pilots should use this product in combination with the Low-Level Significant Weather (SIGWX) forecasts, AIRMETs and SIGMETs (including Convective SIGMETs) for possible Marginal Visual Flight Rules (MVFR) or IFR conditions.
Due to the graphical (and colorful) nature of these products, considerations have been made by the NWS for people who cannot distinguish colors.
Despite these efforts, some shades may be somewhat more difficult to distinguish. A color blindness tool may assist in reading the graphics and can be obtained at http://www.nws.noaa.gov/credits.php#plugins.
5.20.3 Cloud Top Heights Product.
The Cloud Top Heights product provides a detailed set of forecasts of the heights of cloud tops using specified contours.
5.20.3.1 Issuance.
The NWS NCO produces the Cloud Top Heights forecast using the North American Mesoscale (NAM) NWP model.
The Cloud Top Heights forecast product is available on http://www.aviationweather.gov.
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5.20.3.2 Content.
The Cloud Top Heights product (see Figure 5-90, Cloud Top Heights Product—Example) is a computer model forecast of the height of the tops of the clouds covering the sky valid for the indicated hour. The heights of cloud tops are depicted using color-shaded contours at specific intervals.
Forecasts are provided at select time step intervals.
Additional details on the content of this product are provided on http://www.aviationweather.gov.
Figure 5-90. Cloud Top Heights Product—Example
Actual colors and scale may vary depending on upgrades to the product. Refer to the AWC Web page for additional details.
5.20.3.3 Use.
The Cloud Top Heights product is a computer-generated forecast without input from meteorologists. It is the computer’s “best guess” of where clouds will be as well as the height of the cloud tops.
NWP models are much more accurate forecasting winds aloft than they are forecasting cloud tops. Pilots should not expect an equally high degree of
11/14/16 Aviation Weather Services AC 00-45H 5-162 accuracy with these forecasts, especially in areas where there is a high degree of variability in the forecast cloud top heights.
5.20.4 Cloud Layer Product.
The Cloud Layer product provides a detailed set of forecasts of cloud amount and layers using specified contours.
5.20.4.1 Issuance.
The NWS NCO produces the Cloud Layer forecast using a NWP model.
The Cloud Layer forecast product is available on http://www.aviationweather.gov.
5.20.4.2 Content.
The Cloud Layer product is a computer model forecast of cloud amount and information on cloud layers, valid for the indicated hour.
Forecasts are provided at select time step intervals.
Additional details on the content of this product are provided on http://www.aviationweather.gov.
5.20.4.3 Use.
The Cloud Layer product is a computer-generated forecast without input from meteorologists. It is the computer’s “best guess” for cloud layers as their details.
NWP models are much more accurate forecasting winds aloft than they are forecasting cloud layers. Pilots should not expect an equally high degree of accuracy with these forecasts.
5.21 Airport Weather Warning (AWW).
The Airport Weather Warning (AWW) addresses weather phenomena that can adversely impact airport ground operations.
Note: The AWW is not to be confused with the SAW, which the NWS refers to as SAW but is also known by AWW on the Web sites of some weather provider services.
5.21.1 Issuance.
The Airport Weather Warning is issued for select larger airports and is available on NWS WFO Web sites who have responsibility for issuing the TAFs for that airport. The Airport Weather Warning is not available on http://www.aviationweather.gov.
Issuance criteria are established according to local airport requirements. Some examples of criteria are: strong surface winds, freezing rain, heavy snow, and lightning within 5 miles of the airport.
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5.21.2 Airport Weather Warning (AWW) Format and Example.
The AWW is written in a plain language, free-text format.
WWUS82 KJAX 112212 AWWJAX FLZ025-112315-
AIRPORT WEATHER WARNING FOR JACKSONVILLE INTERNATIONAL AIRPORT
NATIONAL WEATHER SERVICE JACKSONVILLE FL 612 PM EDT WED MAR 11 2015 ...AN AIRPORT WEATHER WARNING HAS BEEN ISSUED FOR JACKSONVILLE
INTERNATIONAL AIRPORT FOR STRONG WINDS AND POSSIBLE WINDSHIFT VALID UNTIL 700 PM...
A CLUSTER OF THUNDERSTORMS WILL MOVE EASTWARD AT 12 KNOTS AND AFFECT JACKSONVILLE INTERNATIONAL AIRPORT BY 620 PM. WIND GUSTS OVER 35 KNOTS ARE LIKELY WITH THESE STORMS...AS WELL AS CLOUD- TO-GROUND LIGHTNING AND REDUCED VISIBILITIES FROM HEAVY RAIN.
WINDSHIFTS ACCOMPANYING THE THUNDERSTORMS MAY ALTER THE RUNWAY LANDING PATTERN WITH SOME STRONG WESTERLY WIND GUSTS.
$$
5.21.3 Use.
Information contained in this product may be useful to airport managers, fixed-based operators, airline ground personnel, and others responsible for the safety of ground operations. Ground decisions supported by the AWW information may include: fueling delays during thunderstorms, de-icing frequency, and other similar ground operations.
AWWs are not intended for use by in-flight operations.
5.22 Space Weather.
The expression Space Weather is used to designate processes occurring on the Sun, in Earth’s magnetosphere, ionosphere, and thermosphere, which have the potential to affect the near-Earth environment.
For aviation users, Space Weather can affect GPS navigation and some communications;
specifically, Space Weather can:
• Increase GPS uncertainty. During a severe space weather event, the ionosphere becomes highly disturbed, and GPS receivers cannot lock on the satellite signal, resulting in inaccurate position information as much as tens of meters or more.
• Result in severe downgrade or loss of high frequency (HF) radio communications, which is a mainstay of aviation, especially on polar and transoceanic routes.
The three primary types of space weather concerns for aviation are solar flares, radiation storms, and geomagnetic storms.
5.22.1 NOAA Space Weather Scales.
The NOAA Space Weather Scales communicate current and future space weather conditions and their possible effects on people and systems. The scales describe the