Aviation Weather Services, Advisory Circular 00-45G Change 1 (July 2010) Ceiling & Visiblity Turb High Turb Low Icing Mountain Obscuration Low Level Wind Shear Surface Winds Freezing Level Clear Slower Loop speed Faster Play 18Z 21Z O0Z 03Z G-AIRMET VALID: 1800 UTC MON 26 APR 2010 100 SFC 100 ISSUED: 1445 UTC MON 26 APR 2010 Ceiling & Visibility IFR BR Turb High Turb Low Icing 1637920 —*- Mitn CL6S/ BRI LL Wind LWS € > Sfc Winds Frzg Lvl 0°: 120 Obsch Shear Figure 6-17. G-AIRMET - Turbulence-Low Snapshot Example Section 6: Products for Aviation Hazards Page 6-37
Aviation Weather Services, Advisory Circular 00-45G Change 1 (July 2010)
• Low Level Wind Shear (LLWS)
• LLWS is defined as wind shear below 2000 feet AGL, other than convectively induced, exceeding 10 knots per 100 feet (vector difference between two points in space).
Ceiling & Visiblity Turb High Turb Low Icing Mountain Obscuration Low Level wind Shear Surface Winds Freezing Level Clear Slower Loop speed Faster Play 18Z 21Z 002 |03Z G-AIRMET VALID: 1500 UTC TUE 27 APR 2010 ISSUED: 1445 UTC TUE 27 APR 2010 Ceiling & Visibility Turb High Turb Low Icing 160/120 Obsch Mtn CL65/BR --- LL Wind Shear LLWS < > Sfc Winds → FIZOLV (00: 120 AN Figure 6-18. G-AIRMET - Low-Level Wind Shear (LLWS) Snapshot Example Section 6: Products for Aviation Hazards Page 6-38
Aviation Weather Services, Advisory Circular 00-45G Change 1 (July 2010)
• Strong Surface Winds
• Areas of sustained surface winds greater than 30 knots. The direction and speed of winds are not depicted; only the area where sustained surface winds greater than 30 knots will occur.
Ceiling & Visiblity Turb High Turb Low Icing Mountain Obscuration Low Level Wind Shear Surface Winds Freezing Level Clear Slower Loop speed Faster Play 152 182 002 032 G-AIRMET VALID: 2100 UTC TUE 27 APR 2010 ISSUED: 1445 UTC TUE 27 APR 2010 Ceiling & Visibility Turb High 280] 400 Icing 160/120 Obsch Mitn CL6$/BR-- - LL Wind Shear [LLWS € → Sfo Winds → Figure 6-19. G-AIRMET - Strong Surface Winds Snapshot Example Section 6: Products for Aviation Hazards Page 6-39
Aviation Weather Services, Advisory Circular 00-45G Change 1 (July 2010) Center Weather Advisory (CWA) A Center Weather Advisory (CWA) is an aviation weather warning for conditions meeting or approaching national in-flight advisory (AIRMET, SIGMET or Convective SIGMET) criteria. The CWA is primarily used by aircrews to anticipate and avoid adverse weather conditions in the en route and terminal environments. CWAs are available on the Aviation Weather Center (AWC) Web site at:.
CWA Issuance CWAs are issued by the NWS Center Weather Service Units (CWSUs). CWSU areas of responsibility in the contiguous U.S. are depicted on Figure 6-12. CWSU Anchorage area of responsibility for Alaska is depicted on Figure 6-13.
Figure 6-20. Center Weather Service Unit (CWSU) Areas of Responsibility – Contiguous U.S.
