# Presentation: 511541

## Enhanced Multisensor Precipitation Estimator and Nowcaster

**Improving WFO Flash Flood Services**

**Richard Fulton, Feng Ding,  and Shucai Guan**
**Hydrologic Science and Modeling Branch**
**Hydrology Laboratory**
**Office of Hydrologic Development**
**National Weather Service**
**NWS Office of Science and Technology Seminar Series**
**April 5, 2006**

## The Current Multisensor Precipitation Estimator (MPE)

**An automated & interactive algorithm that estimates**** one-hour rainfall**** ****ending at the top of the hour on a ~4-km HRAP grid**** using WSR-88D Precip. Processing System’s (PPS) Digital Precipitation Array (DPA) products**
**Multisensor****...uses rain gauges and GOES satellite to reduce existing biases in WSR-88D rainfall estimates and produces a suite of radar-gauge-satellite rainfall products**
**Produces**** regional mosaics**** from any desired number of WSR-88Ds**

***For more details, see the Lab’s MPE Training Workshop at http://www.nws.noaa.gov/oh/hrl/papers/papers.htm#wsr88d***

## The Current Multisensor Precipitation Estimator (MPE)(cont.)

**Delivered in AWIPS to RFCs in 2002, WFOs in 2004, to replace and improve upon the existing Stages II & III Precipitation Processing algorithms**
**Designed primarily for RFC use**
**Primary input to RFC and WFO hydrologic forecast models (NWS River Fcst System NWSRFS and Site Specific Hydr. Predictor SSHP ... but not Flash Flood Monitoring & Prediction FFMP)**

## MPE Product Suite

**Radar-only rain mosaic**
**Gauge-only rain mosaic**
**Satellite-only rain mosaic (from NESDIS)**
**Mean field bias-adjusted radar rain mosaic using rain gauges**
**Local bias-adjusted radar rain mosaic using rain gauges (two different methods)**
**Multisensor merged radar+gauge mosaic**
**Multisensor merged radar+gauge+satellite mosaic (coming soon)**

## WFO vs. RFC Requirements for Precipitation Products

**Mainstem river  forecasting**
**4 km resolution (HRAP)**
**1 hour updates of hourly rain**
**Multisensor mosaics of rainfall accumulation**
**Routine manual quality control is modus operandi**
**MPE products**

**Flash flood monitoring & warning**
**1 km resolution (1/4 HRAP)**
**5-15 minute updates of sub-hourly and longer rain**
**Multisensor mosaics of rainfall and rain rates**
**Routine manual quality control may not be feasible**
**Enhanced MPE**** (EMPE) products**
**Multisensor Precipitation Nowcaster**** (MPN) products**

**RFC**

**WFO**

## Enhanced MPE (EMPE) is an Experimental  Prototype with New Features for WFOs

**Higher spatial resolution – 1⁄4 HRAP (~1 km)**
***vs. 1 HRAP (~4 km) in current MPE***
**Higher temporal rainfall resolution – 5-15+ minute rainfall duration**
***vs. one hour in current MPE***
**More frequent updates - 5-15 minutes**
***vs. once per hour at top of hour in current MPE***
**Greater flexibility**
***User configurable and “backward compatible”***

***Same multisensor rainfall estimation technology        & products as in MPE, but with ...***

## History & Status of EMPE

**Initial need identified and AHPS EMPE funding proposal written by Fulton in 2002 and funded  FY 2003-2006**
**Project plan developed and distributed for review in 2002**
**Initial EMPE prototype was completed in 2004 by HSMB’s Hydrometeorology Group (F. Ding,         S. Guan, R. Fulton)**
**In 2004, we set up a real-time 24x7 demonstration in HL for 5 WSR-88Ds in mid-Atlantic region ****(Sterling KLWX, Pittsburgh KPBZ, Charleston KRLX, Blacksburg KFCX, Wakefield KAKQ)**
***Web page displays real-time graphical output products***
**EMPE project is in OSIP Stage 2**

