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WMO Seminar /Workshop for Aeronautical Competencies and

SIGMETs

NAM/CAR Regions

Costa Rica, 25-27 August 2015

TC Sigmets Lawrence Pologne

Caribbean Institute for Meteorology and Hydrology, Barbados

Tropical Cyclone SIGMET (WC SIGMET) based on

Tropical Cyclone Advisory (TCA)

TCACs and Their Responsibilities as required in ICAO Annex 3

Section 3.7 Tropical cyclone advisory centres

A Contracting State having accepted, by regional air navigation agreement, the

responsibility for providing a TCAC shall arrange for that centre to:

a) monitor the development of tropical cyclones in its area of responsibility,

using geostationary and polar-orbiting satellite data, radar data and other

meteorological information;

b) issue advisory information concerning the position of the cyclone centre,

its direction and speed of movement, central pressure and maximum

surface wind near the centre, in abbreviated plain language to:

1) meteorological watch offices in its area of responsibility;

2) other TCACs whose areas of responsibility may be affected; and

3) world area forecast centres, international OPMET databanks, and

centres designated by regional air navigation agreement for the

operation of aeronautical fixed service satellite distribution systems;

and

c) issue updated advisory information to meteorological watch offices for

each tropical cyclone, as necessary, but at least every six hours.

Area of responsibility of Tropical Cyclone Advisory Centre (TCAC)

Manual of Aeronautical Meteorological Practice (DOC 8896)

1.6 TROPICAL CYCLONE ADVISORY CENTRES (TCACs)

TCACs are meteorological centres designated by regional air navigation agreement on

advice from WMO. They monitor the development of tropical cyclones in their areas of

responsibility, using geostationary and polar-orbiting satellite data and other

meteorological information sources (e.g. numerical weather prediction models).

TCACs provide MWOs, providers of international OPMET databanks established by

regional agreement, providers of the aeronautical fixed service (AFS) satellite

distribution systems and, as necessary, other TCACs with advisory information

regarding the position of the centre of the tropical cyclone, its forecast direction and

speed of movement, central pressure and maximum surface wind near the centre of the

cyclone. The advisory information is to be used by MWOs in support of the issuance of

SIGMET information for tropical cyclones. The information is also made available to

aeronautical users through the AFS satellite distribution systems.

Specification of tropical cyclone advisory information as required

in ICAO Annex 3 Appendix 2

5. TROPICAL CYCLONE ADVISORY CENTRES (TCAC)

5.1 Tropical cyclone advisory information

5.1.1 The advisory information on tropical cyclones shall be issued for tropical

cyclones when the maximum of the 1-minute/10-minute mean surface wind speed is

expected to reach or exceed 17 m/s (34 kt) during the period covered by the advisory.

5.1.2 The advisory information on tropical cyclones shall be in accordance with the

template shown in Table A2-2.

5.1.3 Recommendation.— The tropical cyclone advisory information listed in Table

A2-2, when prepared in graphical format, should be as specified in Appendix 1 and

issued using:

a) the portable network graphics (PNG) format; or

b) the BUFR code form, when exchanged in binary format.

Note.— The BUFR code form is contained in WMO Publication No. 306, Manual on

Codes, Volume I.2, Part B — Binary Codes.

Example of Tropical Cyclone Advisory (TCA) from TCAC

Detailed format is defined in ICAO Annex 3 Appendix 2 Section 5 and

Table A2-2 Template for advisory message for tropical cyclone

SIGMET information as required in ICAO Annex 3

7.1 SIGMET information (continued)

7.1.4 Recommendation.— SIGMET messages concerning volcanic ash cloud

and tropical cyclones should be based on advisory information provided by

VAACs and TCACs, respectively, designated by regional air navigation

agreement.

7.1.5 Close coordination shall be maintained between the meteorological

watch office and the associated area control centre/flight information centre to

ensure that information on volcanic ash included in SIGMET and NOTAM

messages is consistent.

