AC 00-45H

Historical

Advisory circular · Aviation Weather Services

Approved
November 14, 2016
Last reviewed
September 13, 2024
This change
This entire document series, all through the H Revision, is canceled.
Cancelled by
AC00-45H CHG 1
Family
AC 00-45 · 10 versions
Revision
H
14 CFR parts
25, 91

Guidance, not mandatory unless a rule or AD requires it. DRS record last changed November 21, 2025.

Show pages 305–316
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11/14/16 Aviation Weather Tools AC 00-45H Appendix A A-3 Contraction Translation Definition VOLCANIC Volcanic Ash Any ash that can be seen by any one or more of the ASH following: satellite imagery (visible, IR, multi-channel or TOMS), PIREPs, ground observations, radar and VAFTAD (In the event volcanic ash is entrained in clouds, the volcanic ash will be treated as visible using the VAFTAD as guidance).

WDLY SCT Widely Scattered Less than 25 percent of area affected.

WDSPR Widespread 50 percent or greater of the area affected.

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11/14/16 Aviation Weather Tools AC 00-45H Appendix B APPENDIX B. STANDARD CONVERSION CHART Figure B-1. Standard Conversion Chart Speed - Distance Temperature Pressure - Altitude Altimeter Setting M/H KTS KM/H °F °c INS. MBS./hPas.

1007 50 INS. MBS./hPas. 100'S 28.5 965 120 FT* 110 -1 80 12 400 • 230 970 90 -170 110 40 13 220 210 100 160 100 14 - 200 190 980 15 - 500 180 29.0 30 - 170 16 160 990 17 • 150 20 18 600 140 130 29.5 - 1000 70 19 120 10 20 - 110 1010 60 700 - 100 21 90 30.0 22

• 80 1020 23 70 800 40 -10 24 • 1030 30 10 25 50 30.5 30 50 26 40 1040 20 40 -20 27 900 30 20 -10 30 28 20

31.0 - 1050 -20 10 10 20 -30 29 10 1000 10 -30 30

- 1060 -40 •-40 31 1050 - -10 M/H KTS KM/H ° F ° C INS. MBS./hPas. 100'S IFT* 31.5 - 1065 * Standard Atmosphere INS. MBS./hPas.

B-1

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11/14/16 Aviation Weather Tools AC 00-45H Appendix C APPENDIX C. DENSITY ALTITUDE CALCULATION To determine density altitude:

1. Set the aircraft's altimeter to 29.92 inches of Mercury. The altimeter will indicate pressure altitude.

2. Read the outside air temperature.

3. Mark the intersection of pressure altitude (horizontal) and temperature (vertical) lines on the chart.

4. Read the density altitude from the diagonal lines.

Figure C-1. Density Altitude Computation Chart 20,000

STANDARD ATMOSPHERE + +

- DENSITY ALTITUDE 15,000 15,000 10,000 10,000 5,000 + 5,000 + + - 5,000 →ZERO + -5,000 -50 -40 -30 -20 -1° Temperature °C 0°C 10 20 30 40 50 -50 -40 -20 0°F 20 40 60 80 100 120 Temperature °F C-1

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11/14/16 Aviation Weather Tools AC 00-45H Appendix D D-1 APPENDIX D. INTERNET LINKS Table D-1. Selected National Weather Service (NWS) Links

NWS WEB SITE LINKS National Weather Service (NWS) Aviation Digital Data Service (ADDS) Aviation Weather Center (AWC) Storm Prediction Center (SPC) Alaska Aviation Weather Unit (AAWU) Center Weather Service Units (CWSU) Weather Forecast Office (WFO) Weather Forecast Office (WFO) Honolulu, HI –Aviation Products Table D-2. Selected Federal Aviation Administration (FAA) Links FAA Web Site Links Federal Aviation Administration (FAA) Air Traffic Control System Command Center (ATCSCC) Flight Service Operations

