Western Alaska Floods
October 23rd, 2025 by Jorel TorresBy J. Torres (CIRA), C. Dierking (GINA) and J. Delamere (GINA).
In Early October 2025, Typhoon Halong developed in the north Philippine Sea, skirted near Japan and eventually trekked eastward into the north Pacific Ocean. The storm became post-tropical, but continued to travel eastward through the north Pacific, then traversed through the Aleutian Islands and made landfall in western Alaska. The Ocean Prediction Center (OPC) surface analysis of the storm track can be viewed from ~00Z, 12 October 2025 to ~15Z, 13 October 2025. The synoptic-scaled system brought Alaska precipitation, hurricane-force winds and significant storm surge that led to widespread inundation, impacting the coastal communities and villages.
OPC Surface Analysis → ~00Z, 12 October 2025 to ~15Z, 13 October 2025
The strong system made landfall along the Alaskan coastline during the early morning hours of 12 October 2025. Air temperatures were in the 30’s and 40’s (in degrees Fahrenheit) while 80+ mph wind gusts were also reported. The prolonged, intense winds aided in the storm surge that inundated the coastal communities. In the AWIPS animation below, the surface observations can be seen overlaid onto the 375-m VIIRS 11.5 µm infrared imagery. The imagery also observes the central low pressure system that moves to the northeast as it approaches the coastline.
Surface Observations overlaid onto VIIRS 11.5 µm from 12-16Z, 12 October 2025
South of the central low pressure system, the GCOM AMSR-2 Sea Surface Winds product observed the wind speeds over the Bering Sea near Nunivak Island and the villages of Kipnuk, AK and Kwigillingok, AK. The sea surface winds were seen from 41 to 60 plus knots (i.e., 47 to 70 plus mph, depicted in orange, dark orange, and red colors) and located south and west of where Kipnuk and Kwigillingok reside. Note, one of the limitations of the AMSR-2 product is that it does not provide data within ~50 km (~31 miles) of land or ice. At this timestamp, the strongest winds of the system would have been observed along the coastline, meaning the most intense winds were not well represented here. The product exhibits a 6-km spatial resolution in AWIPS.
AMSR-2 Sea Surface Winds overland onto VIIRS 11.5 µm at ~1317Z, 12 October 2025
After the system passed, widespread flooding could be seen along the coastline, specifically from Kwigillingok, AK to Kipnuk, AK, and up north to Hooper Bay, AK. The VIIRS Day Land Cloud RGB, at 375-m, shows a daytime before and after image comparison of the new flood extent. Along the coastline, a mix of dark green and dark blue colors indicate new areas of marshy vegetation and inundation. Refer to the inundation within the white boxes.
VIIRS Day Land Cloud RGB –> Before (October 10th) and After (October 12th)
Zooming into the southernmost white box, where Kipnuk and Kwigillingok reside, the finer details of the inundation can be seen at high resolution. A Google map is also provided to help viewers locate the Alaskan villages along the coastline.
Although clouds were scattered across the region, the VIIRS Flood Map product was also able to detect some areas of inundation from the event, seen in green to yellow to red pixels at 375-m. Clouds and cloud terrain shadows are seen in grey and dark grey colors, while land is seen in brown. The flood product can be accessed online via RealEarth and in AWIPS.
VIIRS Flood Map –> 2217Z, 12 October 2025
In addition to storm surge, heavy precipitation was also observed over western Alaska. Moisture satellite products, such as the Blended Total Precipitable Water (TPW) and the Percent of Normal TPW provided a large-scale view of ex-Typhoon Halong, which eventually reorganized and intensified, bringing a plume of moisture that led to precipitation over the region. The Blended TPW product contains microwave data from polar-orbiting satellites, infrared data from geostationary satellites and Global Positioning System (GPS) TPW data. TPW values of ~1 to 2 inches (green to red colors) can be seen over western Alaska.
Blended TPW –> 17Z, 10 October 2025 to 10Z, 13 October 2025
In complement to Blended TPW, the Percent of Normal TPW product showed the significance of the anomalous atmospheric moisture within the system. In this case, exceptionally high percent of normal values (i.e., above normal climatological values of 200% or greater) were captured within the system, seen in yellow and gray colors.
Percent of Normal TPW –> 17Z, 10 October 2025 to 10Z, 13 October 2025
Additional reports and analyses of the event can be viewed below. Refer to the following articles covering the Western Alaska Floods: Anchorage Daily News, The Conversation, and the Alaska Beacon.