## Radar-only 15-min. Rainfall Mosaic

- 1-km grid (EMPE)

- 4-km grid (MPE)

## 1-km Radar-only 15-min. Rainfall Mosaic

**1-km Radar-only 15-min. Rainfall Mosaic**

## 1-km Mean field bias-adjusted Radar          15-min. Rainfall Mosaic

**1-km Mean field bias-adjusted Radar          15-min. Rainfall Mosaic**

## 1-km Multisensor 15-min. Rainfall Mosaic

**1-km Multisensor 15-min. Rainfall Mosaic**

## EMPE Details

**Uses PPS’s ****Digital Storm-total Precipitation (DSP)**** products from multiple radars covering CWA as input**
***Cumulative rainfall updated every volume scan (~ 5 minutes)***
***1 deg x 2 km (higher resolution than 4-km DPA)***
**1 deg x 1 km in future (existing HOSIP project)**
***Digital 256-level equivalent to the Storm Total Precip (STP) 16-level graphical product***
**Differencing of DSPs produces rainfall durations of any arbitrary duration (5 min. to 24+ hours)**
***DPAs cannot provide durations other than whole 1, 2, 3, ... hrs.***
**Demonstrated ability of differenced DSPs to replicate DPA hourly rainfall on HRAP grid**
**Also uses PPS’s ****Digital Hybrid Scan Reflectivity (DHR)**** products to compute instantaneous rain rates**
**Both are remapped and mosaicked onto 1⁄4 HRAP grid (~1 km)**

## Hourly Rainfall from DPAs and Differenced DSPs Matches Well

- Random differences may be due to:
- Slight differences in polar-to-HRAP remapping software between PPS and EMPE
- Temporal interpolation

- One-hour rainfall for mid-Atlantic regional mosaic on 4-km HRAP grid

## EMPE Data Flow

- reflectivity

- PPS

- EMPE

- DHRi and DSPi

- Rain gauges

- Satellite rain
- products

- Lightning data

- Multisensor Rain
- Products

**EMPE Data Flow**

- User params.

## Real-time Web Pagehttp://www.nws.noaa.gov/ohd/hrl/hag/empe_mpn/

**Real-time Web Page****http://www.nws.noaa.gov/ohd/hrl/hag/empe_mpn/**

*Sample EMPE products*

## EMPE User ConfigurationVision is One Configurable EMPE                           that Serves both WFOs and RFCs

**Choose desired spatial grid resolution**
***1⁄4 HRAP****** or ******1 HRAP***
**Choose desired rainfall durations**
***Rainrates,****** ******15 min., 30 min.******, ******1 hr.******, etc. rainfall durations***
**Choose desired run-time delay (~minutes)**
***May depend on each product***
***Gauge-adjusted products may need longer time delays***
**Choose a product generation schedule that satisfies your requirements...**

## EMPE User Configuration (cont.)A Sample Product Generation Schedule

| Time (min.) | EMPE Products |  |  |  |  |
| --- | --- | --- | --- | --- | --- |
|  | Rain Rate (mm/hr) | RMOSAIC 15 min (mm) | BMOSAIC 30 min (mm) | BMOSAIC 60 min (mm) | MMOSAIC 60 min (mm) |
| H+0 | √ | √ | √ | √ √ | √ |
| H+5 | √ |  |  |  |  |
| H+10 | √ |  |  |  |  |
| H+15 | √ | √ |  |  |  |
| ... | √ |  |  |  |  |
| H+30 | √ | √ | √ |  |  |
| ... | √ |  |  |  |  |
| H+45 | √ | √ |  |  |  |
| ... | √ |  |  |  |  |
| H+55 | √ |  |  |  |  |

- Etc.