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11/14/16 Aviation Weather Tools AC 00-45H Appendix E APPENDIX E. WSR-88D WEATHER RADAR NETWORK Figure E-1. WSR-88D Weather Radar Network Sites

KMSK O KMVX KDLH KGGW

OKTEX OKBIS KGYX KELX KABR O КИРУ 40 KCRB O KRIW KUDX KF SD O KARYN киКУ KČỂR KBGL KBBX KDAX /OKEGE кмух KCYS KOAX CA ÖKUEX ILX O KCLEO OKILN KRLX КРВЕ КССК CADIX CKDOX * KMUx EGIX KFTGO O KGLD KIWXO OKEAX KLSX KIND O KHE KI CX KDDCO OKIC ÖKSCF КРАН OKHA OKURX KRAX® KVBX C OKVTX KEYX O к₽≤x KABX LOKSRX Оконк KES OKCAE OKLIX O KNKX (O - KYUX KIWA KEMX KHÖX ÖKEPZ KFDX KMAF • KDYXO СКАМА QKLBB OKFDR OKFWS OKSHV KLZK КРОЕ /KGWO KJAN KMXX O KBMX КЕОХО KgFC O KVA KJCx ОКСІЯ к'Ат KCEK O KLCH КМОВ OKMLE LPLA KOFX KEWX KHGA KTEWÖ OKAMX

PAEC O PAPD OKCRP

A KERO ABYX

PAHG T CBR

PAIH PHEM O

PHYA POUA () RKIK ' E-1

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11/14/16 Aviation Weather Tools AC 00-45H Appendix F F-1 APPENDIX F. AREA FORECASTS (FA)—CONTINENTAL UNITED STATES (CONUS) AND HAWAII Note: To allow for any unforeseen delays in the discontinuance of the FAs for the continental United States (CONUS) and Hawaii, information specific to these products have been retained in AC 00-45H but moved to this Appendix.

The FA contains weather information in a format originally developed in the 1950s. By design, it carries a character count limitation and is prohibited from describing instrument flight rules (IFR) conditions over the CONUS and Hawaii (reserved for Airmen’s Meteorological Information (AIRMET) and significant meteorological information (SIGMET)).

While the FA met aviation weather information needs for many years, today the NWS provides equivalent information through a number of better alternatives. Plans are to discontinue the six FAs covering the CONUS and one FA covering Hawaii, which will then be replaced by digital and graphical products produced by the NWS. No near-term changes are planned for the FAs for Alaska, the Caribbean, or the Gulf of Mexico.

These weather forecast products (described elsewhere in this document), to be consulted in lieu of the FA, together provide information similar to that found in the FA. The information often is in greater resolution and with the added benefit of graphical depiction. They include:

• Significant weather (SIGWX) charts (see paragraph 5.17),

• Aviation forecast discussions (see paragraph 5.20.1),

• Terminal aerodrome forecasts (TAF) (see paragraph 5.11),

• AIRMETs (see paragraph 5.2),

• National digital forecast databases (see paragraph 5.20.2),

• Cloud top height forecast graphics (see paragraph 5.20.3), and

• Cloud layer products (see paragraph 5.20.4).

F.1 CONUS and Hawaii Area Forecast (FA) Issuance.

FAs are issued by the following offices for the following areas:

1. The Aviation Weather Center (AWC).

• CONUS: Six FAs covering separate geographical areas of the CONUS, excluding the Gulf of Mexico coastal waters west of 85W (see Figure F-1, AWC Area Forecast (FA) Regions—CONUS).

2. Weather Forecast Office (WFO) Honolulu, HI.

• Hawaii: The main Hawaiian Islands and adjacent coastal waters extending out 40 nautical miles (NM) from the coastlines (see Figure F-2, WFO Honolulu Area Forecast (FA) Region and WMO Header—Hawaii).

