typhoon forecasting and qpf technique development in cwb kuo-chen lu central weather bureau
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Typhoon Forecasting and QPF Technique Development in
CWB
Kuo-Chen LuCentral Weather Bureau
2
QPF in CWBTyphoon Nora (7315)
Strong gale and 50 ~ 100 mm in South Taiwan are expected
OutlineDefinition
QPF is the expected amount of melted precipitation accumulated over a specified time period over a specified area
DescriptionForecast Products and the performance
Advance approach by ensemble QPFEnsemble Typhoon QPF
Pattern Recognition by Convection Pattern
Conclusion
Grid QPF since 2006
Verification system operates in real time
Issued twice a day on 00z and 12z2.5 km resolution for next 24 hours.
0-12h 12-24h
Verification on 24-h QPF
T.S. improve gradually, Bias reduce significantly on 50 mm
Threat Score Bias
2006
2007
2008
2009
2010
2011
2012
2013
2014
0
0.1
0.2
0.3
0.4
0.5
0.6
2006200720082009201020112012201320140
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5mm
D1: 45-km 222 X 128
D2: 15-km 184 X 196
D3: 5-km 151 X 181
5km
Terrain Peak: 3,271m/3,952m
4 runs/day, 6-hourly updated
(Lee, Hong etc, MIC, CWB)
WRF Prediction System
OBS
Examples of the member QPFs with similar typhoon locationIf the designed is good enough, the answer of the forecast is just inside the stamps
7
80 Ensemble members a day for QPF
Question:Can we provide better QPF by applying the same process as typhoon track forecasting ?
Multi-model consensus:Simple consensus, Selected consensus,
Weighted consensus,,,,,,
8
Advance strategy for Ensemble product
Selected consensus by Typhoon location for typhoon
QPF by convection pattern for
Nowcasting
9
• Select the model QPF cases from ensemble members according to the prior estimate of the typhoon position, then produce the composite rain map and probability products based on the selected samples.
• Maximally use the ensemble QPF based on the optimal track forecast10
Member of QPF map selected by
Typhoon location surrounding the official typhoon forecast track
(Ensemble Typhoon Quantitative Precipitation Forecast, ETQPF)
Subjective Forecast: ETQPF on different Track
TY Fung-wong (2014)TY Matmo (2014)
Obs
ETQPF
Obs
ETQPF
ETQPF performance for the 2014 typhoons
Max:956 mm
Max:995 mmIf track is trustable.ETQPF is also trustable
Hong (2015)
Brief summary of ETQPF
Strength If track forecast is OK, the model QPF is worth to be a guidance Is able to represent the interaction between the environment and typhoon circulationDepend on case, has the potential to capture the mesoscale precipitation process
WeaknessUncertainty to the track forecast
Official track forecast still better than the model forecastDifficult to configure a model that performs THE BEST all the time
Uncertainty from the initial condition and the model physical processLimitation to the model resolution…
How to maximally take advantage of the strength and well handle the uncertainty due to the weakness from the model QPF?
Hong et. al. 2015, Weather and forecasting
Piecewise recognition for selecting the similarity of convection pattern from EPS
Pattern Recognition for convection
(Chen, Huang, Lu etc, MFC, 2014)
Radar Mosaic CV Model simulate CV
Big data/Grand Ensemble Set 3-hourly forecast in ±6hr-Window (5 frames) 22 WEPS members, 4 Lag Runs 22x4x5 = 440 samples
Pattern Recognition: Mining useful information Piecewise, weighted, normalized moment invariant Correlation ?
‒6 h +6 h
Radar CV05/15 1200Z
0-6 -3 63
05/15 00Z
4 lag runs
05/14 18Z
05/14 12Z
05/14 06Z
12 h126 9 1815
18 21 24 3027
24 27 30 3633
12 15 18 2421
Frmo ensemble member N (N=1, 2, …, 22)forecast at target time (say 0 hr)
Sampling, Recognizing and Ranking
TOP 1 ~ 20 by ranking the similarity of Radar CV
Similar Convection Pattern in EPS Case of Meiyu Front
3 hours QPF according to Rank 1 ~ 20
QPF from Similar Convection Pattern in EPS Case of Meiyu Front
3 hours QPF according to Rank 1 ~ 20
QPF from Similar Convection Pattern in EPS Case of Meiyu Front
ETS
3-hourly QPF Verification for consensus During a Mei-Yu Front period in May 2015
Selected consensus (top 20%)
simple consensus0
1.0
Th
reat
Sco
reFcst. hours
Selected Consensus
3 6
Simple Consensus
from 19th12UTC to 25th12UTC May 2015Threshold : above 10 mm/3-h
3 6 9 12
3 6 9 12
20
ConclusionMulti-stage Quantify Precipitation Forecast
Weekly (Qualitative)GFS, Synaptic Analysis, statistics,
analogy, conceptual model1-3 daily QPF (Quantitative)
Regional (Ensemble) Forecast System, Statistics, advanced Ensemble Forecast0-6 hr (or 0-12 hr)
QPFLAPS/STMAS, ARPS, VDRAS,
Cloud model0-1 hr QPFRadar extrap., ANC,
SCAN0 hr
NowcastingRadar, gagues,
lighting
Storm scale data assimilation
Traditional 3d/4d data assimilatoin
Radar Extrapolation
Pattern Recognition
21
THANK YOU FOR YOUR ATTENTION
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