[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 210236
TCDAT5

Tropical Storm Don Discussion Number  28
NWS National Hurricane Center Miami FL       AL052023
300 AM GMT Fri Jul 21 2023

The band of convection noted on the eastern side of Don during the
previous advisory has wrapped around to the western side of the
tropical cyclone tonight. However, Don still is struggling to mix
out the dry air that earlier disrupted its convective structure.
ASCAT-C at 2339 UTC and ASCAT-B at 0026 UTC nicely captured Don's
circulation, and both had a peak wind retrieval of 40 kt, a bit
higher than earlier. However, there have been no changes to the
subjective Dvorak CI numbers from TAFB and SAB this cycle and so the
initial intensity remains 45 kt for this advisory.

Don continues to move west-northwestward at 290/8 kt. The storm is
being steered by a strong low- to mid-level ridge that should
gradually first shift northeastward and then eastward of the cyclone
as a short-wave trough currently over the Great Lakes ejects
eastward into the Canadian Maritimes over the next few days. This
synoptic pattern should result in Don turning to the northwest and
then north over the next 36-48 hours. Afterwards, Don should
complete recurvature northeast into the higher latitudes as it opens
up into a trough. The track guidance consensus has stabilized not
too far off from the prior forecast track, and very few adjustments
were needed to the official NHC track for this forecast cycle.

Don's structure appears quite healthy in the low-levels, per earlier
37 GHz microwave imagery which showed evidence of a closed cyan
ring. However, the combination of dry mid-level air and marginal
(24-25 C) sea surface temperatures appear to be keeping deep
convection (below -50C) in check while it attempts to wrap around
the center. These factors are likely to limit intensification, and
little change in strength is forecast over the next 36 h or so.
Weakening is then forecast to begin by 48 h as Don approaches the
north wall of the Gulf Stream and encounters a more hostile
upper-level flow pattern. Most of the global and regional-hurricane
model guidance show Don ceasing to produce organized convection by
72 h, and the storm is forecast to become post-tropical at that
time, followed by dissipation in 96 h. This forecast is in good
agreement with the consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT  21/0300Z 34.8N  44.7W   45 KT  50 MPH
 12H  21/1200Z 35.4N  46.1W   45 KT  50 MPH
 24H  22/0000Z 36.9N  48.1W   45 KT  50 MPH
 36H  22/1200Z 38.8N  49.9W   45 KT  50 MPH
 48H  23/0000Z 41.1N  50.9W   40 KT  45 MPH
 60H  23/1200Z 43.6N  51.1W   35 KT  40 MPH
 72H  24/0000Z 46.2N  49.6W   30 KT  35 MPH...POST-TROPICAL
 96H  25/0000Z...DISSIPATED

$$
Forecaster Papin
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