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11/14/16 Aviation Weather Tools AC 00-45H Appendix F Figure F-1. AWC Area Forecast (FA) Regions-Continental U.S.

SFO San Francisco

CHI - BOS Salt Lake City ASLC Chicago Boston

DFW MIA

- Dallas/Fort Worth • Miami GULF of Mexico Figure F-2. WFO Honolulu Area Forecast (FA) Region and WMO Header-Hawaii Kauai FAHW31 22-21 Nihau Oạhu Hawaii Kaula Molokai -Maui Lanary Kahoolawe 20 - Hawaii -160 -158 -156 Note: For AWC FAs, "CSTL WTRS" refer to water areas that extend from the coastline to the Flight Information Region (FIR) boundary. "CSTL SXNS" refer to land areas along and near the coastline.

F-2

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11/14/16 Aviation Weather Tools AC 00-45H Appendix F F-3 F.1.1 FA Issuance Schedule.

FAs are scheduled products issued at the following times.

Table F-1. Area Forecast (FA) Issuance Schedule

Boston & Miami (UTC) Chicago & Fort Worth (UTC) San Francisco & Salt Lake City (UTC) Hawaii (UTC) 1st Issuance 0845 DT 0945 ST 0945 DT 1045 ST 1045 DT 1145 ST 0340 2nd Issuance 1745 DT 1845 ST 1845 DT 1945 ST 1945 DT 2045 ST 0940 3rd Issuance 0045 DT 0145 ST 0145 DT 0245 ST 0245 DT 0345 ST 1540 4th Issuance 2140 DT–Daylight Time, ST–St andard Time, UTC–Coordinated Universal Time F.2 Area Forecast (FA) Amendments.

Amendments are issued whenever the weather significantly improves or deteriorates based upon the judgment of the forecaster. These updates are those required to keep forecasts of non-AIRMET conditions representative of existing or expected conditions.

“AMD” is included after the date/time group on the FAA product line. The date/time group on the World Meteorological Organization (WMO) and FAA lines is updated to indicate the time of the correction. The ending valid time remains unchanged.

F.3 Area Forecast (FA) Corrections.

FAs containing errors will be corrected. “COR” is included after the date/time group on the FAA product line. The date/time group on the WMO and FAA lines is updated to indicate the time of the correction. The ending valid time remains unchanged.

F.4 Area Forecast (FA) Format—Continental United States (CONUS).

FAs issued for the CONUS cover the airspace between the surface and 45,000 feet (ft) above mean sea level (AMSL) and include the following forecast sections:

1. Synopsis: A short description of significant synoptic weather systems affecting the area during the 18-hour valid period. This includes the location and movement of pressure systems and fronts. Air mass descriptions may be used in the absence of significant weather systems. References to low ceilings and/or visibilities, strong winds, or any other phenomena that the forecaster considers useful may also be included.

2. Visual flight rules (VFR) Clouds/Weather: A 12-hour specific clouds and weather forecast, followed by a 6-hour categorical outlook giving a total forecast period of 18 hours. This section gives a general description of clouds and weather that cover an area greater than 3,000 square miles (mi2) and are significant to VFR flight operations. The forecasts are referenced to states or geographic areas. States are presented in the order listed within the header of

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11/14/16 Aviation Weather Tools AC 00-45H Appendix F F-4 the FA, however, portions of adjacent states may be grouped together when they are forecast to have similar conditions. The following weather elements, if applicable, are included in the following order for each 12-hour specific forecast:

• Sky condition (coverage, cloud base, and tops) if bases are higher than or equal to 1,000 ft above ground level (AGL) and at or below flight level (FL) 180. Heights are referenced to mean sea level (MSL) unless preceded by AGL or ceiling (CIG). Sky condition is not repeated for each new time group unless it is forecast to change.

• Surface visibilities and associated obstructions when visibility is between 3 and 5 statute miles (sm) and coverage is 3,000 mi2 or greater. When no visibility value is forecast, it is implied to be greater than 5 sm.

