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#713198 (Received by flhurricane at: 4:52 PM 26.Aug.2014) TCDAT4 HURRICANE CRISTOBAL DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL AL042014 500 PM EDT TUE AUG 26 2014 As Cristobal has moved northward around the eastern side of the upper trough it is currently interacting with, the shear has decreased over the cyclone and deep convection has redeveloped near the center. The latest NOAA Hurricane Hunter aircraft found that the pressure had fallen to 984 mb and reported a partial eyewall. The initial intensity of 65 kt is based on a peak 8,000-ft flight-level wind of 75 kt and SFMR winds around 60 kt. Aircraft data and a partial ASCAT pass show that the wind field of Cristobal has expanded significantly in the eastern semicircle, and the initial and forecast wind radii have been adjusted outward. Conditions should be favorable for some strengthening as a tropical cyclone during the next couple of days before the cyclone moves over cooler waters and into a higher shear environment. After that time, the GFS, ECMWF, and UKMET all show an impressive extratropical transition of Cristobal, as it interacts synergistically with a powerful mid-latitude trough in about 3 days. This should result in Cristobal maintaining hurricane-force winds for a time as an extratropical cyclone. The initial motion estimate is 010/12. Cristobal jogged north- northeastward earlier today, but is now moving a bit more to the left. The dynamical model guidance shows a bit of a northward jog tonight as the cyclone moves east of the upper-trough. After that time an acceleration toward the northeast is expected as the subtropical ridge to the southeast propels Cristobal into the mid latitudes by 48 hours. A quick northeastward motion is expected to continue through 4 days with a bend back toward the north-northeast shown at day 5. The track model guidance has shifted a bit to the west this cycle in the short range, and the NHC forecast has been nudged in that direction for the first 36 hours, but lies on the east side of the guidance envelope. At 48 hours and beyond the NHC forecast is largely an update of the previous one and is close to a consensus of the GFS and ECMWF models. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 28.8N 71.4W 65 KT 75 MPH 12H 27/0600Z 30.7N 71.2W 70 KT 80 MPH 24H 27/1800Z 32.9N 70.4W 70 KT 80 MPH 36H 28/0600Z 35.2N 67.6W 75 KT 85 MPH 48H 28/1800Z 38.0N 62.4W 75 KT 85 MPH 72H 29/1800Z 45.5N 47.0W 70 KT 80 MPH...POST-TROP/EXTRATROP 96H 30/1800Z 52.5N 35.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 120H 31/1800Z 60.0N 26.0W 55 KT 65 MPH...POST-TROP/EXTRATROP $$ Forecaster Brennan |