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

 
January 2009 Highlights:
 

 

Well above normal precipitation was recorded across both the northern and southern coasts of Puerto Rico in January, while near normal precipitation was recorded over the remainder of the island. By the end of January 2009, 131% of the normal January precipitation was recorded across the entire island of Puerto Rico. However in San Juan, only 82% of the 30-year normal precipitation was recorded. Across the US Virgin Islands, January precipitation totals on Saint Croix and Saint Thomas varied from 28% to 128% of normal, respectively.
 
Temperatures across Puerto Rico ranged from 48ºF in Adjuntas on the 14th of the month to 91ºF in Ponce on both the 11th and 27th of January. Temperatures across the U.S. Virgin Islands ranged from 59ºF at Beth Upper New Works on Saint Croix, on both January 14th and 28th, to 88ºF, also at Beth Upper New Works on Saint Croix, on January 26th. Other notable temperatures for January 2009 are listed below:
 
Notable January 2009 High Temps: 
 
90ºF in Central Aguirre on January 16th
90ºF in Lajas on January 13th
89ºF at the Rincon Power Plant on January 11th
89ºF in Rio Piedras on January 26th    
Notable January 2009 Low Temps:
 
55ºF in Aibonito on January 13th
55ºF in Cerro Maravilla on January 12th
56ºF in Lajas on January 8th
57ºF in Toro Negro on January 26th
58ºF in Maricao on January 9th
                                                                                                                                               

The highest 24-hour precipitation total for the month of January was 4.38”, which fell along the Rio Blanco on the 22nd of the month. The highest weekly rainfall total also came from the Rio Blanco, with a total of 6.61” accumulating for the week ending the 23rd. Island wide precipitation for Puerto Rico is plotted by island sector and displayed below.



Figure 1 – Island wide precipitation for January 2009

 
Monthly Weather Summary:
 
January marks the climatological beginning to the “dry” season for Puerto Rico. Historically, the Luis Muñoz International Airport in San Juan receives only 3.02” of rain during the month of January, making it the third driest month on the island. Only the months of February and March receive less rainfall. January is also the coolest month of the year, on average, here in Puerto Rico. The average daily temperature for January in San Juan is 76.6ºF, which is 0.3ºF cooler than February, the second coolest month of the year.
 
January 2009 began with the fragmented remnants of a weakening cold front brushing the northern coast of Puerto Rico. These fragments brought above normal precipitation to the northern coastal sections of Puerto Rico over the first few days of the year along with the coolest readings of the month at the airports in San Juan, Saint Thomas and Saint Croix.
 
The dominance of a mid to upper level ridge of high pressure combined with only patchy low level moisture, resulted in a relatively dry period across all of Puerto Rico and the U.S. Virgin islands beginning on the 4th of the month. This relatively dry weather period ended during the 3rd week of the month when a large area of low level moisture in the easterlies combined with an induced surface trough associated with an upper level low, helped to bring significant widespread precipitation to all sectors of Puerto Rico and the northern USVI. This spike in precipitation (as can be seen nicely in Figure 1) strongly contributed to the 131% of normal precipitation that was received across Puerto Rico in January.
 
January 2009 Statistics:
 
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”
 
January 2009 Observations:
 
 
High:     
Low:     
AvgT:   
Pcpn:      
San Juan
83.9ºF (+1.5ºF)
72.9ºF (+2.1ºF)
78.4ºF (+1.8ºF)
2.49”    (-0.53”)
Saint Thomas
83.7ºF    (-2.1ºF)   
72.8ºF    (+0.8ºF)  
78.2ºF    (-0.7ºF)
2.41”      (+.52”)
Saint Croix
83.8ºF     (-0.5ºF)
72.8ºF    (+0.7ºF)
78.3ºF    (+0.1ºF)
0.61”       (-1.55”)
 
January 2009 Extremes:
 
 
High:  
 
Low:  
San Juan
88ºF – January 19th & 21st
69ºF - January 1st
Saint Thomas
86ºF – January 9th
 
68ºF - January 1st
Saint Croix
85ºF - January 25th & 28th                        
65ºF - January 1st
 
January Historical Statistics:
 
Highest January Temperatures on record:
 
San Juan              
92ºF - January 16th, 1982     
92ºF - January 11th, 1981
91ºF – Numerous Times
Saint Thomas      
93ºF - January 3rd, 1996
93ºF - January 5th, 1996
92ºF – Numerous Times
Saint Croix
92ºF – January 30th, 1973
91ºF – January 14th, 1973
90ºF – Numerous Times
 
Lowest January Temperatures on record:
 
San Juan              
61ºF - January 31st, 1962
62ºF – Numerous Times
Saint Thomas
63ºF – January 8th, 1956
63ºF - January 29th, 1996     
64ºF – Numerous Times
Saint Croix
59ºF - January 21st, 1995
61ºF – Numerous Times
 
Wettest Januaries:
 
San Juan              
7.60” January 1977
7.49” January 1969
7.29” January 1998
Saint Thomas      
4.83” January 2006
4.67” January 1995
4.19” January 1956
Saint Croix
7.35” January 1963
5.26” January 2005
4.77” January 1952
 
