Global ocean temperatures at record highs for 3rd consecutive month

For the third consecutive month, global Sea Surface Temperatures (SSTs) were the warmest on record, according to statistics released yesterday by the National Climatic Data Center. August SSTs were 0.57°C (1.03°F) above the 20th century average, breaking the previous August record set in 1998. The record August SSTs were due in part to the continuation of El Niño conditions in the Eastern Pacific, which have substantially warmed a large stretch of the tropical Eastern Pacific Ocean. El Niño conditions are expected to amplify during the coming months, and record or near-record global ocean temperatures will probably continue.

August global surface temperatures 2nd to 6th warmest on record
The globe recorded its second warmest August since record keeping began in 1880, according to NOAA's National Climatic Data Center. NOAA rated the period June - August (summer in the Northern Hemisphere, winter in the Southern Hemisphere) as the third warmest on record, and the year-to-date period, January - August 2009, as the fifth warmest such period on record. NASA's Goddard Institute for Space Studies rated August 2009 as the 6th warmest August on record, and the period June-July-August as the 2nd warmest on record. The August satellite-measured temperatures for the lowest five miles of the atmosphere were between 7th and 9th warmest on record, according to the University of Alabama in Huntsville and Remote Sensing Systems.

Warmest August on record in Australia and New Zealand
Australia had its warmest August on record in 2009, according to the Australian Bureau of Meteorology. Temperatures averaged a remarkable 3.2°C (5.8°F) above average, making August 2009 the most anomalous month ever recorded in Australia. The previous record was set in April 2005, which was 3.1°C (5.6°C) above average. The month's highest temperature, 39.7°C (103°F) at Wyndham Airport on the 31st, fell only 0.3°C short of the Australian record for August. The Australian winter (June-July-August) was the 2nd warmest on record, next to the winter of 1996. New Zealand also experienced its warmest August on record (records go back 155 years).

A cool August and cool summer for the U.S.
For the contiguous U.S., the average August temperature was 0.6°F below average, making it the 30th coolest August in the 115-year record, according to the National Climatic Data Center. The U.S. as a whole was below normal for the summer period (June - August). A recurring upper level trough held the June - August temperatures down in the central states, where Michigan experienced its fifth coolest summer, Wisconsin, Minnesota, and South Dakota their seventh coolest each, Nebraska its eighth, and Iowa its ninth. In contrast, the temperatures in Florida averaged out to be fourth warmest, while Washington and Texas experienced their eighth and ninth warmest summers, respectively.

U.S. precipitation in August was below average, as the month ranked 28th driest in the 115-year record. Arizona had its fourth driest August, New Mexico its fifth, and it was the eighth driest August for Colorado, Utah and Texas. Arizona observed its third driest summer, while both South Carolina and Georgia had their sixth driest. It was the 8th wettest summer on record in the Northeast.

At the end of August, 13% of the contiguous United States was in moderate-to-exceptional drought. This is a drop from the 19% figure observed at the beginning of the year. These extreme drought regions were exclusively in South to Central Texas. However, significant drought relief occurred in this region the second week of September, when a large area of tropical moisture settled in over the region, bringing heavy rains. About 19 percent of the contiguous U.S. fell in the severely to extremely wet categories in August.

Weak El Niño conditions continue
El Niño conditions continue over the tropical Eastern Pacific. Ocean temperatures in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region", were 0.4°C above the threshold for a weak El Niño, according to the Australian Bureau of Meteorology. NOAA's Climate Prediction Center is maintaining an El Niño Advisory. Current conditions and model forecasts favor the continued development of a weak-to-moderate strength El Niño into the Northern Hemisphere Fall 2009, with the likelihood of at least a moderate strength El Niño (3-month Niño-3.4 SST index of +1.0°C or greater) during the Northern Hemisphere Winter 2009-10.

Sea ice extent in the Arctic 3rd lowest on record
August 2009 Northern Hemisphere sea ice extent was the 3rd lowest since 1979, according to the National Snow and Ice Data Center, behind 2006 and 2007. Sea ice extent has increased slightly over the past week, and we have probably reached the minimum for the year. If so, this year's minimum ranks as the 3rd lowest, behind 2007 and 2008. The fabled Northwest Passage appeared to melt free for brief period in August, according to the National Snow and Ice Data Center. This marks the third consecutive year--and third time in recorded history--the Northwest Passage has opened. The Northeast Passage along the north coast of Russia also opened up this year. This is the fourth time in the past five years the Northeast Passage has opened, and the fourth time in recorded history.

