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

 

December 2009 Highlights:

 

 

Temperatures across Puerto Rico ranged from 50ºF in Adjuntas on the 21st of December to 94ºF on Magueyes Island, on the 19th of the month. Temperatures across the U.S. Virgin Islands ranged from 62ºF, December 30th, at Beth Upper New Works on Saint Croix, to 89ºF, observed at Charlotte Amalie on Saint Thomas on the 4th of the month.  Other notable temperatures for December 2009 are listed below:

 

Other Notable December 2009 High Temps:  
93ºF in Rincon on December 19th
93ºF in Ponce on December 3rd  
92ºF in Lajas on December 17th  
91ºF in Aguirre Central on December 15th       
91ºF in Bourinquen on December 5th
90ºF at Coloso and Guayama
Other Notable December 2009 Low Temps:
 
58ºF in Lajas on December 18th    
59ºF in Ponce on December 18th   
59ºF in Toro Negro on December 22nd   
61ºF in Aibonito, Gurabo, Cerro Maravilla and Coloso

 

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

The highest 24-hour precipitation total for the month of December was 9.00”, which fell in Aibonito on the 25th of the month. The highest weekly rainfall also occurred in Aibonito, where 9.19” of rainfall accumulated the week ending December 25th. While just over two inches of rain fell on Saint Croix during the month of December, this was over an inch below normal for the month, and the 12th consecutive month that the Christiansted Airport on Saint Croix received below normal. Not surprisingly, 2009 ranked as the second driest calendar year on record for Saint Croix, second only to 2002.

 

 

 

 Figure 1A – Island wide precipitation for January-December2009

 

 

 

 Figure 1B – Graphical Display of December 2009 precipitation across Puerto Rico and the U.S. Virgin Islands derived from a combination of rain gage and radar data.

 


Monthly Weather Summary:

 

 

December 2009 began with an upper level ridge across the Western Caribbean that helped to limit shower activity across the local islands for much of the month. These fair weather conditions prevailed across the forecast area until Christmas Eve when a large band of moisture stretching from South America northward across Puerto Rico brought cloudy skies and scattered to numerous showers across the region. Several flash flood warnings were issued across the eastern portion of the island due to the heavy rain associated to this band of moisture. The remnants of an old frontal boundary were the last weather feature that affected the forecast area in 2009, with the aforementioned mid to upper level ridge of high pressure limiting the development of significant precipitation across the island for the majority of the month.

   On average, the Luis Muñoz International Airport in San Juan receives 4.57" of rain during the month of December, making December the fifth wettest month on the island, however, this was not the case in 2009. December was considerably above normal, in terms of temperature, and well below normal, in terms of precipitation.  December 2009 ended as the 2nd warmest December on record, the 3rd driest December on record, and the driest month observed in 2009. A total of only 1.83" fell over the course of the month, which was 2.54” below the 30-year average.

 

December 2009 Statistics:
 
Average December Temperatures/Precipitation (NCDC 1971-2000 averages):
 

 
High:     
Low:     
AvgT:    
Pcpn:      
San Juan              
83.2ºF
72.1ºF   
77.7ºF
4.57”
Saint Thomas
86.2ºF   
73.2ºF   
79.7ºF
2.74”
Saint Croix
85.0ºF
72.8ºF
78.9ºF
3.29”

 
December 2009 Observations:
 

 
High:     
Low:     
AvgT:   
Pcpn:      
San Juan
85.6ºF    (+2.3ºF)
74.9ºF    (+2.8ºF)
80.2ºF    (+2.5ºF)
1.83”      (-2.94”) 
Saint Thomas
85.3ºF    (-0.9ºF) 
76.0ºF    (+2.8ºF)
80.6ºF    (+0.9ºF)
3.18”      (+0.44”)
Saint Croix
85.6ºF    (+0.6ºF)
74.2ºF    (+1.4ºF)
79.9ºF    (+1.0ºF)
2.19”      (-1.10”)

 
December 2009 Extremes:
 

 
High:  
 
Low:  
San Juan
89ºF – December 20th                 
71ºF – December 23rd
Saint Thomas
89ºF – December 2nd & 4th   
73ºF – December 22nd & 29th
Saint Croix
88ºF – December 11th & 13th
69ºF – December 30th

