Sigmet : Significant Meteorological Information
是一種用於預報某區域的對飛行安全有影響的航空天氣情況的報文。
源
SIGMETs are issued from Meteorological Watch Offices(MWO)
MWO : Meteorological office designated to maintain watch over meteorological conditions within a defined area or for the purpose of supplying meteorological warnings for specific weather phenomena which may affect the safety of aircraft operations. The US has 3 MWOs : the Aviatin Weather Center (AWC) 、The AAWU（Alaska Aviation Weather Unit），and the WFO (NWS Weather Forecast Office) Honolulu .
言之，MWO這個機構是用來檢測確定空域的航空氣象，並且提供該空域影響飛行安全的氣象信息。在美國，他有三個，分別為AWC、AAWU和WFO。
查詢方法
- All SIGMETs are available on http://www.aviationweather.gov
- SIGMETs for Alaska are also available on the Alaska Aviation WeatherUnit web site
SIGMETs for Hawaii are also available on the NWS Weather Forecast Office(WFO)Honolulu Web site.
以上是官方發佈的辦法，但是我個人更喜歡用skyvector這個網站去查，記住這個網址：skyvector.com , 裡面可以利用的資料信息很豐富了，而且還免費！
規格準
1、所有的高度都是MSL，e.g., 040 指 40 00 MSL ，對於高於或等於18,000ft的，則表示為FL180。
2、經緯度的度和分（degree and minutes）按照以下的格式表示：Nddmm or Sddmm , Wdddmm , or Edddmm 。
SIGT 結構
實例
Header
： TTAAii CCCC YYGGgg [BBB]
TTAAii本例為 WSBZ21
- TT ：Datatype designator，SIGMET的類型。其中WV for Volcanic Ash 火山灰，WC for TropicalCyclone 熱帶氣旋，WS for the other phenimena 其他天氣現象。
- AA ：Country or territory designators ,where the message came from 。下載Manual on the Global Telecommunication System 這本書，搜關鍵詞 Table C1，查詢縮寫意義。
本例BZ指rizil 。
- i i : the bulletin number, assigned in the national level. It’s not so relevant for our simulation. 報文的序號，國家決定，不死心的，怎麼去找我也告訴你，Manual on the Global Telecommunication System 這本書，搜關鍵詞 Table D2 。
CCCC ：the location of the addressed centre disseminating the message. 其實就是劃定的一塊區域的，作用和AA一樣，但是範圍應該縮小了。具體哪找到我就忘記了，強迫症請去Manual on the Global Telecommunication System PART III 查，然後評論分享我一下。
本例 SBRE 為 the Recife FIR（Flight Information Region）
YYGGgg : te date and time of the dissemination of the message.
本例 150430 ，15號0430Z 。
BBB ： Corrction indicator . The BBB indicator shall take the form CCx for corrections to previously relayed bulletins , where x takes the value A for the first correction , B for the second correction , etc. . BBB 用於更正的SIGMET ，格式是CCx ， 如果是更正的第一個版本，則為CCA ，第二個則為CCB 。本例無 。
First line oSIGMET
CCCC SIGMET [n][n]n VALID YYGGgg/YYGGgg CCCC-
CCCC： is the ICO location indicator of the ATS unit serving the FIR or CTA to which the SIGMET refers . In other word , is where the observation/forecast where the SIGMET is issued to．也就是SIGMET 發佈的目標區域。
本例 SBAO ： the Atlantic FIR 。（什麼是FIR ？ 有興趣請看下次更新）
[n] [n] n : Thedaily sequence number in the form [n][n]n, e.g. 1, 2, 01, 02, A01, A02, restarts every day for SIGMETs issued from 0001 UTC. 也就是該SIGMET的系列號。
YYGGgg/YYGGgg : VALID 150435/150835 is the period of validity of the message. It follows the same standard of the date/time of the header. In this case, it means that the message is valid between 0435Z of day 15 and 0835Z of day 15。
本例 SIGMET 有效時間 15號0435Z到15號0835Z 。
CCCC- ：is the ICA location indicator of the MWO originating the message followed by a hyphen, in other word , the station which did the observation/forecast . 監測和預測天氣的站點。
本例 SBRE- ：the Recife FIR 。
SIGMET Main Body
1) Location indicatr of FIR(/UIR) or CTA;
2) Name of the FIR(/UIR ) or CTA;
SBAO ATLANTIC FIR is the Location Indicator and the Name of the FIR that holds the element of observation/forecast. That is, the element of weather report is located inside the SBAO FIR;
3) Description of te phenomenon;
EMBD TS：Embedded Thunderstorms
4) Observed OBS or Foecasted FCST ;
FCST AT 0435Z means the information is a forecast. If OBS was written, it means that the information is an observation. When the information does not come with a time information, it means the exact time of observation/forecast is not known;
5) Location of observtion/forecast 也就是觀察或預測的區域的經緯度
WI S3154 W04804 - S3400 W05000 - S3400 W04625 - S3154 W04804 is the location of the forecast. When WI (Within) is stated, it means that the observation is INSIDE that polygon created by the geographic coordinates;
6) Level (altitude) of he observation/forecast;
格式有：
FLnnn or nnnnM or nnnnFT or SFC/FLnnn or SFC/nnnnM or SFC/nnnnFT or FLnnn/nnn or nnnn/nnnnFT or TOP FLnnn or ABV FLnnn or TOP ABV FLnnn
TOP FL380 is the altitue of observation. The top of those Embedded Thunderstorms inside the polygon above reaches the FL380;
7) Movement or Expected Mvement：MOV or STNR
MOV NE 05KT indicates that the centre of the cloud mass is moving NORTHEAST at the speed of 5 knots (nm/h). If the abbreviation STNR is indicated, it means that the phenomenon is stationary;
8) Changes in intensity：
NTSF (Intensifying)or WKN(Weakening)or NC（no change）
9) Forecasted position at e of SIGMET’s end of validity (optional).
= ： the end of message .
如果和飛友關係不鐵，就別分享這麼認真總結的資料了 ！！
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