**RMOSAIC: Radar Mosaic      BMOSAIC: Bias-adjusted Radar      MMOSAIC:  Multisensor Mosaic**

## EMPE Considerations

**Increased CPU, memory, disk space, and communication bandwidth requirements**
**Digital Storm-total Precipitation (DSP) product issues**
***Wide area distribution is necessary from multiple non-associated radars for mosaicking (DHR also)***
**Revising an existing WSR-88D Request for Change (RC)**
***Don’t apply G-R bias to DSP***
**PPS code needs to be revised; RC was submitted in Feb.**
**Rain gauge issues**
***Rain gauge data is a double-edged sword that requires QC before use***
***WFOs often don’t have resources to do real-time manual gauge QC as at RFCs***
***Automated quality control methods are critical***

## EMPE will be Integrated within NWS Hydrologic Operations

**On-going science infusion in PPS will be reflected in downstream EMPE products ****(e.g., Range Correction Algorithm RCA, rainrate-dependent bias adjustment, dual polarization)**** **
**Science infusion in MPE is on-going ****(e.g., probabilistic QPE, satellite QPE)**
**Provides all necessary input to drive the Multisensor Precipitation Nowcaster**
**Enables/enhances high resolution distributed hydrologic forecast modeling and other flash flood tools ****(distributed hydrologic forecast models, FFMP, flood inundation mapping)**

## Types of Radar QPE Adjustments

**Adjustments using radar data**
***Range-related biases***
**Experimental Range Correction Algorithm (RCA)**
**Beam broadening**
***Rain rate-dependent biases***
**see Probabilistic QPE final report on our web page**
**Adjustments using rain gauges**
***Radar-wide mean field bias (MPE’s Bmosaic)***
***Local bias (MPE’s Lmosaic, P3)***
***Multisensor merging (MPE’s Mmosaic)***
**Adjustments using satellite QPE**
***Multisensor merging (radar+gauge+satellite; under development for MPE)***

## Proposed End-to-End Sequence of                                                Bias Correction Procedures in EMPE/MPN

**“****DSP”**
- -single radar
- -polar grid
- -no adjustments

- PPS

**Range-corrected**
** ****Radar Total Rain **
**“****DSPR”**
- -apply RCA
- corrections scan-to-
- scan in PPS if desired

**Range-corrected**
** ****Inc. Rain Mosaic **
**“****RmosaicR”**
- -mosaic multi-radars
- on 1/4th HRAP grid

- PPS

- EMPE

- EMPE

**Radar Rainrates**
**“****DHR”**
- -single radar
- -polar grid
- -no adjustments

**Range-corrected**
** ****Rainrates**
**“****DHRR”**
- -Apply RCA
- corrections if desired

**Range-corrected**
** ****Rainrate Mosaic **
**“****RRmosaicR”**
-  -mosaic multi-radars
- on 1/4th HRAP grid

- Rain rates

- Rainfall

- ORPG

- AWIPS

- EMPE

**Range-corrected**
**Radar Increm. Rain **
**“****RainR_d”**
- -compute incremental
- rain for any duration d
- by differencing

**Range Adjustment **
**Factor Array**
**“****AFA”**

- RCA/CSSA

- PPS

- EMPE

## Proposed End-to-End Sequence of Bias                                       Correction Procedures in EMPE/MPN (cont.)

**Rainrate Adjusted & **
**MFB/Rng Adjusted**
** ****Increm. Rain Mosaic **
**“****BmosaicRR_d”**
- -Apply rainrate bias
- corrections for duration d

- EMPE

**Rainrate Adjusted &**
**MFB/Rng Adjusted**
** ****Rainrate Mosaic **
**“****RRmosaicRBR”**
- -Apply rainrate bias
- corrections

**Local Bias & **
**Range Adjusted **
**Increm. Rain Mosaic **
**“****LmosaicR_d”**
- -Apply local gauge bias
- corrections for duration d

**Mean Field Bias & **
**Range Adjusted **
**Increm. Rain Mosaic **
**“****BmosaicR_d”**
- -Apply MFB gauge bias
- corrections for duration d
- for each radar

