# Presentation: 289086

## Hydrometeorological Prediction Center Tropical Cyclone Responsibilities and Tropical Cyclone QPF

**Hydrometeorological Prediction Center Tropical Cyclone Responsibilities and Tropical Cyclone QPF**

- Michael J. BrennanScience and Operations Officer
- Hydrometeorological Prediction Center
** ****NOAA in the Carolinas Hurricane Conference **6 May 2008

- 6 May 2008

## Outline

- History of HPC’s Tropical Cyclone (TC) Responsibilities
- Synoptic Reasoning and Track Forecasting
- Tropical Cyclone QPF
- Inland Advisories
- NHC COOP

- 6 May 2008

## History of HPC’s Tropical Cyclone Program Responsibility

- HPC (and its predecessor, NMC) have provided track forecast guidance to NHC for at least the last 30 years
- Initially done because NMC had access to much more global model guidance than NHC
- NHC COOP program
- HPC/NMC has been the official NHC backup since at least 1978
- Overhauled and modernized in 2002-2003
- HPC began providing the rainfall statement for NHC’s public advisories in 2005

- 6 May 2008

## Synoptic Reasoning and Track Forecasting

- HPC provides track forecast guidance (points) to NHC for TCs west of 60°W
- HPC’s synoptic reasoning provided on Hurricane Hotline conference call
- Day 6 & 7 TC positions for HPC medium range charts coordinated with NHC in daily Noon conference call

- Day 6 Forecast of Ernesto

- HPC Medium Range Prog Valid 12Z 31 August 2006

- 6 May 2008

## Synoptic Reasoning and Track Forecasting

- HPC takes advantage of expertise in large-scale pattern diagnosis to compliment NHC track forecast
- HPC track forecast not constrained by continuity and can react more to run-to-run changes in model guidance
- Ensures HPC has working forecast in place for all TCs west of 60°W in case backup for NHC needed

- 6 May 2008

## Tropical Cyclone Rainfall

- 6 May 2008

## U.S. Weather Fatalities

- 6 May 2008

## TC Rainfall –  Major Contributor to Annual Precipitation in Southeastern U.S.

- 2005 Annual Rainfall (mm)

- 2005 TC Rainfall (mm)

- Images Courtesy Frank Marks (AOML/HRD)

**10-20 % of annual rainfall from TCs**

- 6 May 2008

## Factors Impacting Rainfall Distribution in Landfalling TCs

- Storm track (location)
- Diurnal cycle – core rainfall overnight, outer band rainfall during the day
- Topography – enhances rainfall in upslope areas, but decreases past the spine of the mountains
- Wind shear (negative) – leads to a quicker drop-off in rainfall for inland TCs
- Interaction with nearby features (troughs, fronts/jets), extratropical transition can greatly modify rainfall distribution

**Factors Impacting Rainfall ****Distribution in Landfalling TCs**

- 6 May 2008

## Depth of Upper Trough Causing Recurvature Key

- Storms which drop most of their rain left of track recurve due to significant upper troughs in the westerlies
- Rainfall streaks out well north of the system due to jet streaks moving around the upper trough and frontogenesis at the trough’s leading edge
- Trough transitions from positive to negative tilt during interaction with TC
- Storms where most rain occurs to the right of track are steered predominantly by shear lines or through a break in the subtropical ridge
- Rainfall tends to be concentrated near and right of track

- Atallah et al. (2007) *Mon. Wea. Rev.*

- 6 May 2008

## Bertha (1996)

*Norman W. “Wes” Junker*

**250-mb height and wind**

**00Z 13 July **

**15Z 13 July **

**Bertha moving around break in subtropical ridge**
**Upper trough and jet well northwest of Bertha’s track**

- 6 May 2008

## Floyd (1999)

*Norman W. “Wes” Junker*

**250-mb height and wind**

**00Z 16 Sep **

**12Z 16 Sep **

**Floyd interacts with positively-tilted upper trough more directly**
**Precipitation forms in pronounced **** jet entrance region**

- 6 May 2008

## Bertha (1996) vs. Floyd (1999)

- 6 May 2008

## “Predecessor” Rainfall Events

*** *****Coherent area of rain displaced poleward of TC**
** ****Maximum rainfall rates exceeded 100 mm (~ 4 in.) in 24 h **
** ****Moisture transport from TC toward PRE**

**1800 UTC 040830 WSI NOWRAD Radar Mosaic**

**PRE**

**Gaston**

**Slides courtesy Matt Cote & Lance Bosart – SUNY Albany**

**47 PREs associated with 21 TCs were identified during the period from 1998-2006 (~2 PREs per TC)**
**~1/3 of all U.S. landfalling TCs produced at least one PRE**
**	****Five cases where TC did not make U.S. landfall**

