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Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.Intensifying Tropical Storm Dolphin a Threat to Guam
In the Northwest Pacific, Tropical Storm Dolphin is gathering strength in the waters to the east of the U.S. Mariana Islands, and is a threat to bring typhoon conditions to those islands--including Guam--on Thursday. The 8 am EDT Tuesday advisory from the Joint Typhoon Warning Center (JTWC) put Dolphin's winds at 60 mph, and JTWC predicted the storm would reach Category 1 typhoon strength by Wednesday morning (EDT.) The latest 00Z Tuesday run of the European model and 06Z run of the GFS model show Dolphin passing within 50 miles of Guam as an intensifying typhoon sometime between 21 UTC Thursday and 06 UTC Friday (Thursday night U.S. Eastern Daylight Time.) Satellite loops show that Dolphin significantly increased in organization on Tuesday morning, with more low-level spiral banding and an increase in the intensity and areal coverage of its heavy thunderstorms. Sea surface temperatures (SSTs) are near 29°C (84°F), and warm waters extend to great depth along Dolphin's track, giving it plenty of heat energy to draw upon for intensification. Wind shear has fallen to the low range, 5 - 10 knots, and is expected to remain low through Friday. Dolphin should be able to intensify to Category 2 typhoon status by the time it reaches Guam, and may rapidly intensify, potentially affecting Guam as a major Category 3 or stronger typhoon. Guam will likely be the last land area Dolphin will affect, as a strong trough of low pressure should recurve the storm to the north out to sea late this weekend. The GFS model is also advertising that a new tropical storm will form this weekend in the waters east of Guam, but it is too early to be confident of this prediction.
Figure 1. Tropical Storm Dolphin as seen by the MODIS instrument on NASA's Aqua satellite at 02:50 UTC May 12, 2015. At the time, Dolphin had sustained winds of 50 mph. Image credit: NASA.
The last typhoon on Guam: thirteen years ago
The last typhoon to strike Guam was Typhoon Pongsona, which hit the island as a Category 4 super typhoon with 150 mph winds on December 8, 2002. Sustained winds of 144 mph with gusts to 173 mph were recorded on the island, and Andersen Air Force Base was in the eye for two hours. The lowest pressure on Guam was 935 millibars, making Pongsona the third most intense typhoon to strike the island (the others: a 1900 typhoon with a 926 mb pressure, and Typhoon Karen of 1962, at 932 mb). With strong building standards and experience from repeated typhoon strikes (six typhoons in the previous ten years), there were no direct deaths from Pongsona's strike--but one indirect death from flying glass, and 193 injuries. Damage was over $700 million (2002 US$, $918 million 2015 USD), making Pongsona among the five costliest typhoons on the island. The typhoon also caused heavy damage on Rota and elsewhere in the Northern Mariana Islands, and as a result of its impact, the name Pongsona was retired. The last tropical storm to affect Guam was Tropical Storm Saomai of August 2006, which had 50 mph winds when it moved over the island.
Figure 2. Extensive damage on Guam caused by Typhoon Pongsona December 8, 2002. Image credit: Andrea Booher, U.S. Army Corps of Engineers - U.S. Army Corps of Engineers Digital Visual Library.
A record early start to typhoon season
May is exceptionally early for Guam to be worrying about a typhoon; according to NOAA's Historical Hurricane Tracks website, no typhoon has affected the island in the months of February through June since record keeping began in 1945 (one January storm, Typhoon Roy of 1988, did pass near Guam in January, though.) Guam's early typhoon worries this year reflect how crazy-busy the early part of the 2015 typhoon season has been. The Japan Meteorological Agency (JMA) gave Tropical Storm Dolphin its name on May 9. According to statistics from the Japan Meteorological Agency's database from 1951 - 2015 maintained by Digital Typhoon, this was the earliest appearance on record of the Northwest Pacific's seventh named storm of the year. The previous record was May 19, 1971 (Carla.) Usually by this time of year, just two named storms have appeared; the seventh storm of the year typically doesn't form until the third week of July. According to Colorado State University hurricane scientist Phil Klotzbach, the seven storms so far in 2015 have been unusually strong: Northwest Pacific Accumulated Cyclone Energy (ACE) was at record high through May 11 (78.1), just ahead of the old record of 77.7 in 1957. The early and violent start to 2015 typhoon season is due, in part, to exceptionally warm ocean temperatures in the typhoon breeding region between 5 - 10°N near the Date Line. These temperatures have been over 2°C (3.6°F) above average in recent months, due to a strengthening El Niño event.
Storm chaser Jim Edds is on Guam, and will be documenting the impact of Dolphin on the island via his Twitter feed.
Jeff Masters
Figure 1. Tropical Storm Dolphin as seen by the MODIS instrument on NASA's Aqua satellite at 02:50 UTC May 12, 2015. At the time, Dolphin had sustained winds of 50 mph. Image credit: NASA.
The last typhoon on Guam: thirteen years ago
The last typhoon to strike Guam was Typhoon Pongsona, which hit the island as a Category 4 super typhoon with 150 mph winds on December 8, 2002. Sustained winds of 144 mph with gusts to 173 mph were recorded on the island, and Andersen Air Force Base was in the eye for two hours. The lowest pressure on Guam was 935 millibars, making Pongsona the third most intense typhoon to strike the island (the others: a 1900 typhoon with a 926 mb pressure, and Typhoon Karen of 1962, at 932 mb). With strong building standards and experience from repeated typhoon strikes (six typhoons in the previous ten years), there were no direct deaths from Pongsona's strike--but one indirect death from flying glass, and 193 injuries. Damage was over $700 million (2002 US$, $918 million 2015 USD), making Pongsona among the five costliest typhoons on the island. The typhoon also caused heavy damage on Rota and elsewhere in the Northern Mariana Islands, and as a result of its impact, the name Pongsona was retired. The last tropical storm to affect Guam was Tropical Storm Saomai of August 2006, which had 50 mph winds when it moved over the island.
Figure 2. Extensive damage on Guam caused by Typhoon Pongsona December 8, 2002. Image credit: Andrea Booher, U.S. Army Corps of Engineers - U.S. Army Corps of Engineers Digital Visual Library.
A record early start to typhoon season
May is exceptionally early for Guam to be worrying about a typhoon; according to NOAA's Historical Hurricane Tracks website, no typhoon has affected the island in the months of February through June since record keeping began in 1945 (one January storm, Typhoon Roy of 1988, did pass near Guam in January, though.) Guam's early typhoon worries this year reflect how crazy-busy the early part of the 2015 typhoon season has been. The Japan Meteorological Agency (JMA) gave Tropical Storm Dolphin its name on May 9. According to statistics from the Japan Meteorological Agency's database from 1951 - 2015 maintained by Digital Typhoon, this was the earliest appearance on record of the Northwest Pacific's seventh named storm of the year. The previous record was May 19, 1971 (Carla.) Usually by this time of year, just two named storms have appeared; the seventh storm of the year typically doesn't form until the third week of July. According to Colorado State University hurricane scientist Phil Klotzbach, the seven storms so far in 2015 have been unusually strong: Northwest Pacific Accumulated Cyclone Energy (ACE) was at record high through May 11 (78.1), just ahead of the old record of 77.7 in 1957. The early and violent start to 2015 typhoon season is due, in part, to exceptionally warm ocean temperatures in the typhoon breeding region between 5 - 10°N near the Date Line. These temperatures have been over 2°C (3.6°F) above average in recent months, due to a strengthening El Niño event.
Storm chaser Jim Edds is on Guam, and will be documenting the impact of Dolphin on the island via his Twitter feed.
Jeff Masters
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