WunderBlog Archive » Category 6™

Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.

Dujuan Slams into Taiwan; TD 11 Forms in Northwest Atlantic

By: Bob Henson and Jeff Masters 5:05 PM GMT on September 28, 2015

The center of Typhoon Dujuan slammed into the northeast coast of Taiwan near the rural township of Nan’ao at 5:40 pm Monday local time (5:41 am EDT Monday). Dujuan’s highest 1-minute sustained winds were 140 mph at the final advisory (0600 GMT or 2 pm local time Monday) from the Joint Typhoon Warning Center (JTWC) prior to its landfall. Using a different interval for top sustained winds, the Hong Kong Observatory classified Dujuan as a super typhoon. Dujuan was a spectacularly well-structured annular storm as it approached Taiwan, and satellite loops showed little sign of weakening prior to landfall, so Dujuan likely came onshore as a Category 4 typhoon. En route to Taiwan, Dujuan produced a record 181-mph (81.1 m/s) wind gust at the southern Japanese island of Yonagunijima, according to weather.com and the Japan Meteorological Agency.

Figure 1. A stunning true-color view of Typhoon Dujuan from Japan’s Himiwari-8 satellite at sunrise on Sunday, September 27, about 24 hours before the typhoon struck Taiwan. Image credit: JMA, courtesy Dan Lindsey.

Figure 2. A close-up visible image of Typhoon Dujuan at 500-meter resolution, again from Japan’s Himiwari-8 satellite near sunrise on Sunday, September 27. Image credit: JMA, courtesy Dan Lindsey.

Figure 3. An enhanced infrared image from the MTSAT satellite of Typhoon Dujuan at 0801 GMT Monday, September 28, less than two hours before Dujuan made landfall on Taiwan’s northeast coast. Image credit: NOAA/NESDIS.

The powerful right-hand eyewall of Dujuan passed near the urbanized area of Yilan County as Dujuan made landfall. A wind gust of 153 mph (68.4 meters per second) was reported at Su’ao Township, about 20 miles south of Yilan City. At 1500 GMT (11 pm local time or 11:00 am EDT Monday), Taiwan’s Central Weather Bureau (CWB) placed Dujuan at 24.0°N and 120.6°E, or about 70 miles south-southwest of Taipei, which was experiencing the northern edge of the eyewall’s heavy rain. The typhoon angled further toward the west-southwest than expected during its trek over Taiwan, helping to spare Taipei from the worst potential impacts. At 1200 GMT Monday, the JTWC reported that Dujuan’s top sustained 1-minute winds were down to 115 mph. The CWB reported at 1500 GMT that the minimal central pressure at 1500 GMT had risen to 945 millibars, from 925 millibars at 1200 GMT.

Figure 4. A woman uses an umbrella against strong wind and rain brought by Typhoon Dujuan at Tamshui district, New Taipei City on September 28, 2015. More than 7,000 people were evacuated in Taiwan as Dujuan swirled towards the island, gathering strength as it bore down on the east coast. Heavy rain and wind struck the Taipei area well ahead of Dujuan’s core. Image credit: Sam Yeh/AFP/Getty Images.

Figure 5. Radar imagery at 11:18 pm local time (11:18 am EDT) Monday, September 28, showed heavy rains from Typhoon Dujuan still enveloping most of Taiwan, with outer bands stretching to the coast of China. Image credit: Central Weather Bureau, Taiwan.

Torrential rains have been falling over most of Taiwan, with particularly heavy amounts likely over east-facing northern slopes and west-facing southern slopes. Totals as high as 30 inches have already been reported. By Tuesday morning, Dujuan should be making landfall on China’s east coast as a rapidly decaying Category 1 typhoon.

Heavy rains can still be expected as Dujuan recurves into the Yangtze River valley from Tuesday into Wednesday, and these could inflict a major disaster in their own right. Dujuan is a bit stronger than Typhoon Soudelor, which struck Taiwan on August 7, but Soudelor’s track across Taiwan and into China is quite similar to the projections for Dujuan. Soudelor caused at least 26 deaths in China compared to at least 8 in Taiwan, and estimated losses in China of at least $3 billion were much greater than the reported $95 million US in agricultural damage in Taiwan. The Joint Typhoon Warning Center projects Dujuan to strike the China coast within 30 miles of Soudelor’s landfall point near Putian City.

TD 11 worth watching in Northwest Atlantic
Tropical Depression 11 took shape last night in the Northwest Atlantic between the Bahamas and Bermuda. In the grip of moderate to strong northwesterly wind shear (around 20 knots), TD 11 is struggling to organize itself, with an exposed low-level center on Monday morning. Showers and thunderstorms are fairly widespread and have persisted into Monday morning, beyond the typical nighttime convective maximum. The depression is over very warm sea-surface temperatures of around 30°C (86°F), about 1°C above average. As TD 11 moves slowly northwest over the next 2-3 days, it will remain over quite warm SSTs, but wind shear will remain on the strong side, denting TD 11’s potential for growth. Dynamical models are in general agreement in bringing TD 11 to tropical storm strength over the next several days. The high-resolution HWRF model is particularly bullish, with its 00Z and 06Z runs bringing TD 11 to hurricane status by later this week.

