May 2010 Climate Report

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

May 2010 Highlights:

Temperatures across Puerto Rico ranged from 54ºF in Adjuntas on the 7^th of May to 97ºF in Gurabo on May 1^st. Temperatures across the U.S. Virgin Islands ranged from 72ºF, May 6^th at Christiansted Airport on Saint Croix, to 90ºF, recorded at both the Cyril E. King Airport on Saint Thomas and Fort Christiansted on Saint Croix. Other notable temperatures for May 2010 are listed below:

Other Notable May 2010 High’s:

94ºF in Lajas on May 26^th

94ºF in Ponce on May 17^th

93ºF in Juncos on May 1^st

93ºF in Aguadilla on May 17^th

92ºF at Trujillo Alto, Guayama, Dos Bocas and Corozal on various days of the month.

Other Notable May 2010 Low’s:

58ºF in Coloso on May 6^th

61ºF in Toro Negro on May 4^th

62ºF in Maricao on May 7^th

63ºF in Aibonito on May 5^th

63ºF in Ponce on May 6^th

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

The highest 24-hour precipitation total across Puerto Rico for the month of May was 8.00”, which fell at Toro Negro over the 24 hour period ending at 8am May 29^th. The highest weekly rainfall across Puerto Rico occurred at the Maricao Fish Hatchery, where 9.50” of rain accumulated the week ending May 14^th. Across the U.S. Virgin Islands, the highest 24-hour precipitation total was at Coral Bay on Saint John, where 2.72” fell over the 24 hour period ending at 8am on May 8^th. For the week ending May 14^th, 4.40” of rain fell at Coral Bay on Saint John, representing the highest weekly rainfall across the U.S. Virgin Islands for the month of May.

Island wide averaged rainfall through May 28, 2010 for Puerto Rico

Figure 1A – Island wide averaged precipitation (and normals) - by week - for the weeks beginning on January 2nd and ending on May 28, 2010

San Juan Estimated rainfall from AHIPS for the month of May 2010

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

Monthly Weather Summary:

May 2010 began with an area of surface high pressure extending across the eastern Caribbean. This area of surface high pressure slowly shifted eastward into the central Atlantic during the first week of the month, resulting in locally breezy winds across Puerto Rico and the U.S. Virgin Islands. Days after, a series of troughs brought additional moisture and instability across the local region, producing shower and thunderstorm activity, mainly activity across the northern and western sections of Puerto Rico. Towards the middle of the month, deep moisture from the tropics spread northward and prevailed across the local islands for the last two weeks of May. This deep moisture, combined with favorable atmospheric conditions, local effects and a low level trough to the north of Puerto Rico, brought widespread flooding rains across Puerto Rico and the U.S. Virgin Islands the last few days of the month.

Not surprisingly, May 2010 was well above normal in terms of precipitation, with the San Juan area averaging 7.23 inches of rainfall above normal. This surplus in rainfall made May 2010 the 4^th wettest May on record. In fact, May 2010 was also the 9^th wettest month on record since 1956, with the total accumulated precipitation of 31.21" through the end of May representing the wettest start to a year on record. In addition May 2010 finished 1.5 degrees warmer than average, making it the 12^th consecutive month at the Luis Muñoz Marin International Airport in San Juan where the average temperature was above normal.

May 2010 Statistics:

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

High:

Low:

AvgT:

Pcpn:

San Juan

86.3ºF

74.9ºF

80.6ºF

5.29”

Saint Thomas

87.9ºF

75.9ºF

81.9ºF

3.36”

Saint Croix

87.5ºF

75.9ºF

81.7ºF

3.62”

May 2010 Observations:

High:

Low:

AvgT:

Pcpn:

San Juan

87.3ºF (+1.0ºF)

76.9ºF (+2.0ºF)

82.1ºF (+1.5ºF)

12.52” (+7.23”)

Saint Thomas

87.2ºF (-0.7ºF)

78.4ºF (+2.5ºF)

82.8ºF (+0.9ºF)

5.21” (+1.85”)

Saint Croix

87.5ºF (+0.0ºF)

76.9ºF (+1.0ºF)

82.2ºF (+0.5ºF)

6.00” (+2.38”)

May 2010 Extremes:

High:

Low:

San Juan

91ºF – May25^th & 26^th

73ºF – May 2^nd

Saint Thomas

90ºF – May14^th

75ºF – May 2^nd & 5^th

Saint Croix

89ºF – May 13^th & 14^th

72ºF – May 6^th

May Historical Statistics:

Highest May Temperatures on record:

San Juan

96ºF – May 5^th & 11^th, 1980

95ºF – May 21^st, 2005*

*Most recent occurrence

Saint Thomas

97ºF – May 23^rd, 1996*

*Most recent occurrence

Saint Croix

94ºF – May 28^th, 1972

93ºF – May 25^th, 1994*

*Most recent occurrence

Lowest May Temperatures on record:

