July 2010 Climate Report

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

July 2010 Highlights:

Temperatures across Puerto Rico ranged from 55ºF in Adjuntas on the 7^th of July to 99ºF in Corozal on July 9^th. Temperatures across the U.S. Virgin Islands ranged from 61ºF, July 19^th at Beth Upper New Works on Saint Croix, to 93ºF, recorded July 14^that the Cyril E. King Airport on Saint Thomas. Other notable temperatures for July 2010 are listed below:

Other Notable July 2010 High’s:

98ºF in Ponce on July 25^th

95ºF in Gurbao on July 12^th

95ºF in Aguadilla on July 17^th

94ºF at Dos Bocas on July 11^th

94ºF in Rio Piedras on July 12^th

93ºF in Lajas, Guayama, Palmarejo,

San Juan and Juncos.

Other Notable July 2010 Low’s:

63ºF in Aibonito on July 23^rd

63ºF in Toro Negro on July 19^th

63ºF in Maricao on July 23^rd

64ºF in Cerro Maravilla on July 12^th

66ºF in Ponce on July7^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 July was 5.40”, which fell in Ensenada over the 24 hour period ending at 8 am July 21^st. The highest weekly rainfall across Puerto Rico occurred in San Lorenzo for the second month in a row, where 10.07” of rain accumulated the week ending July 23^rd. Across the U.S. Virgin Islands, the highest 24-hour precipitation total fell at East End on Saint John, where a record 4.55” fell over the 24 hour period ending at 8 am on July 20^th. For the week ending July 23^rd, 10.58” of rain fell at Coral Bay on Saint John, representing the highest weekly rainfall across the U.S. Virgin Islands for the month of July.

Graphical display of precipitation across Puerto Rico from January 2nd, 2010 through July 30th, 2010

Figure 1A – Island wide averaged precipitation (and normals) - by week - for the weeks beginning on January 2nd and ending on July 30th, 2010

July 2010 Rainfall composite using Radar and Rain Gage Data

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

Monthly Weather Summary:

July 2010 began with showers and isolated thunderstorms across several sectors of Puerto Rico as the result of an upper level low inducing low level troughiness across the region. Widespread rainfall amounts around 2 inches accompanied this event. Days after, much drier weather returned to the region, with only passing trade wind showers observed across eastern sections of Puerto Rico and the U.S. Virgin Islands each morning, with scattered afternoon showers and thunderstorms observed across western Puerto Rico each afternoon. By mid July, several tropical waves had reached the local area. A broad area of disturbed weather associated with the strongest tropical wave brought a very moist and unstable air mass across the local islands around the 20^th of the month, resulting in widespread showers and areas of flooding across portions of the forecast area. By the end of the month, the widespread heavy rains ended, and once again, shower and thunderstorm activity shifted to a more typical pattern, with areas of locally induced activity.

Statistically, July 2010 was well above normal, in terms of precipitation. At the Luis Muñoz Marin International Airport in San Juan, the monthly precipitation total was 8.52”, was 4.36” above normal. Across the U.S. Virgin Islands, precipitation was also well above normal, with the wettest July on record recorded at the Cyril E. King Airport on Saint Thomas. In terms of temperature, 2010 has been an unusually warm year across the northeastern Caribbean. The highest monthly temperature in San Juan was 93 degrees on both July 7^thand 10^th, and the low temperature fell to 73 degrees on July 23^th. At the end of the month, the average temperature was 0.8 degrees above normal, which marked the 14^th consecutive month of above normal temperatures recorded in San Juan.

July 2010 Statistics:

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

High:

Low:

AvgT:

Pcpn:

San Juan

87.4ºF

76.9ºF

82.2ºF

4.16”

Saint Thomas

90.4 ºF

77.8ºF

84.1ºF

2.42”

Saint Croix

89.3ºF

78.0ºF

83.7ºF

2.79”

July 2010 Observations:

High:

Low:

AvgT:

Pcpn:

San Juan

88.2ºF (+0.8ºF)

77.9ºF (+1.0ºF)

83.0ºF (+0.8ºF)

8.52” (+4.36”)

Saint Thomas

89.2ºF (-1.2ºF)

80.0ºF (+2.2ºF)

84.6ºF (+0.5ºF)

7.45” (+5.03”)

Saint Croix

88.9ºF (-0.4ºF)

78.7ºF (+0.7ºF)

83.8ºF (+0.1ºF)

5.48” (+2.38”)

July 2010 Extremes:

High:

Low:

San Juan

93ºF – July7^th & 10^th

73ºF – July 23^rd

Saint Thomas

93ºF – July14^th

72ºF – July 21^st

Saint Croix

92ºF – July 11^th

75ºF – July 21^st & 22^nd

July Historical Statistics:

Highest July Temperatures on record:

