January 2010 Climate Report

January 2010 Climate Report for Puerto Rico and the U.S. Virgin Islands

January 2010 Highlights:

Temperatures across Puerto Rico ranged from 48ºF in Adjuntas on the 30^th of January to 94ºF in Gurabo, on the 4^th of the month. Temperatures across the U.S. Virgin Islands ranged from 61ºF, January 25^th, at Beth Upper New Works on Saint Croix, to 86ºF, recorded at the Christiansted Fort, Red Hook Bay, the Christiansted Airport and the Cyril E. King Airport, all on various days during the month of January. Other notable temperatures for January 2010 are listed below:

Other Notable January 2010 High Temps:

91ºF in Ponce on January 28^th

91ºF in Rio Piedras on January 28^th

90ºF in Lajas on January 22^nd

90ºF at the Borinquen Airport on January 22^nd

Other Notable January 2010 Low Temps:

57ºF in Toro Negro on January 12^th

58ºF in Cerro Maravilla on January 29^th

58ºF in Aibonito on January 29^th

60ºF in Lajas, Ponce, Arecibo and Maricao on various days of January

^{*If multiple occurrences, all dates above reflect the latest occurrence of the month.}

The highest 24-hour precipitation total for the month of January was 4.71”, which fell at the Guajataca Dam on the 14^th of the month. The highest weekly rainfall occurred in Rio Piedras, where 10.56” of rainfall accumulated the week ending January 15^th. Across the U.S. Virgin Islands, the lowest rainfall total for the month came from Red Hook Bay on Saint Thomas, where only 1.53” of rainfall accumulated during the month of January, and the highest rainfall accumulated at Coral Bay on Saint John, where 3.58” of rainfall was recorded.

Figure 1A – Island wide averaged precipitation (and normals) - by week - for the month of January 2010

Figure 1B – Graphical Display of January 2010 precipitation across Puerto Rico and the U.S. Virgin Islands derived from a combination of rain gage and radar data.

Monthly Weather Summary:

January 2010 began with a strong area of high pressure that brought southeasterly trade winds, record temperatures and limited shower activity across much of Puerto Rico and the U.S. Virgin Islands. These generally fair weather conditions prevailed until the second week of the month, when an old frontal boundary stalled along the northern periphery of the Puerto Rico and the northern U.S. Virgin Islands for several days. By the middle of the month, several precipitation records had been set across the San Juan Metro area as a result. New records were set on both January 13^th and 14^th at the Luis Muñoz Marin (LMM) International Airport in San Juan, when 2.56" and 3.51” of rain fell respectively (which together combined to make the wettest two day period ever recorded during the month of January). Not surprisingly, several flash flood warnings were issued during this event, with the San Juan Metro Area and the northeastern sections of Puerto Rico being the hardest hit areas.

Generally fair weather conditions then prevailed across the local islands for much of the remainder of the month, with more typical trade wind showers responsible for much more modest rainfall accumulations across Puerto Rico and the U.S. Virgin Islands. Also of note during January, hazy skies were noted from time to time across the local islands due to continued volcanic ash emissions from the Soufriere Hills Volcano on the island of Montserrat.

On average, 3.02" of rainfall accumulates at the LMM International Airport during the month January, making January the third driest month of the year. However January 2010 was far from dry, with a total of 11.07" of rain accumulating at LMM International Airport in San Juan. This was an incredible 8.05" above normal, easily breaking the previous January record for rainfall, which was 7.60”, set back in 1977. The 11.07” recorded in one month also represented the 23^rd wettest month on record in San Juan, well shy of the wettest month, December 1981, when 16.81” of rain fell at the LMM International Airport.