- 6 May 2008

**Notes:**
Cote WAF 6-07 Slide 4

## Southeast Recurvatures

**Southeast Recurvatures**

** ****7/11 (64%) produced at least one PRE**
** ****16 PREs from 7 TCs**
** ****Influential geographical features:**
**	****- Gulf of Mexico           ****	****- Atlantic Ocean           ****	****- Appalachians**

-  Approximate point of PRE formation

**Slides courtesy Matt Cote & Lance Bosart – SUNY Albany**

- 6 May 2008

**Notes:**
Cote WAF 6-07 Slide 7

## PRE Statistics 

**Bosart and Carr (1978) conceptual model of antecedent rainfall from Agnes (1972)**

**PRE Statistics **

_**Separation Distance**_
**1086 ± 482 km                        Median:  935 km**
_**Event Duration**_
**14 ± 7 h                                   Median:  12 h**
_**Time Lag**_
**45 ± 29 h                         Median:  36 h**

**Slides courtesy Matt Cote & Lance Bosart – SUNY Albany**

- 6 May 2008

**Notes:**
Cote WAF 6-07 Slide 9

## Track-Relative Location of PREs

**Track-Relative Location of PREs**

**26**

**12**

**9**

**PRE Locations Relative to TC Track 1998–2006**

- Potential for flooding in areas not directly impacted by TC rainfall

- Potential for excessive flooding beginning **before** arrival of TC rainfall

**Slides courtesy Matt Cote & Lance Bosart – SUNY Albany**

- 6 May 2008

**Notes:**
Figure 20 Cote Thesis

## Southeast Recurvatures CompositeTime of PRE InitiationMatt Cote & Lance Bosart – SUNY Albany

**700 hPa Ht (dam) and UVM (****μ****b s****-1****)**

**925 hPa Ht (dam), θ****e ****(K), and 200 hPa wind speeds (m s****-1****)**

** ****Significant midlevel trough with weak UVM well poleward of TC**
** ****Deep meridional flow transports tropical moisture up East Coast**

** ****PRE forms:                                    ****	****	****	****- in right-entrance region of ****	****	****	****	****	****	****intensifying upper-level jet**
**	****	****-****	****on western edge of ****θ****e ****ridge**

- 6 May 2008

**Notes:**
Cote-CSTAR-7May07. Slide 22

## Tropical Cyclone QPF

- 6 May 2008

## Tropical Cyclone QPF

- HPC provides rainfall guidance for all TCs with land impacts
- Rainfall statements included in NHC’s public advisories and HPC’s advisories on inland systems
- Detailed QPF guidance to WFOs and RFCs for river and flood forecasting

- TROPICAL STORM ERNESTO ADVISORY NUMBER 30 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1100 PM EDT THU AUG 31 2006 **RAINFALL TOTALS OF 5 TO 10 INCHES ARE POSSIBLE FROM NORTHEASTERN SOUTH CAROLINA INTO THE MID-ATLANTIC STATES...AND THE SOUTHERN AND CENTRAL APPALACHIANS THROUGH SATURDAY...WITH ISOLATED MAXIMUM AMOUNTS OF 15 INCHES.**

- 6 May 2008

## How Much QPF?

- Depends on multiple factors
- Availability of moisture
- Moisture at T=0
- Moisture flux – more important than the initial moisture!
- Intensity of Precipitation
- Speed and direction of movement
- Training cells
- Structured banding
- Enhancement by boundaries and/or topography
- Precipitation efficiency
-  _*No “proven” Quantitative method for QPF Yet!*_

- 6 May 2008

## HPC TC QPF

**HPC TC QPF**

- HPC TC QPF process incorporates:
- Global models
- GFS, ECMWF
- Mesoscale models
- NAM
- Ensembles
- SREF
- Hurricane models
- GFDL, HWRF
- Climatological models
- R-CLIPER
- Satellite techniques
- TRaP
- Extensive in-house _[TC rainfall climatology](http://www.hpc.ncep.noaa.gov/tropical/rain/tcrainfall.html)_ and research
- Official NHC track forecast

- 6 May 2008

## HPC TC QPF Methodology

- Forecasts made in 6-h increments from 0-84 h and in one 48-h period for days 4-5 by 3 forecast desks:
- Day 1 QPF
- Day 2/3 QPF
- Medium Range (Days 4-5)
- Starting point is model closest to NHC track forecast
- Usually GFS
- Locate relevant synoptic scale and mesoscale features (troughs, fronts, etc.)
- Use conceptual models, current structure, and pattern recognition to modify/shift QPF
- Use TRaP and recent satellite and radar imagery to analyze current structure and rainfall rates

