1. Tropical Cyclone Rainfall over Puerto
Rico and its relations to Environmental
and Storm Specific Factors
José J. Hernández Ayala
PhD Student
Department of Geography
University of Florida
2. Objectives and Importance
• Understand how environmental and storm specific factors affect TC
rainfall over Puerto Rico.
• Identify the most important factors that cause TC rainfall variability.
• Heavy rainfall from tropical depression Isabel in October of 1985
triggered one of the deadliest mudslide events in North American
history killing 130 people (Jibson, 1989; Larsen and Simon, 1993).
4. Problem Statement
• Which factors or conditions affect tropical cyclone rainfall variability over
the island of Puerto Rico?
• Intensity?
• Horizontal Translation Speed?
• Environmental Moisture?
• Proximity to Storm Center?
• Vertical Wind Shear?
• Storm Center Location?
• Storm Duration?
5. Literature on TCs and Puerto Rico
• Puerto Rico is subject to frequent and severe impacts from Hurricanes (Dunn and Miller
1964, Simpson & Riehl 1981, Diaz & Pulwarty 1997).
• The frequency with which a tropical cyclone passes directly over Puerto Rico is
small (Scatena and Larsen, 1991).
• A comprehensive study of hurricanes in P.R based on meteorological principles
and the historical record is lacking (Boose, Serrano &Foster 2004).
• Storm rainfall totals of 500 mm are common for hurricanes in Puerto Rico (Riehl, 1979).
• Some Caribbean storms have reportedly produced more than 2000 mm (Gupta, 1988).
6. Area of Study
• Puerto Rico is located 18.5
˚N & 66.5˚ W.
• The total population of the
island is approximately 3.7
million.
8. Data Sources
• Daily Rainfall from 32 rain gauges in mm (NCDC)
• Tropical Cyclone Tracks from 1970-2010 (IBTrACS)
• Daily Environmental Variables (NCEP/NCAR)
• Puerto Rico Digital Elevation Model (USGS)
9. Methods
• Tracks within 500 km of PR were selected with a GIS.
• 86 TCs were identified using this parameters.
• Daily rainfall data for each specific period for each TC was obtained.
• An averaged total rainfall value for all 32 stations was calculated for each TC.
• Data for 12-24 hr. for one day, add up other days with 12 hr. >
• Independent variables were measured using the same parameters used for rainfall,
10. Variables
Table 1. Storm specific characteristics and environmental factor variables used in this study.
Storm Specific Factors Abbreviation Units
Circulation Center Latitude LAT º
Circulation Center Longitude LON º
Proximity to Storm Center PRX km
Storm Duration DUR hrs.
Maximum Sustained Winds VMX ms-1
Horizontal Translation Speed HTS ms-1
Environmental Factors Abbreviation Units
Total Precipitable Water TPW mm
Mid-level Relative Humidity (Avg. 500-700 hPa) MRH %
Wind Shear (850-200 hPa) West To East WSU ms-1
Wind Shear (850-200 hPa) South To North WSV ms-1
12. Statistical Tests and Models
• Pearson Correlation Tests was implemented to look at the relationship
between each individual factor and TC rainfall.
• Varimax Rotated Principal Component Analysis (PCA) was employed to
reduce the number of factors and group them in new components that
account for independent variable correlations.
• Principal Component Regression (PCR) was used to model the
components contribution to tropical cyclone rainfall variability.
• Mann-Whitney U Test was employed to compare the factors associated
with the highest and lowest rainfall producing storms.
13. Results: Descriptive Statistics
Table 2. Descriptive statistics of storm specific and
environmental factors associated with the 86 TCs
analyzed.
Minimum Maximum Mean
LAT 13.5 22.8 17.9
LON -70.6 -61 -65.5
PRX* 1 499.9 239.7
DUR 12 102 41.5
HTS 3.15 13.17 6.3
VMX 11.11 72.28 28.3
TPW 30.31 53.74 44.7
MRH 23.45 74.32 49.8
WSU -10.79 32.08 9.9
WSV -16.30 12.46 .22
*1 means landfall
Table 3. Tropical cyclones that produced more than 50 mm rainfall over the
island of Puerto Rico.
TC Max Intensity Year TCR (mm) Rank
Eloise TD 1975 279.15 1
Georges* H3 1998 271.43 2
David H5 1979 237.56 3
Hortense* H1 1996 209.74 4
Jeanne* TS 2004 190.35 5
Isabel TS 1985 186.72 6
Chris TD 1988 158.91 7
Grace TS 1997 122.35 8
Frederic* TS 1979 106.28 9
Olga* TS 2007 99.89 10
Lenny H3 1999 99.37 11
Claudette* TD 1979 98.93 12
Debby H1 2000 94.86 13
Debby TD 1982 85.96 14
Hugo* H4 1989 84.14 15
Marilyn H2 1995 76.35 16
Dean TS 2001 73.21 17
Klaus TS 1984 72.01 18
Mindy TS 2003 66.92 19
Carmen TD 1974 64.76 20
Odette TS 2003 58.43 21
Earl H3 2010 57.35 22
Luis H4 1995 53.2 23
*Tropical cyclones that made landfall.
14. Results: Correlation Tests
Table 4. Pearson correlation coefficients for each of
the predictor’s relationship with TC average total
rainfall.
Factors Correlation Coefficients Significance
TPW 0.716 0.000
PRX -0.678 0.000
MRH 0.565 0.000
DUR 0.542 0.000
LON -0.357 0.001
HTS -0.288 0.007
VMX 0.144 0.184
WSV -0.106 0.333
LAT 0.073 0.503
WSU 0.011 0.923
Table 5. Pearson correlation coefficients of variables that were found
to be significantly correlated with average total TC rainfall.
TPW PRX MRH DUR HTS LON
TPW 1 -0.342** 0.593** 0.338** -0.319** -0.373**
PRX -0.342** 1 -0.265** -0.591** 0.133 -0.001
MRH 0.593** -0.265** 1 0.214** -0.183 -0.452**
DUR 0.338** -0.591** 0.214** 1 -0.545** 0.130
HTS -0.319** 0.133 -0.184 -0.545** 1 -0.050
LON -0.373** -0.001 -0.452** 0.130 -0.050 1
**Correlation is significant at 0.01
24. Conclusions
• Heavy rainfall occurred across Puerto Rico when tropical
cyclones were within a distance of 233 km or less to the
island.
• Also when moisture environments exceeded 44.5 mm of
precipitable water and 44.5% of mid-level relative humidity.
• While moving slowly with speeds of 6.4 ms-1 or less and
extending more to the west .
25. Future Research
• Future work will examine the contribution of TCs to the rainfall
climatology of Puerto Rico.
• The spatial distribution of TC rainfall over the island and its
relationship with topography.
• Future research will also focus on understanding the relationship
between TC rainfall and extreme flooding events over the island.
