Month: August 2019

Aug. 31, 2019 – Update #2 – NASA Watches as Category 4 Hurricane Dorian Still Heads for Northwestern Bahamas

The latest National Hurricane Center (NHC) advisory has Hurricane Dorian on a collision course with the northwestern Bahamas sometime on Sunday and moving near the Florida east coast late Monday into Tuesday.  Still a Category 4 some fluctuations in intensity are likely within the storm, but Dorian is expected to remain a powerful hurricane during the next
few days.

NOAA-NASA’s Suomi NPP satellite, GCOM-W1 and NOAA-20 all passed over Dorian in that order, right around the 2:00 am EDT NHC advisory, each observing unique features.

At 1:58 am EDT (0558 UTC) on Aug. 31, 2019, Suomi NPP caught Dorian on the west side of the scan showing a well-defined eye that can be easily seen along with different cloud bands.  A lone lightning strike is seen within the storm in the southern portion. Infrared imagery also spotted tropospheric convective gravity waves flowing away from the intense storm.  The NHC remarked at 2:00 pm EDT (1800 UTC) that Hurricane Dorian was exhibiting a very distinct eye 15 nautical miles across.

Roughly 50 minutes later at 2:48 am EDT (0648 UTC), NOAA-20 flew over Dorian close to top-down. The infrared imagery continues to show convection gravity waves consistent with an intense storm.  The successive passes showed the rotation of the storm at high resolution. The zoomed out Day Night Band imagery showed the structure of Dorian quite well, even though there was no moonlight present, along with mesospheric gravity waves being flung far away from the storm.

It is only when a storm is well developed that the refined eye appears giving forecasters an idea of the center of circulation.  Aircraft and dropsonde information also provide crucial information about the surrounding environment of the storm, albeit at select points within the storm.

 

At 2:23 am EDT the AMSR2 instrument on the Global Change Observation Mission – Water “Shizuku” satellite (GCOM-W1), a Japan Aerospace Exploration Agency satellite, caught Dorian on the western side of the scan and the well-defined eye was evident as well as hints of perhaps a secondary set of convection about halfway around the inner eye. While nothing was mentioned about an eyewall replacement occurring in the 5am NHC advisory it is possible that the Advanced Microwave Scanning Radiometer 2 (AMSR2) caught one of the eyewall replacement cycles.

Dorian is currently located latitude 26.1N and longitude 73.9W about 205 miles (325 hkm) east of Great Abaco in the Bahamas and about 385 miles (625 km) east of West Palm Beach, FL.  The Air Force reconnaissance plane recorded the maximum sustained winds remain consistent at 150 mph (240 km/h).  As a point of comparison Category 5 strength winds begin at 157 mph (251 km/h). Hurricane Dorian’s movement has slowed to 8 mph (13 km/h) which gives this storm more time over open warm waters to continue to gain strength.  The barometric pressure is steady at 945 mb.

Hurricane-force winds extend outward up to 30 miles (45 km) from the center and tropical-storm-force winds extend outward up to 115 miles (185 km).

For more information on the storm visit:  https://www.nhc.noaa.gov

By Lynn Jenner
NASA Goddard Space Flight Center

Aug. 31, 2019 – Update #1 – NASA Satellites Following Hurricane Dorian On Its Trek Westward

On Friday evening of Aug. 30, Dorian attained Category 4 status on the Saffir-Simpson Hurricane Wind Scale which means the storm is packing 130 – 156 mph (209-251 km/h) winds.  The second change in the storm was the turn it took during the nighttime hours which now has the storm potentially not making direct landfall on Florida but rather Georgia and the Carolinas.  However, it should be noted that this track could change once again.  According to the National Hurricane Center (NHC): “Significant impacts could also occur even if the center of Dorian stays offshore. With the change in the forecast, the risk of strong winds and life-threatening storm surge is increasing along the coasts of Georgia and South Carolina during the middle of next week.”

NASA’s Aqua satellite was on duty measuring the cloudtop temperatures in the powerful storm on Aug. 30, 2019. These very cold clouds with temperatures as cold or colder than minus 63 degrees Fahrenheit are tightly wound in a large area around the very well defined eye of the storm. Cloud top temperatures that cold indicate strong storms with the potential to generate heavy rainfall.