- 6 May 2008

## HPC TC QPF Methodology

- Use climatology (PRISM, R-CLIPER, TC Rainfall Climatology) to:
- Adjust amounts and numerical guidance biases
- Depict areas of terrain that could be significantly impacted
- Provide a reality check
- Create TC rainfall statements for the Public Advisories
- Day 1-3 forecasts issued by 06z/10z/18z/22z
- Day 4-5 forecasts and 5-day total graphic issued at 00z/12z

**HPC TC QPF Methodology**

**Day 1-3 QPF**

**Day 1-5 QPF**

- 6 May 2008

## TC Rainfall ClimatologyUnited States TC Rain Maxima By State

- 6 May 2008

**Notes:**
Knowing the maximum that has fallen from tropical cyclones in the past acts as a check in forecasting extreme events.  In this slide are the maximum known amounts per state for the United States.

## Ensembles

- Can help quantify degree of confidence in a forecast and identifying range of possible solutions
- Examine spaghetti plot of precipitation isohyets from ensemble members to see areas of overlap and spread
- _Don’t_ use ensemble mean QPF – dampens extreme events

**1” isohyets from SREF members**

- 6 May 2008

## HPC QPF Verification

- 24-hour Day 1 QPFs have been verified since 1961
- Verified on common 32-km grid based on manual observational precipitation analysis performed at HPC
- TC QPF verification has been performed on a “regional” scale for the past 3 seasons
-  Precipitation from a TC may straddle more than one region
-  Other systems may influence precipitation in a region
- New for 2007 – ECMWF QPF verification

- HPC QPF Verification Regions

- 6 May 2008

## Verification Metrics

-  **Threat Score****      **
_***                ***__***Correct ***__***                  ***__***.***_
***(Forecast + Observed - Correct)***
**Measures fraction of observed and/or forecast events that were correctly predicted; Sensitive to hits, penalizes both misses and false alarms**
**For a perfect forecast:**
-     **Correct = Forecast = Observed **
**    ****	****to yield a TS of 1**
**The worst possible forecast****:**
**	****Correct = 0, yields a TS of zero**

- 6 May 2008

## Verification Metrics

_***           ***__***Forecast          _***__ __***        ***_***Observed***
**Gauges accuracy of areal/station coverage of specified threshold amount, regardless of accuracy in location **
**Ideal forecast:**
***Forecast = Observed ***
**    ****	****	****     ******** ****Bias = 1**

**Verification Metrics**

- 6 May 2008

## Seasonal Verification

- Verification of all Day 1 QPF for TCs and TC remnants with precipitation impacts in the CONUS
- 2005: Arlene, Cindy, Dennis, Katrina, Ophelia, Rita, Tammy, Wilma (8)
- 2006: Alberto, Ernesto (2)
- 2007: Andrea, Barry, Erin, Gabrielle, Humberto, Henriette (East Pacific), TD 10, Noel (8)
- Seasonal threat score and bias from HPC, GFS, NAM, and ECMWF computed
- Major changes occurred to all three models during this period
- Difficult to identify consistent biases from season to season

- 6 May 2008

## 2005 Seasonal Verification

- NAM tends to under-forecast TC precipitation, especially at higher thresholds
- GFS has best model bias from 1-6 in.; NAM best at 0.5 in.
- ECMWF TS competitive with GFS across all thresholds; ECMWF bias slightly lower than GFS
- HPC Bias generally too high, especially at higher thresholds
- HPC TS better than the NAM and GFS at all thresholds for tropical systems in 2005

**Threshold (.in)**

- 6 May 2008

## 2005 Seasonal VerificationHPC D1 TS Improvement over NAM/GFS

**2005 Seasonal Verification****HPC D1 TS Improvement over NAM/GFS**

**1313.79 %**

**3393.15 %**

- NAM

- GFS

- 6 May 2008

## 2006 Seasonal Verification

**Threshold (.in)**

- ECMWF had highest model threat score across all thresholds through 4 in.
- GFS and ECMWF had biases near 1 through 3 in. threshold
- GFS had pronounced high bias at 4 in. and above
- HPC showed most improvement in TS at higher amounts at the expense of high bias
- NAM showed lowest TS and worst bias for amounts of 3 in. or greater

- 6 May 2008

## 2007 Seasonal Verification

**Threshold (.in)**

- GFS provided best overall model QPF guidance
- HPC showed low bias at highest thresholds, reversing trend of 2005 and 2006
- ECMWF performance worse than previous years, especially above 2 in. threshold
- NAM continued to have lowest TS and severe low bias at high amounts
- HPC had a better or the same TS as the best model for all 2007 TC total stats Days 1-3 (except amounts > 3” on Day 2)

- 6 May 2008

## Gabrielle

- Gabrielle Rainfall Analysis by David Roth - HPC

- 1

- 3

- 5

- 7

- Isolated area of heavy rainfall along central NC coast
- Not well-predicted by models which struggled with track and structure of the system
- HPC showed significant improvement on heavier amounts, particularly on day 2

