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HURRICANE CRISTOBAL DISCUSSION NUMBER  23
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL042014
500 AM AST FRI AUG 29 2014

Cristobal has begun extratropical transition.  The cloud pattern has
become much less symmetric and central convection has decreased,
along with dry air eroding the southern flank of the cyclone. Dvorak
classifications are a little lower and support an intensity of about
70 kt for this advisory.  The hurricane has now moved across the
north wall of the Gulf Stream over much colder waters.  This
change in environment usually causes a significant weakening of
a tropical cyclone, but in this case strong baroclinic forcing
should delay the cyclone's demise.  Post-tropical Cristobal will
likely remain a powerful extratropical cyclone over the north
Atlantic through early Sunday. Beyond that time, the system is
forecast to merge with another low near southern Greenland
and lose its identity.

The hurricane continues to accelerate, and the motion is now
055/43 kt with Cristobal moving rapidly within the mid-latitude
flow.  Dynamical track guidance indicates that this general motion
will continue during the next couple of days with a decrease
in forward speed and a small leftward turn due to Cristobal
interacting with the low near southern Greenland in the next day or
two.  The official track forecast is close to the dynamical model
consensus and the latest guidance from the Ocean Prediction Center.


FORECAST POSITIONS AND MAX WINDS

INIT  29/0900Z 42.1N  51.7W   70 KT  80 MPH
 12H  29/1800Z 45.4N  45.4W   65 KT  75 MPH...POST-TROP/EXTRATROP
 24H  30/0600Z 49.3N  39.1W   65 KT  75 MPH...POST-TROP/EXTRATROP
 36H  30/1800Z 52.9N  32.3W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  31/0600Z 59.0N  24.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 72H  01/0600Z...ABSORBED

$$
Forecaster Blake

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