Daniel briefly becomes a major hurricane overnight, now on a weakening trend
Daniel defied the odds last night and became the 2012 Pacific hurricane season's second major hurricane. Dvorak satellite imagery shortly after the previous blog revealed a ring of -75 °C cloud tops wrapping fully around the eye. Satellite-derived intensity estimates from UW-CIMSS peaked at 5.8/125 mph with NESDIS' Satellite Analysis Branch (SAB) and NHC's Tropical Analysis Forecasting Branch (TAFB) both at 5.0/105 mph. Since then, Daniel has been gradually weakening as it traverses sub-25 °C Sea Surface Temperatures. As of the latest advisory from the National Hurricane Center, the storm was located at 15.3 °N 126.3 °W (position accurate within 10 nm), or about 1190 miles west-southwest of the southern tip of Baja California. Maximum sustained winds have decreased to 100 mph, making it a minimal Category 2 hurricane on the Saffir-Simpson Hurricane Wind Scale, and the minimum barometric pressure has risen to 974 millibars. Daniel is moving west at 15 mph well away from land. Visible satellite loops reveal that Daniel had been holding its own during the afternoon hours with a well-defined, mostly clear eye with deep convection in the eyweall. However, recent trends show convection is diminishing and the eye is becoming obscured. I think it is safe to say that this is the beginning of the end for the tropical cyclone. Or, at least I hope it is.
Figure 1. Evening visible satellite imagery of Hurricane Daniel.
Figure 2. Dvorak satellite imagery of Hurricane Daniel at peak intensity.
The forecast for Daniel
Nothing has changed. Daniel is continuing on a westward motion along the southern periphery of a strong mid-level ridge of high pressure positioned over the US Central Plains. This ridge is expected to build westward with time, which may allow a south-of-west movement after 72 hours out. A majority of the model guidance has shifted southward with time, and it appears that Hawaii will not see any significant effects from Daniel. Regardless, increased surf, numerous rain showers, and gusty winds should affect the big settlement of Hilo by the weekend.
Now that Daniel has begun its gradual weakening trend, the intensity forecast should be much easier. The cyclone is now passing over Sea Surface Temperatures near 24 °C and Relative Humidity values have now fallen into the low-40s (%). Additional weakening should occur over the next 120 hours as the cyclone enters an increasingly dry environment. The latest SHIPS model does show a slight increase in SSTs by 120 hours out, but no re-intensification is forecast due to higher wind shear by that time, and dissipation into a remnant low should have occurred by that time. The forecast lies near the LGEM and National Hurricane Center's, showing weakening below hurricane status between 24-36 hours out and dissipation by the end of the period.
...FORECAST POSITIONS AND MAX WINDS...
INIT 09/0300Z 15.3N 126.3W 85 KT 100 MPH
12H 09/1200Z 15.4N 128.5W 80 KT 90 MPH
24H 10/0000Z 15.6N 131.4W 70 KT 80 MPH
36H 10/1200Z 15.7N 134.6W 60 KT 70 MPH
48H 11/0000Z 15.6N 137.8W 45 KT 50 MPH
72H 12/0000Z 15.3N 143.7W 35 KT 40 MPH
96H 13/0000Z 15.2N 149.1W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 14/0000Z 14.7N 149.8W 25 KT 30 MPH...POST-TROP/REMNT LOW