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Hurricane KARINA Forecast Discussion Number 8
2014-08-14 22:46:33| National Hurricane Center (East Pacific)
Issued at 200 PM PDT THU AUG 14 2014 000 WTPZ41 KNHC 142046 TCDEP1 HURRICANE KARINA DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112014 200 PM PDT THU AUG 14 2014 Despite moderate northeasterly vertical wind shear, Karina has managed to develop a closed mid-level eye with a diameter of around 10-12 nmi since the previous advisory as noted in recent SSMI/S and AMSU microwave imagery. Visible satellite imagery also indicates that a cloud-filled eye has appeared in the middle of the nearly circular CDO during past hour or so. Satellite intensity estimates are a consensus T4.0/65 kt, and ADT estimates from UW-CIMSS ADT have been steady at T4.4/75 kt for the past couple of hours. As a result of these data, the intensity has been increased to 65 kt. The initial motion estimate is 270/13 kt, which is based primarily on passive microwave satellite position fixes. Karina's apparent westward acceleration is likely due to the low-level center moving or reforming underneath the well-defined mid-level eye. As a result, this westward jog is expected to be a temporary motion, and Karina should slow down somewhat in the near-term. Otherwise, the hurricane is expected to remain on a basic westward track for the next 4 days as Karina is steered by a deep-layer ridge to its north. Afterwards, the cyclone is expected to slow down significantly and make a turn toward the west-southwest or southwest as Karina begins to interact with possible multiple tropical cyclones developing in the central Pacific and eastern Pacific basins. As mentioned in the previous discussion, rather than committing to any one particular model solution this far out in time, the NHC track forecast instead just shows a significant slow down in Karina's motion. The official forecast track is just an extension of the previous advisory track, and lies south of the consensus model TVCE, near the extreme southern edge of the NHC guidance envelope. The GFS-based SHIPS model indicates that the vertical shear is expected to increase to near 20 kt during the 12-24 hour period, while the shear vector veers around to the east. Given the well-defined and small eye mentioned previously, some additional strengthening is expected while Karina remains in favorable thermodynamic and oceanic environments. By 36 hours and beyond, the shear is forecast to decrease significantly, but this will occur when the cyclone is moving over marginal SSTs. The result is that a general leveling off of the intensity is expected, although there could obviously be some fluctuations in the intensity due to internal eyewall dynamics that can not be forecast this far in advance. The official intensity forecast remains well above the consensus model ICON due to the persistent weakening of Karina shown by the GFDL and HWRF models thus far, and instead follows the trend of the SHIPS and LGEM models. FORECAST POSITIONS AND MAX WINDS INIT 14/2100Z 17.1N 117.6W 65 KT 75 MPH 12H 15/0600Z 17.4N 119.1W 75 KT 85 MPH 24H 15/1800Z 17.8N 121.3W 80 KT 90 MPH 36H 16/0600Z 18.1N 123.6W 80 KT 90 MPH 48H 16/1800Z 18.2N 125.8W 80 KT 90 MPH 72H 17/1800Z 18.1N 129.5W 80 KT 90 MPH 96H 18/1800Z 17.7N 132.6W 75 KT 85 MPH 120H 19/1800Z 17.6N 134.2W 70 KT 80 MPH $$ Forecaster Stewart
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