152 
 WTNT41 KNHC 052050
 TCDAT1
 
 HURRICANE JOAQUIN DISCUSSION NUMBER  33
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL112015
 500 PM AST MON OCT 05 2015
 
 Joaquin's cloud pattern has actually improved somewhat since the
 previous advisory with a cloud-filled eye having briefly appeared
 in visible satellite imagery. Also, the eye has remained distinct
 on the Bermuda radar at an altitude above 32,000 feet. Satellite
 intensity estimates are T4.5/77 kt from SAB, T4.3/72 kt from the
 NHC AODT technique, and T4.0/65 kt from TAFB. Based on the distinct
 eye feature noted in visible satellite imagery and radar data, the
 intensity is being maintained at 75 kt for this advisory. This
 intensity is also supported by dropsonde data from the NASA WB-57
 aircraft, which has been conducting research in Joaquin for the
 Office of Naval Operation's Tropical Cyclone Intensity experiment.
 
 The initial motion estimate is 030/10 kt. Joaquin is rounding the
 northwestern periphery of a weak ridge located to its southeast,
 and will be entering the faster mid-latitude westerlies by Tuesday
 morning. The result should be a gradual turn toward the northeast
 accompanied by a modest increase in forward speed tonight and
 Tuesday, followed by more significant acceleration toward the
 east-northeast at forward speeds of near 30 kt by Wednesday. The
 official forecast track is a tad to the left of the previous
 advisory track, and basically lies down the middle of the tightly
 packed guidance envelope through 36 hours. At 48-120 hours, the
 extratropical forecast track is based on guidance provided by the
 NOAA Ocean Prediction Center.
 
 The deep-layer vertical wind shear is expected to remain at less
 than 20 kt for the next 24 hours or so, which should allow for
 Joaquin to only slightly weaken. By 36 hours and beyond, westerly
 vertical wind shear is forecast by the global and regional models to
 increase to more than 30 kt when Joaquin will be moving over sub-24C
 sea-surface temperatures. The expected result should be steady
 weakening and a transition to a large and expanding extratropical
 low pressure system over the much cooler waters of the north
 Atlantic by 48 hours. However, the GFS and ECMWF models are
 suggesting that Joaquin could get a baroclinic boost as it interacts
 with a frontal system and strong jetstream and, as a result, the
 intensity forecast does not show the typical rapid decay rate of a
 tropical cyclone moving over 17C-20C SSTs on days 3-5. The NHC
 intensity forecast is similar to the previous advisory and follows
 the intensity consensus model IVCN through 36 hours, and then is
 based on guidance provided by the Ocean Prediction Center for the
 48-120 hour period.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  05/2100Z 35.8N  64.0W   75 KT  85 MPH
  12H  06/0600Z 37.1N  61.7W   70 KT  80 MPH
  24H  06/1800Z 38.7N  57.3W   70 KT  80 MPH
  36H  07/0600Z 40.0N  51.0W   65 KT  75 MPH
  48H  07/1800Z 41.4N  43.4W   60 KT  70 MPH...POST-TROP/EXTRATROP
  72H  08/1800Z 44.0N  28.8W   55 KT  65 MPH...POST-TROP/EXTRATROP
  96H  09/1800Z 45.6N  20.7W   50 KT  60 MPH...POST-TROP/EXTRATROP
 120H  10/1800Z 48.0N  14.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 
 $$
 Forecaster Stewart