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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

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