The NOAA Coral Reef Watch (CRW) satellite twice-weekly 50 km coral bleaching alert area product presented here outlines the areas where bleaching thermal stress currently reaches various bleaching stress levels, based on our satellite sea surface temperature monitoring. The bleaching thermal stress levels are defined in the table below based on the current values of the NOAA CRW coral bleaching HotSpot and Degree Heating Weeks (DHW) products.

Please note that locations with a current status of Bleaching Watch or No Stress recently may have been exposed to thermal stress. Although these two levels classify the current thermal stress condition, they do not take into account the recent stress history that is measured by Degree Heating Weeks. When the instantaneous thermal stress during the current twice-weekly time period drops to Bleaching Watch or No Stress level from a previously higher level, this product does not present any information on accumulated thermal stress during the past 12 weeks up to the previous twice-weekly period. Hence, a coral reef that is at Aert Level 2 one week may drop to Bleaching Watch or No Stress the following week. Please refer to CRW's Degree Heating Weeks (DHW) Product for information on the accumulated thermal stress during the past 12 weeks.

This product is updated twice-weekly on every Monday morning and Thursday morning, U.S. Eastern Time. CRW's methodology webpage provides detailed information about CRW products.

NOAA Coral Reef Watch (CRW) has been providing satellite global near-real-time 50 km (0.5 by 0.5-degree spatial resolution precisely) monitoring of thermal stress that causes mass coral bleaching to the U.S. and international coral reef communities since 1997. Our operational monitoring products, including HotSpot and Degree Heating Week (DHW), derived from our operational nighttime SST measured by POES AVHRR, have been very successful in detecting and monitoring the thermal stress that causes coral bleaching.