[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 070842
TCDAT5

Hurricane Danielle Discussion Number  25
NWS National Hurricane Center Miami FL       AL052022
900 AM GMT Wed Sep 07 2022

Danielle's cloud pattern has significantly improved over the past 6
hours.  The banding eye feature has warmed back up and cleared out,
and the cloud tops are cooling in two prominent curved bands located
in the north and south semicircles.  The subjective Dvorak T-numbers
from TAFB and SAB have increased, and a UW-CIMSS OPEN-AIIR satellite
intensity analysis yields 70-75 kt.  These data and the earlier
SAROPS surface wind retrieval support raising the initial intensity
to 70 kt for this advisory.

Danielle should continue moving over marginally warm waters for
just a few more hours, so some fluctuations in strength, similar to
what the cyclone has just undergone, are still possible.
Satellite imagery and global model data indicate that a
favorable position of a polar jet finger associated with the
approaching baroclinic zone may be dynamically influencing
Danielle's short-term intensification.  By early Thursday, the
cyclone is expected to traverse a sharp sea surface temperature
gradient of 20C or less.  These cooler waters, along with the
eventual loss of dynamic forcing should cause a gradual weakening
trend through the early next week.

Danielle's initial motion is estimated to be northeastward, or
050/12 kt.  Once again, there is no significant change to the NHC
forecast philosophy.  The hurricane should continue accelerating in
response to a vigorous baroclinic system approaching from the
northwest midway between Newfoundland and Danielle.  Danielle
is forecast to interact and merge with the system mentioned above
late Thursday night into Friday.  Over the weekend, the large
post-tropical storm-force low is expected to slip south back into
the deep-layer mid-latitude westerlies, turn south-southeastward to
southeastward, and continue in this general heading through early
next week.  The NHC forecast is similar to the previous one and is
close to the various multi-model consensus aids.

Danielle is producing a vast area of very rough seas over the
central-north Atlantic. More information can be found in the
High Seas Forecasts issued by the Ocean Prediction Center under
AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSFAT1.php.  The UK Met Office also has
information in High Seas Forecasts for the west Central and east
Central sections issued under WMO header FQNT21 EGRR and on the web
at metoffice.gov.uk/weather/specialist-forecasts/coast-and-sea/high-
seas-forecast


FORECAST POSITIONS AND MAX WINDS

INIT  07/0900Z 43.4N  38.1W   70 KT  80 MPH
 12H  07/1800Z 44.4N  35.9W   70 KT  80 MPH
 24H  08/0600Z 46.3N  33.4W   65 KT  75 MPH
 36H  08/1800Z 48.6N  32.0W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  09/0600Z 50.5N  32.7W   55 KT  65 MPH...POST-TROP/EXTRATROP
 60H  09/1800Z 50.0N  34.7W   50 KT  60 MPH...POST-TROP/EXTRATROP
 72H  10/0600Z 48.6N  33.9W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  11/0600Z 43.9N  23.8W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  12/0600Z 42.2N  15.1W   35 KT  40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Roberts
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