Aviation Reports, Forecasts and Warnings I

Aviation Reports, Forecasts and Warnings I

SPECI criteria Element Crosswind Supplementary information Special report in the SPECI code form crosswind based on the 10-minute mean wind changes from less than 20 knots to 20 knots or more and vice versa (operational limits of aircrafts following Annex 3) Vicinity: approach and climb out area taken to be 13 km

Speci Alert

Artificial gusts due to aircraft operations Jet engine blasts More than just hot air It can cause damage and upsets during ground operations if encountered at close range Almost every commercial jet operating manual has a diagram showing the aircraft's jet blast "damage profile" as measured from the tail.

Effect of jet blast on surface wind observations

Artificial gusts due to aircraft operations (cont) Wake vortices All aircrafts produce wake vortices when in flight The strongest vortices are produced by heavy aircraft, flying slowly, in a clean configuration During takeoff and landing, the vortices sink toward the ground and move laterally away from the runway when the wind is calm. A 3 to 5 knot crosswind will tend to keep the upwind vortex in the runway area and may cause the downwind vortex to drift toward another runway

Effect of wake vortex on surface wind observations 1

Effect of wake vortex on surface wind observations 2

How to discriminate artificial gusts from natural gusts?

A method Frequency distribution of normalized wind speed u n = (u( max U) /σ / u on a day with no aircraft operations confirms to a normal distribution This holds for all types of weather, including thunderstorms Tests indicated that gusts are likely to be artificial with u n > 5

Comparing u and u n

Program developed by HKO Extract and prepare 3-second 3 and 10-minute mean wind speeds from AMOS. Calculate normalized 3- second mean wind speed If within the 10-minute observation reporting period: a point with normalized 3-second mean wind speed greater than 5, the corresponding difference between the 3-second 3 and 10- minute mean winds is greater than 5 m/s, the corresponding 10-minute mean wind speed is greater than 5.0 m/s and the standard deviation is greater than 0.5 The point will be marked suspicious and will be shown

Limitation Unable to detect False alarm

Haze on 20 Nov 2002 (visibility down to 4200m at 1340H) Photo taken at 1340H

spreading of haze

Fog edging towards HKIA

Quick Reference of Reflectivity and Rainfall Rate Reflectivity (dbz) Rainfall Rate (mm/h) 30 2.7 35 5.6 40 11.5 45 23.7 50 48.6 55 99.9 60 205.0

Correlation between Reflectivity and Visibility

Lightning data over satellite: http://flash.ess.washington.edu/l_plot_weather_map.jpg

Short-range range Warning of Intense Rainstorms in Localized Systems (SWIRLS) Tracking Radar Echoes by Correlation (TREC)

TREC winds analysis

TREC winds analysis of Typhoon Victor (9712) over Hong Kong at 19:00HKT on 2 August 1997

Calibration of radar reflectivity using rainguage measurements

One hour rainfall forecast by SWIRLS

Group Tracking of Echoes (GTREC)

Rainstorm Analysis and Prediction Integrated Data- processing System (RAPDIS) Merging precipitation prediction from SWIRLS and the 5-km NHM

Lightning cells grouping

Lightning cells forecast 30 mins forecast position

Hook/finger shape echo pattern Identification of possible hail Hook/finger shape echo WER or Vault

Overhang echoes Overhang echoes Weak Echo Region Embryo curtain Vertical cross-section radar image

Hail Warning product

Alert of mesocyclone Azimuthal shear >= 12 m/s; Reflectivity >= 15 dbz; ; and Area of echo satisfying the above criteria >= 0.3 km2. SHEAR_TDR06 applied to 0.6 PPI data of TDWR; SHEAR_TDR60 applied to 6 6 PPI data of TDWR; SHEAR_TMS00 applied to 0 0 PPI data of TMS (Tai Mo Shan radar); and SHEAR_TCR00 applied to 0 0 PPI data of TCR (Tate s Cairn radar).

Possible mesocyclone identified on radar

Types of sea breezes at CLK: Type I local sea breeze circulation resulting from winds converging from all directions of the HKIA when the CLK island is heated up. This results in opposite wind directions at the two ends of the runway; Type II winds converging to Lantau Island resulting in north to northwesterly winds on the runways; and Type III larger scale circulation with west to southwesterly winds flowing from CLK to the New Territories.

