2/10/03F.Marks1 Development of a Tropical Cyclone Rain Forecasting Tool Frank D. Marks NOAA/AOML, Hurricane Research Division, Miami, FL QPE Techniques in TCs TRMM and gauges QPF Techniques in TCs R-CLIPER 2002 Storms Where do we go from here? Support from NOAA JHT and NASA TRMM and CAMEX

2/10/03F.Marks2 DATA: TMI R estimates for 245 storms (December ), globally, yielding 2121 events, from TD to CAT5 (Lonfat et al 2003) TMI events by Intensity Storm IntensityEvents% TD/TS Category Category Total ,000 hourly gauge estimates in 46 US landfalling hurricanes ( ) (DeMaria 2003) QPE techniques in TCs:

2/10/03F.Marks3 QPE techniques (continued): TMI and gauge R, 10 km annuli, PDF 1 dBR from mm h -1. Stratify by intensity and motion.

2/10/03F.Marks4 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:

2/10/03F.Marks5 R- CLIPER Radial distribution of R for gauge and TMI climatology consistent. TMI peak R increases with intensity: 3 mm h -1 TD/TS; 7.2 mm h -1 CAT 1-2; 12.5 mm h -1 CAT 3-5. TMI peak R radius decreases with storm intensity.

2/10/03F.Marks6 color contours denote R total (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”

2/10/03F.Marks7 Andrew 92 Danny 97 Floyd 99 Allison 01 R-CLIPER underestimates area of R total by factor of 2 using CDF. R-CLIPER Cases 20% 50% 90% PMM R-CLIPER/Gauge R total 50% 90% % of gauges % of area

2/10/03F.Marks8 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. Atlantic14255 East Pacific15281 Central Pacific348 Total32584

2/10/03F.Marks9 QPF in Landfalling TCs Gauge TRMM

2/10/03F.Marks10 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 R max along track, with a probability of heavy rain right or left of track. RCLIPER R max increases when storm slows or turns. Model shows symmetry and asymmetry. Comparison with Models Rogers et al 2002

2/10/03F.Marks12 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.

2/10/03F.Marks13 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 R and duration. 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 :

2/10/03F.Marks14 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 and globally Develop methodology to validate NWP forecasts. GOAL: Understand and describe TC rain using climatology. Improve TC rain QPF.

2/10/03F.Marks15 QPE techniques in TCs: TMI, radar and gauge compared to R probability distributions by Miller (1958) and Frank (1977).

2/10/03F.Marks16 QPE Techniques in TCs Scale dependence: 10-s PMS sample area ~1 m -2 1-h gauge sample area ~1-16 km 2 (wind speed dependent) 1-h radar sample area 16 km 2 TMI sample are 25 km 2 PDF narrower and skewed toward lower R with increasing scale

2/10/03F.Marks17 QPF techniques in TCs: Simplest TC QPF predicts R max : R max =RDV s -1 Kraft’s "rule of thumb”: R max =130.8 V s -1 R max =cm, V s =m s -1, R=0.49 cm h -1 & D=10 3 km. Tropical Rainfall Potential (TRaP) uses satellite R- estimates No adjustments for intensity, topography, etc.

2/10/03F.Marks18 R-CLIPER Cases 7.7” 4.2” 13.5” 31” 10” 6.7”