WindshearWindshear and Turbulenceand TurbulenceAl ti S iAl ti S iAlerting ServicesAlerting Services

Hong Kong ObservatoryHong Kong ObservatoryDecember 2010December 2010

Frequency distribution by Frequency distribution by hhmonthmonth

Significant windshear:Significant windshear:Significant windshear:Significant windshear:1 in 500 flights1 in 500 flightsSignificant turbulence:Significant turbulence:Significant turbulence:Significant turbulence:1 in 2000 flights1 in 2000 flights 2nd peak

1st peak

Typical weather scenarios for Typical weather scenarios for i d h d b li d h d b lwindshear and turbulencewindshear and turbulence

Winds blowing across terrainWinds blowing across terrainWinds blowing across terrainWinds blowing across terrain(terrain(terrain--induced)induced)Sea breezeSea breeze decreasingSea breezeSea breezeGust frontsGust fronts

decreasingfrequency of occurrence

MicroburstsMicroburstsLowLow--level jetslevel jetsjj

Monitoring networkMonitoring networkMonitoring networkMonitoring network

AnemometerAnemometer

TDWR

Weather buoy

Wind profilerLIDAR

Automatic detection algorithmsAutomatic detection algorithmsAutomatic detection algorithmsAutomatic detection algorithms

HKO develops a number of windshear HKO develops a number of windshear HKO develops a number of windshear HKO develops a number of windshear detection algorithms:detection algorithms:

AnemometerAnemometer based Windshear Alerting Rules based Windshear Alerting Rules ––AnemometerAnemometer--based Windshear Alerting Rules based Windshear Alerting Rules ––Enhanced (AWARE)Enhanced (AWARE)LIDAR Windshear Alerting System (LIWAS)LIDAR Windshear Alerting System (LIWAS)LIDAR Windshear Alerting System (LIWAS)LIDAR Windshear Alerting System (LIWAS)

WTWS also shows alerts based on TDWR WTWS also shows alerts based on TDWR data and hilltop algorithmdata and hilltop algorithmdata and hilltop algorithm.data and hilltop algorithm.

AWAREAWAREAWAREAWARE

Based on Based on Based on Based on anemometers anemometers (ground(ground--truth truth Tai Mo To (g(gdata)data)Skillful in Skillful in

Weatherbuoys

Weatherbuoys

detecting sea detecting sea breeze, gust breeze, gust f d f d front and front and shear lineshear line

Sea breeze case on 3 November 2005Sea breeze case on 3 November 2005Sea breeze case on 3 November 2005Sea breeze case on 3 November 2005

10 windshear 10 windshear 10 windshear 10 windshear reports (+15 to reports (+15 to +20 knots) over +20 knots) over +20 knots) over +20 knots) over 07LA between 07LA between 0515 and 0539 0515 and 0539 0515 and 0539 0515 and 0539 UTCUTC

LIWASLIWASLIWASLIWASBased on glideBased on glide--ggpath scan of path scan of the LIDARthe LIDAROperational Operational since Dec 2005since Dec 2005since Dec 2005since Dec 2005For arrival For arrival corridors onlycorridors onlycorridors onlycorridors only

Scanner

Graphicaldisplay

Signal processing computer –RASP (Real time Accessed Signal

Transceiver

RASP (Real-time Accessed Signal Processor)

Inside the LIDAR shelter

LIDAR PrincipleLIDAR PrincipleLIDAR PrincipleLIDAR Principle

LIDAR versus TDWRLIDAR versus TDWR

LIDAR k b t LIDAR works best in fine weather

TDWR works bestin rainy weather

Major Parameters of LIDARMajor Parameters of LIDARMajor Parameters of LIDARMajor Parameters of LIDAR

