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Tropical Storm Kristy Discussion Number  13
NWS National Hurricane Center Miami FL       EP132018
800 PM PDT Thu Aug 09 2018

Recent 37-GHz microwave images show that Kristy's low-level
structure has improved markedly with a solid cyan ring and multiple
low-cloud spiral bands.  Inner-core convection has increased too,
and recent infrared satellite imagery is suggesting the possible
development of a ragged eye.  Although 00Z Dvorak estimates were a
consensus T3.5 from TAFB and SAB, the continued improvement in
structure supports an initial intensity of 60 kt.  Given the
cyclone's well-defined structure, Kristy could become a hurricane
overnight or early Friday while it remains over sufficiently warm
water and in a low-shear environment.  After that time, cooler
waters and gradually increasing shear will cause the winds in the
circulation to slowly diminish, with deep convection likely
dissipating, and Kristy becoming post-tropical, by 72 hours.  The
updated NHC intensity forecast is a little higher than the guidance
in the first 12 hours but then is similar to the previous forecast
and close to the HCCA guidance and the ICON intensity consensus
thereafter.

Kristy is moving slightly east of due north, or 010/6 kt.  There
has been little change in the tune of the various track models.
The GFS and HWRF continue to show Kristy being pulled north-
northeastward by Tropical Storm John, while the ECMWF and UKMET
models show less interaction and have Kristy turning west-
northwestward by 36-48 hours with more ridging to the north.  This
might be a classic case of why the consensus approach can work so
well.  So far, with 72 hours of forecasts for Kristy under our belt,
the GFS and the ECMWF have been the two worst-performing track
models, each having a significant eastward and westward bias,
respectively.  The various consensus aids, on the other hand, have
proven to be the most skillful so far.  For that reason, the NHC
track forecast continues to be down the middle of the guidance
envelope, close to a blend of the HCCA and TVCX aids.


FORECAST POSITIONS AND MAX WINDS

INIT  10/0300Z 17.4N 129.9W   60 KT  70 MPH
 12H  10/1200Z 18.4N 129.5W   65 KT  75 MPH
 24H  11/0000Z 19.7N 129.1W   60 KT  70 MPH
 36H  11/1200Z 20.7N 129.0W   55 KT  65 MPH
 48H  12/0000Z 21.4N 129.1W   45 KT  50 MPH
 72H  13/0000Z 23.2N 129.5W   35 KT  40 MPH...POST-TROPICAL
 96H  14/0000Z 25.5N 130.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  15/0000Z 27.0N 131.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Berg

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