Quiet in the Atlantic
The remains of Hurricane Fred are generating a very small amount of heavy thunderstorm activity near 23N, 61W. These thunderstorms were generating winds up to 35 mph, according to this morning's QuikSCAT pass. However, QuikSCAT also showed that the remains do not have a surface circulation, and the organization of ex-Fred has degraded to point where NHC is no longer mentioning the system on their Tropical Weather Outlook. Water vapor satellite loops show that ex-Fred continues to suffer from dry air thanks to an upper-level low pressure system, and it is unlikely that Fred will ever regenerate. None of the computer models call for any tropical cyclones to develop anywhere in the Atlantic over the next seven days.


Figure 1. Two views of the eye of Super Typhoon Choi-wan. Left: the eye at 01:25 UTC 9/16/09, when Choi-wan was a Category 5 storm with 160 mph winds. Right: the eye at 03:40 UTC 9/17/09, when Choi-was was a Category 4 storm with 150 mph winds. Image credit: MODIS Rapid Response System.

Typhoon Choi-Wan no longer a Category 5 storm
This year's first Category 5 tropical cycloneTyphoon Choi-Wan, has fallen to Category 4 strength after spending 42 hours as a 160 mph Category 5 storm. Choi-Wan--in Cantonese, a type of cloud--is over the open ocean south of Japan, and is not expected to impact any land areas. Choi-wan passed over tiny Alamagan Island, population 15, yesterday. All residents on the island were reported safe.

On this day twenty years ago
At 1 am AST on September 17, 1989, Hurricane Hugo made a direct hit Guadeloupe, pounding the island with Category 4 sustained winds of 140 mph. A storm surge of up to 2.5 meters (8 feet) topped by high battering waves smashed ashore. Hugo wreaked massive devastation on Guadeloupe, destroying 10,000 homes, leaving 35,000 of the island's 340,000 people homeless. Four people died and 107 were injured. An additional seven people were killed three days after the storm when a medical helicopter crashed while evacuating victims. Hugo's winds knocked the airport control tower out of commission, and almost completely destroyed the town of St. Francious, on the island's eastern end. Debris blocked at least 30% of the island's roads. Agriculture suffered massive losses that took years to recover from, as Hugo flattened 100% of the banana crop, 60% of the sugar cane crop, and ruined nearly all of the island's coconut palms. Most of the island's fishing fleet was wiped out, and total damage to the island from Hugo amounted to $880 million. Hugo was the strongest hurricane to hit the island since the legendary 1899 San Ciriaco Hurricane--the longest-lived Atlantic hurricane of all time--which brought 150 mph winds to Guadeloupe.


Figure 2. AVHRR visible satellite image of Hurricane Hugo taken on September 17, 1989. Image credit: Google Earth rendition of the NOAA HURSAT data base.

Hugo continued northwest and pulverized its next target, the island of Montserrat, several hours later. Though the eye missed Monserrat, the severe right front quadrant of Hugo's eyewall, still packing sustained winds of 140 mph, pounded the island. Nearly every home on Monserrat was destroyed or heavily damaged, leaving 11,000 of the island's 12,000 people homeless. Numerous schools, hospitals, and churches were destroyed, along with the police department, the government headquarters, and the main power station. Twenty foot waves in the harbor of the main town, Plymouth, destroyed the 180-foot stone jetty, and heavy rains of up to seven inches created mudslides that at the foot of Chances Peak that destroyed 21 homes. Ten people were killed on Montserrat, 89 injured, and damage topped $260 million, making it the most expensive hurricane in the island's history. Elecrtic, water, and telephone service were disrupted for weeks, necessitating a massive U.S. and British relief effort.


Figure 3. Hugo's storm surge inundates the coast of Montserrat Island. Image credit: NOAA photo library.

The nearby islands of St. Kitts, Antigua, St. Martin, Anguilla, and Dominica did not receive a blow from Hugo's eyewall, but damage was heavy nonetheless. One person was killed on Antigua, and 30% of the homes damaged. Dominica suffered the loss of 80% of its banana crop, and landslides cut off many towns for days. Shoreline erosion damage and crop losses totaled $43 million on St. Kitts, where one person was killed.

Jeff Masters