NASA’s Earth Observing System Data and Information System (EOSDIS) Worldview application provides the capability to interactively browse over 700 global, full-resolution satellite imagery layers and then download the underlying data. Many of the available imagery layers are updated within three hours of observation, essentially showing the entire Earth as it looks “right now.” This natural-color image was collected by NOAA-NASA’s Suomi NPP satellite on Aug. 30, 2019.

The NHC’s analysis of the storm which was released it 8am on Aug. 31, 2019 has Dorian gaining strength and moving westward.  Its current location is latitude 25.8N and longitude 73.0W which is about 445 miles (713 km) east of West Palm Beach, FL and 280 miles (450 km) east of the northwestern Bahamas. Its maximum sustained winds are 145 mph (230 km/h) which puts it well into Category 4 status. Dorian is moving west at 12 mph. The barometric pressure inside the storm has dropped to 944 mb.

Hurricane-force winds extend outward up to 30 miles (45 km) from the center and tropical-storm-force winds extend outward up to 105 miles (165 km).

A Hurricane Warning is in effect for…
* Northwestern Bahamas excluding Andros Island

A Hurricane Watch is in effect for…
* Andros Island

Hurricane conditions are expected in the hurricane warning area across the northwestern Bahamas by Sunday, with tropical storm winds beginning tonight.

The NHC will release its next complete advisory at 11am EDT.  For more information on this storm visit:  https://www.nhc.noaa.gov

By Lynn Jenner
NASA’s Goddard Space Flight Center

Aug. 30, 2019 – Update #3 -NASA Satellites On-Hand As Dorian Becomes a Category 3 Hurricane

As Hurricane Dorian was upgraded to a Category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale, NASA’s fleet of satellites were gathering data during the day to assist weather forecasters and scientists.  At 2:oo pm EDT the National Hurricane Center (NHC) posted a supplemental advisory. NHC reports that “extremely dangerous  Hurricane Dorian poses a significant threat to Florida and the northwestern Bahamas.  The Hurricane Hunter plane finds Dorian is now a major hurricane.”

NASA’s Global Precipitation Measurement mission satellite uses its IMERG algorithm with data from a fleet of satellites to provide global estimates of the precipitation within the storm every 30 minutes.  This map displays the estimated rainfall accumulation for the region from August 27th – August 30th, prior to Dorian becoming a Category 3 storm.

NOAA-NASA’s Suomi NPP satellite uses its complement of instruments onboard to dissect storms and provide information on many different aspects of the hurricane including storm strength, cloudtop temperature, circulation, and rainfall, among others, within the structure of the storm.  The next three images are all from the Suomi NPP satellite and its instruments which help scientists figure out the intensity of the storm and help predict where it will ultimately end up.

Hurricane Dorian is currently at latitude 24.8N and longitude 70.3W which is about 445 miles (715 km) east of the northwestern Bahamas and about 625 miles (1005 km) east of West Palm Beach, FL.   The NHC forecast is: “A slower west-northwestward to westward motion should begin tonight and continue into early next week. On this track, the core of Dorian should move over the Atlantic well north of the southeastern and central Bahamas today and tomorrow, be near or over the northwestern Bahamas on Sunday, and be near the Florida peninsula late Monday.”

Currently the storm’s maximum sustained winds are 115 mph (185 km/h) with higher gusts, and is moving northwest at 10 mph (17 km/h).  Hurricane-force winds extend outward up to 25 miles (35 km) from the center and tropical-storm-force winds extend outward up to 105 miles (165 km). The minimum central pressure is 970 mb.

The summary of watches and warnings in effect have not changed since the last NHC update at 11:00 am EDT.

For more information and updates, visit:  https://www.nhc.noaa.gov

By Lynn Jenner
NASA’s Goddard Space Flight Center

Aug. 30, 2019 – Update #2 – Hurricane Dorian Marching Slowly Across Atlantic

The National Hurricane Center (NHC) in Miami reports that an Air Force plane is finding Dorian a “little stronger” as of the 8:00am EDT advisory put out today, Aug. 30, 2019.  Data from an Air Force Reserve reconnaissance aircraft indicate that maximum sustained winds have increased to near 110 mph (175 km/h) with higher gusts. That is in keeping with what weather forecasters are predicting for the storm.

On Aug. 29, 2019, NASA’s Aqua satellite captured this infrared image with the AIRS instrument which analyzed cloud top temperatures in the storm.  The coldest temperatures AIRS found were in the center of the storm where the strongest thunderstorms are found.  These storms were as cold as or colder than minus 63 degrees Fahrenheit (minus 53 degrees Celsius).  NASA research has found that cloud top temperatures that cold indicate strong storms with the potential to generate heavy rainfall.