7.1.6 SIGMET messages shall be issued not more than 4 hours before the

commencement of the period of validity. In the special case of SIGMET

messages for volcanic ash cloud and tropical cyclones, these messages shall be

issued as soon as practicable but not more than 12 hours before the

commencement of the period of validity. SIGMET messages for volcanic ash

and tropical cyclones shall be updated at least every 6 hours.

Preparation of Tropical Cyclone SIGMET:

• based on observed/forecast position and intensity (max

wind) given in Tropical Cyclone Advisory, estimate the

time when TC entering into or leaving out of your FIR;

• work out validity period; OBS time & position; FCST

FCST time & position;

• based on radar and satellite images, or based on

graphical TCA, estimate the coverage of CB;

• tropical cyclone SIGMET can be worked out rather

straight forward.

TC SIGMET

Scenario A - TC currently outside

Piarco FIR and is expected to enter

into Piarco FIR at Tin within 12 hours

Scenario B - TC currently within

Piarco FIR and is expected to stay

within Piarco FIR at or before Tn + 6

hours

TC SIGMET

Scenario C - TC currently within Piarco

FIR and is expected to move out of

Piarco FIR at Tout before Tn + 6 hours

Scenario D - TC crossing Piarco FIR

(TC currently outside Piarco FIR and is

expected to enter into Piarco FIR at Tin

within 12 hours and to move out of

Piarco FIR at Tout before Tin + 6 hours)

TC SIGMET

Scenario A - TC currently outside

Piarco FIR and is expected to enter into

Piarco FIR at Tin within 12 hours

• Before the commencement of TC SIGMET, convection may

affect FIR or area of responsibility.

• In some states, SIGMET not yet valid will not be included in

VOLMET/D-VOLMET. The convection should be warned

by a convective SIGMET such as EMBD TS.

• When the TC SIGMET becomes valid, the convective

SIGMET may be cancelled.

TC SIGMET

Scenario C - TC currently

within Piarco FIR and is

expected to move out of Piarco

FIR at Tout before Tn + 6 hours

• Similarly, when TC moved out of FIR or area of

responsibility, convection would most likely affect FIR or

area of responsibility.

• The convection should be warned by a convective SIGMET

such as EMBD TS.

• When the TC SIGMET becomes invalid, the convective

SIGMET may be issued.

ICAO Annex 3 Appendix 6

SIGMET information concerning thunderstorms or a tropical cyclone

shall not include references to associated turbulence and icing.

Example of SIGMET information for severe turbulence

If tropical cyclone or thunderstorm SIGMET has been

issued for an area and a special air-report of turbulence

or icing within that area is received, then you may

consider the special air-report is covered by SIGMET,

even though turbulence or icing SIGMET is not issued

for that area.

• Example: • WCNU20 TNCC 042100

TNCC SIGMET 3 VALID 042100/050300 TNCC-

TNCC CURACAO FIR TC ERNESTO OBS AT 2100Z N1480 W07010 CB TOPS FL500 120NM FROM

CENTER MOV W 16 KT INTENSIFYING

FCST 0300Z TC CENTER N1510 W07180=

WC SIGMET

Procedures for preparing SIGMET information in SIGMET Guide

Scenario A: TC currently outside Piarco FIR is expected to enter into Piarco

FIR at Tin (within 12 hours)

Examples of WC SIGMET

A1-Weather Situation:

At around 20070814 2130 UTC, a tropical cyclone (without a name by that time) was

observed with location (centre) outside Piarco FIR (tropical depression). It was

expected that the tropical cyclone would (i) intensify into a tropical storm (i.e.,

maximum wind reaching 34 kt requirement) later and (ii) enter into Piarco FIR at

around 20070815 0500UTC (i.e., within 12 hours). By that time, a SIGMET for TS

(No.5, valid 142130/150130 ) had been issued to warn the widespread embedded

TS/CB clouds in the eastern area of Piarco FIR, which considered to be associated

with the TC.

