NCST Technical Investigation of 

Hurricane Maria (Puerto Rico)

Hazard Characterization Project

Project Leaders: DongHun Yeo and Scott Weaver

NCST Advisory Committee Meeting, June 8-9, 2022
Background: Hazards from Hurricane Maria (HM)

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• Puerto Rico was subjected to multiple hazards due to HM: extreme winds, coastal inundation, and heavy 

rainfall, causing inland flooding and landslides

• Accurate characterization of multiple hazards is of fundamental importance for projects across the HM 

program

• HM caused extensive damage to instrumentation, introducing significant challenges in hazard 

quantification

• A combination of measurements and modeling is required to characterize spatial and temporal variation of 

hazards

 Peak gust wind speed (flat terrain)

Total rainfall accumulation

Source: NOAA/WPC

Coastal inundation above ground level

Source: NOAA/NHC Hurricane Maria track PRELIMINARY

up to 140 mph (63 m/s) up to 6 ft (1.8 m)

Density of landslide sites

Source: USGS

up to 40 in (100 cm) more than 25 landslides/km2
Wind Hazard

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Motivation: Characterizing Topographic Speed-Up

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• Preliminary analysis showed that Puerto Rico’s mountainous topography could increase peak gust wind 

speeds by as much as 80 % when compared to the same weather pattern over flat terrain

• Quantifying this “topographic speed-up” is important in order to have an accurate understanding of 

wind loads experienced by buildings and infrastructure

PRELIMINARY

Topographic Speedup Factor (TSF) at 10 m elevation

TSF(z) = 

Peak gust speed with topo. corrections, U(z)

Peak gust speed without topo. corrections, U0(z)
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Wind Tunnel Testing Field Measurements Wind Field Modeling

Yabucoa

Mayagüez

CFD Simulations

Wind Hazard

Project Plans

• Evaluate wind speed-up effects associated with Puerto Rico’s topography using wind tunnel testing 

in conjunction with field measurements and Computational Fluid Dynamics (CFD) simulations

• Develop a hurricane wind-field model that accurately characterizes the wind environment 

associated with Hurricane Maria’s impact on Puerto Rico, including topographic effects

Objective

• Characterize the wind environment associated with Hurricane Maria’s impact on Puerto Rico, 

including topographic effects
Hospital Bella Vista site

Wind tunnel measurements:

• Completed testing of generic ridge and plateau models with smooth surfaces

• Completed additional Cobra probe profile measurements over bare turntable to inform calculation of 

topographic speedup factors

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Recent Progress: Wind Tunnel Testing

Data processing and analysis:

• Completed post-processing of PIV (Particle Image Velocimetry)/Cobra probe data from Mayagüez 

topographic model to develop time series of 3D velocity across the measurement domain, along 

with summary statistics

PRELIMINARY

Time-avg. longitudinal wind velocity data

of the Mayagüez model (wind direction 230°)

Generic topographic models 

with smooth surfaces

Contract with University of Florida to support wind tunnel testing tasks: model fabrication and testing

Ridge model

Plateau model

[m/s]
Recent Progress: Field Measurements

• Completed collection of one-year long continuous gust wind speed/direction data from all anemometers 

on three towers in Yabucoa region since March 2021

• Reviewed the collected data for quality assurance and quality control

• Developed software tools to read raw measurement data, calculate statistics at synchronized time 

intervals, and store the resulting data in a format that facilitates analysis

• Started 2nd year data acquisition in March 2022

7 Three communication towers [YMN, ECY, YTA]

(+ one weather station tower [YAB]) for field measurements

Contract with University of Florida/WeatherFlow to support anemometer installation/maintenance and data recording

Yabucoa 

Maunabo Norte 

Tower (YMN)

El Cocal Yabucoa 

Tower (ECY)

Yabucoa Tanque de Agua 

Tower (YTA)

Yabucoa-El Negro 

Tower (YAB)

Credit: WeatherFlow

Credit: WeatherFlow

Field measurements from Tower YMN: 

horizontal gust wind (March 2021 - May 2022)
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• Performed quantification of numerical error uncertainties in simulation results (generic cases)