Section 6: Products for Aviation Hazards Page 6-40
Aviation Weather Services, Advisory Circular 00-45G Change 1 (July 2010)
Figure 6-21. CWSU Anchorage, AK (PAZA) Area of Responsibility
CWAs are valid for up to two (2) hours and may include forecasts of conditions expected to begin within two (2) hours of issuance. If conditions are expected to persist after the advisory’s valid period, a statement to that effect is included in the last line of the text. Additional CWAs will subsequently be issued as appropriate. Notice of significant changes in the phenomenon described in a CWA is provided by a new CWA issuance for that phenomenon. If the forecaster deems it necessary, CWAs may be issued hourly for convective activity.
CWA Criteria CWAs are used in the four (4) following situations:
• Precede an Advisory o When the AWC has not yet issued an advisory, but conditions meet or will soon meet advisory criteria.
• Refine an existing Advisory o To supplement an existing AWC advisory for the purpose of refining or updating the location, movement, extent, or intensity of the weather event relevant to the ARTCC’s area of responsibility.
• Highlight significant conditions not meeting Advisory criteria o When conditions do not meet advisory criteria, but conditions, in the judgment of the CWSU meteorologist, will adversely impact air traffic within the ARTCC area of responsibility.
• To cancel a CWA when the phenomenon described in the CWA is no longer expected.
CWA Format
Section 6: Products for Aviation Hazards Page 6-41
Aviation Weather Services, Advisory Circular 00-45G Change 1 (July 2010)
Figure 6-22. Center Weather Advisory (CWA) Decoding Example
Table 6-8. Decoding a Center Weather Advisory (CWA) Line Content Description 1 ZDV ARTCC Identification 2 Phenomenon Number (single digit, 1-6) CWA Product Type (UCWA/CWA) 032140 Beginning and/or issuance UTC date/time 2 ZDV ARTCC Identification CWA Product Type 2 Phenomenon Number (single digit, 1-6) 02 Issuance Number (issued sequentially for each Phenomenon Number) VALID TIL 032340Z Ending valid UTC date/time 3 FROM FMN TO 10N FMN TO 20NE FMN TO 10E FMN TO FMN Phenomenon Location 4 ISOLD SEV TS NR FMN MOVG NEWD 10KTS. TOP FL410. WND GSTS TO 55KTS. HAIL TO 1 INCH RPRTD AT FMN. SEV TS CONTG BYD 2340Z Phenomenon Description
Time permitting, any CWA overlapping into another center's airspace is coordinated and a statement is included in the text, e.g., SEE ZOB CWA 201 FOR TS CONDS IN ZOB CTA (CTA is control area). If issuance prior to coordination is necessary, a statement regarding the area(s) affected is included in the text, e.g., LINE TS EXTDS NW INTO ZOB CTA.
AIRMETs/SIGMETs being augmented by the CWA will be referenced in a text remark, e.g.
SEE CONVECTIVE SIGMET 8W.
The CWA in Figure 6-14 is decoded as follows:
Section 6: Products for Aviation Hazards Page 6-42
Aviation Weather Services, Advisory Circular 00-45G Change 1 (July 2010) (Line 1) Center Weather Advisory issued for the Denver ARTCC (ZDV) CWSU. The “2” after ZDV in the first line denotes this is the second meteorological event of the local calendar day.
This CWA was issued/begins on the 3rd day of the month at 2140 UTC.
(Line 2) The Denver ARTCC (ZDV) is identified again. The “202” in the second line denotes the phenomena number again (2) and the issuance number (02) for this phenomenon. This CWA is the valid until the 3rd day of the at 2340 UTC.
(Line 3) From Farmington, New Mexico to 10 nautical miles north of Farmington, New Mexico to 20 nautical miles northeast of Farmington, NM to 10 nautical mile east of Farmington, New Mexico to Farmington, New Mexico.
(Line 4) Isolated severe thunderstorms near Farmington moving northeastward at 10 knots.
Tops to Flight Level 410. Wind gusts to 55 knots. Hail to one inch reported at Farmington.
Severe thunderstorms continuing beyond 2340 UTC.
