[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 241435
TCDAT2

TROPICAL STORM KARL DISCUSSION NUMBER  41
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122016
1100 AM AST SAT SEP 24 2016

Data from the last NOAA Hurricane Hunter aircraft mission into Karl
earlier this morning found peak flight-level winds of 63 kt at 8,000
ft and a peak SFMR wind of 47 kt.  Based on these data, the initial
intensity is held at 55 kt for this advisory, but this could be a
little generous.  The latest minimum central pressure based on a
dropsonde from the aircraft is 994 mb.  Karl is still expected to
strengthen, but it seems likely that this will be at least partly
due to baroclinic effects, as the global models shows Karl
intensifying while the shear increases to over 50 kt by 24 hours.
The new NHC intensity forecast follows this trend, and keeps Karl as
a 70-kt cyclone with a very large wind field when it becomes
post-tropical in 36 hours.  The circulation of Karl should be
absorbed by a large extratropical cyclone over the north Atlantic
by 48 hours, as shown in the global model solutions.

The aircraft last fixed the center on the southeastern side of the
deep convection, and the initial motion estimate is now 050/16.
Karl should accelerate quickly northeastward ahead of a broad
deep-layer trough moving into the Atlantic until it is absorbed,
with the forward speed expected to reach 50 kt by 36 hours.  The new
NHC track forecast is an update of the previous one and remains near
the middle of the tightly packed guidance envelope.

The track, intensity, and wind radii forecast of Karl's post-
tropical phase has been coordinated with the Ocean Prediction
Center.

FORECAST POSITIONS AND MAX WINDS

INIT  24/1500Z 32.8N  62.7W   55 KT  65 MPH
 12H  25/0000Z 34.8N  58.8W   60 KT  70 MPH
 24H  25/1200Z 38.9N  50.6W   70 KT  80 MPH
 36H  26/0000Z 45.0N  39.9W   70 KT  80 MPH...POST-TROPICAL
 48H  26/1200Z...ABSORBED

$$
Forecaster Brennan
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