a NOAA hurricane hunter aircraft reported that the central pressure continues to slowly rise and the eye has become poorly defined on a radar image transmitted from the aircraft. Peak flight-level winds were 105 kt in the northwest quadrant from 7000 ft...which would support surface winds of about 90 kt. This makes Isabel a category two hurricane on the Saffir-Simpson scale. Water vapor imagery continues to show dry air in the western part of the circulation... and the convection has weakened markedly over past few hours. Recent images...however...show an improvement in the outflow pattern northwest of the center. The initial motion is 330/7. There has been no significant change to the track forecast. Isabel is on the west side of a deep-layer ridge extending from the Canadian Maritimes south-southeastward to east of the hurricane. A broad area of westerly flow is over the central and eastern United States...with a shortwave trough lifting northeastward through the Great Lakes. Large-scale models indicate that the ridge should build westward as the shortwave lifts out... which should cause Isabel to move in a general north- northwesterly direction through 72 hr. With the deterioration of the central core...additional weakening seems likely over the next 24 hours. Most of the model guidance continues to show increasing anticyclonic outflow over Isabel as a result of a digging and negatively-tilted upper-level trough that should interact with the hurricane in the 24 hours prior to landfall. For this reason...the official forecast allows for some restrengthening. It is possible...however...that the circulation could become so disrupted over the next day or so that Isabel would be unable to respond to the more favorable upper-level forcing. Forecaster Franklin |
WooHoo! Great news!