Examples
ZME1 CWA 081300
ZME CWA 101 VALID TIL 081500
FROM MEM TO JAN TO LIT TO MEM OCNL TS MOV FM 26025KT. TOPS TO FL450.
Center Weather Advisory issued for the Memphis, Tennessee ARTCC on the 8th day of the month at 1300 UTC. The 1 after the ZME in the first line denotes this CWA has been issued for the first weather phenomenon to occur for the local calendar day. The 101 in the second line denotes the phenomenon number again (1) and the issuance number (01) for this phenomenon.
The CWA is valid until the 8th of the month at 1500 UTC. From Memphis, Tennessee to Jackson, Mississippi to Little Rock, Arkansas to Memphis, Tennessee. Occasional thunderstorms moving from 260 degrees at 25 knots. Tops to flight level 450.
ZLC3 CWA 271645
ZLC CWA 303 VALID TIL 271745 CNL CWA 302.
SEE CONVECTIVE SIGMET 8W.
Center Weather Advisory issued for the Salt Lake City, Utah ARTCC on the 27th day of the month at 1645 UTC. The 3 after the ZLC in the first line denotes this CWA has been issued for the third weather phenomenon to occur for the local calendar day. The 303 in the second line denotes the phenomenon number again (3) and the issuance number (03) for this phenomenon. The CWA is valid until the 27th day of the month at 1745 UTC. CWA number 302 has been cancelled. See Convective SIGMET 8W.
ZME1 CWA 040100 Section 6: Products for Aviation Hazards Page 6-43
Aviation Weather Services, Advisory Circular 00-45G Change 1 (July 2010) ZME CWA 101 VALID TIL 040300
VCY MEM SEV CLR ICE BLW 020 DUE TO FZRA. NUMEROUS ACFT REP RAPID ACCUMULATION OF ICE DRG DES TO MEM. NO ICE REPS ABV 020. CONDS CONTG AFT 03Z. NO UPDATES AFT 040200Z.
Center Weather Advisory issued for the Memphis, Tennessee ARTCC on the 4th day of the month at 0100 UTC. The 1 after the ZLC in the first line denotes this CWA has been issued for the first weather phenomenon to occur for the local calendar day. The 101 in the second line denotes the phenomenon number again (1) and the issuance number (01) for this phenomenon. The CWA is valid until the 4th day of the month at 0300 UTC. For the Memphis, Tennessee vicinity. Severe clear icing below 2,000 feet MSL due to freezing rain. Numerous aircraft report rapid accumulation of icing during descent to Memphis. No icing reports above 2,000 feet MSL.
Conditions continuing after 0300 UTC. No updates after 4th day of the month at 0200 UTC.
ZNY5 UCWA 021400
ZNY CWA 502 VALID TIL 021600 FROM BGM TO 18WNW JFK TO HAR TO SLT TO BGM NUMEROUS ACFT REP SEV TURB AND WS BLW 020.
CONDS EXTD NE INTO ZBW CTA. CONDS EXP TO CONT AFT 16Z.
Center Weather Advisory issued for the New York ARTCC on the 2nd day of the month at 1400 UTC. The 5 after the ZNY in the first line denotes this CWA has been issued for the fifth weather phenomenon to occur for the local calendar day. The 502 in the second line denotes the phenomenon number again (5) and the issuance number (02) for this phenomenon. The CWA is valid until the 2nd day of the month at 1600 UTC. From Binghamton, New York; to 18 nautical miles west-northwest of New York (JFK Airport), New York; to Harrisburg, Pennsylvania;
to Slate Run, Pennsylvania; to Binghamton, New York. Numerous aircraft report severe turbulence and wind shear below 2,000 feet MSL. Conditions extending northeast into Nashua, New Hampshire control area. Conditions expected to continue after 1600 UTC.
ZNY4 UCWA 041500
ZNY CWA 401 VALID TIL 041700 40N SLT TO 18WNW JFK DEVELOPING LINE TS 25 NM WIDE MOV 24020KT. TOPS ABV FL350.