Posted in: Uncategorized, | Comments closed
Dense Fog across the High Plains
October 15th, 2025 by Jorel TorresDense Fog Advisories blanketed the high plains earlier this morning, extending from Nebraska to Wyoming and northern Colorado. National Weather Service (NWS) Weather Forecast Offices (WFOs) published social media posts online to remind the general public of how dense the fog could be, with less than a 1/4 mile visibility possible across their respective County Warning Areas (CWA). Social media posts from WFO Boulder, CO and WFO North Platte, NE can be seen below.
Hourly surface observations show the widespread fog initially located over Nebraska (and South Dakota), which then spread westward towards Wyoming and southward across northeastern Colorado.
Surface Observations from ~0400Z to ~1400Z , 15 October 2025
High temporal resolution imagery from geostationary satellites (10-min, Full Disk ABI data) shows the evolution of the fog, seen in ‘aqua to grey’ colors within the Nighttime Microphysics RGB. The GOES RGB exhibits a 2-km spatial resolution.
GOES ABI Nighttime Microphysics RGB from ~0400Z to ~1400Z, 15 October 2025
The JPSS VIIRS version of the Nighttime Microphysics RGB captures the fine details of the fog and low stratus at 750-m spatial resolution. Four overpasses from JPSS satellites passed over the domain from ~0800 to ~0940Z, 15 October 2025.
JPSS VIIRS Nighttime Microphysics RGB from ~0800Z to ~0940Z, 15 October 2025
Additionally, nighttime visible imagery observed the reflected moonlight off of the fog and low stratus, while capturing the emitted lights from cities and towns across Colorado, Wyoming and Nebraska. The product also has a spatial resolution of 750-m.
NOAA-20 VIIRS NCC at 0849Z, 15 October 2025
Posted in: Uncategorized, | Comments closed
Nighttime Visible Imagery over the Atlantic
October 3rd, 2025 by Jorel TorresOver the past two weeks, a few hurricanes (Gabrielle, Humberto, and Imelda) traversed over the Atlantic Ocean, and either skirted along or directly impacted the United Kingdom (U.K.) territory of Bermuda. Nighttime visible imagery provided from the VIIRS Near-Constant Contrast (NCC) product captured the synoptic scaled systems across the Atlantic.
Note, for the best optimal viewing of VIIRS NCC, it is recommended to be used during the full moon phase of the lunar cycle (i.e., from ~2 days after the first quarter to ~2 days after the last quarter), since the illumination of features at night is a function of moon phase and elevation above the horizon. However, VIIRS NCC may also be utilized during the new moon phase of the lunar cycle (i.e., moonless nights) to observe atmospheric and surface features, which are predominately illuminated by nightglow. During this period, emitted lights (e.g., city lights) will appear significantly brighter than their surroundings, while atmospheric and surface features (e.g., clouds, snow and ice cover) will appear dim and fuzzy.
VIIRS NCC observes Category 4 – Hurricane Gabrielle at 0549Z, 23 September 2025
At this time stamp, Gabrielle was a Major Hurricane, but stayed east of Bermuda and eventually became a post-tropical cyclone, impacting the Portuguese Azores later that week. While the image is taken during a moonless night, the eye of the hurricane can still be discerned in the imagery. Emitted city lights from Bermuda are seen west of the hurricane as well.
VIIRS NCC observes Category 5 – Hurricane Humberto at 0559Z, 28 September 2025
Humberto experienced peak intensities of 160+ mph winds, where the large cyclone churned through the Atlantic over the course of a week and migrated anticyclonically (clockwise) around Bermuda before dissipating to the north/northeast of the territory. The image below shows the magnitude of Humberto while it was classified as a Category 5 hurricane. The cyclone was located northeast of Puerto Rico and the U.S. and British Virgin Islands. Notice the scattered emitted city lights across the islands.
VIIRS NCC observes Category 1 – Hurricane Imelda at 0632Z, 1 October 2025
Hurricane Imelda and its eye, was located northeast of the Bahamas, and directly east of Florida. Later that day, Imelda intensified into a Category 2 hurricane, before making landfall in Bermuda. Imelda brought heavy precipitation and flooding along with high winds to the remote island. West of Imelda, saturated emitted city lights can be observed along the southeastern U.S., spanning from Florida to the Carolinas.
Posted in: Uncategorized, | Comments closed
Typhoon Ragasa
September 25th, 2025 by Jorel TorresOver the last 48-hours, Typhoon Ragasa barreled through the South China Sea and its forecasted to make landfall in the Guangdong Province of China by 24 September 2025. Chinese megacities like Hong Kong and Macao reside along the coastline of the Guangdong Province, and have been put on high alert of the incoming storm. Typhoon Ragasa has already battered the northern Philippines producing significant rainfall, flooding, and high winds that led to widespread damage to infrastructure and also triggered landslides.