• Weather (e.g., precipitation, including thunderstorms, fog, haze, blowing dust) if it results in visibilities of 3 to 5 sm.

• Significant wind information (direction and speed) if the surface wind is sustained at 20 knots (kts) or greater and/or gusts are greater than or equal to 25 kts.

A 6-hour categorical outlook follows the 12-hour specific clouds and weather forecast. At a minimum, the category of the expected prevailing condition (e.g., IFR, Marginal Visual Flight Rules (MVFR), and VFR) is stated in the outlook. If IFR or MVFR, the cause is listed (e.g., CIG, fog (FG), and mist (BR)). VFR stands alone except for wind (WND), thunderstorms (TSRA) and precipitation types (without intensities). The contraction “WND” is appended to any category if the sustained surface wind is expected to be 20 kts or more, or surface wind gusts are expected to be 25 kts or more during the majority of the 6-hour outlook period.

Figure F-3. Area Forecast (FA)—CONUS Communication and Product Header—Example

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11/14/16 Aviation Weather Tools AC 00-45H Appendix F Table F-2. Decoding a CONUS Area Forecast (FA) Communication and Product Header Line Content Description DFW Area Forecast region identifier Indicates VFR clouds and weather forecast 1 FA Product type 120945 Issuance and beginning of valid date/time (UTC) 2 SYNOPSIS AND VFR CLDS/WX forecast message Statement of weather information contained in this 3 SYNOPSIS VALID UNTIL 130400 Synopsis valid date and time CLDS/WX VALID UNTIL 122200...OTLK VALID The clouds and weather section valid time. The valid date 4 122200-130400 and time of the outlook.

5 OK TX AR TN MS AL Description of the area for which the FA is valid.

Figure F-4. Area Forecast (FA)-Clouds and Weather Element-Example

S CNTL AND SERN TX AGL SCT-BKNO10. TOPS 030. VIS 3-5SM BR. 14-16Z BCMG AGL SCT 030. 19Z AGL SCT050. OTLK..VFR.

OK PNHDL AND NW..AGL SCT030 SCT-BKN100. TOPS FL200. 15Z AGL SCTO40 SCT100. AFT 20Z SCT TSRA DVLPG..FEW POSS SEV. CB TOPS FL450. OTLK...VFR.

REMAINDER OF STATE..CIG BKNO20. TOPS 050. VIS 3-5SM 14Z AGL SCT-BKN040. TOPS 100. 18Z CIG BKN060.

TOPS FL180. 22Z SCT TSRA DVLPG.,FEW POSS SEV. CB TOPS ABV FL450. OTLK...VFR.

F-5

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11/14/16 Aviation Weather Tools AC 00-45H Appendix F F-6 Figure F-4, Area Forecast (FA)—Clouds and Weather Element—Example is decoded as follows:

South central and southeast Texas:

Scattered to broken bases at 1,000 feet above ground level (AGL). Tops at 3,000 feet above mean sea level (MSL). Visibility 3 to 5 statute miles in mist. Between 1400 and 1600 UTC…clouds bases becoming scattered at 3,000 feet AGL. 1900 UTC…scattered bases at 5,000 feet AGL. 12 to 18 hour categorical outlook…VFR.

Oklahoma:

Panhandle and northwest…scattered bases at 3,000 feet AGL, scattered to broken bases at 10,000 feet AGL. Tops at flight level 20,000 feet MSL. 1500 UTC…scattered bases at 4,000 feet AGL, scattered bases at 10,000 feet AGL. After 2000 UTC…scattered thunderstorms with rain showers developing…a few possible severe.

Cumulonimbus tops to flight level 45,000 feet MSL. Outlook…VFR.

Remainder of the state…Ceilings broken at 2,000 feet AGL. Tops at 5,000 feet MSL.