 

December Historical Statistics:

 
Highest December Temperatures on record:
 

San Juan              
94ºF – December 6th, 1989
91ºF – December 24th, 1995*
*Most recent occurrence   
Saint Thomas     
92ºF – December 26th, 1995*
*Most recent occurrence
Saint Croix
92ºF – December 27th, 1995
90ºF – December 10th, 1998*
*Most recent occurrence

 
Lowest December Temperatures on record:
 

San Juan              
63ºF – December 22nd, 1964
64ºF – December 25th, 1967*
*Most recent occurrence
Saint Thomas
62ºF – December 5th, 1972
63ºF – December 24th, 1991, December 7th & 27th, 1972
64ºF – December 10th, 1982*
*Most recent occurrence
Saint Croix
61ºF – December 29th, 1982 & December 24th, 1964
62ºF – December 28th, 1980
63ºF - December 26th, 1991*
*Most recent occurrence

 
Wettest Decembers:
 

San Juan              
16.81” December 1981
11.79” December 2001
10.00” December 1961
Saint Thomas     
9.87” December 1960
7.45” December 1957
6.66” December 1981
Saint Croix
14.03” December 1960
9.07”   December 1975
7.86”   December 2001

 
Driest Decembers:
 

San Juan              
0.68” December 1963
1.02” December 1997
1.83” December 2009
Saint Thomas
0.25” December 1985*
0.63” December 1963
1.76” December 1956
*4 days missing data
Saint Croix
0.75” December 2008
0.79” December 1963
0.89” December 1958

 
 

2000-2009 Decade in Review:

 
Decadal Observations for San Juan, Puerto Rico:
 
Decadal December High Temperatures:

2000’s
 
1990’s
 
1980’s
 
1970’s
 
1960’s
 
1950’s*
83.8ºF
 
84.4ºF
 
84.5ºF
 
83.7ºF
 
83.3ºF
 
83.5ºF

 
Decadal December Low Temperatures:

2000’s
 
1990’s
 
1980’s
 
1970’s
 
1960’s
 
1950’s*
72.8ºF
 
72.5ºF
 
72.4ºF
 
73.3ºF
 
71.1ºF
 
69.5ºF

 
Decadal December Average Temperatures:

2000’s
 
1990’s
 
1980’s
 
1970’s
 
1960’s
 
1950’s*
78.3ºF
 
78.5ºF
 
78.4ºF
 
78.5ºF
 
77.2ºF
 
76.5ºF

 
Decadal December Precipitation:

2000’s
 
1990’s
 
1980’s
 
1970’s
 
1960’s
 
1950’s*
5.19”
 
4.08”
 
5.36”
 
4.57”
 
4.54”
 
4.84”

* 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 - December precipitation deviations 2000's

 Figure 6 - 2009 precipitation deviations for San Juan, Saint Thomas, and Saint Croix

 

Looking ahead toward the month of January:

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

 
High:     
Low:     
AvgT:   
Pcpn:      
San Juan              
82.4ºF
70.8ºF   
76.6ºF
3.02”
Saint Thomas
85.8ºF   
72.0ºF   
78.9ºF
1.89”
Saint Croix
84.3ºF
72.1ºF
78.2ºF
2.16”

 
 

Moon/Sun/Tide Data for the month of January:

                The sun rises at 6:57 am AST on New Years morning and sets at 6:00 pm AST, in San Juan, Puerto Rico. This represents a total of 11 hours and 3 minutes of daylight. By January 31st, the sun will rise at 6:58 am AST and set at 6:18 pm AST, providing a total of 11 hours and 20 minutes of daylight, or a total increase in 17 minutes over the course of the month. At Charlotte Amalie on Saint Thomas, the sun will rise at 6:52 am AST and set at 5:55 pm AST on the 1st of the month. By the end of the month, the sun will rise at 6:53 am AST and set at 6:13 pm AST, also representing a total increase in daylight of 17 minutes for the month.
 
                For the month of January, a full moon will be observed on the 30th of the month at 2:18 am AST. There will also be a new moon on the 15th of the month at 3:11 am AST. The last quarter of the moon will be observed on the 7th of January and the first quarter of the new moon will be observed on the 23rd of the month.
 
                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.

 


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.