Examples of WC SIGMET - continued

Answer A1:

WCCA31 TTPP 142134

TTZP SIGMET 6 VALID 150500/151100 TTPP-

TTZP PIARCO FIR TC NN FCST AT 0500Z N1200 W03830 CB TOP FL400 WI 330NM OF

CENTRE MOV W 25Kt INTSF

FCST 1100Z TC CENTRE N1200 W03903=

Data type: ? Country designator: CA

Bulletin number: 31 Location indicator of MWO: TTPP

Location indicator of Piarco FIR: TTZP Sequential No. before: 5

Issued time: 200708142134 UTC Forecast Tin: 200708150500 UTC

TC name: no name Forecast location (Tin): N1200, W03830

Level: CB TOP FL400 WI 330NM of CENTRE Movement: W, 25Kt

Intensity: intensifying Forecast location (Tin+6) : N1200, W03903

Structure of SIGMET:

WMO AHL:T1T2A1A2ii CCCC1 YYGGgg [CCx]

First Line:CCCC2 SIGMET [nn]n VALID YYGGgg/YYGGgg CCCC1-

Body Line:<CCCC2> <NAME> FIR TC <NAME> OBS[FCST] AT <TIME> <LOCATION>

<LEVEL> <MOVEMENT> <INTENSITY> <FORECAST> <TIME> TC CENTRE <POSITION>=



When the SIGMET 5 for thunderstrom was going to expire at 200708150130UTC,

update(extend) the SIGMET 5?



Location indicator of PIARCO FIR: TTZP Sequential No. : ?

Forecast location : South OF N1500, East OF W039 Level: TOP FL400

Movement: W, 25Kt Intensity: intensifying

Structure of SIGMET :



Body Line:<CCCC2> <PHENOMENON> OBS[FCST] [AT <TIME>] <LOCATION> <LEVEL>

<MOVEMENT> <INTENSITY>=

Answer A2:

WSCA31 TTPP 150118


TTZP PIARCO FIR EMBD TS FCST S OF N1500 E OF W039 TOP FL400 MOV W 25Kt

INTSF=

Examples of WC SIGMET-continued


Several hours later (150200 UTC), the situation remained more or less the same

(tropical cyclone outside PIARCO FIR) except that there were some adjustments in

forecast timing and position. Update the previous WC SIGMET (SIGMET 6)?




Forecast Tin: 15 0530 UTC TC name: no name

Forecast location (Tin) : N1220, W03920 Level: CB TOP FL400 WI 300NM of CENTRE

Movement: W, 20Kt Intensity: intensifying

Forecast location (Tin+6) : N1230, W03950






Answer A3:

WCCA31 TTPP 150200


TTZP PIARCO FIR TC NN FCST AT 0530Z N1220 W03920 CB TOP FL400 WI 180NM OF

CENTRE MOV W 10KT INTSF FCST 1130Z TC CENTRE N1230 W03950=



Due to the adjustment of TC forecast position, the WS SIGMET 1 for

thunderstorm was also necessary to update.



Location indicator of Piarco FIR: TTZP Sequential No. : ?

Start of Validity: 150315UTC Forecast location : South OF N1530, East OF W03920

Level: TOP FL400 Movement: W, 20Kt

Intensity: intensifying






Answer A4:

WSCA31 TTPP 150313


TTZP PIARCO FIR EMBD TS FCST S OF N1530 E OF W03920 TOP FL400 MOV W 20Kt

INTSF=

Scenario B: TC currently within PIARCO FIR and is expected to stay within

PIARCO FIR at or before Tn + 6 hours

Examples of WC SIGMET -continued

B1-Weather Situation:

At around 20070415 0340UTC, it was confirmed that the tropical cyclone had

already been intensified into a tropical storm (given name: DEAN) and entered

into PIARCO FIR at around 0300UTC. Should the previous WC SIGMET

(SIGMET 2) be updated immediately? Or should SIGMET 3 be cancelled first?


Answer B1:

WCCA31 TTPP 150340


TTZP PIARCO FIR TC DEAN OBS AT 0300Z N1210 W03900 CB TOP FL400 WI 330NM OF

CENTRE MOV W 25Kt NC FCST 0900Z TC CENTRE N1210 W03920=




Observed: At around 200715 0300 UTC Confirmed time: 200715 0340 UTC

TC name: DEAN Forecast location (Tobs) 1: N1210, W03900

Level: CB TOP FL400 WI 330NM of CENTRE Movement: W, 25Kt

Intensity: No change Forecast location (Tobs+6) 2: N1210, W03920






Notes/ Questions and Answers

SIGMET 4 was issued at 0340UTC but the observation time was 0300UTC. Why?