• Developed and implemented a canopy model to account for effects of forest on flow field above 

complex topography

• Collected vegetation information (tree height, leaf area index, leaf area density profile) from 

satellite/LiDAR datasets for simulating flow above forest in Yabucoa

Recent Progress: CFD Simulations*

Tree canopy height in Yabucoa 

Source: NASA

PRELIMINARY

Finest grid

Coarsest grid

Simulation results and their uncertainties 

as a function of grid refinement

* OpenFOAM (open source) CFD code is used

[m]
Recent Progress: Wind Field Modeling

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• Completed improvements to Hurricane Maria wind-field model including:

o Development and implementation of an automation procedure for optimization of model fitting to 

observed data

o Incorporation of additional surface-level meteorological observations

o Quantification of uncertainty associated with parameters of the wind-field model

• Model provides time histories of wind speed and direction across Puerto Rico during Hurricane Maria

Updated peak gust wind speed map 

(not including topographic speedup effects)

Contract with Applied Research Associates to support wind field modeling tasks

Feb. 2022 update

Comparison of max. gust wind speed: 

Model data vs. Observations

Feb. 2022 update

1 mph = 0.447 m/s

Peak gust wind speed without topographic effects [mph]
Wind Hazard: Next Steps

Wind tunnel testing 

• Complete post-processing and curation of the exp. data from generic and Yabucoa topographic models

• Analyze the wind tunnel data and complete the uncertainty quantification of the measurements

Field measurements

• Measure anemometer orientation for improvement of accuracy in wind direction measurements

• Continue data collection for 2nd year ( ~ March 2023)

• Analyze the field data for topographic speed-up effects in Yabucoa

CFD

• Perform simulations accounting for the effects of forest cover on wind flow over topography in Yabucoa 

• Complete the validation of CFD models against wind tunnel testing data and field measurements

Wind field model

• Complete updates to topographic effects model based on comparisons with wind tunnel measurements

• Complete development of final wind field model to provide time histories of wind speed and wind 

direction across Puerto Rico for the duration of Hurricane Maria

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Other Hazards

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Motivation: Characterizing Wind and Water Impacts

Maria (2017)

Katrina (2005)

Joplin (2011)

• Impacts from other hazards such as storm surge or inland extreme rainfall cause the greatest 

economic damages and loss of life

• Extreme amounts of rainfall were observed across the entirety of Puerto Rico during Hurricane Maria

• Rainfall is a primary source of both flooding and landslides. Accurate rainfall measurements play an 

important role for post-windstorm investigations of other water hazards 

Source: NOAA/NCEI

U.S. Billion-Dollar Weather and Climate Disaster Events 1980-2021 (CPI-Adjusted)
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Project Plans

• Conduct outreach to other federal agencies and organizations regarding data sources and 

modeling capabilities that may be available to better characterize the hazards and their spatial 

and temporal variation

• Assess an array of in-situ and remotely-sensed rainfall observations to better understand 

measurement platform differences as a function of event severity and/or other relevant 

parameters (e.g., topography)

• Evaluate the sub-daily rainfall evolution as a function of measurement platform and event 

severity to better understand the evolution of measurement biases and temporal relationships 

with the primary wind hazard

Other Hazards

Objective

• Document other hazards associated with the hurricane, including storm surge, rainfall, flooding, and 

landslides
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Recent Progress: Rainfall Data (1/3)

Data sources identified*

- Pre-Hurricane Maria maps: Precipitation frequency maps (NOAA, 2008) 

- Hurricane Maria data: 

• Ground data: Rain gauges (NWS, USGS), NCEP Stage IV

• Satellite data: IMERG, CMORPH-CDR, PDIR-NOW, PERSIANN-CCS, CHIRPS

• Hindcast data: WRF (Weather Research and Forecast) model simulation

- Post-Hurricane Maria maps: N/A 

Recent progress

- Collected 5 additional datasets (underlined above):

• In-situ data: 5-min USGS gauge station data from San Juan Weather Forecast Office, NOAA (Mr. José Alamo)

• Three remotely-sensed satellite datasets

• 5-min WRF hindcast simulation data

* Underlined for new data sources

Gauge (USGS and NWS) Satellite ensemble Simulation (WRF)

0

5

15

40

100

250

500 [mm]

Total precipitation: Sept. 19-21, 2017

NCEP Stage IV (“Gold” standard)
Recent Progress: Rainfall Data (2/3)

• Performed rainfall analysis: Hurricane Irma vs. Hurricane Maria

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Total precipitation: 

H. Irma (Sep. 5-7, 2017)

 vs. 

