Tag: Bertha 2020

May 28, 2020 – NASA Looks at Inland Rainfall from Post Tropical Cyclone Bertha

NASA’s GPM core satellite analyzed rainfall generated from post-tropical cyclone Bertha as it continues to move toward the Great Lakes.

Bertha formed into a tropical storm on May 27, about 30 miles off the South Carolina coast. By 9:30 a.m. EDT, Bertha made landfall along the coast of South Carolina, east of Charleston. Data from NOAA and CORMP buoys showed that maximum sustained winds increased to near 50 mph (80 kph) before landfall. By 2 p.m. EDT, Bertha weakened to a tropical depression and heavy rainfall spread across the Carolinas. By 11 p.m. EDT, heavy rainfall spread across western North Carolina and southwest Virginia into West Virginia. At that time, the center of Bertha was located about 95 miles (150 km) south-southwest of Roanoke, Virginia. By May 28, Bertha had become a post-tropical cyclone.

A Post-Tropical Storm is a generic term for a former tropical cyclone that no longer possesses sufficient tropical characteristics to be considered a tropical cyclone. Former tropical cyclones that have become fully extratropical, subtropical, or remnant lows, are three classes of post-tropical cyclones. In any case, they no longer possess sufficient tropical characteristics to be considered a tropical cyclone. However, post-tropical cyclones can continue carrying heavy rains and high winds.

On May 28, flash flood watches were in effect for central West Virginia and a small part of coastal North Carolina through early morning. NOAA’s National Weather Service Weather Prediction Center in College Park Md. noted, “Bertha is expected to produce total rain accumulations of around one inch from West Virginia through eastern Ohio, southern and western Pennsylvania and far western New York, and 1 to 2 inches from South Carolina across eastern North Carolina into southeast Virginia. Isolated maximum storm total amounts of 4 inches are possible in southern Pennsylvania and parts of the Carolinas and southeast Virginia. This rainfall may produce life threatening flash flooding, aggravate and prolong ongoing river flooding, and produce rapid out of bank rises on smaller rivers.”

The Global Precipitation Measurement mission or GPM satellite provided a look at Bertha’s rainfall rates on May 28 at 1:21 a.m. EDT (0521UTC). GPM found heaviest rainfall over south central West Virginia, where rain was falling at rates of 1 inch (25 mm) per hour. A large area of light rain northwest of the center was falling at around 0.2 inches (less than 5 millimeters) per hour.

At 5 a.m. EDT (0900 UTC), the center of Post-Tropical Cyclone Bertha was located near latitude 38.3 degrees north and longitude 80.8 degrees west, about 80 miles (130 km) north-northwest of Roanoke, Virginia. The post-tropical cyclone is moving toward the north near 28 mph (44 kph) and this motion is expected to continue through midday Thursday, May 28, followed by a turn to the north-northeast. Maximum sustained winds are near 25 mph (35 kph) with higher gusts. The estimated minimum central pressure is 1012 millibars.

Bertha is expected to weaken and dissipate by Thursday evening as it crosses the eastern Great Lakes.

Tropical cyclones/hurricanes are the most powerful weather events on Earth. NASA’s expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.

GPM is a joint mission between NASA and the Japan Aerospace Exploration Agency, JAXA.

By Rob Gutro
NASA’s Goddard Space Flight Center

---

May 28, 2020 – Four Views of Tropical Storm Bertha Data from NASA’s GPM Core Satellite

The Global Precipitation Measurement Mission or GPM core satellite provides a look at precipitation around the world. GPM works with a constellation of other satellites to provide a global picture of precipitation and storms. In this collage of data gathered on Tropical Storm Bertha, there are four different views of data from GPM. The GPM core satellite passed over the southeastern coast of the U.S. on May 27 at 8 a.m. EDT (1200 UTC) and captured data on Tropical Storm Bertha as it was nearing landfall in South Carolina. These four images provided different insight to forecasters about the storm.

The Global Precipitation Measurement (GPM) Microwave Imager (GMI) instrument is a multi-channel, conical- scanning, microwave radiometer– an essential role in near-global-coverage. The upper left panel is the low frequency (10 and 18 GHz) composite from GMI. “These channels are excellent at detecting liquid precipitation over ocean and show the rain band impinging on the North Carolina/South Carolina coast,” said S. Joseph Munchak, Research Meteorologist and GPM Deputy Project Scientist for Ground Validation at NASA’s Goddard Space Flight Center in Greenbelt, Md. “But due to the high emissivity from soil and vegetation over land, they are less useful [over land areas].”

The lower left image is a composite from the 37 and 89 GHz channels. In addition to detecting liquid precipitation over the ocean, these higher frequencies are excellent for capturing ice-phase precipitation over land and water, which is depicted by the light gray colors, and show the curved storm structure quite well.

The lower right comes from the highest frequencies on GMI, which are sensitive to water vapor and ice clouds, and show a similar pattern to the ice precipitation from the 37/89 GHz channels.

The upper right image was created from a special type of data that only GMI provides – a “polarization difference” at 166 GHz.  “When this difference is positive, it means that the ice in the clouds must be horizontally aligned (think of ice crystals as pancakes oriented parallel to the ground),” Munchak said. “Understanding exactly what type of ice crystals produce this signal, and how it can be used to improve precipitation estimation and modeling, is an area of ongoing research at NASA Goddard.”