Peak pulse energy 2 mJPeak pulse energy 2 mJPeak pulse energy 2 mJPeak pulse energy 2 mJWavelength 2 Wavelength 2 μμmmRange resolution ~100 mRange resolution ~100 mMaximum range ~10 km (weather Maximum range ~10 km (weather g (g (dependent)dependent)Unambiguous velocity range Unambiguous velocity range --20 m/s to 20 m/s to Unambiguous velocity range Unambiguous velocity range 20 m/s to 20 m/s to 20 m/s (extendable to 20 m/s (extendable to --40 m/s to 40 40 m/s to 40 m/s with reduction in range)m/s with reduction in range)m/s with reduction in range)m/s with reduction in range)

Safety IssuesSafety IssuesSafety IssuesSafety Issues

Cl ifi d Cl 1M d IEC Cl ifi d Cl 1M d IEC Classified as Class 1M under IEC Classified as Class 1M under IEC 6082560825--1 (IEC 2001) and Class 3b under 1 (IEC 2001) and Class 3b under ANSI Z136 1ANSI Z136 1 20002000ANSI Z136.1ANSI Z136.1--20002000

Could be harmful if viewed with optical aidsCould be harmful if viewed with optical aidsSafety measuresSafety measures

Sector blankingSector blankingggScan rate interlockScan rate interlockLaser Safety Officer appointedLaser Safety Officer appointedy ppy pp

Schematic diagram of dual LIDAR operation(after relocation)( )

laser beams

glide pathN

GlideGlide--path scanpath scanGlideGlide path scanpath scan

3 deg for arrival corridors6 deg for departure corridors

Windshear rampWindshear rampWindshear rampWindshear rampSustained change of headwind:Sustained change of headwind: Ramps prioritized Ramps prioritized

di di headwind change from one headwind change from one ““statestate””to anotherto another

Headwind

according to a according to a metricmetric

ΔVappV

HVS /)( 3

3/1

Δ=

ΔV H

HHDistance/time

LIWAS algorithmLIWAS algorithmggMeasure headwind Measure headwind

data along the glide data along the glide Generate Generate windshear windshear g gg g

pathpathwindshear windshear alerts to alerts to WTWSWTWS

Generate headwind Generate headwind profileprofile

Identify windshear rampIdentify windshear ramp

What LIWAS sees in 30 August 2004 What LIWAS sees in 30 August 2004 casecasecasecase

Windshear event on 30 March 2005Windshear event on 30 March 2005

Wi d h Wi d h Windshear reports :Windshear reports :

0005 07RA 0005 07RA --15 KT 4NM15 KT 4NM0005 07RA 0005 07RA 15 KT 4NM15 KT 4NM0029 07RA 0029 07RA --30 KT 1NM30 KT 1NM0032 07RA 35 KT 1NM0032 07RA 35 KT 1NM0045 07RA 25 KT 1NM0045 07RA 25 KT 1NM0049 07LA 0049 07LA --20 KT 20 KT 2NM2NM2NM2NM

Wind direction, speed and headwind derived from on-board data from aircraft arriving at 0049 UTC.

24KT

LIWASheadwindheadwind profile

Winds Blowing Across Terrain Winds Blowing Across Terrain (T i(T i i d d)i d d)(Terrain(Terrain--induced)induced)

Easterly to southwesterly windsEasterly to southwesterly winds(e.g. in spring time and in tropical cyclone situation)(e.g. in spring time and in tropical cyclone situation)

Winds Blowing Across Terrain Winds Blowing Across Terrain (T i(T i i d d)i d d)(Terrain(Terrain--induced)induced)

Northwesterly to northeasterly windsNorthwesterly to northeasterly windsy yy y(e.g. in northeast monsoon in winter time)(e.g. in northeast monsoon in winter time)

Sea breezeSea breezeSea breezeSea breezeDevelops under sunny weatherDevelops under sunny weatherS b i h h ili i dS b i h h ili i dSea breeze converges with the prevailing windSea breeze converges with the prevailing wind

Sea breeze front

Background flflow

S BSea Breeze

Usually headwind gainUsually headwind gain

Sea breezeSea breezeFlying through a sea breeze front could Flying through a sea breeze front could experience headwind loss as wellexperience headwind loss as wellexperience headwind loss as wellexperience headwind loss as well