At 8:00 am EDT (1200 UTC), the NHC reported that “the the center of Hurricane Dorian was located near latitude 24.2 North, longitude 69.4 West. Dorian is moving toward the northwest near 12 mph (19 km/h), and this motion is expected to continue through today. A slower west-northwestward to westward motion is forecast to begin tonight and continue through the weekend. On this track, Dorian should move over the Atlantic well east of the southeastern and central Bahamas today, approach
the northwestern Bahamas Saturday, and move near or over portions of
the northwestern Bahamas on Sunday.”

Dorian is expected to strengthen during the next few days, and become a major hurricane later today (Aug. 30). Dorian is likely to remain an extremely dangerous hurricane while it moves near the northwestern Bahamas and approaches the Florida peninsula through the weekend.

Currently hurricane-force winds extend outward up to 25 miles (35 km) from the center, and tropical-storm-force winds extend outward up to 105
miles (165 km).  Yesterday the barometric pressure inside the storm was 991 mb.  Today the minimum central pressure just reported by the Air Force reconnaissance plane was 972 mb (28.70 inches).  The lower the barometric pressure in hurricanes, the higher the wind speeds— and the more dangerous the storm.

Hurricane conditions are possible within the watch area by Sunday, with tropical storm conditions possible by Saturday night or Sunday morning.

A life-threatening storm surge will raise water levels by as much as 10 to 15 feet above normal tide levels in areas of onshore winds in the northwestern Bahamas. Near the coast the surge will be accompanied by large and destructive waves.

Dorian is expected to produce the following rainfall accumulations this weekend into the middle of next week:

Northwestern Bahamas and coastal sections of the Southeast United States…6 to 12 inches, isolated 15 inches.
Central Bahamas…1 to 2 inches, isolated 4 inches.

This rainfall may cause life-threatening flash floods.

Swells are likely to begin affecting the east-facing shores of the Bahamas and the southeastern United States coast during the next few days. These swells are likely to cause life-threatening surf and rip current conditions.

For updated forecasts, visit NOAA’s NHC: www.nhc.noaa.gov

By Lynn Jenner
NASA’s Goddard Space Flight Center

Aug 30, 2019 – Update #1 – NOAA’s GOES-East and GOES-15 Capture Dorian’s Movement in the Atlantic

This short animated GIF shows night and day movement of Dorian across the Atlantic from Aug. 29, 2019 at 11:30 pm (EDT) to Aug. 30, 2019 at 9:00 am (EDT).

A second image provided by the U.S. Naval Research Laboratory shows a visible satellite image of Dorian taken by NOAA’s GOES-15 at 8:00 am EDT.

Ongoing coverage of this storm will be provided by NASA during the day today and over the Labor Day weekend.

For more information, visit: https://www.nhc.noaa.gov

By Lynn Jenner
NASA’s Goddard Space Flight Center

Aug. 29, 2019 – NASA Estimates Heavy Rainfall in Hurricane Dorian

Hurricane Dorian is packing heavy rain as it moves toward the Bahamas as predicted by NOAA’s NHC or National Hurricane Center. NASA analyzed the storm and found heavy rainfall in the storm.

NASA has the ability to peer under the “hood” or clouds of a tropical cyclone and estimate the rainfall rates occurring. After looking into Dorian’s clouds, imagery was generated using the Integrated Multi-satEllite Retrievals for GPM or IMERG “early run” product, at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. IMERG uses a constellation of satellites united by the GPM Core Observatory to provide global observations of Earth’s precipitation every 30 minutes.

IMERG estimated rainfall accumulations for the region affected by Hurricane Dorian over the 24 hour period of August 27 at (7:59 a.m. EDT) 11:59 UTC to August 28 at (7:59 a.m. EDT) 11:59 UTC. “The data indicates that up to 120 mm (4.72 inches) of rainfall accumulated in certain regions during the 24 hour period,” said Jacob Reed of NASA Disasters Program, GPM at NASA Goddard.

NHC said that Dorian is expected to produce the following rainfall accumulations this weekend into early next week: The central Bahamas…2 to 4 inches, isolated 6 inches; the northwestern Bahamas and coastal sections of the Southeastern United States…4 to 8 inches, isolated 12 inches. This rainfall may cause life-threatening flash flood.