- 6 May 2008

## GabrielleDay 3 QPF valid for 24-h ending 12Z 10 September 2007

- HPC

- GFS

- NAM

- ECMWF

- HPC showed some skill at 1” threshold
- All models had zero bias for amounts greater than 0.5”

**Threshold (.in)**

- 6 May 2008

## GabrielleDay 2 QPF valid for 24-h ending 12Z 10 September 2007

- HPC successfully forecasted location of maximum rainfall and showed major improvement over the models for amounts > 0.50”
- Higher HPC TS at 3” came at expense of high bias
- NAM had best model forecast – only model to depict any amounts > 1”

- HPC

- GFS

- NAM

- ECMWF

**Threshold (.in)**

- 6 May 2008

## GabrielleDay 1 QPF valid for 24-h ending 12Z 10 September 2007

- HPC and model QPF displaced too far northeast
- None of the models hit the amounts > 1”
- The NAM had the best TS for 0.50” & 1”
- All of the models had a high bias through 2” except ECMWF

- HPC

- GFS

- NAM

- ECMWF

**Threshold (.in)**

- 6 May 2008

## HPC Inland TC Advisories

- 6 May 2008

## HPC Inland Advisories

- HPC issues advisories on TCs that have moved inland and weakened below tropical storm strength but still pose a threat of heavy rains and flash floods in the CONUS or adjacent areas within Mexico
- Advisories continue even if the low-level TC remnant center dissipates as long as flood threat remains
- HPC advisories cease when threat of flash flooding has ended
- Advisories issued at 03, 09, 15, and 21 UTC under the following headers:
- Atlantic: TCPAT(1-5); WTNT3(1-5) KWNH
- East Pacific: TCPEP(1-5); WTPZ3(1-5) KWNH
- Links to HPC advisories can be found on HPC webpage, NHC webpage and graphical TWO

- 6 May 2008

##  HPC Inland Advisories

- Primarily focus on potential for heavy rain and flash flooding
- Contents of HPC advisories include:
- Headline describing the current event
- General summary of current watches, warnings, and advisories
- Description of the current location, maximum sustained winds, movement, and minimum central pressure of the system
- Table listing precipitation induced by the system
- Description of the evolution and forecast for the system
- Statement including time of next HPC advisory or, if the final  HPC advisory, where to find subsequent information
- Forecast for the position of the surface center (if it still exists) as long as the system is a flash flooding threat for the CONUS

- 6 May 2008

## HPC Inland Advisories Issued Annually 2002-2007

- 6 May 2008

## NHC Continuity of Operations Plan

- 6 May 2008

## NHC COOP

- HPC is the designated backup for NHC (since at least late 1970s)
- HPC will assume forecast responsibility for Atlantic and East Pacific TCs in the event of communications outage or other problems at NHC
- Approximately 20 HPC forecasters trained in:
- TC analysis and forecasting
- Use of ATCF software
- Hurricane Program Policy

- 6 May 2008

## NHC COOP

- Major technical effort to maintain software, scripts, code and to update with annual changes to products, graphics, etc.
- Annual in-house exercise, planned and unannounced backup drills performed to maintain proficiency
- Implementation of COOP designed to be seamless and transparent to users
- Operational NHC products reproduced
- NHC website maintained

- 6 May 2008

## NHC COOP

- COOP program overhaul began in 2002-2003
- 2002
- Simple communications tests to ensure NHC products could be transmitted from HPC
- 2003
- All GS-14 and many GS-13 forecasters trained for NHC backup
- Began back-up drills on active TCs (issuing full forecast package)
- 2005
- Began issuing East Pacific TWO on the 1st Tuesday of every month to test communications and proficiency

- 6 May 2008

## NHC COOP

- HPC has never officially taken over for NHC, but there have been at least two close calls:
- 2003 or 2004: NHC requested backup due to communications problems, but recovered before HPC had to issue products
- Hurricane Andrew (1992): NHC sent forecasters to NMC for backup prior to the storm hitting Miami, but NHC remained up during and after the storm

- 6 May 2008

## Acknowledgements

- HPC Staff, especially
- Mark Klein
- Jessica Clark
- David Roth
- Wes Junker
- Chris Lauer of TPC

- 6 May 2008

## Questions??

**Medium Range**

**Surface Analysis**

**Basic Wx**

**NESDIS**

**Tropical/****Winter Wx**

**Model Diag.**

**QPF**

**Media Room**

- _[http://www.hpc.ncep.noaa.gov/](http://www.hpc.ncep.noaa.gov/)_

**Michael.J.Brennan@noaa.gov**

- 6 May 2008