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413
WTNT43 KNHC 161443
TCDAT3

Post-Tropical Cyclone Helene Discussion Number 37
NWS National Hurricane Center Miami FL AL082018
1100 AM AST Sun Sep 16 2018

Helene’s cloud pattern has transformed into that of an
extratropical cyclone, with a large area of cold cloud tops
located well to the north and northwest of the center. An ASCAT
pass that caught the eastern portion of the circulation revealed
maximum winds of 40 to 45 kt, therefore the initial wind speed
remains 45 kt for this advisory. The global models suggest that
the system will strengthen slightly today due to baroclinic
processes, and this is reflected in the official forecast.
Weakening is anticipated by late Monday, and the system is forecast
to be absorbed by a larger low pressure to the northwest of the
United Kingdom by Tuesday morning.

The cyclone is moving quickly northeastward or 055/25 kt. Now that
the system is embedded within the mid-latitude westerlies, a
northeastward motion with some additional increase in forward speed
is expected over the next day or so. The global models remain in
good agreement on the track of the post-tropical low, and the new
official forecast is an update of the previous advisory.

This is the last NHC advisory on this system. Interests in Ireland
and the United Kingdom should consult products from their local
meteorological service for information about potential impacts from
the post-tropical cyclone. Local forecasts and warnings for the UK
can be found on the website of the UK Met Office at
https://www.metoffice.gov.uk/. Local forecasts and warnings for
Ireland can be found on the website of Met Eireann
at https://www.met.ie/.

FORECAST POSITIONS AND MAX WINDS

INIT 16/1500Z 43.8N 25.7W 45 KT 50 MPH…POST-TROPICAL
12H 17/0000Z 45.8N 21.2W 50 KT 60 MPH…POST-TROP/EXTRATROP
24H 17/1200Z 49.0N 14.8W 50 KT 60 MPH…POST-TROP/EXTRATROP
36H 18/0000Z 52.8N 6.2W 40 KT 45 MPH…POST-TROP/EXTRATROP
48H 18/1200Z…ABSORBED

$$
Forecaster Brown

AIRPRESS LOADED

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