Three types of sea breezes at CLK:

Estimating seabreeze onset time at CLK The equation is a extension of the simple circulation model described in the book of Holton. Many of the parameters in the equation have pre-assigned values, except the following which is read in real-time: v0 is the background wind at 05:30am, represented by the average of the u-component u at stations at WGL, TMT, NLS, TMS and R2C T0 is the initial land-sea tempearture difference(at 0530am), which uses air temperature at HKA and sea temperature reading from North Point at 2:00pm the day d before P0 is the pressure at the circulation base, using pressure at HKA P1 is the pressure at the circulation top, using pressure at NLS

Limitation of equation: only applies to seabreeze days at CLK, its estimation is irrelevant when seabreeze is not occuring. may not have a solution when background easterly wind is too strong for seabreeze to reach the shore, when temperature on land is too low(like after a strong cold surge), when the initial prevailing wind is already westerlies

Example of sea breeze onset time calculation: Seabreeze onset time estimated for 20050722(YYYYMMDD). Background wind is already westerly, seabreeze onset time can't be determined The calculation of seabreeze onset time is based on the following raw input at 05:30 HKT: Wind Stn: WGL, Direction: 190 degree, Force: 3.4 m/s Stn: R2C, Direction: 263 degree, Force: 2.0 m/s Stn: TMS, Direction: 220 degree, Force: 7.3 m/s Stn: TMT, Direction: 133 degree, Force: 3.3 m/s Stn: NLS, Direction: 264 degree, Force: 6.6 m/s Pressure Stn: HKA 1001.4 hpa Stn: NLS 3277 hpa Temperature HK Airport: 28.9 degrees Sea temperature at North Point: 28.0 degrees (Note: reading taken n at 14:00H yesterday)

Sea breeze index Bernoulli s s equation ρ 1 U 2 ρ 2 U 2 P 1 + -------- = P 2 + ------- 2 2 1 gh -------------- ( 2gh + U 2 ) = 2 ----------- T overland T overwater T overland - T overwater U 2 = 2gh(---------------------------- ----------------------------) SBI = ±(U 2 /ΔT) T overwater

Expected parameters Land-sea temperature difference Wind strength Cloudiness Stability

Scatter plot of U 2 with Land-sea temperature difference

Method Cloudiness 6 >= 6 oktas and meanrh (925 850 hpa) ) >=80% No sea breeze SBI > 7 or SBI < 0 where SBI = U 2 6 (CLK Max Temp SST 6 )

Strong wind probability due to tropical cyclone

Percentage probability for typhoon

TIPS create overlay

Cut point to show the time of entering different overlay

Probability Forecast of Strong / Gale Winds /Croswind at CLK Airport HKO s Shipping Warning track Isopleths of probability of occurrence of strong/gale force winds ( kidneys( kidneys ) ) in CLK Uncertainties derived from spread of model forecast TC positions with respect to model ensemble forecast or position errors collected from past statistics

Basic Principles HKO s s Shipping Warning track Isopleths of probability of occurrence of strong/gale force winds (a.k.a. kidneys )) in CLK Uncertainties derived from spread of model forecast TC positions with respect to model ensemble forecast or position errors collected from past statistics

Basic Principles Probabilities can be calculated based on: Statistical scheme - Forecast position errors of shipping warning tracks during 1999-2002 taken as the uncertainties in forecast positions. Model Spread scheme - spread of individual model forecast position from model ensemble taken as the uncertainties in forecast positions.

User Interface

Forecast probability time series

LAPS (Local Analysis and Prediction System) FSL/NOAA univariate analyses (u, v, ω,, T, q, h, S/F, ) + variational dynamic balancing scheme (u, v, ω, h) variational moisture analysis comprehensive cloud analysis diabatic initialization capability for NHM Efficient (~ 5 mins) http://laps.fsl.noaa.gov laps.fsl.noaa.gov/

Implementation of LAPS in HKO LAPS Resolution Forecast period 1, 5, 10 km Hourly (analysis only) Data ingested synops, HK and GD AWS, wind profiler, AMDAR, GMS5, QuikSCAT, Radar data ingested reflectivity and Doppler wind + TREC wind Computer platform IBM SP

Local Analysis and Prediction System Model lga background synops HK/GD AWS Kalman filter QC surface Surface wind, pp, temp, RH, etc WP/RASS wind 3D wind radiosonde temp 3D temp GPS Radar dbz Doppler wind cloud moisture Cloud cover, 3D RH, cloud ω GMS5/GOES9 q l, q i, q s, q r, q h Satellite sounding balance Balanced 3D u,v,ω, φ TREC wind AMDAR/PIREP lapsprep Initial data for WRF MM5 RAMS Model initialization

TC-LAPS wind speed analysis of Typhoon Imbudo (10, 5, 1 km) 10 km 925hPa 5 km 925hPa 18UTC 23/07/2003 1 km surface

TC-LAPS Nowcasting First guess Observations Analysis Nowcast ORSM Observations + LAPS + LE SWIRLS Wind, pressure forecasts ORSM = Operational Regional Spectral Model (JMA) LAPS = Local Analysis and Prediction System (FSL, NOAA) SWIRLS = Short-range Warning of Intense Rainstorm in Localized Systems (HKO) LE = Linear Extrapolation (along any TC track)

Tropical cyclone nowcast product

http://www.ecmwf.int/products/forecasts/d/charts

Thank You, and Any question?