Gust frontGust frontGust frontGust frontLeading edge of cool air spreading out from the Leading edge of cool air spreading out from the downdraft of intense stormsdowndraft of intense stormsdowndraft of intense stormsdowndraft of intense stormsHeadwind gainHeadwind gain

Characteristics of windshear and Characteristics of windshear and b l HKIAb l HKIAturbulence at HKIAturbulence at HKIA

Most are terrainMost are terrain--induced induced TransientTransient and and sporadicsporadicGain and lossGain and loss events can events can coco--existexistGenerally more significant on south runway due Generally more significant on south runway due y g yy g yto closeness to hillsto closeness to hills

Windshear is transient and sporadicWindshear is transient and sporadicWindshear is transient and sporadicWindshear is transient and sporadicSmallSmall--scale disturbances over scale disturbances over RWY 25LRWY 25LRWY 25LRWY 25L

30 August 2004

Windshear is transient and sporadicWindshear is transient and sporadicWindshear is transient and sporadicWindshear is transient and sporadic

Arrows show the movement of the windshear Arrows show the movement of the windshear features in the next 4 minutes

Windshear is transient and sporadicWindshear is transient and sporadicWindshear is transient and sporadicWindshear is transient and sporadic306000

20

25

4000

5000

path

(ft) L

IDA

R

Headwind profile @ 14:41 UTCHeadwind profile @ 14:43 UTC

153000

6-de

gree

glid

e R

's radial veloc

5

10

1000

2000

Hei

ght o

f city (knots)

6-degree glide path

0-1012

Distance from runway end (NM)

0Runway corridor 25 LD

Sequence of headwind changes reversed in 2 minutes!Sequence of headwind changes reversed in 2 minutes!

Headwind gain and loss could coHeadwind gain and loss could co--existexistHeadwind gain and loss could coHeadwind gain and loss could co existexist

Sinking

Lifting+20Kt

Sinking-11Kt

Sinking-17Kt Lifting

+12Kt07LA

TerrainTerrain--induced windshear and turbulenceinduced windshear and turbulencei i –– points to notepoints to note

SmallSmall sized and evolving sized and evolving SmallSmall--sized and evolving sized and evolving rapidlyrapidlyWindshear and turbulence Windshear and turbulence

Time Aircraft Type Intensity Location3:50 - None reported -Windshear and turbulence Windshear and turbulence

as experienced by an as experienced by an aircraft may at times differ aircraft may at times differ

4:00 A330 15 kt loss 3MF4:02 B747-400 25-29 kt gain 2MF4:04 B747-400 None reported -4:10 B767 15 kt gain 2MFyy

from the conditions from the conditions reported by the preceding reported by the preceding

d h i i f d h i i f

g

A day in March 2000Landings on RWY 07L

and the ensuing aircraft, and the ensuing aircraft, and from the alerts and from the alerts providedprovidedprovided.provided.

Gentle windshear rampa p

07LA null report of07LA, null report of windshear at 10:00 UTC, 16 April 2005

But … sometimes there could be unexpected reports

(*)

07LA, report of 20-knot headwind gain at 600 feet at 03:53 UTC 29 August 2005600 feet at 03:53 UTC, 29 August 2005

Gentle windshear ramps at departure Gentle windshear ramps at departure ididcorridorcorridor

TDWRTDWRTDWRTDWR

To detect To detect To detect To detect microburst and WS microburst and WS associated with associated with

i i convective stormsconvective storms~12 km NE of HKIA~12 km NE of HKIAR d t 60 R d t 60 Radar antenna ~60 m Radar antenna ~60 m AMSLAMSLRunways approx Runways approx Runways approx. Runways approx. aligned with TDWR aligned with TDWR radialradial

TDWR

Hong Kong International AirportHong Kong International Airport

TDWR is purposeTDWR is purpose--built built Radar to detect Radar to detect microburst and windshear microburst and windshear

