Visible imagery of Typhoon Halong from the NOAA-20 satellite, captured October 7, 2025. [Credit: NOAA]
When the remnants of a Typhoon Halong slammed into southwestern Alaska, NOAA satellites provided critical support for forecasting the impacts and assisting with the recovery.
At one time a strong tropical cyclone spinning just east of Japan, Typhoon Halong traversed thousands of miles across the Pacific on a path set for Alaska. When the remnants of Halong came ashore on October 12, 2025, it brought hurricane-force winds, storm surge and coastal flooding to remote communities. The United States Coast Guard, Alaska Air National Guard, and Alaska Army National Guard were deployed for search and rescue, as well as disaster response, after homes and roadways were washed away. Halong was one of the most impactful ex-tropical systems to impact Alaska, and similar to the remnants of Typhoon Merbok that hit the state in 2022.
Buildings at the Umkumiut village on Nelson Island, Alaska sustained damage after post ex-Typhoon Halong made landfall. [Credit: NOAA ShoreZone]
Halong displaced over a thousand residents in coastal towns and villages, leading to one of the largest airlift evacuations in Alaska history. Many communities' water systems and electricity were offline for weeks following the storm.
NOAA satellites captured images and critical data of Halong, providing vital information on how this storm impacted coastal Alaska.
Typhoon Halong
Typhoons are tropical cyclones with winds of at least 74 mph that occur in the western North Pacific region, including areas around the Philippines, Japan, and China. These storms are called hurricanes east of the International Dateline in the Northern Hemisphere, consisting of the eastern Pacific and Atlantic Ocean. Typhoons can occur year-round in the West Pacific basin, though most often during the late summer through late fall.
Halong formed as a tropical storm on October 5, in the northern Philippine Sea, strengthening into a typhoon the next day. On October 7, the storm underwent rapid intensification, becoming a powerful Category 4 typhoon with maximum sustained winds of 135 mph.
Infrared imagery of Typhoon Halong via Japan's Himawari-9 satellite shows it strengthening into a Category Four storm south of Japan, October 6–7, 2025. Infrared imagery measures heat radiating off clouds, which allows for feature classification and identification as well as reveals a storm's intensity. [Credit: Japan Meteorological Agency]
Post-Typhoon Halong
Moving northeastward across the Pacific, Halong merged with an extratropical storm. As it transitioned into a post-tropical storm, it maintained hurricane-force winds of over 80 mph. It also grew larger, similar to Hurricane Sandy in 2012. The figure below captures the striking Air Mass RGB from NOAA’s GOES West satellite as Halong reaches the Alaska coastline.
Shown in this enhanced color Air Mass RGB imagery from GOES West, remnants of Typhoon Halong move across the North Pacific (bottom-left) on October 10 and make landfall in southwest Alaska on October 12, 2025. [Credit: NOAA/NESDIS/STAR GOES West]
Air Mass RGB imagery is used to study large-scale weather patterns. It provides information about the temperature and moisture content of the air masses in and around a tropical cyclone. This information is key to determine the intensity, forecast and path of a storm.
Landfall in Alaska
NOAA’s Joint Polar Satellite System (JPSS) NOAA-20 and NOAA-21 satellites captured the storm making landfall with prolonged, intense winds over 80 mph on the afternoon of October 12, with the Advanced Technology Microwave Sounder (ATMS) instrument. The images show intense, multi-layer structural characteristics of ex-Typhoon Halong as it battered the coast. ATMS microwave frequencies passed through the upper clouds to reveal the internal structure of the cyclone, a key to estimating its intensity. The ATMS images in the figure below show areas of intense and hidden convection (thunderstorms) sweeping inland from the Bering Sea. On the ground, these features brought strong, downburst-like wind gusts up to 60 mph.
Comparison of NOAA-21 and NOAA-20 ATMS 165.5 GHz channel antenna temperature (left) and 165.5 GHz channel scattering index (right) when the storm made landfall. “X” marks the location of the cyclone center with the eastward-pointing black triangle representing the location of downburst wind occurrence near Huslia, AK. Inset ATMS images (middle) show cyclone structural details, including a prominent feeder rainband (“RB”) and discrete convective storms (“CS”) east of the cyclone center. [Credit: NOAA]
Flooding in Alaska
Halong caused a damaging storm surge as it came ashore in the flat terrain of the Yukon and Kuskokwim River deltas. After the system passed, widespread flooding could be seen along the coastline with the Visible Infrared Imaging Radiometer Suite (VIIRS) Day Land Cloud RGB. Below, the red boxes indicate the extent of the coastal flooding in the daytime before (top) and after (bottom) imagery from VIIRS.
Before and after images of the coastal flooding in southwest Alaska from VIIRS instrument on NOAA-21. [Credit: NOAA]
The coastal floods reached up to 60 miles inland, sweeping homes from their foundations and causing numerous diesel and oil spills. Most of the Alaskan residents that were severely impacted from Halong lived in remote regions. These communities have few paved roads that are not connected to the state’s highway system and depend on boats and planes for transportation. This made evacuation difficult and has made rebuilding a challenge.
The data and information gathered from NOAA satellites during Halong can help inform and improve forecasting and warning capabilities for the next large-scale weather event, helping emergency managers more effectively prepare and respond to remote locations like southwest Alaska, where preparation and evacuation efforts remain a challenge. The impact of this data on the response to future storms showcases the critical role of NOAA’s satellites in keeping Americans across the nation safe and informed in the face of severe weather.