000 WTNT41 KNHC 020241 TCDAT1 HURRICANE JOAQUIN DISCUSSION NUMBER 17 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015 1100 PM EDT THU OCT 01 2015 The eye of Joaquin contracted in satellite imagery late this afternoon, but has become obscured by cirrus clouds since that time. Recent microwave imagery and aircraft observations have not shown any indications of an eyewall replacement, but the intensity appears to have leveled off for now. The aircraft has measured peak 700-mb flight-level winds of 123 kt and reliable SFMR surface winds of 116 kt, which support an initial wind speed of 115 kt. Satellite images show that the outflow is well established over the hurricane and some additional strengthening is possible during the next 12 hours or so. After that time, there could be some fluctuations in intensity due to eyewall replacement cycles. Joaquin is forecast to encounter increasing southwesterly shear in 2 to 3 days, which is expected to cause some weakening during that time. However, Joaquin is expected to remain a large and powerful hurricane for the next several days. The NHC intensity forecast is near the upper-end of the guidance in the short-term, and is close to the intensity consensus throughout the remainder of the forecast period. Recent reconnaissance fixes suggest that Joaquin has turned westward and slowed down, with an initial motion of 260/3. The mid- to upper-level ridge that has been steering Joaquin southwestward is expected to quickly weaken overnight while a mid- to upper-level trough over the southeastern United States deepens and cuts off. This should cause Joaquin to turn northward on Friday, and move north-northeastward at a faster forward speed Friday night and Saturday. The model envelope has again shifted eastward, with the GFDL and NAVGEM models now joining the other dynamical models which keep Joaquin offshore of the United States east coast. This has required another eastward shift to the NHC forecast, but it still lies to the west of the multi-model consensus and the most recent runs of the GFS and ECMWF models. The updated track is closest to the GFS ensemble mean. Additional eastward adjustments could be required to the official forecast overnight. Surface and reconnaissance aircraft data indicate that Joaquin's wind field has expanded during the past 24 hours. The initial and forecast wind radii have been adjusted outward accordingly. The increase in size has resulted in the issuance of a Tropical Storm Warning for eastern Cuba where wind gusts above tropical-storm- force have already been observed. KEY MESSAGES: 1. Joaquin's slow motion means that extremely dangerous conditions will continue over portions of the warning areas in the Bahamas well into Friday. 2. The forecast models continue to indicate a track farther away from the United States east coast and the threat of direct impacts from Joaquin in the Carolinas and mid-Atlantic states appears to be decreasing. However, the threat of impacts in Bermuda has increased and a Tropical Storm or Hurricane Watch could be required for that island on Friday. 3. Efforts to provide the forecast models with as much data as possible continue, with twice daily NOAA G-IV jet missions in the storm environment, and extra NWS balloon launches. 4. Even if Joaquin moves out to sea, strong onshore winds associated with a frontal system will create minor to moderate coastal flooding along the coasts of the mid-Atlantic and northeastern states through the weekend. In addition, very heavy rains, not associated with Joaquin, are expected to produce flooding over portions of the Atlantic coastal states. Please see products issued by local NWS Forecast Offices. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 22.9N 74.6W 115 KT 130 MPH 12H 02/1200Z 23.2N 74.7W 120 KT 140 MPH 24H 03/0000Z 24.7N 74.4W 120 KT 140 MPH 36H 03/1200Z 26.6N 73.4W 115 KT 130 MPH 48H 04/0000Z 29.0N 72.0W 105 KT 120 MPH 72H 05/0000Z 33.4N 70.2W 90 KT 105 MPH 96H 06/0000Z 37.0N 68.3W 70 KT 80 MPH 120H 07/0000Z 42.0N 61.0W 60 KT 70 MPH $$ Forecaster Brown