Chek Lap Kok AirportChek Lap Kok Airport associated with associated with convective stormsconvective stormsRaytheon Raytheon –– Hardware Hardware SupplierSupplier

Chek Lap Kok AirportChek Lap Kok Airport

unobstructed view of airportunobstructed view of airportSupplierSupplierLincoln Lab Lincoln Lab –– AlgorithmsAlgorithmsSame model as US FAA’s Same model as US FAA’s 45 TDWRs operational at 45 TDWRs operational at

TDWRTDWR60m above PD;60m above PD;

reduce clutters from seareduce clutters from seaeasily accessibleeasily accessible

ppUS airportsUS airports

reduce clutters from sea reduce clutters from sea and landand land

easily accessibleeasily accessibleby transportby transport

583583

12 km from airport;12 km from airport;roughly align with runway directionroughly align with runway direction

300300

465465

751751

869869

766766

721721

747747

934934

869869

Beams align well with runwayBeams align well with runway

Radial winds roughly measuring headwindsRadial winds roughly measuring headwindsRadial winds roughly measuring headwindsRadial winds roughly measuring headwinds

88ºº 1010ºº

1414ºº 1818ºº

Special features of TDWRSpecial features of TDWRSpecial features of TDWRSpecial features of TDWRNarrow antenna beamwidthNarrow antenna beamwidthNarrow antenna beamwidthNarrow antenna beamwidth

0.5 deg.0.5 deg.Good sidelobe performanceGood sidelobe performanceGood sidelobe performanceGood sidelobe performanceExcellent target differentiationExcellent target differentiation

Highly stable KlystronHighly stable Klystron--based based Highly stable KlystronHighly stable Klystron--based based transmittertransmitter

Able to detect reflectivity below Able to detect reflectivity below --20 dBZ 20 dBZ Able to detect reflectivity below Able to detect reflectivity below 20 dBZ 20 dBZ (can detect some returns even in rainless (can detect some returns even in rainless conditions)conditions)

Special features of TDWR Special features of TDWR pp(Cont.)(Cont.)

Advanced velocity dealiasing algorithmAdvanced velocity dealiasing algorithmEmploys dual PRFs in the lowest scan to Employs dual PRFs in the lowest scan to p yp yuniquely determine unambiguous velocity uniquely determine unambiguous velocity datadataVelocity dealiasing at higher elevations Velocity dealiasing at higher elevations based on assumption of vertical continuity based on assumption of vertical continuity f l itf l itof velocityof velocity

Unambiguous velocity range Unambiguous velocity range 80 m/s to 80 m/s80 m/s to 80 m/s--80 m/s to 80 m/s80 m/s to 80 m/s

Special features of TDWR Special features of TDWR pp(Cont.)(Cont.)

Range dealiasing algorithmRange dealiasing algorithmLow PRF scan at lowest elevation to provide Low PRF scan at lowest elevation to provide ppinitial view of radar echo returns from the initial view of radar echo returns from the longest rangelongest rangeThis information is then used to predict This information is then used to predict the expected degree of obscuration in the expected degree of obscuration in hi h l l s shi h l l s shigher level scanshigher level scans

Special features of TDWR Special features of TDWR pp(Cont.)(Cont.)

Powerful clutter removal mechanismPowerful clutter removal mechanismA 55 dBZ filter to low velocity data (A 55 dBZ filter to low velocity data (--2 to 2 to y (y (2 m/s) to remove stationary clutter2 m/s) to remove stationary clutterA pointA point--target removal algorithm to remove target removal algorithm to remove moving objects (aircraft, birds and ships) moving objects (aircraft, birds and ships) UserUser--defined 30 dBZ clutter polygons to defined 30 dBZ clutter polygons to remove areas contaminated with moving remove areas contaminated with moving clutters (traffic, trees)clutters (traffic, trees)

Scanning strategyScanning strategyScanning strategyScanning strategy

Change of modeChange of mode- Specifically, only one of the following within the Hazardous Scan Sector is needed tothe Hazardous Scan Sector is needed to switch the TDWR from Monitor to Hazardous Weather Mode:Weather Mode:

• a region of 30 dBz (level 2 precipitation)• a gust front detection ora gust front detection, or • a wind-shear or microburst detection.