For more information about GPM, visit: www.nasa.gov/gpm

By Rob Gutro / S. Joseph Munchak
NASA’s Goddard Space Flight Center

May 27, 2020 – Short-lived Bertha Brought Heavy Rains to Parts of Florida

Bertha was a named storm for just the briefest of periods, becoming a tropical storm on the morning of Wednesday, May 27 at 8:30 am EDT just one hour before it made landfall along the South Carolina coast near Charleston. Using satellite and other observations, NASA calculated the large rainfall totals that it generated over parts of Florida early in its short lifetime.

After making landfall, Bertha quickly weakened into a tropical depression and was then accelerated northward by the southerly flow between a deep trough of low pressure over the Mississippi Valley to the west and a ridge of high pressure located just off the U.S. East Coast. Because of this, rainfall totals over the Carolina’s were not very heavy.  Bertha’s biggest impact actually occurred when it was still in the formation process, before it became organized enough to be named.

On Monday May 25, a trough (elongated area) of low pressure became established over the Florida Straits, initiating shower and thunderstorm activity in the region. Over the next day, as this trough, which extended eastward over the warm waters of the Gulf Stream and eventually led to Bertha, slowly moved northward up the Florida peninsula, it provided a focus for showers and thunderstorms, which brought heavy rains to southeast Florida.

Calculated Rainfall Totals

NASA’s Integrated Multi-satellitE Retrievals for GPM (IMERG) algorithm, combines observations from a fleet of satellites, in near-realtime, to provide near-global estimates of precipitation every 30 minutes. IMERG surface rainfall accumulations were calculated for the period from May 23 to 27, 2020, for the southeastern U.S.  The heaviest rainfall totals are located over southeastern Florida and the northern Bahamas where upwards of 150 to 200 mm (~6 to 8 inches) of rain are shown to have fallen. Miami received over 7 inches in one 24-hour period.  Rainfall totals over South Carolina where Bertha made landfall, however, are much lighter on the order 25 to 50 mm (~1 to 2 inches) or more as the storm moved quickly on.

The rainfall calculation was visualized in an image produced with the Giovanni online data system, developed and maintained by the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC).

What is IMERG?

IMERG is a satellite-based rain estimate is somewhat coarse in resolution and can miss short-lived, intense storm-cells, but the IMERG algorithm often does captures the large-scale features of storms wherever they form in the world.  While the United States is fortunate to have a network of ground radars that can provide higher-resolution precipitation estimates, in other parts of the world, notably over most of the world’s oceans, the IMERG rain estimate is an important reference point.

This near-real time rain estimate comes from the NASA’s IMERG algorithm, which combines observations from a fleet of satellites, in near-real time, to provide near-global estimates of precipitation every 30 minutes. By combining NASA precipitation estimates with other data sources, we can gain a greater understanding of major storms that affect our planet.

IMERG fills in the “blanks” between weather observation stations. IMERG satellite-based rain estimates can be compared to that from a National Weather Service ground radar.  Such good detection of large rain features in real time would be impossible if the IMERG algorithm merely reported the precipitation observed by the periodic overflights of various agencies’ satellites.  Instead, what the IMERG algorithm does is “morph” high-quality satellite observations along the direction of the steering winds to deliver information about rain at times and places where such satellite overflights did not occur.  Information morphing is particularly important over the majority of the world’s surface that lacks ground-radar coverage.

Image from NASA Goddard using IMERG data archived at:  https://giovanni.gsfc.nasa.gov/giovanni/.

By Steve Lang / Rob Gutro 
NASA Goddard Space Flight Center

---

May 27, 2o20 – NASA-NOAA Satellite Sees Tropical Storm Bertha Organizing

The second tropical storm of the North Atlantic Ocean hurricane season has formed off the coast of South Carolina. NASA-NOAA’s Suomi NPP satellite provided forecasters with a visible image of Tropical Storm Bertha as it was organizing.

On May 27, NOAA’s National Hurricane Center (NHC) issued a Tropical Storm Warning in effect from Edisto Beach, SC to South Santee River, SC.

The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard Suomi NPP provided a visible image of developing Tropical Storm Bertha late on May 26. The imagery showed strong thunderstorms were circling the center of circulation.

Satellite imagery on May 27 at 8:30 a.m. EDT showed the area of disturbed weather that NHC has been tracking over the past day or so quickly became better organized. The circulation had become better defined and the center had reformed beneath the area of deep convection. Those strongest storms were located just off the South Carolina coast.

At 8:30 a.m. EDT (1230 UTC), the center of Tropical Storm Bertha was located near latitude 32.7 degrees north and longitude 79.4 degrees west. Bertha’s center of circulation was just 30 miles (50 km) east-southeast of Charleston, South Carolina.

Bertha is moving toward the northwest near 9 mph (15 kph) and this motion is expected to continue through tonight. Maximum sustained winds are near 45 mph (75 kph) with higher gusts. Bertha is expected to weaken to a tropical depression after moving inland and become a remnant low tonight. The estimated minimum central pressure is 1009 millibars.

Bertha is expected to produce total rain accumulation of 2 to 4 inches with isolated totals of 8 inches across eastern and central South Carolina into west central to far southeastern North Carolina and southwest Virginia.  This rainfall may produce life-threatening flash flooding.

NHC said, “The system will be moving inland very shortly and little, if any, additional strengthening is expected.  Once inland, the small tropical cyclone should weaken rapidly and dissipate over central North Carolina on Thursday [May 28].”

Tropical cyclones/hurricanes are the most powerful weather events on Earth. NASA’s expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.

By Rob Gutro 
NASA Goddard Space Flight Center