- EMPE

**LB/Rng Adjusted**
**Multisensor Rain**
**Mosaic **
**“****MLmosaicR_d”**
- -Apply multisensor merging
- using gauges for duration d

**Rate/MFB/Rng Adj.**
** ****Multisensor Rain**
**Mosaic **
**“****MmosaicRR_d”**
- -Apply multisensor merging
- using gauges for duration d

- EMPE

**Mean Field Bias &**
**Range Adjusted **
**Rainrate Mosaic **
**“****RRmosaicRB”**
- -Apply MFB gauge bias
- corrections for each radar

- MPN

- AWIPS

- FFMP
- HL-RDHM
- NWSRFS
- SSHP

## Looking into the Future to Increase Flash Flood Warning Lead Times

**Rainfall nowcasting****:   Extrapolating current (radar) rainfall observations into the very near future (1-3 hours)**
***Predictability of rain depends on predictability of rainfall system...convective vs. stratiform & seasonal dependence***
**NWS currently has no rainfall nowcasting capability that is integrated quantitatively within hydrologic fcst operations**
***SCAN Categorical QPF algorithm, WSR-88D Storm Cell Identification and Tracking (SCIT) used for visual analysis only***
***UK Met Office has been doing this for a while***
**Even simpler automated nowcast techniques have potential to move us to the next flash flood warning ****performance level**** ****(possibly ~ten minutes vs. current few minutes)**
***We can automate and quantify what goes on in a forecaster’s head when they view radar loops***

## Multisensor Precipitation Nowcaster (MPN)- For Flash Flood Forecasting -

**Automatically produces deterministic 1-hr rainfall forecasts and flash flood threat probabilities using extrapolation techniques**
**4-km forecast grids, updated every 5-15 minutes as needed**
**Multisensor – uses WSR-88D radar with rain gauge-based mean field bias adjustments**
**Regional – uses mosaicked WSR-88Ds covering the county warning area**
**Is integrated with EMPE;   EMPE produces all necessary input data to drive it**

## History and Status of MPN

**MPN is an extension of HL’s Flash Flood Potential (FFP) algorithm**
***FFP was originally single-radar, single-sensor***
***AHPS supported the upgrade to multiradar, multisensor using EMPE product input***
**Initial AHPS funding proposal for MPN written by Fulton in 2002 and funded FY 2003-2006**
**Project plan developed and distributed for review in 2002**
**Initial MPN prototype was completed in 2004 by HSMB’s Hydrometeorology Group (S. Guan, F. Ding, R. Fulton)**
**In 2004, we set up a real-time 24x7 demonstration in HL for 5 WSR-88Ds in mid-Atlantic region   ****(Sterling KLWX, Pittsburgh KPBZ, Charleston KRLX, Blacksburg KFCX, Wakefield KAKQ)**
**Web page shows real-time graphical output products**
**MPN project is in OSIP Stage 2**

## MPN has Two Components

**Rainfall Projection**** algorithm**
***Produces 1-hour gridded rainfall nowcasts based on extrapolation of recent WSR-88D and rain gauge observations***
**Flash Flood Threat Assessment**** algorithm**
***Computes observed and forecasted gridded probabilities of exceeding 1-, 3-, and 6-hr Flash Flood Guidances (FFG)***

## MPN Data Flow

- RFC1 FFG

**Assessment**

**Projection**

**Multisensor Precipitation Nowcaster**

- User
- adaptable
- params.

- Bias-adj
- rain rate
- mosaics

- Bias-adj
- 15-min rainfall
- mosaics

- RFC2 FFG

- RFC3 FFG

- Gridded
- FFG mosaic

- Products

**EMPE**

## MPN Details

**Generates one-hour rainfall nowcasts on HRAP grid (~4 km) with 5-15 minute update frequency as needed**
***Meager justification currently for going to higher spatial resolution***
***Extending forecasts beyond 1 hour is easily doable, but accuracy degrades quickly beyond ~1 hour in summer convection***
**Local pattern matching technique using two consecutive gridded radar rain rate mosaics ~15-20 minutes apart produces local storm motion vectors**
***Vectors delineate storm motion at a ~20 km grid scale***
***Automated vector quality control***
**Advect and integrate current mean field bias-adjusted rain rate mosaic one hour into future using observed storm vectors**
***Several progressive spatial smoothing options are available to minimize forecast error***
**Local lagrangian storm growth and decay can be accounted for in forecasts if desired**