H. Maria (Sep. 19-21, 2017)

NCEP Stage IV

Satellite ensemble

Hurricane Irma Hurricane Maria

• H. Maria produced more rain 

across Puerto Rico compared to 

H. Irma

• The satellite ensemble significantly 

underestimated the rainfall for 

H. Maria relative to NCEP Stage IV, 

but the agreement was better for 

H. Irma

-150 -50 -20 0 5 15 25

Relative difference in total rainfall [%]

Relative difference: (Satellite ensemble - NCEP Stage IV ) / NCEP Stage IV
Recent Progress: Rainfall Data (3/3)

• Assessed hourly precipitation data

 - Average across Puerto Rico

 - Average for each study region: San Juan, Utuado, Caguas, and Humacao

16 Hourly precipitation: Sept. 19-21, 2017

San Juan

Utuado

Caguas Humacao

Across Puerto Rico San Juan Region
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Recent Progress: Flood Data

Data sources identified*

- Pre-Hurricane Maria map: Flood risk map (FEMA 2009-2017) 

- Hurricane Maria data:

 1) Storm surge: Estimated storm surge inundation (NOAA/CERA 2017) 

 2) Inland Flood: University of Bristol (in progress)

- Post-Hurricane Maria map: Flood risk maps (FEMA 2021), National storm surge hazard maps (NOAA 2018) 

Post-Hurricane Maria flood risk map (100-year floodplain)

Source: FEMA Estimated inland flooding area (H. Maria) 

Source: Univ. of Bristol

Recent progress

- Provided rainfall estimates to collaborators at University of Bristol as input for inland flood modeling for Hurricane 

Maria (underlined above)

- Collected post-hurricane Maria flood risk dataset (underlined above) and shared with the broader team to support 

analyses

* Underlined for new data sources

Flood area (depth > 0.1 m)

River channel

PRELIMINARY

A (No base flood elevation determined)

A99 (Protected by Federal flood control system)

AE (Base flood elevation determined)

AH (Shallow flooding)

AO (River or stream flood hazard)

VE (Coastal flooding area with storm wave hazard)

X (500-year floodplain)

Flood 

Hazard 

Zones
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Recent Progress: Landslide Data

Data sources identified*

- Pre-Hurricane Maria maps: Landslide susceptibility map: USGS (2012) 

- Hurricane Maria data: USGS (2017, 2019)

- Post-Hurricane Maria landslide susceptibility map: USGS (2020)

2019 2017

Landslide density during H. Maria (Source: USGS) 

Post-H. Maria (2020)

Low

Moderate

High

Very High

Extremely High

Landslide susceptibility

Landslide susceptibility maps (Source: USGS)

Pre-H. Maria (2012)

Low

Moderate

High

Very High

Landslide susceptibility

Recent progress

- Collected additional dataset on Hurricane Maria landslide density (underlined above)

- Compiled pre- and post-Hurricane Maria landslide risk maps and shared with the broader team to support analyses

* Underlined for new data sources
Other Hazards: Next Steps

Outreach for data

• Continue identifying data sources and modeling for other hazards

Rainfall Data

• Finalize comparative analysis of ground-based and space-based rainfall measurement platforms for 

Hurricane Maria

• Conduct ensemble WRF modeling of Hurricane Maria to augment measurements and characterize 

variability in rainfall estimates.

• Conduct climatological analysis of rainfall data sets to contextualize the historical magnitude of 

Hurricane Maria’s rainfall

Flood Data

• Evaluate the impact of variable rainfall measurements on flood estimates for Hurricane Maria using 

flood modeling methodologies in collaboration with academic scientists

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NCST Technical Investigation of 

Hurricane Maria’s Impacts on Puerto Rico

Hazard Characterization Project

Project Leaders: DongHun Yeo (NIST) and Scott Weaver (NIST)

Project Team: Luis Aponte (Univ. of Puerto Rico at Mayagüez), Dereka 

Carroll-Smith (PREP Research Associate, Univ. of Maryland-College Park), Joel 

Cline (NOAA), Yunjae Hwang (PREP Research Associate, Johns Hopkins 

University), Marc Levitan (NIST), Joe Main (NIST), Cynthia Rivas (NIST)

Contractor Teams: Applied Research Associates, Univ. of Florida, WeatherFlow

Acknowledgement: Rameche Somassoundirame (former PREP Research 

NCST Advisory Committee Meeting, June 8-9, 2022

Associate, Johns Hopkins University), University of Bristol (collaborator)