San Juan

95ºF – July 10^th, 1981

94ºF – July 8^th, 1995*

*Most recent occurrence

Saint Thomas

98ºF – July 27^th, 1994

97ºF – July 24^th, 1994*

*Most recent occurrence

Saint Croix

94ºF – July 8^th & 20^th, 1972

93ºF – July 10^th, 2007*

*Most recent occurrence

Lowest July Temperatures on record:

San Juan

69ºF – July 1^st, 1959

70ºF – July 8^th, 1961*

*Most recent occurrence

Saint Thomas

70ºF – July 28^th, 1994*

*Most recent occurrence

Saint Croix

67ºF – July 19^th, 1979

68ºF – July 22^nd, 1992 &

July 19^th, 1960

Wettest Julys:

San Juan

9.35” July 1961

8.92” July 2006

8.52” July 2010

Saint Thomas

7.45” July 2010

7.41” July 1958

5.74” July 2005

Saint Croix

7.62” July 1958

6.91” July 1964

6.17” July 1960

Driest Julys:

San Juan

1.12” July 1974

1.69” July 1971

1.75” July 2008

Saint Thomas

0.03” July 2007

0.24” July 1956

0.74” July 1994

Saint Croix

0.49” July 1976

0.95” July 2009

1.09” July 2002

2000-2010 Decade in Review:

July 2010 marked the 14^th consecutive month of above normal temperatures in San Juan. July 2010 was also the 3rd wettest July on record in San Juan and ranked as the wettest July on record at Cyril E. King Airport on Saint Thomas and the seventh wettest July at the Christiansted Airport on Saint Croix. In fact, 2010 has generally been a very wet year to date across Puerto Rico and the Northeastern Caribbean, 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. A summary of July 2010 data for San Juan along with the previous 6 decades of data from San Juan has also been included below.

Decadal Observations for San Juan, Puerto Rico:

Decadal July High Temperatures:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*88.2ºF*	*88.8ºF*	*88.6ºF*	*89.6ºF*	*88.5ºF*	*87.3ºF*	*87.3ºF*

Decadal July Low Temperatures:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*77.9ºF*	*77.4ºF*	*76.7ºF*	*77.2ºF*	*77.4ºF*	*75.5ºF*	*74.0ºF*

Decadal July Average Temperatures:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*83.0ºF*	*83.1ºF*	*82.7ºF*	*83.4ºF*	*83.0ºF*	*81.4ºF*	*80.7ºF*

Decadal July Precipitation:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*8.52”*	*5.29”*	*5.47”*	*3.84”*	*3.16”*	*6.05”*	*5.22”*

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

San Juan Temperature deviations for the month of July since 2000

Figure 2 - Temperature deviations for San Juan, PR

Saint Thomas USVI temperature deviations for the month of July since 2000

Figure 3 - Temperature deviations for Saint Thomas, VI

Saint Croix USVI temperature deviations for the month of July since 2000

Figure 4 - Temperature deviations for Saint Croix, VI

Precipitation deviations for the USVI and San Juan, PR for the month of July since 2000

Figure 5 - July 2000's precipitation deviations from normal

Year to date percent of normal precipitation for San Juan, PR and the USVI

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

Looking ahead toward the month of August:

Looking ahead, August is the 4th wettest month across Puerto Rico, with the Luis Muñoz International Airport in San Juan receiving 5.22” of rainfall on average, 1.06” more than the month of July. A record 11.31” of rain fell in August 1988 and the driest August on record came in August 1994, when just 1.83” of rainfall was recorded in San Juan. The average high temperature at the Luis Muñoz International Airport in San Juan for August is 82.4ºF, making August statistically the warmest month of the year. The updated outlook for the remainder of the 2010 Atlantic hurricane season indicates a 100% chance of a normal or above normal hurricane season based partly on the La Niña Advisory that was issued on August 5^th. The official ENSO discussion can be viewed at:

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

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

High:

Low:

AvgT:

Pcpn:

San Juan

87.8ºF

77.0ºF

82.4ºF

5.22”

Saint Thomas

90.8ºF

77.7ºF

84.3ºF

3.50”

Saint Croix

89.7ºF

77.9ºF

83.8ºF

3.81”

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

The sun rises at 6:02 am AST and sets at 6:59 pm AST, in San Juan, Puerto Rico on August 1^st. This represents a total of 12 hours and 57 minutes of daylight. By August 31^st, the sun will rise at 6:10 am AST and set at 6:40 pm AST, providing a total of 12 hours and 30 minutes of daylight, or a total decrease in 27 minutes over the course of the month.

At Charlotte Amalie on Saint Thomas, the sun will rise at 5:58 am AST and set at 6:54 pm AST on the 1^st of the month. By the end of the month, the sun will rise at 6:05 am AST and set at 6:35 pm AST, representing a total decrease in daylight of 26 minutes over the course of the month.

For the month of August, a full moon will be observed on the 24^th of the month at 3:05 pm AST. There will also be a new moon on the 9^th of the month at 11:08 pm AST. The last quarter of the moon will be observed on the 3^rd of August and the first quarter of the new moon will be observed on the 16^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