- The TDWR switches from HazardousThe TDWR switches from Hazardous Weather to Monitor Mode when the above Hazardous Weather Mode constraints areHazardous Weather Mode constraints are absent for half an hour.

Winds Blowing Across Terrain Winds Blowing Across Terrain (T i(T i i d d)i d d)(Terrain(Terrain--induced)induced)

Another example:Another example:Another example:Another example:

Severe tropical stormSevere tropical stormHagupit(11 September 2002)

MicroburstMicroburstMost violent form of downdraft from Most violent form of downdraft from thunderstormsthunderstormsthunderstormsthunderstormsTypical horizontal extent: a few kmTypical horizontal extent: a few kmHeadwind increase Headwind increase > Downdraft > Downdraft > Tailwind > Tailwind Headwind increase Headwind increase --> Downdraft > Downdraft --> Tailwind > Tailwind increaseincrease

“Symmetric” microburst

Some notes on microburstSome notes on microburstSome notes on microburstSome notes on microburstMicroburst can be Microburst can be asymmetric. Downdraft asymmetric. Downdraft yycolumn can hit the column can hit the ground at an angle.ground at an angle.Strong terrainStrong terrain--induced induced ggwindshear (loss of 30 windshear (loss of 30 knots or greater), knots or greater), coupled with rain, may coupled with rain, may ca se TDWR to iss e ca se TDWR to iss e cause TDWR to issue cause TDWR to issue microburst alerts.microburst alerts.Don’t expect the typical Don’t expect the typical sequence of events (gain sequence of events (gain sequence of events (gain sequence of events (gain preceding downdraft preceding downdraft followed by loss)!followed by loss)!

Bandaid shapes – microbursts detected by TDWRTDWR microburst algorithm searches for significant TDWR microburst algorithm searches for significant TDWR microburst algorithm searches for significant TDWR microburst algorithm searches for significant divergence radial sheardivergence radial shearWind loss (Velocity difference) across divergence region Wind loss (Velocity difference) across divergence region i mp t d if i mp t d if is computed, if is computed, if

loss >= 15 kts AND reflectivity >= 30 dBZloss >= 15 kts AND reflectivity >= 30 dBZ--> declare as microburst shape> declare as microburst shape

Microburst bandaid shapes showing ‘20 kts loss’

6 d PP l0.6 deg PPI VelocityGSD actually showing 0.6 deg PPI Reflectivity

TDWR Alphanumeric AlertsTDWR Alphanumeric AlertsShear integration of windshear across microburst shape Shear integration of windshear across microburst shape ––g pg pto reduce false alarms (probability only)!to reduce false alarms (probability only)!Alerts rounded to nearest 5 ktsAlerts rounded to nearest 5 kts‘MBA’ is alerted when loss >= 30 kts‘MBA’ is alerted when loss >= 30 kts‘WSA’ is alerted when loss < 30 kts‘WSA’ is alerted when loss < 30 kts

40 kts loss shown on shape

07L 25R

1NM 2NM 3NM

Alerts shown on GSD: 07LD WSA 25K- 2MD

25RA WSA 25K- 2MF

‘D – Departure’

‘F – Final’

LowLow--level jetlevel jetjjNarrow band of strong windsNarrow band of strong winds

ll ff f d ( l dll ff f d ( l dUsually affects aircraft on departure (steeper glide Usually affects aircraft on departure (steeper glide path)path)R l i l i f HKIAR l i l i f HKIARelatively infrequent at HKIARelatively infrequent at HKIA

Microwave radiometerMicrowave radiometerMicrowave radiometerMicrowave radiometer

Observations in a windshear eventObservations in a windshear eventObservations in a windshear eventObservations in a windshear event

