August 2010 Climate Report

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

August 2010 Highlights:

Temperatures across Puerto Rico ranged from 55ºF in Adjuntas on the 3^rd of August to 97ºF in Gurabo on August 29^th. Temperatures across the U.S. Virgin Islands ranged from 69ºF, August 28^th at Beth Upper New Works on Saint Croix, to 94ºF, recorded at the Cyril E. King Airport on Saint Thomas August 24^th. Other notable temperatures for August 2010 are listed below:

Other Notable August 2010 High’s:	Other Notable August 2010 Low’s:

96ºF in Aguadilla on August 29^th	60ºF in Ponce on August 31^st
96ºF in Rio Piedras on August 23^rd	62ºF in Toro Negro on August 21^st
96ºF in Ponce on August 28^th	63ºF in Maricao on August 2^nd
95ºF in Juncos on August 29^th	65ºF in Aibonito on August 21^st
95ºF in Guayama on August 30^th	67ºF in Trujillo Alto on August 15^th
94ºF in San Juan, Trujillo Alto, Lajas,	68ºF in Rio Piedras, Lajas, Arecibo
Palmarejo and Corozal	and Corozal

^{*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 August was 4.26”, which fell in Toro Negro over the 24 hour period ending at 8am August 31^st. The highest weekly rainfall across Puerto Rico occurred in Paraiso, where 7.56” of rain accumulated the week ending August 13^th. Across the U.S. Virgin Islands, the highest 24-hour precipitation total fell at the Cyril E. King Airport on Saint Thomas, where a record 3.02” fell over the 24 hour period ending at midnight on August 30^th. For the week ending September 3^rd, 3.28” of rain fell at Beth Upper New Works on Saint Croix, representing the highest weekly rainfall across the U.S. Virgin Islands for the month.

Island wide rainfall from across Puerto Rico from January 2 - September 3, 2010.

Figure 1A – Island wide averaged precipitation (and normals) - by week - for the weeks beginning on January 2nd and ending on September 3rd, 2010

Estimated Rainfall for August 2010 using a combination of radar and rain gage data.

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

Monthly Weather Summary:

August 2010 began under the synoptic influence of an upper level low (TUTT) centered over Hispaniola. This feature enhanced shower and thunderstorm coverage across the local islands, especially across western sections of Puerto Rico the first few days of the month. On August 3^rd, an area of unsettled weather over the Atlantic waters was declared Tropical Storm Colin. This storm did not affect the local area as it moved west northwest and away from the region. Days after, a mid to upper level ridge established across the region, resulting in fair weather conditions across the local islands.

Tropical waves, upper level lows as well as low level troughs affected the forecast area during the second and third weeks of the month. As a result, several rounds of disturbed weather persisted across the area. The last week of the month was very active in terms of tropical cyclones. Hurricane Danielle did not have a direct impact across the local islands but brought enough deep moisture across the local islands allowing for active weather across the northern half of Puerto Rico. On August 29^th, a tropical storm warning and a hurricane watch were issued for Puerto Rico and the Virgin Islands due to the proximity of Hurricane Earl. This system tracked approximately 100 miles northeast of San Juan and left rainfall accumulations up to 5.98 inches in municipality of Naguabo.

Statistically, August 2010 was above normal in terms of both temperatures and precipitation. At the Luis Muñoz Marin International Airport in San Juan, the monthly precipitation total of 8.40” was 3.18” above normal. In terms of temperature, the average temperature was 1.8 degrees above normal in August, marking the 15^th consecutive month of above normal temperatures recorded in San Juan. The highest monthly temperature in San Juan reached 93 degrees on August 21^st, and the lowest temperature fell to 76 degrees on August 30^th.

August 2010 Statistics:

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

	San Juan	Saint Thomas	Saint Croix
High:	87.8ºF	90.8 ºF	89.7ºF
Low:	77.0ºF	77.7ºF	77.9ºF
AvgT:	82.4ºF	84.3ºF	83.8ºF
Pcpn:	5.22”	3.50”	3.81”

August 2010 Observations:

	San Juan	Saint Thomas	Saint Croix
High:	89.3ºF (+1.5ºF)	90.0ºF (-0.8ºF)	89.3ºF (-0.4ºF)
Low:	79.1ºF (+2.1ºF)	80.7ºF (+3.0ºF)	77.7ºF (-0.2ºF)
AvgT:	84.2ºF (+1.8ºF)	85.3ºF (+1.0ºF)	83.5ºF (-0.3ºF)
Pcpn:	8.40” (+3.82”)	5.49” (+1.99”)	3.43” (-0.38”)

August 2010 Extremes:

	San Juan	Saint Thomas	Saint Croix
High:	94ºF – August 5^th	94ºF – August 24^th	92ºF – August 24^th
Low:	76ºF – August 30^th	78ºF – August 30^th	73ºF – August 20^th & 21^st

August Historical Statistics:

Highest August Temperatures on record:

San Juan	Saint Thomas	Saint Croix
97ºF – August 21^st, 1980	99ºF – August 4^th, 1994 &	95ºF – August 25^th, 1999 &
96ºF – August 20^th, 1980 &	August 8^th, 1979	August 19^th, 1972
August 23^rd, 1974	98ºF – August 13^th, 1994*	94ºF – August 3^rd & 4^th, 1972
95ºF – August 26^th, 2009*	*Most recent occurrence	93ºF – August 8^th, 2009*
*Most recent occurrence		*Most recent occurrence

Lowest August Temperatures on record:

