October 2009 Climate Report

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

October 2009 Highlights:

Temperatures across Puerto Rico ranged from 54ºF in Adjuntas on the 31^st of October, to 95ºF, observed in both Aguadilla and Ponce, on the 6^th and 30^th of the month respectively. Temperatures across the U.S. Virgin Islands ranged from 65ºF, at Beth Upper New Works on Saint Croix on October 26^th, to 92ºF, at the Charlotte Amalie Airport on Saint Thomas on the 7^th of the month. Other notable temperatures for October 2009 are listed below:

Other Notable October 2009 High Temps:

94ºF in Lajas on October 9^th

94ºF in Magueyes on October 20^th

94ºF at Dos Bocas on October 4^th

94ºF in Corozal on October 25^th

93ºF in Guayama, Mayaguez, Gurabo, San Juan and Trujillo Alto

Other Notable October 2009 Low Temps:

61ºF in Cerro Maravilla on October 30^th

61ºF in Ponce on October 11^th

62ºF in Toro Negro on October 22^nd

64ºF in Aibonito on October 22^nd

64ºF in Maricao on October 22^nd

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

The highest 24-hour precipitation total for the month of October was 3.60”, which fell in Morovis on the 11^th of the month. The highest weekly rainfall total occurred at Cerro Maravilla, where 8.56” of rainfall accumulated the week ending October 16^th. While an additional 2.57” of rainfall accumulated on Saint Croix during the month of October, this was well below the normal 5.22” normally received during the month, leaving the first 10 months of the year at 52% of normal, which remains the driest start to a year on record for Saint Croix.

Figure 1A – Island wide precipitation forJanuary-October2009

Figure 1B – Graphical Display of October2009 precipitation across Puerto Rico and the U.S. Virgin Islands derived from a combination of rain gage and radar data.

Monthly Weather Summary:

Moisture associated with the remnants of the Tropical Storm Henri aided the development of numerous showers and isolated thunderstorms across the interior and southwestern sections of Puerto Rico during the first week of October. While the remainder of the month was relatively quiet weather wise, several tropical waves did cross the local islands during October. These tropical waves bought brief surges of moisture; however, rainfall accumulations for October 2009 were mainly influenced by typical mesoscale-driven nocturnal/diurnal showers. Due to the lack of significant widespread weather events, by the end of the month, rainfall totals across San Juan, Saint Thomas and Saint Croix all ended up well below normal, however due to widespread locally driven shower activity across the interior and western sections of Puerto Rico, an average of 96% of the normal precipitation was received island wide.

Due to the mainly locally driven weather pattern observed during October 2009, several flash flood warnings and flood advisories were issued across the north central, northwestern and western interior sections of the island, where the most persistent heavy rain fell. Hazy skies were noted over some areas, mostly associated with dust coming from the Saharan regions of Africa; however some of this haze was partly due to emissions from the Soufriere Hills Volcano on Montserrat. On October 23^rd a huge smoke plume was reported during CAPECO/Gulf refinery explosion. This situation created very unhealthful conditions, especially during the night time, when the pollutants were trapped under the nocturnal inversion along the north coast of the island. Terminal Doppler weather radar imagery showed that this smoke plume extended as far west as Manati.

October 2009 is one of the warmest Octobers on record, averaging 2.8 degrees above normal in San Juan. At Luis Muñoz Marin International Airport, a low temperature of 80 degrees or warmer was recorded a record 11 times. Details on the abnormal temperatures can be found at http://www.srh.noaa.gov/sju/?n=record110109. The highest temperature at the Luis Muñoz International Airport was 93 degrees on October 23^rd and the minimum temperature fell to 76 degrees on October 18^th. October ended with a weak frontal boundary across our regional waters and associated strong low pressure system to our north, which produced large long period north northeast swells and large breaking waves along the northern coasts of the local islands.