Visibilities 3 to 5 statute miles in mist. 1400 UTC…scattered to broken bases at 4,000 feet AGL. Tops at 10,000 feet MSL. 1800 UTC…ceilings broken 6,000 feet AGL. Tops to flight level 18,000 feet MSL. 2200 UTC…scattered thunderstorm with rain showers developing…a few possibly severe. Cumulonimbus tops above flight level 45,000 feet MSL. 12-18 hour categorical outlook…VFR.

F.4.1 FA—CONUS Examples.

F.4.1.1 FA—Boston (BOS) Example.

FAU.41 KKCI 081745 (ICAO product header) FA1W (NWS AWIPS Communication header) BOSC FA 081745 (Area forecast region, product type, issuance date/time)

SYNOPSIS AND VFR CLDS/WX SYNOPSIS VALID UNTIL 091200 CLDS/WX VALID UNTIL 090600...OTLK VALID 090600-091200

ME NH VT MA RI CT NY LO NJ PA OH LE WV MD DC DE VA AND CSTL WTRS .

SEE AIRMET SIERRA FOR IFR CONDS AND MTN OBSCN.

TS IMPLY SEV OR GTR TURB SEV ICE LLWS AND IFR CONDS.

NON MSL HGTS DENOTED BY AGL OR CIG.

.

SYNOPSIS...18Z CDFNT 30N PQI-40E MPV-ALB-20N JHW LN. STNR FNT 20N JHW-ECK LN. STNR FNT EWC-ROD-IND LN. TROF 210SE SIE-170SE ECG LN CONTG SWD. HIGH WRN NC. 12Z STNR FNT FM LOW NR FWA ALG 20N CLE- JHW-ALB-30NNE BOS LN. CDFNT 30NNE BOS-120SE BGR LN. CDFNT FM LOW NR FWA ALG PXV-50SE FAM LN CONTG SWWD. HIGH NR ODF.

.

ME NH VT NRN ME...SCT040 BKN060 TOP FL250. OCNL BKN040. SCT -SHRA/ISOL -TSRA. CB TOP FL350. 21Z BKN040. ISOL -SHRA. WND W G25KT. 03Z SKC. OTLK...VFR.

VT/NRN NH/RMNDR ME MTNS...SCT-BKN040 BKN060 TOP FL250. SCT SHRA/ISOL TSRA. CB TOP FL350. 03Z BKN040. OCNL VIS 3-5SM BR.

OTLK...MVFR CIG BR.

SRN NH/RMNDR ME...SCT040 BKN100 TOP FL250. OCNL BKN040 IN WDLY SCT -SHRA/ISOL -TSRA BECMG AFT 19Z SCT TSRA. TS POSS SEV. CB TOP

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11/14/16 Aviation Weather Tools AC 00-45H Appendix F F-7 FL400. 04Z BKN020. WDLY SCT -SHRA. OTLK...MVFR CIG SHRA BR.

.

MA RI CT CT CSTL PLAIN/RI/SERN MA...SKC. 21Z SCT040. ISOL TSRA. CB TOP FL400. 03Z SKC. OCNL VIS 3-5SM BR. OTLK...IFR CIG BR.

RMNDR...SCT100. 19Z SCT040 BKN100 TOP 160. SCT TSRA POSS SEV. CB TOP FL450. 02Z BKN040. WDLY SCT SHRA. OTLK...MVFR CIG BR.

.

NY LO LO/N CNTRL-NERN NY...SCT-BKN040 BKN060 TOP 160. SCT SHRA/ISOL TSRA. CB TOP FL350. 03Z BKN040. WDLY SCT -SHRA. OTLK...MVFR CIG SHRA.

WRN-S CNTRL NY...BKN040 OVC060 TOP 160. SCT -TSRA. CB TOP FL450.

03Z BKN030. SCT SHRA. OTLK...MVFR CIG SHRA.