WTWS +Forecaster90

100

WTWS70

80

90

GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (5 min)GLYGA (1 min)

60

70

fDet

ectio

n

40

50

Perc

enta

ge o

f

20

30

P

G and R (1 min)G and R (5 min)G or R (1 min)

0

10

G or R (1 min)G or R (5 min)Radiometer

00 10 20 30 40 50 60 70 80 90 100

Percentage of Time on Alert

ShortShort--range LIDARrange LIDARShortShort range LIDARrange LIDAR

+ WS reports

Observations by the existing Observations by the existing LIDARLIDARLIDARLIDAR

SummarySummarySummarySummary

SurfaceSurface--based anemometersbased anemometersSurfaceSurface based anemometersbased anemometersLIDARLIDARTDWRTDWRTDWRTDWRWind profilerWind profilerOther new instruments, e.g. microwave Other new instruments, e.g. microwave radiometer and shortradiometer and short--range LIDARrange LIDARgg

User educationUser educationUser educationUser education

Windshear bookletWindshear bookletWindshear bookletWindshear bookletWindshear postersWindshear postersB i fi h i li B i fi h i li Briefing at the airlines Briefing at the airlines

Major topics of discussionMajor topics of discussionMajor topics of discussionMajor topics of discussion

Nature of windshear at Hong Kong Nature of windshear at Hong Kong Nature of windshear at Hong Kong Nature of windshear at Hong Kong International AirportInternational AirportDetection methodsDetection methodsDetection methodsDetection methodsDiscrepancy between detected and Discrepancy between detected and

i d i d hi d i d hexperienced windshearexperienced windshearDifferent practices of windshear reporting by Different practices of windshear reporting by pilotspilots

Trend arrowTrend arrowTrend arrowTrend arrow

Trend arrowTrend arrowTrend arrowTrend arrow

User group meetingsUser group meetingsUser group meetingsUser group meetings

Windshear and Turbulence Warning System Windshear and Turbulence Warning System Windshear and Turbulence Warning System Windshear and Turbulence Warning System Working Group (WTWS WG)Working Group (WTWS WG)Low Level Wind Study Working Group Low Level Wind Study Working Group Low Level Wind Study Working Group Low Level Wind Study Working Group (LLWS WG)(LLWS WG)

ParticipantsParticipantsParticipantsParticipants

Met serviceMet serviceMet. serviceMet. serviceAir traffic controlAir traffic controlAi d dAi d dAirport standardAirport standardFlight standardFlight standardAirline representativeAirline representativePilot representativePilot representativePilot representativePilot representative

WTWS WGWTWS WGWTWS WGWTWS WG

Review of Review of windshearwindshear service (objective vs service (objective vs Review of Review of windshearwindshear service (objective vs. service (objective vs. subjective)subjective)New instrument developmentsNew instrument developmentsNew instrument developmentsNew instrument developmentsIssues of instrument maintenanceIssues of instrument maintenanceNew procedural developmentsNew procedural developmentsWindshearWindshear phraseologyphraseologyp gyp gy

LLWS WGLLWS WGLLWS WGLLWS WG

Wind study of effect of buildings/structures Wind study of effect of buildings/structures Wind study of effect of buildings/structures Wind study of effect of buildings/structures on the airflowon the airflowWindshear warning criteriaWindshear warning criteriaWindshear warning criteriaWindshear warning criteriaDeployment of instruments for detecting low Deployment of instruments for detecting low l l i d ffl l i d fflevel wind effectslevel wind effects

Publication Publication ……Publication Publication ……

HKO homepage: www.weather.gov.hkp g gHKO email address: outreach@hko.gov.hkIFALPA homepage: www.ifalpa.orgGAPAN homepage: www.gapan.org

Automatic AlertsAutomatic AlertsAutomatic AlertsAutomatic Alerts

Issued by WTWS (Windshear and Turbulence Warning Issued by WTWS (Windshear and Turbulence Warning y ( gy ( gSystem) covering 3 NM from runway thresholdsSystem) covering 3 NM from runway thresholdsNominal update rate 1 min.Nominal update rate 1 min.