October 2009 Statistics:

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

High:

Low:

AvgT:

Pcpn:

San Juan

87.5ºF

75.6ºF

81.6ºF

5.06”

Saint Thomas

89.5ºF

76.2ºF

82.9ºF

5.57”

Saint Croix

88.5ºF

75.9ºF

82.2ºF

5.22”

October 2009 Observations:

High:

Low:

AvgT:

Pcpn:

San Juan

89.9ºF (+2.4ºF)

79.0ºF (+3.4ºF)

84.4ºF (+2.8ºF)

3.62” (-1.44”)

Saint Thomas

88.5ºF (-1.0ºF)

79.0ºF (+2.8ºF)

83.8ºF (+0.9ºF)

2.27” (-3.30”)

Saint Croix

88.9ºF (+0.4ºF)

76.9ºF (+1.0ºF)

82.9ºF (+0.7ºF)

2.57” (-2.65”)

October 2009 Extremes:

High:

Low:

San Juan

93ºF – October 23^rd

76ºF – October 18^th

Saint Thomas

92ºF – October 7^th

77ºF – October 14^th & October 22^nd

Saint Croix

91ºF – October 4^th & 6^th

72ºF – October 21^st & October 22^nd

October Historical Statistics:

Highest October Temperatures on record:

San Juan

98ºF – October 9^th, 1981

97ºF – October 13^th, 1987*

*Most recent occurrence

Saint Thomas

97ºF – October 14^th, 1994*

*Most recent occurrence

Saint Croix

99ºF – October 1^st, 1972

97ºF – October 11^th, 1995

95ºF – October 4^th, 1972

Lowest October Temperatures on record:

San Juan

67ºF – October 20^th, 1959

68ºF – October 30^th, 2001*

*Most recent occurrence

Saint Thomas

66ºF – October 27^th-29^th, 2007

68ºF – October 15^th, 1954

69ºF – October 10^th, 1956*

*Most recent occurrence

Saint Croix

65ºF – October 23^rd, 1983*

*Most recent occurrence

Wettest Octobers:

San Juan

15.06” October 1970

11.94” October 2005

11.25” October 2006

Saint Thomas

12.49” October 2005

12.45” October 1974

12.39” October 1954

Saint Croix

16.20” October 1977

12.95” October 1990

11.79” October 1954

Driest Octobers:

San Juan

1.17” October 1979

1.63” October 1963

1.74” October 1992

Saint Thomas

1.77” October 1953

2.00” October 1988

2.21” October 1979

Saint Croix

1.05” October 1964

1.10” October 2002

1.23” October 1960

2000-2009 Decade in Review:

Decadal Observations for San Juan, Puerto Rico:

Decadal October High Temperatures:

2000’s		1990’s		1980’s		1970’s		1960’s		1950’s*
*88.2ºF*		*88.6ºF*		*89.2ºF*		*88.3ºF*		*87.5ºF*		*87.4ºF*

Decadal October Low Temperatures:

2000’s		1990’s		1980’s		1970’s		1960’s		1950’s*
*76.4ºF*		*76.1ºF*		*75.5ºF*		*76.4ºF*		*74.2ºF*		*72.6ºF*

Decadal October Average Temperatures:

2000’s		1990’s		1980’s		1970’s		1960’s		1950’s*
*82.3ºF*		*82.4ºF*		*82.4ºF*		*82.4ºF*		*80.8ºF*		*81.0ºF*

Decadal October Precipitation:

2000’s		1990’s		1980’s		1970’s		1960’s		1950’s*
*6.20”*		*4.48”*		*5.58”*		*6.29”*		*4.85”*		*7.16”*

* 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 - October precipitation deviations 2000's

Figure 6 - Year-to-Date precipitation deviations for San Juan, Saint Thomas, and Saint Croix

Looking ahead toward the month of November:

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

High:

Low:

AvgT:

Pcpn:

San Juan

85.1ºF

74.0ºF

79.6ºF

6.17”

Saint Thomas

87.8ºF

74.9ºF

81.4ºF

5.28”

Saint Croix

87.0ºF

74.3ºF

80.7ºF

5.55”

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

The sun rises at 6:24 am AST on the 1^st of November and sets at 5:52 pm AST, in San Juan, Puerto Rico. This represents a total of 11 hours and 28 minutes of daylight. By November 30^th, the sun will rise at 6:40 am AST and set at 5:47 pm AST, providing a total of 11 hours and 07 minutes of daylight, or a total decrease of 21 minutes over the course of the month. At Charlotte Amalie on Saint Thomas, the sun will rise at 6:19 am AST and set at 5:47 pm AST on the 1^st of the month. By the end of the month, the sun will rise at 6:35 am AST and set at 5:42 pm AST, also representing a total decrease in daylight of 21 minutes for the month.

For the month of November, a full moon will be observed on the 2^nd of the month at 3:14 pm AST. There will also be a new moon on the 16^th of the month at 3:14 pm AST. The first quarter of the moon was observed on the 25^th of October and the last quarter of the moon will be observed on the 9^th of November.

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