October 2009 Climate Report for Puerto Rico and the U.S. Virgin Islands

 
October 2009 Highlights:
 
Temperatures across Puerto Rico ranged from 54ºF in Adjuntas on the 31st of October, to 95ºF, observed in both Aguadilla and Ponce, on the 6th and 30th of the month respectively. Temperatures across the U.S. Virgin Islands ranged from 65ºF, at Beth Upper New Works on Saint Croix on October 26th, to 92ºF, at the Charlotte Amalie Airport on Saint Thomas on the 7th of the month. Other notable temperatures for October 2009 are listed below:
 

Other Notable October 2009 High Temps:      
94ºF in Lajas on October 9th  
94ºF in Magueyes on October 20th  
94ºF at Dos Bocas on October 4th
94ºF in Corozal on October 25th         
93ºF in Guayama, Mayaguez, Gurabo, San Juan and Trujillo Alto
Other Notable October 2009 Low Temps:
 
61ºF in Cerro Maravilla on October 30th   
61ºF in Ponce on October 11th    
62ºF in Toro Negro on October 22nd    
64ºF in Aibonito on October 22nd  
64ºF in Maricao on October 22nd  
 

*If multiple occurrences, all dates above reflect the most recent occurrence of the month.

The highest 24-hour precipitation total for the month of October was 3.60”, which fell in Morovis on the 11th of the month. The highest weekly rainfall total occurred at Cerro Maravilla, where 8.56” of rainfall accumulated the week ending October 16th. While an additional 2.57” of rainfall accumulated on Saint Croix during the month of October, this was well below the normal 5.22” normally received during the month, leaving the first 10 months of the year at 52% of normal, which remains the driest start to a year on record for Saint Croix.

 

Figure 1A – Island wide precipitation forJanuary-October2009

Figure 1B – Graphical Display of October2009 precipitation across Puerto Rico and the U.S. Virgin Islands derived from a combination of rain gage and radar data.

 

 

Monthly Weather Summary:
 
Moisture associated with the remnants of the Tropical Storm Henri aided the development of numerous showers and isolated thunderstorms across the interior and southwestern sections of Puerto Rico during the first week of October. While the remainder of the month was relatively quiet weather wise, several tropical waves did cross the local islands during October. These tropical waves bought brief surges of moisture; however, rainfall accumulations for October 2009 were mainly influenced by typical mesoscale-driven nocturnal/diurnal showers. Due to the lack of significant widespread weather events, by the end of the month, rainfall totals across San Juan, Saint Thomas and Saint Croix all ended up well below normal, however due to widespread locally driven shower activity across the interior and western sections of Puerto Rico, an average of 96% of the normal precipitation was received island wide.
Due to the mainly locally driven weather pattern observed during October 2009, several flash flood warnings and flood advisories were issued across the north central, northwestern and western interior sections of the island, where the most persistent heavy rain fell. Hazy skies were noted over some areas, mostly associated with dust coming from the Saharan regions of Africa; however some of this haze was partly due to emissions from the Soufriere Hills Volcano on Montserrat. On October 23rd a huge smoke plume was reported during CAPECO/Gulf refinery explosion. This situation created very unhealthful conditions, especially during the night time, when the pollutants were trapped under the nocturnal inversion along the north coast of the island. Terminal Doppler weather radar imagery showed that this smoke plume extended as far west as Manati. 
October 2009 is one of the warmest Octobers on record, averaging 2.8 degrees above normal in San Juan. At Luis Muñoz Marin International Airport, a low temperature of 80 degrees or warmer was recorded a record 11 times. Details on the abnormal temperatures can be found at http://www.srh.noaa.gov/sju/?n=record110109. The highest temperature at the Luis Muñoz International Airport was 93 degrees on October 23rd and the minimum temperature fell to 76 degrees on October 18th. October ended with a weak frontal boundary across our regional waters and associated strong low pressure system to our north, which produced large long period north northeast swells and large breaking waves along the northern coasts of the local islands.
 
 
October 2009 Statistics:
 
Average October Temperatures/Precipitation (NCDC 1971-2000 averages):
 

 
High:     
Low:     
AvgT:   
Pcpn:      
San Juan              
87.5ºF
75.6ºF    
81.6ºF
5.06”
Saint Thomas
89.5ºF    
76.2ºF    
82.9ºF
5.57”
Saint Croix
88.5ºF
75.9ºF
82.2ºF
5.22”

 
October 2009 Observations:
 

 
High:     
Low:     
AvgT:   
Pcpn:      
San Juan
89.9ºF     (+2.4ºF)
79.0ºF     (+3.4ºF) 
84.4ºF     (+2.8ºF) 
3.62”       (-1.44”) 
Saint Thomas
88.5ºF     (-1.0ºF)  
79.0ºF     (+2.8ºF) 
83.8ºF     (+0.9ºF) 
2.27”       (-3.30”) 
Saint Croix
88.9ºF     (+0.4ºF)
76.9ºF     (+1.0ºF)
82.9ºF     (+0.7ºF)
2.57”       (-2.65”)