EXTRM SERN NY-LONG ISLAND...SKC. 21Z SCT040. ISOL TSRA. 03Z SKC.

OCNL VIS 3-5SM BR. OTLK...IFR CIG BR.

RMNDR NY...BKN050 TOP 160. SCT TSRA POSS SEV. CB TOP FL450. 03Z BKN040. SCT SHRA. OTLK...MVFR CIG SHRA.

.

PA NJ WRN-N CNTRL PA...BKN040 OVC060 TOP FL220. SCT TSRA. CB TOP FL400.

03Z BKN060. SCT SHRA NWRN/N CNTRL PA. OTLK...VFR SWRN PA...MVFR CIG SHRA NWRN/N CNTRL PA.

S CNTRL-NERN PA...BKN060 TOP FL220. ISOL TSRA BECMG AFT 20Z SCT TSRA. CB TOP FL400. 03Z OVC060. SCT SHRA NERN PA. OTLK...MVFR CIG SHRA NERN PA. MVFR CIG BR S CNTRL PA.

SERN PA-NRN NJ...SCT060. AFT 21Z ISOL TSRA. CB TOP FL400. 03Z SKC OR SCT CI. OTLK...VFR.

SRN NJ...SKC OR SCT CI. OTLK...VFR.

.

OH LE LE/NRN 1/2 OH...BKN030 OVC060 TOP FL220. SCT TSRA POSS SEV. CB TOP FL450. OTLK...MVFR CIG TSRA.

SWRN 1/4 OH...SCT040 BKN100 TOP FL220. SCT TSRA POSS SEV. CB TOP FL450. 03Z BKN060. WDLY SCT TSRA. OTLK...MVFR CIG TSRA.

SERN 1/4 OH...SCT050 BKN100 TOP FL220. OCNL BKN050 IN WDLY SCT TSRA.

TS POSS SEV. CB TOP FL400. 03Z BKN060. OTLK...VFR.

.

WV W WV PNHDL-NWRN...SCT100.. 19Z BKN060 TOP FL220. TIL 03Z SCT SHRA/WDLY SCT TSRA. CB TOP FL450. OTLK...VFR.

SW...SCT080. AFT 20Z ISOL TSRA. CB TOP FL400. 01Z SCT100 SCT CI. OTLK...VFR.

SERN WV...SCT070. 01Z SKC. OTLK...VFR BECMG 09Z IFR BR.

RMNDR...SCT080. 20Z SCT080 BKN100 TOP FL220. ISOL TSRA. CB TOP FL400. 03Z SCT-BKN CI. OTLK...VFR BECMG 09Z IFR BR.

.

MD DC DE VA NRN 1/2 APLCNS...SCT080. 20Z SCT080 BKN100 TOP FL220. ISOL TSRA.

CB TOP FL400. 03Z SCT-BKN CI. OTLK...VFR BECMG 09Z IFR BR.

SRN 1/2 APLCNS...SCT070. 01Z SKC. OTLK...VFR BECMG 09Z IFR HZ BR.

SERN VA CSTL SXNS...SCT040. 04Z SCT-BKN100 TOP FL250. OTLK...VFR.

DC/DE/RMNDR MD/RMNDR VA...SCT040. 00Z SKC OR SCT CI. OTLK...VFR.

.

CSTL WTRS ME/NH...SCT040 BKN100 TOP FL250. WDLY SCT SHRA/TSRA DVLPG 20-22Z.

CB TOP FL400. OTLK...VFR SHRA.

RMNDR N OF ACK...SKC. BECMG 2123 SCT040 BKN100 TOP FL250. WDLY SCT SHRA/TSRA. CB TOP FL400. OTLK...VFR SHRA.

S OF 30NE ORF-150SE SIE LN...SCT040 SCT CI. 03Z SCT-BKN100 TOP FL250. OTLK...VFR.

RMNDR...SCT060. 00Z SKC OR SCT CI. OTLK...VFR.

…