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Quantitative Precipitation Forecasting in Hurricanes ...

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Development of a Tropical Cyclone Rain Forecasting ToolFrank D. MarksNOAA/AOML, Hurricane Research Division, Miami, FL 33149
QPE Techniques in TCsTRMM and gaugesQPF Techniques in TCsR-CLIPER2002 StormsWhere do we go from here?
Support from NOAA JHT and NASA TRMM and CAMEX
DATA:TMI R estimates for245storms (December 1997-2000), globally, yielding2121events, from TD to CAT5 (Lonfat et al 2003).1998-2000 TMI events by IntensityStorm Intensity Events %TD/TS 1361 64Category 1-2 548 26Category 3-5 212 10Total 2121560,000 hourly gauge estimates in 46 US landfalling hurricanes (1948-2000) (DeMaria 2003)
QPE techniques in TCs:
QPE techniques (continued):TMI and gauge R, 10 km annuli, PDF 1 dBR from 0.3-300 mm h-1. Stratify by intensity and motion.
Develop R-CLIPER from gauge and TMI climatology for operational and model QPF comparisons.Project R-climatology along NHC forecast track.
QPF techniques in TCs:
R-CLIPER
Radial distribution of R for gauge and TMI climatology consistent.TMI peak R increases with intensity: 3 mm h-1TD/TS; 7.2 mm h-1CAT 1-2; 12.5 mm h-1CAT 3-5.TMI peak R radius decreases with storm intensity.
color contours denote Rtotal(inches, peak at landfall listed)
Position and intensity from best track (6 h)
R-CLIPER Cases
7.7”
4.8”
15.9”
4.1”
8.6”
Andrew 92
Danny 97
Floyd 99
Allison 01
R-CLIPER underestimates area of Rtotalby factor of 2 using CDF.
R-CLIPER Cases
20%
50%
90%
PMM R-CLIPER/Gauge Rtotal
50%
90%

% of gauges
% of area
QPF in Landfalling TCs
For 2002 season ran 584 forecasts in 32 storms in the ATL, EPAC, and CPAC for both the gauge and TRMM R-CLIPER.
QPF in Landfalling TCs
Gauge
TRMM
Where do we go from here?
R-CLIPER ran operationally in 2002 at NHC.Provides benchmark for evaluation of other QPF techniques.Develop data products for hurricane specialists.Compare R-CLIPER forecasts to models and 6-h average rainfall amounts on HPC 1°X1° grid.Work with HPC to provide track guidance after landfall.
RCLIPER
RCLIPER Rmaxalong track, with a probability of heavy rain right or left of track.RCLIPER Rmaxincreases when storm slows or turns.Model shows symmetry and asymmetry.
Comparison with Models
Rogers et al 2002
QPF in Landfalling TCs
ISSUES:Are we providing our users what they need? Different users have different needs.How do we develop an evaluation/validation system for high-resolution QPF product?How will it be used operationally (probabilistic)?NEEDS:New products developed for forecasters and hydrologists.New display products to convey uncertainty to forecaster and others.
TCs pose significant QPF problem. i.e., Hurricanes Mitch (1998), Floyd (1999), and TS Allison (2001).Last 30 years majority of TC deaths caused by flooding (Rappaport 2000).Flooding is a function of Randduration.Enhanced rainfall from orography and fronts.QPF limited by complexity of precipitation processes and lack of microphysics data.Improved TC QPF challenge of USWRP.
Why TC QPF is important:
QPE techniques in TCs:
STRENGTHS:TMI and PR.Strength global coverage with single instrument.Hourly gauges and WSR-88D.Strength temporal resolution over long time.NEED:Develop R climatology in TCs regionally andgloballyDevelop methodology to validate NWP forecasts.GOAL:Understand and describe TC rain using climatology.Improve TC rain QPF.
QPE techniques in TCs:
TMI, radar and gauge compared to R probability distributions by Miller (1958) and Frank (1977).

QPE Techniques in TCs
Scale dependence:10-s PMS sample area ~1 m-21-h gauge sample area ~1-16 km2(wind speed dependent)1-h radar sample area 16 km2TMI sample are 25 km2PDF narrower and skewed toward lower R with increasing scale
QPFtechniquesin TCs:
Simplest TC QPF predicts Rmax:Rmax=RDVs-1Kraft’s "rule of thumb”:Rmax=130.8 Vs-1Rmax=cm, Vs=m s-1, R=0.49 cm h-1& D=103km.Tropical Rainfall Potential (TRaP) uses satellite R-estimatesNo adjustments for intensity, topography, etc.
R-CLIPER Cases
7.7”
4.2”
13.5”
31”
10”
6.7”

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Quantitative Precipitation Forecasting in Hurricanes ...