*Pt. 1:  Rainfall Projection Algorithm*

## MPN Projection ProductsOne-hour Rainfall Forecast

## MPN Projection ProductsOne-hour Rain Rate Forecast

## MPN Projection ProductsStorm Motion Vectors and Reliability

## MPN Details

**Compares both observed and forecasted rainfall with 1, 3, and 6-hr FFGs on the HRAP grid**
***Could be enhanced to do basin averaging if integrated into FFMP***
**Computes both observed and forecasted gridded probabilities of exceeding FFGs**
***Maximum exceedance probabilities of all three durations (1-hr, 3-hr, 6-hr),***
**e.g., 3-hr forecast exceedance probabilities are computed from 2 hours of past observed rain and 1 hour of forecast rain and then compared with 3-hr FFGs**
***“******Storm-total” exceedance probabilities (Critical Rainfall Probabilities)***

*Pt. 2:  Flash Flood Threat Assessment Algorithm*

## MPN Assessment ProductsFFG Exceedance Probabilities

## MPN Assessment ProductsCritical Rainfall Probabilities

- At end of the rain event

## Real-time Web Pagehttp://www.nws.noaa.gov/ohd/hrl/hag/empe_mpn/

**Real-time Web Page****http://www.nws.noaa.gov/ohd/hrl/hag/empe_mpn/**

*MPN products*

## MPN Verification:Are the Nowcasts Any Good?

**Verification of forecasted instantaneous rain rates and hourly forecast accumulations...**
***Against radar observations (completed)***
**Fulton and Seo (2000)**
**Guan, Ding, Fulton, Kitzmiller (2005)**
***Against rain gauge observations (in progress)***

**Fulton and Seo, 2000: A prototype operational 0-1 hour radar-based Flash Flood   ****	****Potential algorithm.  15****th**** Hydrology Conference.**
**Guan, Ding, Fulton, Kitzmiller, 2005:  Preliminary results for the 0-1 hour Multisensor ****	****Precipitation Nowcaster.  32****nd**** Radar Meteorology Conference.**

## Example 1 – Visually ComparingForecasts and Observations

- Obs.

- Fcst.

- NFL

## Example 2 – Visually ComparingForecasts and Observations

- Obs.

- Fcst.

- NFL

**Example 2 – Visually Comparing****Forecasts and Observations**

## MPN Forecast Verification Against Radar Rainfall Observations: 1-hr Rainfall

- Statistics computed on HRAP grid

- 27 historical flash flood events examined from 18 locations around the U.S. over ten years

- +77%

- -43%

- +106%

**MPN Forecast Verification Against Radar Rainfall Observations: 1-hr Rainfall**

## MPN Forecast Verification Against Radar Rainfall Observations: 1-hr Rainfall

**MPN Forecast Verification Against Radar Rainfall Observations: 1-hr Rainfall**

- Bias=
- Σ(fcst rain)/Σ(obs rain)

- Rain gauge data was not used

## Using Rainfall Nowcasts in a         Distributed Hydrologic Forecast   Model (HL-RDM)

**Forecast hydrographs using 1-hr MPN rain nowcasts are consistently better than assuming zero QPF based on 9 intense rain events**
***Reed, Fulton, Zhang, Guan (2006)***
**Demonstrated potential flash flood lead time gained**
**A component of S. Reed’s HOSIP project “Distributed Hydrologic Modeling for Flash Flood Forecasting”**
**Potential for use in Site Specific Hydrologic Predictor (SSHP)**
**Potential for linking hydro forecasts to high-res GIS-based flood inundation mapping capabilities for emergency managers**