A t ti WS Al tA t ti WS Al tAutomatic WS AlertsAutomatic WS Alerts

Mi b Al (MBA)Mi b Al (MBA)Microburst Alert (MBA)Microburst Alert (MBA)Generated by TDWR (Terminal Doppler Generated by TDWR (Terminal Doppler W h R d ) d i d i WTWS W h R d ) d i d i WTWS Weather Radar) and integrated into WTWS Weather Radar) and integrated into WTWS RunwayRunway--oriented wind speed loss >= 30 kt and oriented wind speed loss >= 30 kt and

i d b i it tii d b i it tiaccompanied by precipitationaccompanied by precipitation

Windshear Alert (WSA)Windshear Alert (WSA)RunwayRunway--oriented wind speed loss or gain >= 15 oriented wind speed loss or gain >= 15 ktkt

A t ti TURB Al tA t ti TURB Al tAutomatic TURB AlertsAutomatic TURB Alerts

M d i i iM d i i iModerate or severe in intensityModerate or severe in intensityWith reference to heavy category aircraftWith reference to heavy category aircraft

W i P id d ATISW i P id d ATISWarnings Provided on ATISWarnings Provided on ATIS

I d b A i i M FI d b A i i M FIssued by Aviation Met. ForecastersIssued by Aviation Met. ForecastersBased on pilot reports, forecasting rules Based on pilot reports, forecasting rules developed from case studies, past 30developed from case studies, past 30--min min TDWR (windshear and microburst), past 30TDWR (windshear and microburst), past 30--min WTWS (turbulence), realmin WTWS (turbulence), real--time time conditions as revealed by TDWR, LIDAR, conditions as revealed by TDWR, LIDAR, etc.etc.

Alert PhraseologyAlert Phraseology

Very common to have multiple occurrences of Very common to have multiple occurrences of

Alert PhraseologyAlert Phraseology

Very common to have multiple occurrences of Very common to have multiple occurrences of windshear on same corridor in HKwindshear on same corridor in HKWTWS consolidates multiple events into ONE WTWS consolidates multiple events into ONE WTWS consolidates multiple events into ONE WTWS consolidates multiple events into ONE integrated alertintegrated alert

TDWR alerts higher priority than WTWS alertsTDWR alerts higher priority than WTWS alertsg p yg p ySinking shear (loss events) higher priority than lifting Sinking shear (loss events) higher priority than lifting shear (gain events)shear (gain events)

i i i i l i i i i lMax intensity given in alertsMax intensity given in alerts

Alert PhraseologyAlert PhraseologyE.g. APP to RWY 25LE.g. APP to RWY 25L

Alert PhraseologyAlert Phraseology

-30 +15RWY 25L

‘Caution ‘Caution Microburst Microburst Minus 30 knots on Minus 30 knots on final approachfinal approach’ ’ (instead of specific location as in US)(instead of specific location as in US)( p )( p )Note:Note:

The max intensity (The max intensity (--30 kt) can occur anywhere along 30 kt) can occur anywhere along h dh dthe corridorthe corridor

First encounter (+15 kt @ 3NM) not the worst First encounter (+15 kt @ 3NM) not the worst encounter (encounter (--30 kt @ 1NM)30 kt @ 1NM)encounter (encounter ( 30 kt @ 1NM)30 kt @ 1NM)

Alert PhraseologyAlert PhraseologyE.g. APP to RWY 25LE.g. APP to RWY 25L

Alert PhraseologyAlert Phraseology

-15 +20RWY 25L

‘Caution Windshear‘Caution Windshear MinusMinus 15 knots on 15 knots on final approachfinal approach’’Note:Note:Note:Note:

Some may report Some may report --15 kt, while others +20 kt (especially 15 kt, while others +20 kt (especially those who conducted a missed APP on encounter of the those who conducted a missed APP on encounter of the l f h )l f h )lifting shear)lifting shear)