NASA finds little improvement in Miriam’s structure


Credit: NASA JPL/Heidar Thrastarson

When NASA's Aqua satellite passed over Tropical Storm Miriam Aug. 27 and infrared data showed slight improvement from the day before. On Aug. 28, wind shear was still affecting the storm.

NASA's Aqua satellite passed Tropical Storm Miriam on Aug. 27 at 6:35 a.m. EDT (1035 UTC). The Atmospheric Infrared Sounder or AIRS instrument analyzed the storm in infrared light which provides temperature information. Temperature is important when trying to understand how strong storms can be. The higher the cloud tops, the colder and the stronger they are.

AIRS saw coldest cloud top temperatures being pushed slightly east of center by light vertical wind shear. Those cloud top temperatures were as cold as minus 63 degrees Fahrenheit (minus 53 degrees Celsius). Storms with cloud top temperatures that cold have the capability to produce heavy rainfall. At the time of the Aqua satellite overpass, Miriam's cloud pattern and overall convective organization had improved from earlier in the day.

On Tuesday, August 28, 2018, the National Hurricane Center (NHC) noted that Miriam's cloud pattern had still not improved very much from Aug. 27. On Aug. 29, microwave data showed the low-level center still slightly displaced from the deep convection due to about 11.5 mph (10 knots/18.5 kph) of northwesterly wind shear.

At 5 a.m. EDT (2 a.m. PDT/0900 UTC), the center of Tropical Storm Miriam was located near latitude 14.0 degrees north and longitude 133.5 degrees west. That's about 1,480 miles (2,380 km) east-southeast of Hilo, Hawaii. Miriam was moving toward the west near 12 mph (19 kph), and the NHC said this motion is expected to continue through Wednesday. A turn toward the northwest and north-northwest is expected Thursday, Aug. 30 and Friday, Aug. 31.

Maximum sustained winds remain near 65 mph (100 kph) with higher gusts. Some strengthening is forecast during the next 48 hours, and Miriam is expected to become a hurricane later today or tonight.

For updated forecasts, visit the National Hurricane Center website:


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Rob Gutro