**Reed, Fulton, Zhang, Guan, 2006:  Use of 4-km, 1-hr precipitation forecasts to drive a distributed hydrologic model for flash flood prediction.  20****th**** Hydrology Conference.**

-   Lead times are computed relative to the simulated peak time.
-   All results shown are for CAVESP (90 km2) and single Event (7/2004)

- Lead Time = 4 hrs

- Peak errors of different forecasts relative to simulated flows as a function of lead time

- Lead Time = 3 hrs

- Lead Time = 2 hrs

**Hydrograph Forecast Accuracy at Different Lead Times   (Reed et al. 2006)**

**Lead time gained over zero QPF**

- Forecast
- time

- Forecast
- time

- Forecast
- time

**Notes:**
Note that I did not compute the statistically adjusted peaks for Cave Springs like in the last slide because there was not enough observed data. The basic fit for this event is excellent.

## Historical Performance of NWS     Flash Flood Warning Lead Time

**NEXRAD **
**Implementation**

**FFMP**
**Implementation**

**Historical Performance of NWS     Flash Flood Warning Lead Time**

## Recent and Projected WFO Flash Flood Warning Performance

*Flash Flood Warning Lead Time *
*Flash Flood Warning Accuracy*

|  | FY03
Actual | FY04
Actual | FY05
Actual | FY06
Goal | FY12
Goal |
| --- | --- | --- | --- | --- | --- |
| Lead Time (minutes) | 41 | 48 | 54 | 48 | 51 |
| Accuracy (%) | 89 | 89 | 88 | 89 | 91 |

**Recent and Projected WFO Flash Flood Warning Performance**

***EMPE and MPN, when integrated with other WFO hydrology tools, have the potential to greatly increase future performance***

## An Integrated Future Vision for QPE/QPN

** ****= Current HOSIP Projects in Hydromet Group**

- External
-  Users

- Distrib./Ensemble
- Hydro. Models,
- E-FFMP

***AWIPS***

- Current

- 5 Yrs

- 10 Yrs

- Enhanced
- MPE
-  Multi-radar
-  Multisensor
- - Probabilistic
-  1⁄4 HRAP (1 km)
-  5-60 min. rain
- durations
- - 5-15 min. updates

- Rain
- Gauges

- Auto-QC

- Satellite
- QPE

- NWP
- Analyses

***AWIPS***

- *

- *

- *

- Enhanced
- PPS
- - Single radar
- - Polarimetric
- - Probabilistic
- - 1⁄4 km x 1⁄2 deg
- - 4 min. updates

- HCA
- (REC)

- RCA

- CSSA

***ORPG***

- *

- *

- *

- *

- Deterministic
- Multisensor QPE
- + Uncertainty
- Info

- PQPE Bias
- & Uncertainty
- Processor
- (Radar-only + Multisensor)

- Deterministic
- Radar-only QPE
- + Uncertainty
- Info

***AWIPS***

- *

- MPN
-  1-3 hr rainfall
- nowcasts
- - HRAP (4 km)
- Multi-radar
- Multisensor
- - Probabilistic
- - 5-15 min. update

- NWP
- Forecasts

- Satellite
- QPN

- Short-term
- Deterministic Rainfall
- Nowcasts +
- Uncertainty Info

***AWIPS***

- *

- PQPN Bias &
- Uncertainty
- Processor

***AWIPS***

- QC Rain
- Gauges

## Conclusion

**The Enhanced Multisensor Precipitation Estimator and Nowcaster can enable improved WFO performance results and new diverse flash flood services**

## For more information on activities to improve WSR-88D rainfall estimation in the Hydrology Lab...

**Visit the Hydromet Group’s web page**
- http://www.nws.noaa.gov/oh/hrl/hag/hag.htm
**Visit our WSR-88D publications web page**
- http://www.nws.noaa.gov/oh/hrl/papers/papers.htm#wsr88d
- All the papers referenced herein are located there

- The End