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Tropical Storm HENRI


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TROPICAL STORM HENRI DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082015
500 AM AST FRI SEP 11 2015

Overall, Henri's cloud pattern has become slightly better organized
since the last advisory.  While nearly all of the cyclone's deep
convection is still located well to the northeast of the center, a
relatively new convective burst over this area has grown in coverage
and cloud tops have cooled.  Subjective Dvorak classifications
remain below tropical storm strength, but the initial intensity held
at 35 kt due to the cyclone's increasing forward speed and somewhat
improved satellite presentation.

Southerly shear appears to be diminishing over the cyclone, as has
been forecast by the large-scale models.  The lower shear could
allow for some additional intensification to take place during the
next 12 hours or so while it remains over warm-enough waters.
However, the continued presence of dry air in the near-storm
environment and Henri's disorganized appearance suggest that any
intensification should be negligible. After the cyclone crosses the
northern wall of the Gulf Stream in less than 18 hours,
substantially lower sea surface temperatures and increasingly stable
air should induce weakening soon after that.  A plausible alternate
scenario, presented by some of the global models, is that Henri
could degenerate into a trough later today.  The cyclone or its
remnants are forecast to undergo extratropical transition in about
36 hours, with the system likely to be absorbed by a larger
extratropical cyclone by 72 hours.  The new intensity forecast is
very similar to the previous one.

The initial motion estimate is 010/14.  Henri is expected to
accelerate north-northeastward and then northeastward during the
next day or so as it encounters the fast-paced flow ahead of a deep
longwave trough digging into eastern North America and the western
Atlantic. The post-tropical cyclone or its remnants should then turn
east-northeastward over the north Atlantic. The new track forecast
is adjusted to the left of the previous forecast and lies on the
right side of the guidance envelope.

The latter part of this forecast, when the storm is expected to be
post-tropical, is partially based on guidance provided by NOAA's
Ocean Prediction Center.


FORECAST POSITIONS AND MAX WINDS

INIT  11/0900Z 36.2N  60.3W   35 KT  40 MPH
 12H  11/1800Z 39.0N  59.3W   40 KT  45 MPH
 24H  12/0600Z 43.0N  56.4W   40 KT  45 MPH
 36H  12/1800Z 46.5N  52.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
 48H  13/0600Z 48.9N  45.9W   35 KT  40 MPH...POST-TROP/EXTRATROP
 72H  14/0600Z...ABSORBED

$$
Forecaster Kimberlain

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