San Juan	Saint Thomas	Saint Croix
70ºF – August 24^th & 26^th, 1956	64ºF – August 1^st & 2^nd, 1972	63ºF – August 17^th, 1978
71ºF – August 23^rd, 2000*	67ºF – August 12^th, 1956	67ºF – August 31^st, 1979 &
*Most recent occurrence	70ºF – August 18^th, 1982*	August 16^th, 1978
	*Most recent occurrence	68ºF – August 2^nd, 1983*
		*Most recent occurrence

Wettest Augusts:

San Juan	Saint Thomas	Saint Croix
11.31” August 1988	8.54” August 1963	11.41” August 1979
9.52” August 2000	8.22” August 2005	11.04” August 1989
9.38” August 1979	6.71” August 1955

Driest Augusts:

San Juan	Saint Thomas	Saint Croix
1.83” August 1984	0.70” August 1993	1.35” August 2005
1.93” August 1982	0.98” August 1991	1.40” August 1980
1.94” August 1991	1.26” August 2002	1.51” August 2009

2000-2010 Decade in Review:

August 2010 marked the 15^th consecutive month of above normal temperatures in San Juan. Thanks to a recent study on El Niño and the Southern Oscillation, it was noted that this string on abnormally warm temperatures was likely influenced by a strong El Niño which persisted across the tropical Pacific through April 2010. Additionally, with a La Niña advisory now in effect, it is thought that this string of abnormally warm temperatures could come to an end in the upcoming months.

Thanks to record rainfall associated with Hurricane Earl as it passed to the northeast of the local islands from August 30^th – 31^st, August 2010 was another abnormally wet month across the local islands. By the end of the month, 157% and 161% of the normal monthly precipitation accumulated at Charlotte Amalie on Saint Thomas and in San Juan respectively. Additionally, as of September 1^st, 2010, this year continues to be on track to be the wettest year on record in San Juan, with the latest cooperative weather data indicating the island had received 138% of its normal precipitation through the 1^stof the month.

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. Additionally, a summary of the August 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 August High Temperatures:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*89.3ºF*	*89.0ºF*	*89.4ºF*	*89.9ºF*	*88.3ºF*	*87.8ºF*	*88.1ºF*

Decadal August Low Temperatures:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*79.1ºF*	*77.6ºF*	*77.3ºF*	*77.0ºF*	*77.3ºF*	*75.6ºF*	*74.1ºF*

Decadal August Average Temperatures:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*84.2ºF*	*83.3ºF*	*83.3ºF*	*83.4ºF*	*82.8ºF*	*81.6ºF*	*81.1ºF*

Decadal August Precipitation:

2010	2000’s	1990’s	1980’s	1970’s	1960’s	1950’s
*8.40”*	*5.92”*	*4.83”*	*5.08”*	*5.27”*	*6.13”*	*6.45”*

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

Temperatures since 2000 for the month of August in San Juan, PR.

Figure 2 - Temperature deviations for San Juan, PR

Temperatures since 2000 for the month of August on Saint Thomas, USVI.

Figure 3 - Temperature deviations for Saint Thomas, VI

Temperatures since the year 2000 for the month of August on Saint Croix, USVI

Figure 4 - Temperature deviations for Saint Croix, VI

August precipitation since the year 2000 for San Juan, PR, Saint Thomas, USVI and Saint Croix, USVI.

Figure 5 - August 2000's precipitation deviations from normal

2010 Year to Date Precipitation Deviations from normal for San Juan, PR, Saint Thomas, USVI and Saint Croix, USVI.

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

Looking ahead toward the month of September:

Looking ahead, September marks the peak of hurricane season across Puerto Rico and the U.S. Virgin Islands. Additionally, September is the 2^nd wettest month on average in San Juan, with the Luis Muñoz International Airport receiving 5.60” of rainfall. (A record 15.15” of rain fell in September 1996 and the driest September on record was September 1987, when only 1.73” of rainfall was recorded in San Juan). The mean temperature at the Luis Muñoz International Airport in San Juan for September is 82.2ºF, which is tied with July for the 2^nd warmest month of the year (August is the warmest month on average, with a average temperature of 82.4ºF. The August 2010 outlook for the remainder of the 2010 Atlantic hurricane season indicates a 100% chance of a normal or above normal hurricane season. This outlook is based on strengthening La Niña conditions and multi-decadal conditions. The latest official discussion from the climate prediction center regarding the current hurricane season outlook can be viewed at: http://www.cpc.noaa.gov/products/outlooks/hurricane.shtml

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

	San Juan	Saint Thomas	Saint Croix
High:	87.8ºF	90.2ºF	89.2ºF
Low:	76.5ºF	76.9ºF	76.8ºF
AvgT:	82.2ºF	83.6ºF	83.0ºF
Pcpn:	5.60”	5.34”	5.36”

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

The sun rises at 6:10 am AST and sets at 6:39 pm AST, in San Juan, Puerto Rico on September 1^st. This represents a total of 12 hours and 29 minutes of daylight. By September 30^th, the sun will rise at 6:15 am AST and set at 6:14 pm AST, providing a total of 11 hours and 59 minutes of daylight, or a total decrease in 30 minutes over the course of the month. The transition from summer to fall begins on September 23^rd, which marks the first full day of autumn.

At Charlotte Amalie on Saint Thomas, the sun will rise at 6:05 am AST and set at 6:34 pm AST on the 1^st of the month. By the end of the month, the sun will rise at 6:10 am AST and set at 6:09 pm AST, representing a total decrease in daylight of 30 minutes over the course of the month.

For the month of September, a full moon will be observed on the 23^rd of the month. There will also be a new moon on the 8^th of the month. The last quarter of the moon was observed on the 1^st and the first quarter of the new moon will be observed on the 15^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.

Click here to return to the local data/records section of the NWS San Juan climate page

National Weather Service Weather Forecast Office