 
October 2009 Extremes:
 

 
High:  
 
Low:  
San Juan
93ºF – October 23rd
76ºF – October 18th
Saint Thomas
92ºF – October 7th   
77ºF – October 14th & October 22nd
Saint Croix
91ºF – October 4th & 6th
72ºF – October 21st & October 22nd

 
October Historical Statistics:
 
Highest October Temperatures on record:
 

San Juan              
98ºF – October 9th, 1981
97ºF – October 13th, 1987*
*Most recent occurrence  
Saint Thomas      
97ºF – October 14th, 1994*
*Most recent occurrence
Saint Croix
99ºF – October 1st, 1972
97ºF – October 11th, 1995
95ºF – October 4th, 1972

 
Lowest October Temperatures on record:
 

San Juan              
67ºF – October 20th, 1959
68ºF – October 30th, 2001*
*Most recent occurrence
Saint Thomas
66ºF – October 27th-29th, 2007
68ºF – October 15th, 1954
69ºF – October 10th, 1956*
*Most recent occurrence
Saint Croix
65ºF – October 23rd, 1983*
*Most recent occurrence

 
Wettest Octobers:
 

San Juan              
15.06” October 1970
11.94” October 2005
11.25” October 2006
Saint Thomas      
12.49” October 2005
12.45” October 1974
12.39” October 1954
Saint Croix
16.20” October 1977
12.95” October 1990
11.79” October 1954

 
Driest Octobers:
 

San Juan              
1.17” October 1979
1.63” October 1963
1.74” October 1992
Saint Thomas
1.77” October 1953
2.00” October 1988
2.21” October 1979
Saint Croix
1.05” October 1964
1.10” October 2002
1.23” October 1960

 

 

 

2000-2009 Decade in Review:
 
Decadal Observations for San Juan, Puerto Rico:
 
Decadal October High Temperatures:

2000’s
 
1990’s
 
1980’s
 
1970’s
 
1960’s
 
1950’s*
88.2ºF
 
88.6ºF
 
89.2ºF
 
88.3ºF
 
87.5ºF
 
87.4ºF

 
Decadal October Low Temperatures:

2000’s
 
1990’s
 
1980’s
 
1970’s
 
1960’s
 
1950’s*
76.4ºF
 
76.1ºF
 
75.5ºF
 
76.4ºF
 
74.2ºF
 
72.6ºF

 
Decadal October Average Temperatures:

2000’s
 
1990’s
 
1980’s
 
1970’s
 
1960’s
 
1950’s*
82.3ºF
 
82.4ºF
 
82.4ºF
 
82.4ºF
 
80.8ºF
 
81.0ºF

 
Decadal October Precipitation:

2000’s
 
1990’s
 
1980’s
 
1970’s
 
1960’s
 
1950’s*
6.20”
 
4.48”
 
5.58”
 
6.29”
 
4.85”
 
7.16”

* Records for San Juan began on January 1st, 1956

 

 Figure 2 - Temperature deviations for San Juan, PR

 Figure 3 - Temperature deviations for Saint Thomas, VI

 Figure 4 - Temperature deviations for Saint Croix, VI

 Figure 5 - October precipitation deviations 2000's

 Figure 6 - Year-to-Date precipitation deviations for San Juan, Saint Thomas, and Saint Croix

  

Looking ahead toward the month of November:

 
Average November Temperatures/Precipitation (NCDC 1971-2000 averages):
 

 
High:     
Low:     
AvgT:   
Pcpn:      
San Juan              
85.1ºF
74.0ºF    
79.6ºF
6.17”
Saint Thomas
87.8ºF    
74.9ºF    
81.4ºF
5.28”
Saint Croix
87.0ºF
74.3ºF
80.7ºF
5.55”

 
 
Moon/Sun/Tide Data for the month of November:
 
                The sun rises at 6:24 am AST on the 1st of November and sets at 5:52 pm AST, in San Juan, Puerto Rico. This represents a total of 11 hours and 28 minutes of daylight. By November 30th, the sun will rise at 6:40 am AST and set at 5:47 pm AST, providing a total of 11 hours and 07 minutes of daylight, or a total decrease of 21 minutes over the course of the month. At Charlotte Amalie on Saint Thomas, the sun will rise at 6:19 am AST and set at 5:47 pm AST on the 1st of the month. By the end of the month, the sun will rise at 6:35 am AST and set at 5:42 pm AST, also representing a total decrease in daylight of 21 minutes for the month.
 
                For the month of November, a full moon will be observed on the 2nd of the month at 3:14 pm AST. There will also be a new moon on the 16th of the month at 3:14 pm AST. The first quarter of the moon was observed on the 25th of October and the last quarter of the moon will be observed on the 9th of November.
 

                Links to additional sunrise/sunset data, phases of the moon, as well as tide data can all be found by clicking on the climate link of the National Weather Service San Juan homepage (www.srh.noaa.gov/sju) and then clicking on the Astronomical tab.


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