Figure 6. Latest satellite image of Tropical Depression 11.

Figure 7. The five-day forecast for TD 11 from the National Hurricane Center.

Upper-level steering currents forecast for later this week feature strong southerly flow between an eastern U.S. trough and a western Atlantic ridge, which suggests TD 11 (or its remnants) should be heading in the general direction of southern New England toward the end of this week. The high-resolution HWRF and GFDL models lean the most strongly toward a potential landfall threat for Long Island by around Friday, while the global-scale ECMWF and GFS tend to keep TD 11 further to the east and considerably weaker. The official NHC outlook intensifies TD 11 only to minimal tropical storm status and transitions it to post-tropical status by Friday morning as it approaches New England, where it should be merging with a frontal zone. The best global models are typically more reliable than the high-resolution mesoscale models beyond about 2-3 days, but the newly upgraded HWRF has demonstrated impressive skill on several storms this year. TD 11 bears watching, as there seems at least a modest possibility of the system approaching the northeast U.S. coast as a subtropical or tropical storm.

Figure 8. Radar-estimated rainfall from 99L from the Pensacola, Florida radar ending at noon EDT Monday showed several areas of 6+ inches of rain had fallen.

99L in Gulf of Mexico bringing heavy rain to the Gulf Coast
A Flash Flood Warning is posted for the Florida Panhandle near Pensacola and Flood Watches are up for the coast from Southeast Louisiana to Sarasota, Florida as an area of low pressure (Invest 99L) centered at 11 am EDT Monday over the south-central Gulf of Mexico, about 300 miles west-northwest of Key West, moves north-northeastwards at about 10 mph. A channel of low-level moisture running from 99L toward an upper-level low in Texas combined with upper-level moisture filtering in from Tropical Storm Marty (see below) to bring torrential rains of 7.50" to Mobile, Alabama on Sunday, making it their 10th wettest calendar day on record. This is the first time since records began in 1871 that the city has seen two 7+ inch rainfall days in one year; the city had 7.28" of rain on April 12. 99L is producing a large area of disorganized showers and thunderstorms that extends from western Cuba northward across the eastern Gulf of Mexico, but no well-defined surface circulation exists, as seen on satellite loops. A separate non-tropical low pressure system associated with the upper low can be seen over the northwestern Gulf of Mexico, and is bringing a few heavy rain showers to the Texas and Western Louisiana coast. By Tuesday morning, the center of 99L will push inland over the Florida Panhandle. High wind shear of 20 - 30 knots should limit the potential for 99L to organize into a named storm, and our top three models for predicting tropical cyclone genesis are showing little development of this system. 99L will likely bring heavy rains of 2 - 3" from Southeastern Louisiana to the Florida Panhandle. In their 8 am EDT Monday Tropical Weather Outlook, NHC gave the disturbance 2-day and 5-day odds of development of 30%. The Hurricane Hunters were in the air on Monday afternoon to investigate 99L.

Figure 9. MODIS image of Tropical Storm Marty approaching Mexico as seen from NASA's Terra satellite on Sunday, September 27, 2015, at 3:30 pm EDT. At the time, Marty had top winds of 60 mph. Image credit: NASA.

Tropical Storm Marty a dangerous heavy rain threat for Mexico's Pacific coast
Tropical Storm Marty has intensified to just below hurricane strength, with top winds of 70 mph at 11 am EDT Monday, as the storm drifts northwards at 3 mph towards the Pacific coast of Mexico to the northwest of Acapulco. With Marty stuck in a region of weak steering currents and likely to remain just offshore through Wednesday, the storm is a dangerous storm for the Pacific coast of Mexico. Heavy rains of 6 - 12" are likely to cause dangerous flooding and mudslides today through Wednesday. As of 8 am EDT Sunday, Petacalco on the coast received 3.62" of rain in 24 hours, though rainfall amounts for the 24-hour period ending on Monday morning were generally less than one inch along the Mexican coast. Further intensification of the storm appears unlikely, due to high wind shear of 15 - 25 knots, close proximity to the coast, and the potential for Marty to upwell cool water from the depths that will diminish the storm's energy supply. An Air Force hurricane hunter aircraft will investigate Marty on Monday afternoon. The models are split on whether or not Marty will eventually make landfall this week, and the 3 to 5-day official forecast from NHC should be considered low-confidence.

Figure 10. MODIS image of Tropical Storm Niala skirting the Big Island of Hawaii as seen from NASA's Terra satellite on Sunday, September 27, 2015, at approximately 4 pm EDT. At the time, Niala had top winds of 50 mph, but its low-level center had become exposed to view due to high wind shear. Image credit: NASA.

Tropical Storm Niala spares Hawaii
Tropical Storm Niala passed about 150 miles south of the Big Island on Sunday, bringing a few heavy rain showers to the island, but not enough to cause flooding. The Flash Flood Watch for the island has been cancelled, but a High Surf Advisory remains in effect on Monday for waves of 5 to 8 feet along east and southeast facing shores of The Big Island. At 11 am EDT Monday, Niala had weakened to a tropical depression, and was moving west-southwest at 10 mph away from Hawaii. Niala should continue to weaken in the face of high wind shear, becoming a remnant low by Monday night.

Bob Henson and Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.