[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 302032
TCDAT3

Hurricane Lorenzo Discussion Number  34
NWS National Hurricane Center Miami FL       AL132019
500 PM AST Mon Sep 30 2019

The wind field of Lorenzo continues to expand, with a trio of
scatterometer overpasses showing that tropical-storm-force winds now
extend up to 270 n mi from the center, while hurricane-force winds
can be found up to 90 n mi from the center. A cloud-covered eye has
been apparent throughout the day and cloud-top temperatures
surrounding the eye have remained fairly consistent. The most recent
Dvorak CI values from TAFB and SAB suggest Lorenzo is maintaining
its strength at 90 kt, which will remain the initial intensity for
this advisory. A drifting NOAA buoy near the eyewall of Lorenzo
recently reported a pressure of 964.8 mb, supporting the minimum
central pressure of 957 mb.

Lorenzo continues moving north-northeastward at 13 kt, around the
northwestern periphery of a subtropical ridge to its southeast. Over
the next couple of days Lorenzo will be accelerated northeastward by
increasing southwesterly flow ahead of a mid-latitude trough
amplifying across the central Atlantic. This motion should take the
core of Lorenzo near the western Azores late Tuesday and early
Wednesday. The forecast track confidence remains high through 72
hours. After that time, global models have come into a little better
agreement on the future track of Lorenzo, with a turn to the right
toward Ireland or the U.K. as a weakening extratropical low. The
official forecast track is just a little to the right of the
previous one and lies near the consensus aids.

The environment surrounding Lorenzo is not expected to change much
through tonight, and therefore the intensity should remain fairly
steady. On Tuesday, the hurricane should begin gradually weakening
as drier air entrains into the circulation and the system moves over
progressively cooler waters. By 48 hours, the interaction with the
approaching trough, an associated cold front, and very strong
southwesterly shear will help transition Lorenzo into an
extratropical low. This transition is expected to be complete by 72
hours. The low is then expected to weaken and dissipate shortly
after 96 hours. The official forecast was increased through
the first 48 hours to reflect a more steady intensity in the near
term, and then is blended close to the previous forecast after that
time.

Key Messages:

1.  Lorenzo is expected to bring hurricane and tropical storm force
winds to the Azores beginning Tuesday night, and these conditions
will continue into Wednesday.  Hurricane and Tropical Storm Warnings
are now in effect for the Azores.

2.  Large swells generated by Lorenzo will continue to spread across
much of the north Atlantic basin during the next few days.  These
swells will produce life-threatening surf and rip currents.


FORECAST POSITIONS AND MAX WINDS

INIT  30/2100Z 30.9N  42.1W   90 KT 105 MPH
 12H  01/0600Z 32.8N  40.5W   90 KT 105 MPH
 24H  01/1800Z 36.1N  36.7W   85 KT 100 MPH
 36H  02/0600Z 40.3N  31.4W   80 KT  90 MPH
 48H  02/1800Z 45.9N  25.0W   75 KT  85 MPH
 72H  03/1800Z 55.2N  14.8W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  04/1800Z 56.3N  10.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  05/1800Z...DISSIPATED

$$
Forecaster Latto
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