Whenever the main convection is pushed away from the center of a tropical cyclone, it weakens. Imagine the center of a storm looking like a haystack, and wind shear or strong winds blow the top of the haystack away. That's what's happening with Julia.
Infrared imagery from the Atmospheric Infrared Sounder (AIRS) instrument that flies on NASA's Aqua satellite revealed that Julia's cloud top temperatures are warming today. Yesterday, those cloud top temperatures were colder than -65 degrees Fahrenheit. Today, they are less cold indicating that they're not as high, i.e., the thunderstorms are not as strong. The rule for thunderstorms is that the higher they are, the more powerful they are. When the cloud top heights fall, so does the storm's punch.
In addition, the sea surface temperatures where Julia is now located are between 78 and 80 degrees Fahrenheit (26-27 Celsius). A tropical cyclone needs sea surface temperatures of at least 80F to maintain intensity. As Julia continues to track to the north, the sea surface temperatures will continue to cool, taking away her fuel. That's why the National Hurricane Center has forecast additional weakening of Julia over the next 48 hours.
|Contact: Rob Gutro|
NASA/Goddard Space Flight Center