San Juan

66ºF – May 5^th, 1962

67ºF – May 6^th, 1962 & May 18^th, 1957

68ºF – May 2^nd, 1963*

*Most recent occurrence

Saint Thomas

66ºF – May 5^th, 1974

68ºF – May11^th, 1986*

*Most recent occurrence

Saint Croix

63ºF – May 4^th, 1992

64ºF – May 15^th, 1975 & May 15^th, 1972

65ºF – May 8^th, 1982*

*Most recent occurrence

Wettest Mays:

San Juan

14.99” May 1965

13.59” May 1958

12.80” May 1986

Saint Thomas

16.39” May 1960

9.98” May 1979

9.80” May 198

Saint Croix

14.03” May 1981

11.38” May 2001

8.89” May 1987

Driest Mays:

San Juan

0.44” May 1972

0.48” May 1973

1.04” May 1975

Saint Thomas

0.06” May 2008

0.28” May 2007

0.47” May 1973

Saint Croix

0.22” May 1974

0.28” May 2005

0.37” May 2003

2000-2010 Decade in Review:

May 2010 marked the 12^th consecutive month of above normal temperatures in San Juan. May 2010 was also the 4th wettest May on record in San Juan and ranked among the top 10 wettest at both the Cyril E. King Airport on Saint Thomas and the Christiansted Airport on Saint Croix. In fact, 2010 has generally been a very wet year to date across Puerto Rico, so far ranking as the wettest start to a year since record keeping began in San Juan. For a look at temperature and precipitation deviations for San Juan, Saint Thomas and Saint Croix from their NCDC averages, see Figures 2 to 6 below.

Decadal Observations for San Juan, Puerto Rico:

Decadal May High Temperatures:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*87.3ºF*	*87.4ºF*	*87.8ºF*	*88.2ºF*	*87.4ºF*	*86.0ºF*	*85.4ºF*

Decadal May Low Temperatures:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*76.9ºF*	*75.6ºF*	*75.4ºF*	*75.0ºF*	*75.0ºF*	*73.2ºF*	*71.9ºF*

Decadal May Average Temperatures:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*82.1ºF*	*81.5ºF*	*81.6ºF*	*81.6ºF*	*81.2ºF*	*79.6ºF*	*78.6ºF*

Decadal May Precipitation:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*12.52”*	*5.02”*	*4.35”*	*7.59”*	*4.25”*	*6.41”*	*8.13”*

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

Temperature deviations for the month of May since 2000 for San Juan

Figure 2 - Temperature deviations for San Juan, PR

Temperature deviations for the month of May since 2000 on Saint Thomas

Figure 3 - Temperature deviations for Saint Thomas, VI

Temperature deviation for the month of May since 2000 for Saint Croix

Figure 4 - Temperature deviations for Saint Croix, VI

Precipitation Deviations for the month of May since 2000 for Puerto Rico and the USVI

Figure 5 - May 2000's precipitation deviations from normal

Year to date plot of percent of normal precipitation received across Puerto Rico and the USVI

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

Looking ahead toward the month of June:

Looking ahead, June is the 5th driest month across Puerto Rico, with the Luis Muñoz International Airport in San Juan receiving 3.52” of rainfall on average. A record 10.96” of rain fell in June 1965 and the driest June on record was June 1985, when only 0.29” of rainfall was recorded in San Juan. The average temperature at the Luis Muñoz International Airport in San Juan for June is 82.1ºF, making June the 4^th warmest month of the year. Presently, we are experiencing ENSO-neutral conditions with a La Niña Watch now in effect.

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf

This transition has an impact on expectations for the hurricane season, with NOAA currently forecasting a 95% of a near or above normally active hurricane season.

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

High:

Low:

AvgT:

Pcpn:

San Juan

87.6ºF

76.6ºF

82.1ºF

3.52”

Saint Thomas

89.5ºF

77.4ºF

83.5ºF

2.35”

Saint Croix

88.6ºF

78.1ºF

83.4ºF

2.30”

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

The sun rises at 5:47 am AST and sets at 6:57 pm AST, in San Juan, Puerto Rico on June 1^st. This represents a total of 13 hours and 10 minutes of daylight. By June 30^th, the sun will rise at 5:51 am AST and set at 7:05 pm AST, providing a total of 13 hours and 14 minutes of daylight, or a total increase in 4 minutes over the course of the month. The summer solstice, or the longest day of the year in the Northern Hemisphere, will be celebrated on June 21^st, with a total of 13 hours and 15 minutes of daylight in San Juan.

At Charlotte Amalie on Saint Thomas, the sun will rise at 5:43 am AST and set at 6:52 pm AST on the 1^st of the month. By the end of the month, the sun will rise at 5:47 am AST and set at 7:00 pm AST, representing a total increase in daylight of 4 minutes over the course of the month.

For the month of June, a full moon will be observed on the 26^th of the month at 7:30 am AST. There will also be a new moon on the 12^th of the month at 7:15 am AST. The last quarter of the moon will be observed on the 4^th of June and the first quarter of the new moon will be observed on the 19^th 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