On Aug. 29 at 5 a.m. EDT (0900 UTC), NOAA’s NHC said the center of Hurricane Dorian was located near latitude 20.5 degrees north and longitude 66.6 degrees west. That puts Dorian’s center about 150 miles (240 km) north-northwest of San Juan, Puerto Rico and about 425 miles (685 km) east-southeast of the southeastern Bahamas.

Dorian is moving toward the northwest near 13 mph (20 kph), and this general motion is expected to continue through Friday.  A west-northwestward motion is forecast to begin Friday night and continue into the weekend.

Maximum sustained winds are near 85 mph (140 kph) with higher gusts. Strengthening is forecast during the next few days, and Dorian is expected to become a major hurricane on Friday. The minimum central pressure based on earlier Air Force Reserve Hurricane Hunter data is 991 mb (29.27 inches).

NHC said “On this track, Dorian should move over the Atlantic well east of the southeastern and central Bahamas today and on Friday, and approach the northwestern Bahamas on Saturday.”

Interests in the northwestern and central Bahamas should monitor the progress of Dorian. Swells are likely to begin affecting the east-facing shores of the Bahamas and the southeastern United States coast during the next few days.  These swells are likely to cause life-threatening surf and rip current conditions.

For updated forecasts, visit NOAA’s NHC: www.nhc.noaa.gov

By Rob Gutro
NASA’s Goddard Space Flight Center

Aug. 28, 2019 – Update #2 – NASA Sees Dorian Become a Hurricane

NASA’s Terra satellite passed over the northwestern Atlantic Ocean as Dorian reached hurricane status during the afternoon of August 28, 2019.

On Aug. 28, 2019 at 1:30 p.m. EDT, the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA’s Terra satellite provided a visible image of Dorian near St. Thomas and the U.S. Virgin Islands. At 2 p.m. EDT, the National Hurricane Center noted, “Satellite and radar images indicate that the cloud pattern has become better organized during the past several hours.”

Dorian strengthened over the warm waters of the eastern Caribbean Sea and was officially designated a Category 1 hurricane on the Saffir-Simpson Hurricane Wind Scale at 2 p.m. EDT.

At 2 p.m. EDT, a Hurricane Warning is in effect for Vieques and Culebra, the U.S. Virgin Islands and the British Virgin Islands. The National Hurricane Center issued a Tropical Storm Warning for Puerto Rico with a Hurricane Watch also in effect as changing conditions warrant.

NOAA’s National Hurricane Center or NHC said that at 2 p.m. EDT (1800 UTC), the center of Hurricane Dorian was located near latitude 18.3 degrees north and longitude 65.0 degrees west. That puts Dorian directly over the island of St. Thomas.

Dorian is moving toward the northwest near 13 mph (20 kph), and this motion is expected to continue for the next day or two. Maximum sustained winds have increased to near 75 mph (120 kph) with higher gusts. Hurricane-force winds extend outward up to 20 miles (30 km) to the north and east of the center. Tropical-storm-force winds extend outward up to 80 miles (130 km) primarily to the east of the center. An elevated weather station on Buck Island just south of St. Thomas reported a sustained wind of 82 mph (132 kph) and a gust of 111 mph (178 kph). The estimated minimum central pressure from nearby observations is 997 millibars.

NOAA’s National Hurricane Center provided three key messages for Dorian:

1. Hurricane conditions are expected in the U.S. and British Virgin Islands, Culebra, and Vieques today. Tropical storm conditions are expected in Puerto Rico today with hurricane conditions possible.
2. Heavy rainfall over portions of Puerto Rico and the U.S. and British Virgin Islands could produce flash flooding during the next couple of days. Heavy rains are expected to occur over portions of the Bahamas, Florida, and elsewhere in the southeastern United States later this week and into early next week.
3. The risk of dangerous storm surge and hurricane-force winds is increasing in the central and northwestern Bahamas and along the Florida east coast, although it is too soon to determine where these hazards will occur. Residents in these areas should ensure that they have their hurricane plan in place and not focus on the exact forecast track of Dorian’s center.

On this track, Dorian should continue to move near or over the U.S. and British Virgin Islands this afternoon and then move over the open Atlantic well east of the southeastern Bahamas. Dorian is forecast to continue strengthening during the next few days over the Atlantic waters.

For updated forecasts, visit: www.nhc.noaa.gov

By Rob Gutro
NASA’s Goddard Space Flight Center