January 2010 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 2010 Observations:

High:

Low:

AvgT:

Pcpn:

San Juan

83.6ºF (+1.2ºF)

72.3ºF (+1.5ºF)

78.0ºF (+1.4ºF)

11.07” (+8.05”)

Saint Thomas

83.4ºF (-2.4ºF)

74.0ºF (+2.0ºF)

78.7ºF (-0.2ºF)

3.42” (+1.53”)

Saint Croix

84.5ºF (+0.2ºF)

71.9ºF (-0.2ºF)

78.2ºF (+0.0ºF)

1.77” (-0.39”)

January 2010 Extremes:

High:

Low:

San Juan

89ºF – January2^nd & 5^th

68ºF – January 29^th

Saint Thomas

86ºF – January30^th

71ºF – January 30^th

Saint Croix

86ºF – January 14^th

69ºF – January 2^nd & 3^rd

January Historical Statistics:

Highest January Temperatures on record:

San Juan

92ºF – January 16^th, 1983 &

January 11^th, 1982

91ºF – January 21^st, 1995*

*Most recent occurrence

Saint Thomas

93ºF – January 3^rd & 5^th, 1996

92ºF – January 13^th, 1996*

*Most recent occurrence

Saint Croix

92ºF – January 30^th, 1973

91ºF – January 14^th, 1973

91ºF – January 26^th, 1973*

*Most recent occurrence

Lowest January Temperatures on record:

San Juan

61ºF – January 31^st, 1962

62ºF – January 25^th, 1968*

*Most recent occurrence

Saint Thomas

63ºF – January 29^th, 1996

January 8^th, 1996

64ºF – January 20^th, 2000*

*Most recent occurrence

Saint Croix

61ºF – January 21^st, 2000*

*Most recent occurrence

Wettest Januarys:

San Juan

11.07” January 2010

7.60” January 1977

7.49” January 1969

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 Januarys:

San Juan

0.61” January 1978

0.69” January 1983

0.94” January 1960

Saint Thomas

0.76” January 2007

0.82” January 1991*

0.87” January 1976

*1 day missing data

Saint Croix

0.54” January 1977

0.60” January 2009

0.63” January 1960

2000-2010 Decade in Review:

January 2010 was significantly warmer in terms of temperature and significantly wetter than normal (as compared to the 30-year NCDC normals) across the San Juan Metro area. A comparison of how January 2010 stacks up compared to the previous 6 decades can be found in the table below. A comparison of January 2010 to the previous 10 Januaries in San Juan, Charlotte Amalie and Christiansted can be found in Figures 2-6.

Decadal Observations for San Juan, Puerto Rico:

Decadal January High Temperatures:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*83.6ºF*	*82.5ºF*	*83.6ºF*	*84.1ºF*	*83.0ºF*	*82.7ºF*	*81.8ºF*

Decadal January Low Temperatures:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*72.3ºF*	*71.2ºF*	*71.3ºF*	*70.7ºF*	*72.0ºF*	*69.3ºF*	*67.9ºF*

Decadal January Average Temperatures:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*78.0ºF*	*76.9ºF*	*77.4ºF*	*77.4ºF*	*77.5ºF*	*76.0ºF*	*74.8ºF*

Decadal January Precipitation:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*11.07”*	*3.90”*	*4.09”*	*2.34”*	*2.68”*	*3.05”*	*4.36”*

* Records for San Juan began on January 1^st, 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 - January 2000's precipitation deviations from normal

Figure 6 - January 2010 precipitation deviations for San Juan, Saint Thomas, and Saint Croix

Looking ahead toward the month of February:

February marks the middle of dry season across the local islands. February is the driest month of the year at Charlotte Amalie Airport on Saint Thomas and the second driest month at both the Christiansted Airport on Saint Croix and the Luis Muñoz Marin Airport in San Juan. Temperature wise, February tends to be one of the coolest months of the year across the local islands, with average temperatures generally in the mid to upper 70s.

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

71.9ºF

78.1ºF

1.94”

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

The sun rises at 6:58 am AST and sets at 6:18 pm AST, in San Juan, Puerto Rico on February 1^st. This represents a total of 11 hours and 20 minutes of daylight. By February 28^th, 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 in 26 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 1^st of the month. By the end of the month, the sun will rise at 6:39 am AST and set at 6:25 pm AST, representing a total increase in daylight of 25 minutes for the month.

For the month of February, a full moon will be observed on the 28^th of the month at 12:38 pm AST. There will also be a new moon on the 13^th of the month at 10:51 pm AST. The last quarter of the moon will be observed on the 5^th of February and the first quarter of the new moon will be observed on the 21^st 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.

National Weather Service Weather Forecast Office