Practical Exercise et simulated assessment : Thunderstorm, icing, turbulence
1. Your team need to produce a TS SIGMET, a ICING SIGMET and a TURBULENCE SIGMET.
Info needed:
TS SIGMET
-
CB max top
CB qualifiers : FRQ TS (TSGR or TSGR PSLB +FC) SQLN TS (TSGR or TSGR PSLB +FC)
Direction and speed
Trend :Intensifying/weakening/no change
ICING SIGMET
-
Base FL, Top FL
Direction and speed
Trend :Intensifying/weakening/no change
TURBULENCE SIGMET
-
Base FL, Top FL
Direction and speed
Trend :Intensifying/weakening/no change
2. Would you need to include these infos (severe TS, ICING or TURB) into another forecast
product?
3. AMF assessment :Appropriate techniques
3.1a Forecasting severe thunderstorms

Demonstrates ability to forecast the intensity, extent, movement and tops:
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o
o
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o
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Verifies upstream data for intensity and visibilities in thunderstorms;
Uses satellite imagery to determine extent, evolution and movement;
Compares IR cloud-top temperature to soundings to determine tops;
Determines thunderstorm tops using radar;
Uses different NWP models and compares to reality;
Considers synoptic patterns (warm front vs. cold front thunderstorms);
Verifies different convective indices (K, LI, SWEAT, etc.);
Coordinates with other weather offices;
Determines the 0-6km mean wind for thunderstorm movement.
Demonstrates ability to forecast wind gust strength and wind shear:
o Verifies upstream data;
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o
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o
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Verifies upper-level winds using soundings (model and actual);
Uses the Doppler radar to locate possible mesocyclones and potential gusts;
Uses satellite imagery to determine whether gust fronts are present;
Coordinates with other weather offices for wind warnings.
Demonstrates ability to forecast thunderstorms:
o Knows the necessary ingredients for thunderstorm formation (moisture, instability
and trigger);
o Uses water vapour imagery to locate jet streams (right-entrance and left-exit
regions) and shortwaves;
o Uses radar extrapolation tool to determine arrival time and duration;
o Enumerates different indices/clues that indicate a thunderstorm might be severe
(overshooting tops, hail, meso, strong winds, etc.).
3.1b Forecasting turbulence

Demonstrates ability to forecast type: MECH, CAT, LEE WV
o
o
o
o
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Knows the formation criteria for different types of turbulence;
Considers local effects;
Uses different types of satellite imagery for clues of turbulence (transverse
bands, mountain waves, etc.);
Uses NWP models to determine levels and hence the type;
Determines surface stability (MECH vs. LLWS);
Verifies the Outgoing Flux field to locate lee waves (vertically-propagating);
Compares NWP model soundings to actual soundings;
Knows the moderate and severe MECH wind criteria;
Verifies soundings to determine moderate-to-severe wind shear levels.

Demonstrates ability to forecast severity:
o Uses different tools;
o Knows the difference between moderate and severe mechanical turbulence
(wind force);
o Uses water vapour imagery (strong moisture contrasts, well-defined transverse
bands, etc.);
o Considers synoptic patterns (deformation zones, etc.);
o Monitors PIREPs.

Demonstrates ability to forecast base, top, onset, duration and dissipation time for the
phenomenon:
o
o
o
Uses different tools;
Verifies IR cloud-top temperature and compares to soundings to determine level
of tropopause and tops of lee wave turbulence;
Verifies soundings to determine levels of moderate-to-severe wind shear.
3.1d Forecasting icing

Demonstrate ability to forecast type: CLR, MXD, RIME
o Considers synoptic patterns;
o Knows which type of icing is most dangerous and why;
o Accurately explains what each type of icing is associated to;
o Uses NWP soundings for profiles (warm nose) and cloud type and compares to
actual soundings;
o
o
Uses satellite imagery to determine cloud type and therefore icing type;
Monitors PIREPs.

Demonstrates ability to forecast severity: LGT, MDT, SEV
o Considers synoptic patterns;
o Uses NWP soundings for profiles and cloud type and compares to actual
soundings;
o Uses satellite imagery to determine cloud type;
o Monitors PIREPs;

Demonstrates ability to forecast base/top, onset, duration and dissipation time:
o Uses NWP models and compares to reality;
o Uses satellite imagery and extrapolates clouds;
o Uses model soundings to forecast base and top;
o Monitors PIREPs.
4. Decode a TS, ICING and TURBULENCE SIGMET
SIGA0E
KZNY SIGMET ECHO 2 VALID 201330/201730 KKCINEW YORK OCEANIC FIR FRQ TS OBS AT 1330Z WI N3200 W05645 - N2645
W05700 - N2645 W06845 - N3045 W06915 - N3200 W05645. TOP FL450.
MOV ESE 15KT. NC.
ENOB SIGMET E02 VALID 201401/201801 ENVNENOB BODO OCEANIC FIR OCNL SEV TURB FCST WI 30 NM FM LINE N7620 E01000 AND N7720 - E03000 FL200/290 MOV SE NC=
NZZO SIGMET 27 VALID 201424/201824 NZKLNZZO AUCKLAND OCEANIC FIR SEV ICE FCST WI S3820 W14030 - S3800
W13700 - S4110 W13830 - S4750 W13450 - S4620 W14000 - S4120 W14300 S3820 W14030 3000FT/FL160 STNR NC=
Find the following info for TS :
- CB max tops
- CB qualifier
- Direction and speed
- Intensifying/weakening/no change
Find the following info for ICING :
- FL base and top
- Direction and speed
- Intensifying/weakening/no change
Find the following info for TURBULENCE :
- FL base and top
- Direction and speed
- Intensifying/weakening/no change