[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 170243
TCDAT5

Hurricane Teddy Discussion Number  19
NWS National Hurricane Center Miami FL       AL202020
1100 PM AST Wed Sep 16 2020

Teddy has been a perplexing hurricane thus far.  The infrared
satellite presentation appears rather impressive, with the center
embedded beneath a Central Dense Overcast with cloud tops as cold
as -85 degrees Celsius.  Despite the presentation, however, Dvorak
estimates from TAFB and SAB are a consensus T4.5/77 kt, and
objective estimates range between 70-75 kt.  Teddy's initial
intensity is therefore set just above these estimates at 80 kt.

A recent ASCAT pass indicated that Teddy's center is a little
farther to the southwest than previously estimated.  However, the
long-term motion remains toward the northwest (315/11 kt).  The
track forecast remains straightforward the the next 3 days, with
the guidance in good agreement that a mid-tropospheric high over
the central Atlantic will drive the hurricane northwestward toward
the western Atlantic.  There is a little more spread among the
track models on days 4 and 5, related to timing differences on
exactly where and how fast Teddy begins to recurve ahead of an
approaching mid-latitude trough coming from the northeastern United
States.  The new NHC track forecast has been nudged westward during
the first 3 days to account for the initial position adjustment,
but otherwise it's still close to the previous prediction even with
the increasing model spread on days 4 and 5.

An upper-level trough situated to the northwest of Teddy is causing
about 10-15 kt of deep-layer southwesterly shear over the
hurricane, and some model analyses suggest that there could be
stronger shear in a layer below the level of the upper-level
outflow.  The deep-layer shear is expected to increase a bit during
the next day or so, but this should be offset by a favorable
thermodynamic environment, allowing for some intensification during
that time.  The shear might relax by days 3 and 4, but then the
thermodynamic environment becomes a little less conducive for
strengthening.  In particular, Teddy may move over the cold wake
of Hurricane Paulette, and the SHIPS guidance indicates that
relatively warm upper-level temperatures could be a negative
factor.  All that said, the NHC intensity forecast lies near the
top end of the guidance envelope, showing Teddy peaking in
intensity in a couple of days and then only gradually weakening
through the end of the forecast period.


FORECAST POSITIONS AND MAX WINDS

INIT  17/0300Z 17.8N  51.5W   80 KT  90 MPH
 12H  17/1200Z 18.9N  52.6W   85 KT 100 MPH
 24H  18/0000Z 20.3N  54.1W   95 KT 110 MPH
 36H  18/1200Z 21.8N  55.6W  100 KT 115 MPH
 48H  19/0000Z 23.5N  57.1W  100 KT 115 MPH
 60H  19/1200Z 25.3N  59.1W   95 KT 110 MPH
 72H  20/0000Z 27.0N  61.1W   95 KT 110 MPH
 96H  21/0000Z 30.0N  64.0W   90 KT 105 MPH
120H  22/0000Z 35.0N  64.0W   90 KT 105 MPH

$$
Forecaster Berg
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