A number of factors, such as radar/satellite images, Dvorak analysis, wind

reports, etc., had to be taken into account to fix the location as well as the

intensity of tropical cyclone. This took some time.

During the gap period of 40 minutes (observation time at 0300UTC and commencement of validity period at 0340UTC of SIGMET 4), there would be no valid WC SIGMET to warn tropical cyclone (SIGMET 2 has not become valid yet). Would this be a problem?

The hazardous weather brought by tropical cyclone should be the CB

clouds which should have been covered by WS SIGMET 3.

• Does SIGMET 4 cover the widespread thunderstorms/CB clouds given in SIGMET 3? And what should be done? Cancel SIGMET 3?


Answer A4:

WSCA31 TTPP 150313


TTZP PIARCO FIR EMBD TS FCST S OF N1530 E OF W03920 TOP FL400 MOV W 20KMH

INTSF=

Answer B1:

WCCA31 TTPP 150340


TTZP PIARCO FIR TC DEAN OBS AT 0300Z N1210 W03900 CB TOP FL400 WI 330KM OF

CENTRE MOV W 25KMH NC FCST 0900Z TC CENTRE N1210 W03920=

Procedures for preparing SIGMET information in SIGMET Guide

• Cancel SIGMET 3


Answer B2:

WSCA31 TTPP 150344


TTZP PIARCO FIR CNL SIGMET 3 150315/150715=

Answer B1:

WCCA31 TTPP 150340


TTZP PIARCO FIR TC DEAN OBS AT 0300Z N1210 W03900 CB TOP FL400 WI 330KM OF

CENTRE MOV W 25KMH NC FCST 0900Z TC CENTRE N1210 W03920=

Answer A4:

WSCA31 TTPP 150313


TTZP PIARCO FIR EMBD TS FCST S OF N1530 E OF W03920 TOP FL400 MOV W 20KMH

INTSF=

Scenario C: TC currently within PIARCO FIR and is expected to move out

of PIARCO FIR at Tout before Tn + 6 hours


C1-Weather Situation:

At around 20070817 0040UTC, the tropical cyclone was expected to move out of

the PIARCO FIR at around 20070817 0300UTC. The following SIGMET was

issued with a shorter validity period ending at 0300UTC.

Data type: WC Country designator: CA



Observed: 17 0000 UTC Confirmed time: 17 0040 UTC

Forecast Tout: 17 0300 UTC TC name: DEAN

Forecast location (Tobs) : N1500, W06424

Level: CB TOP FL400 WI 330NM of CENTRE Movement: WNW, 20Kt

Intensity: No Change Forecast location (Tout): N1530, W06530






Answer C1:

WCCA31 TTPP 170040


TTZP PIARCO FIR TC DEAN OBS AT 0000Z N1500 W06424 CB TOP FL400 WI 330NM OF

CENTRE MOV NW 20Kt NC FCST 0300Z TC CENTRE N1530 W06530=



C2-Weather Situation:

The TC moved out of PIARCO FIR at 0300UTC. When the WC SIGMET 1

became invalid (after 0300UTC ), there were widespread thunderstorms/CB

clouds continuing to affect PIARCO FIR. What should be done?




Start of Validity: 170250UTC Forecast location : North OF N1500, East OF W06500

Level: TOP FL380 Movement: NW, 20Kt

Intensity: weakening

Answer A4:

WSCA31 TTPP 170248


TTZP PIARCO FIR EMBD TS FCST N OF N1800 E OF E10810 TOP FL380 MOV NNW 20Kt

WKN=






Significant weather (SIGWX) Chart

ICAO Annex 3 Appendix 2

1.3.3 Items included in SIGWX forecasts

SIGWX forecasts shall include the following items:

a) tropical cyclone provided that the maximum of the 10-minute mean surface

wind speed is expected to reach or exceed 17 m/s (34 kt);

......

Significant weather (SIGWX) Chart

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