LINE TS EXTDS NW INTO ZOB CTA.
Urgent Center Weather Advisory issued for the New York ARTCC on the 4th day of the month at 1500 UTC. The 4 after the ZNY in the first line denotes this CWA has been issued for the fourth weather phenomenon to occur for the local calendar day. The 401 in the second line denotes the phenomenon number again (4) and the issuance number (01) for this phenomenon. The CWA is valid until the 4th day of the month at 1700 UTC. From 40 nautical miles north of Slate Run, Pennsylvania; to 18 nautical miles west-northwest of New York (JFK Airport), New York.
Section 6: Products for Aviation Hazards Page 6-44
Aviation Weather Services, Advisory Circular 00-45G Change 1 (July 2010) Developing line of thunderstorms 25 nautical miles wide moving from 240 degrees at 20 knots.
Tops above flight level 350. The line of thunderstorms extends northwest into the Oberlin, Ohio control area.
A dditional Products for Convection The National Weather Service (NWS) in addition to the SIGMETs, Convective SIGMETs, and CWAs already discussed, offers a few more products informing the aviation community about the potential for convective weather.
Convective Outlooks (AC) The NWS Storm Prediction Center (SPC) issues narrative and graphical convective outlooks to provide the contiguous U.S. NWS Weather Forecast Offices (WFOs), the public, media and emergency managers with the potential for severe (tornado, wind gusts 50 knots or greater, or hail 1 inch diameter size or greater) and non-severe (general) convection and specific severe weather threats during the following three days. The Convective Outlook defines areas of slight risk (SLGT), moderate risk (MDT) or high risk (HIGH) of severe thunderstorms for a 24-hour period beginning at 1200 UTC. The Day 1 and Day 2 Convective Outlooks also depict areas of general thunderstorms (GEN TSTMS), while the Day 1, Day 2, and Day 3 Convective Outlooks may use SEE TEXT for areas where convection may approach or slightly exceed severe criteria.
The outlooks are available on the SPC Web site.
Issuance Convective Outlooks are scheduled products issued at the following times:
Table 6-9. Convective Outlook Issuance Schedule Convective Outlook Issuance Time (UTC) Valid Period (UTC) Day 1 0600 1200 – 1200 1300 1300 – 1200 1630 1630 – 1200 2000 2000 – 1200 0100 0100 – 1200 Day 2 0600 (Daylight Savings Time) 0700 (Standard Time) Day 2/1200 – 1200 1730 Day 2/1200 – 1200 Day 3 0730 (Daylight Savings Time) 0830 (Standard Time) Day 3/1200 – 1200 SPC corrects outlooks for format and grammatical errors and amends outlooks when the current forecast does not or will not reflect the ongoing or future convective development.
Section 6: Products for Aviation Hazards Page 6-45
Aviation Weather Services, Advisory Circular 00-45G Change 1 (July 2010)
Figure 6-23. Day 1 Categorical Convective Outlook Graphic Example
Format of the Categorical Convective Outlook Narrative
SPC AC ddhhmm [SPC - issuing office, AC – product type, ddhhmm – date and time the product was issued
DAY (ONE, TWO OR THREE) CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK time am/pm time zone day mon dd yyyy VALID DDHHMM – DDHHMMZ
THERE IS A (SLIGHT, MODERATE, HIGH) RISK OF SEVERE THUNDERSTORMS TO THE
RIGHT OF LINE (LIST OF ANCHOR POINTS AND DIRECTION AND DISTANCE IN STATUTE MILES FROM THE LINE). THE LINE WILL ENCLOSE THE AREA OF RISK.
THERE MAY BE ONE OR MORE AREAS OF RISK AT THE APPROPRIATE LEVEL OF RISK. WHEN A MODERATE OR HIGH RISK IS FORECAST, THE INDIVIDUAL STATES ARE ALSO LISTED WITH THE TWO LETTER POSTAL STATE IDENTIFIERS.
GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM (LIST OF ANCHOR POINTS AND DIRECTION AND DISTANCE IN STATUTE MILES FROM THE LINE). THERE MAY BE ONE OR MORE AREAS OF GEN TSTMS LISTED.
Section 6: Products for Aviation Hazards Page 6-46
Aviation Weather Services, Advisory Circular 00-45G Change 1 (July 2010) …AREA OF CONCERN #1…
AREAS OF HIGHEST RISK ARE DISCUSSED FIRST (HIGH SEVERE RISK,
MODERATE SEVERE RISK, SLIGHT SEVERE RISK, APPROACHING SEVERE LIMITS). THE FORECAST PROVIDES A NARRATIVE TECHNICAL DISCUSSION.
…AREA OF CONCERN #2…
NARRATIVE TECHNICAL DISCUSSION
$$
…FORECASTER NAME… MM/DD/YY
Watch Notification Messages The NWS Storm Prediction Center (SPC) issues Watch Notification Messages to alert the aviation community, NWS offices (WFOs), the public, media and emergency managers to organized thunderstorms forecast to produce tornadic and/or severe weather in the conterminous U.S.
SPC issues three types of Watch Notification Messages: Aviation Watch Notification Message, Public Severe Thunderstorm Watch Notification Message and Public Tornado Watch Notification Message. They are available on the SPC Web site.
Aviation Watch Notification Message SPC issues Aviation Watch Notification Messages to alert the aviation community to organized thunderstorms forecast to produce tornadic and/or severe weather as indicated in Public Watch Notification Messages.
Format of an Aviation Watch Notification Message
SPC AWW ddhhmm WWnnnn SEVERE TSTM ST LO DDHHMMZ - DDHHMMZ AXIS...XX STATUTE MILES EITHER SIDE OF A LINE
XXDIR CCC/LOCATION ST/ - XXDIR CCC/LOCATION ST ..AVIATION COORD.. XX NM EITHER SIDE /XXDIR CCC - XXDIR CCC HAIL SURFACE AND ALOFT..X X/X INCHES. WIND GUSTS..XX KNOTS.
MAX TOPS TO XXX. MEAN STORM MOTION VECTOR DIR/SPEED
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Aviation Weather Services, Advisory Circular 00-45G Change 1 (July 2010)
Figure 6-24. Aviation Watch Notification Message Decoding Example Table 6-10. Decoding a Severe Weather Watch Bulletin Line Content Description 1 SPC AWW 132101 Issuing office Product Type Issuance date/time 2 WW568
TORNADO OK 132130Z – 140300Z Watch number Watch Type States affected Valid date/time period 3 AXIS..80 STATUTE MILES EAST AND WEST OF A LINE...
Watch axis 4 50SSE FSI/FORT SILL OK/ - 20NW
PNC/PONCA CITY OK/ Anchor points 5 …AVIATION COORDS.. 70NM E/W/ 21E SPS – 43S ICT/ Aviation coordinates 6 HAIL SURFACE AND ALOFT…3 INCHES.
WIND GUSTS..70 KNOTS. MAX TOPS TO
550. MEAN STORM MOTION VECTOR 26030.
Type, intensity, max tops, and mean storm motion using standard contractions.
The Severe Weather Watch Bulletin in Figure 6-16 is decoded as follows:
(Line 1) Alert Severe Weather Watch Bulletin (AWW), issued by the Storm Prediction Center on the 13th at 2101Z,
(Line 2) for Tornado Watch number 568 (WW568) for Oklahoma, valid from the 13th at 2130Z until the 14th at 0300Z.
(Line 3) The Tornado Watch area is along and 80 statute miles east and west of a line from
(Line 4) 50 statute miles south southeast of Fort Sill (Lawton), OK to 20 statute miles northwest of Ponca City, OK.
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