Himawari-9, a geostationary satellite operated by the Japan Meteorological Agency, provides observations of the typhoon at a high temporal refresh rate of every 10 minutes (i.e., Full Disk sector). The Himawari-9 AHI GeoColor product animation captures the cyclone offshore, south of Hong Kong, and moving westward towards the Chinese coastline from ~16-19Z, 23 September 2025. During the nighttime, GeoColor not only monitored the massive typhoon and observed its well defined eye, but the product also consists of a static, background city lights layer that helps viewers identify the populated areas that may be impacted by the storm.
Himawari-9 AHI GeoColor Product from 1600-1850Z, 23 September 2025
The Advected Layer Precipitable Water (ALPW) product, derived from multiple polar-orbiting satellites, captured the horizontal moisture transport of Ragasa over a ~30 hour period, as the typhoon trekked westward over the South China Sea. Refer to the ALPW animation below. The 4-panel product depicts precipitable water values within four atmospheric layers: from the surface to 850-mb (top-left), 850-700mb (top-right), 700-500mb (bottom-left), and 500-300mb (bottom-right). Note, the center of the typhoon can be spotted in the surface to 850mb precipitable water layer. The high moisture transport lead to torrential rainfall and flooding over southern China as Ragasa made landfall.
ALPW Product observations from 5Z, 22 September 2025 to 13Z, 23 September 2025
At ~9Z, 24 September 2025, Typhoon Ragasa made landfall near Hailing Island, China. VIIRS imagery from JPSS polar-orbiting satellites observed the typhoon as it moved towards the Chinese coastline prior to landfall. The infrared imagery is at a 375-m spatial resolution and shows the evolution of the typhoon, the typhoon’s eye and the convective bands.
VIIRS 11.45 um (I-5 Band) from ~5Z, 23 September 2025 to ~6Z, 24 September 2025
Posted in: Uncategorized, | Comments closed
Rio Blanco County, Colorado – Wildfires
August 12th, 2025 by Jorel TorresOn 2 August 2025, two wildfires initiated in Rio Blanco County, located in western Colorado. As of 11 August 2025, the Lee Fire burnt over 116,000 acres with 7% containment. Within the past three days, the fire has rapidly moved to the south towards Garfield County that includes the town of Rifle, Colorado. At the time of this blog entry, the Lee Fire was the 5th largest fire in Colorado state history and is still growing. The second fire, named the Elk Fire, burned over ~14,000 acres and is 30% contained while located east of the Lee Fire. Refer to the Google Map image that shows the approximate fire perimeter extent of both fires on 11 August 2025.
GOES-19 ABI 3.9 um imagery observes the emitted hotspots from both fires (i.e., white and red pixels) throughout the afternoon on 2 August 2025, where clouds (i.e., grey and black pixels that exhibit colder brightness temperatures) also move over the scene.
GOES-19 ABI 3.9um, 5-min temporal resolution, from ~16-02Z, 2 August 2025
After a few days of fire growth, on 5 August 2025, VIIRS observed the fire hotspots, intensities, and smoke from both wildfires. Refer to the VIIRS 4-panel below. Note, the elongated smoke plume, shown distinctly in the VIIRS Visible (0.64 um) and Day Fire RGB imagery that extends ~240 miles eastward towards the Front Range of Colorado. Smoke was also observed along the northern Interstate-25 corridor later that day.
VIIRS 4-Panel –> Top Left: Visible, Top Right: VIIRS Day Fire RGB, Bottom-Left: VIIRS 3.7 um, and Bottom-Right: VIIRS Fire Temperature RGB at 2040Z, on 5 August 2025
A 10-day VIIRS 3.7 um animation shows the evolution of the fires over western Colorado. Notice both fires have an initial rapid fire spread to the east, then the Lee Fire perimeter advances to the south after 8 August 2025. The shortwave infrared imagery is at 375-m, where black pixels indicate the fire hotspots. Notice the white pixels within the fire perimeter as well; this indicates that the VIIRS sensor is saturating, since it’s observing very intense fire pixels. VIIRS exhibits a low saturation temperature of 95C (or 368K), where any fire pixels that are observed above that temperature threshold will produce unrealistic cold pixel anomalies.
VIIRS 3.7um (I4) – Day and Night observations from 2-11 August 2025
Posted in: Uncategorized, | Comments closed