Driest Januaries:
 
San Juan              
0.61” January 1978
0.69” January 1983
0.94” January 1960              
Saint Thomas
0.76” January 2008
0.82” January 1991
0.87” January 1976
Saint Croix
0.54” January 1977
0.61” January 2009
0.63” January 1960
 
 
2000-2009 Decade in Review:
 
For the city of San Juan, January 2009 ended up being the warmest January of the past decade (see Figure 2). The average temperature of 78.4ºF was tied for the 6th warmest January dating back to 1956, when records began in San Juan. The average low temperature of 72.9ºF was the 4th warmest average low temperature recorded for the month and the average high temperature of 83.9ºF reflected the 18th warmest January on record. While January temperature observations across the U.S. Virgin Islands were also generally higher than those observed this past decade, the average temperatures departed only -0.7ºF and +0.1ºF from the long term averages across Saint Thomas and Saint Croix respectively (see figures 3 & 4). The temperature deviation for the city of San Juan was +1.8ºF compared to the 30-year average.
 
 
Figure 2 – Temperature deviations for San Juan, PR 
 
 
Figure 3 – Temperature deviations for Saint Thomas, VI
 

Figure 4 – Temperature deviations for Saint Croix, VI
 
 
 
Precipitation wise, the island of Saint Croix received only 0.61” of rainfall (28% of normal) in January 2009, which was the second driest January on record for the island (records for Saint Croix date back to March 1951). The 2.41” of rainfall (128% of normal) recorded on Saint Thomas represented the 12th wettest January on record and the 2.49” of rainfall (82% of normal) that accumulated in San Juan represented the 18th driest January on record. However, across the entire island of Puerto Rico, 131% of normal precipitation was recorded for the month. Below are the precipitation deviations from long term averages for San Juan (SJU), Saint Thomas (STT) and Saint Croix (STX).
. 

Figure 5 – January precipitation deviation 2000’s
  
 
 
Decadal Observations for San Juan, Puerto Rico:
 
Decadal January High Temperatures:
2000’s
 
1990’s
 
1980’s
 
1970’s
 
1960’s
 
1950’s*
82.5ºF
 
83.6ºF
 
84.1ºF
 
83.0ºF
 
82.7ºF
 
81.8ºF
 
Decadal January Low Temperatures:
2000’s
 
1990’s
 
1980’s
 
1970’s
 
1960’s
 
1950’s*
71.2ºF
 
71.3ºF
 
70.7ºF
 
72.0ºF
 
69.1ºF
 
67.9ºF
 
Decadal January Average Temperatures:
2000’s
 
1990’s
 
1980’s
 
1970’s
 
1960’s
 
1950’s*
76.8ºF
 
77.4ºF
 
77.4ºF
 
77.5ºF
 
75.9ºF
 
74.8ºF
 
Decadal January Precipitation:
2000’s
 
1990’s
 
1980’s
 
1970’s
 
1960’s
 
1950’s*
3.90”
 
4.09”
 
2.34”
 
2.68”
 
3.06”
 
4.36”
* Records for San Juan began on January 1st, 1956
 
Looking ahead toward the month of February:
 
As of February 3rd, 2009, the Eastern interior of Puerto Rico was the only section of Puerto Rico classified as being abnormally dry and no sector of the island was classified as experiencing drought conditions. With continued ENSO neutral conditions in the Tropical Pacific and possibly the development of La Niña conditions in the coming months, we can expect temperature trends to be slightly above normal and precipitation trends to be slightly below normal as suggested by previous climatological studies for the northeastern Caribbean.
 
Average February Temperatures/Precipitation (NCDC 1971-2000 averages):
 
 
High:     
Low:     
AvgT:   
Pcpn:      
San Juan              
82.8ºF    
70.9ºF
76.9ºF
2.30”
Saint Thomas
85.9ºF    
71.9ºF    
78.9ºF    
1.51”
Saint Croix
84.3ºF
72.1ºF
78.2ºF
1.94”
 
 
Moon/Sun/Tide Data for the month of February:
 
                The sun rises at 6:58 am AST on the 1st of February and sets at 6:19 pm AST, in San Juan, Puerto Rico. This represents a total of 11 hours and 21 minutes of daylight. By February 28th, the sun will rise at 6:44 am AST and set at 6:30 pm AST, providing a total of 11 hours and 46 minutes of daylight, or a total increase of 25 minutes over the course of the month. At Charlotte Amalie on Saint Thomas, the sun will rise at 6:53 am AST and set at 6:14 pm AST on the 1st of the month. By the end of the month, the sun will rise at 6:39 am AST and set at 6:26 pm AST, representing a total increase of 26 minutes of daylight for the month.
 
                For the month of February, a full moon will be observed on the 9th of the month at 10:49 am AST. There will also be a new moon on the 24th of the month at 9:35 pm AST. The first quarter of the moon will be observed on the 2nd and the last quarter of the moon will be observed on the 16th.
 
                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.weather.gov/sju) and then clicking on the Astronomical tab.

 


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