[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 270858
TCDAT3

Hurricane Lorenzo Discussion Number  19
NWS National Hurricane Center Miami FL       AL132019
500 AM AST Fri Sep 27 2019

Lorenzo has maintained its impressive structure in satellite imagery
this morning. The hurricane still has a fairly clear eye surrounded
by very cold cloud tops. A 0423 UTC AMSR2 overpass showed a small
break in the deepest convection in the southwest eyewall of the
hurricane, but given how cloud tops have cooled since then, I
suspect that did not last long. Satellite intensity estimates have
not changed substantially since the last advisory, so the initial
intensity remains 125 kt.

The hurricane is moving steadily north-northwestward at 12 kt. The
track guidance is in remarkably good agreement on Lorenzo's track
and confidence in the forecast is high. Lorenzo should turn
northward and then northeastward during the next few days as it
moves around the western edge of a mid-level ridge centered over the
eastern Atlantic. By the end of the forecast period, Lorenzo will
likely accelerate northeastward ahead of mid-latitude trough
approaching from the west. The official track forecast is basically
unchanged since the last advisory and now sits right in the middle
of the guidance envelope.

The NHC intensity forecast is also mostly unchanged since the last
advisory. Although SHIPS diagnostics suggest that moderate
southwesterly shear could soon affect the cyclone, not much change
in strength is anticipated for the next 24 hours since Lorenzo will
be moving over slightly warmer waters and an eyewall replacement
cycle does not seem imminent. Gradual weakening is then anticipated
through early next week due to a modest increase in shear and a
decrease in available ocean heat content. Short-term fluctuations in
intensity related to eyewall replacement cycles are also possible
during that time. The NHC forecast remains on the high side of the
guidance for the first 24 hours, and is close to HCCA after that.

FORECAST POSITIONS AND MAX WINDS

INIT  27/0900Z 18.6N  42.1W  125 KT 145 MPH
 12H  27/1800Z 20.1N  42.9W  125 KT 145 MPH
 24H  28/0600Z 21.8N  43.5W  120 KT 140 MPH
 36H  28/1800Z 23.5N  43.8W  115 KT 130 MPH
 48H  29/0600Z 25.1N  43.4W  110 KT 125 MPH
 72H  30/0600Z 28.7N  41.4W  100 KT 115 MPH
 96H  01/0600Z 33.3N  37.7W   95 KT 110 MPH
120H  02/0600Z 40.0N  30.5W   85 KT 100 MPH

$$
Forecaster Zelinsky
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