[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT41 KNHC 140240
TCDAT1

Tropical Storm Iota Discussion Number   3
NWS National Hurricane Center Miami FL       AL312020
1000 PM EST Fri Nov 13 2020

Satellite images show that Iota has changed little during the past
several hours.  Deep convection is organized in fragmented bands
around the center, except in the northwestern quadrant where there
is a dry slot.  All of the satellite intensity estimates are
around 35 kt, and therefore, the initial intensity is held at that
value.

Iota has been drifting to the south-southwest during the past
several hours, however, the steering currents are expected to become
more pronounced soon.  A strong and sprawling mid-level ridge
currently centered over the Gulf of Mexico will shift eastward and
build to the north of the tropical cyclone.  Since this ridging is
expected to remain well established to the north of Iota during the
next several days, a general westward motion is expected through the
forecast period.  The NHC track forecast takes the core of Iota to
the Nicaragua and Honduras coasts in about 3 days. However,
conditions are expected to deteriorate along that part of the coast
before the center arrives.  The latest models are in fairly good
agreement, except for the HWRF which is a northern outlier, and the
NHC track forecast lies near the middle of the guidance envelope.
This forecast is a little slower than the previous one.

An upper-level trough to the west of Iota is expected to move west
and dissipate on Saturday.  This should leave the storm in favorable
conditions of 29-30 C waters, and in an air mass of low wind shear
and high moisture this weekend and early next week.  These
conditions support steady to possibly rapid intensification until
Iota makes landfall.  The main question is how strong will Iota
become before it crosses the coast. The SHIPS Rapid Intensification
Index shows a 55 percent chance of Iota strengthening 65 kt or more
before it makes landfall, which is about 11 times the climatological
mean.  The NHC intensity forecast is an update of the previous one,
and shows Iota strengthening to a major hurricane in about 60 hours.

Key Messages:

1. Iota is expected to strengthen and be a major hurricane when it
approaches the coast of Central America.  There is a risk of
dangerous wind, storm surge, and rainfall impacts across portions of
Nicaragua and Honduras beginning Monday. Hurricane Watches
will likely be issued for a portion of this area on Saturday.

2. Through Wednesday, heavy rainfall from Tropical Storm Iota will
likely lead to life-threatening flash flooding and river flooding
across portions of northern Colombia and Central America. Flooding
and mudslides in Honduras and Nicaragua could be exacerbated by
Hurricane Eta's recent effects there.


FORECAST POSITIONS AND MAX WINDS

INIT  14/0300Z 13.6N  74.2W   35 KT  40 MPH
 12H  14/1200Z 13.5N  74.9W   45 KT  50 MPH
 24H  15/0000Z 13.7N  76.0W   55 KT  65 MPH
 36H  15/1200Z 14.0N  77.6W   70 KT  80 MPH
 48H  16/0000Z 14.3N  79.5W   85 KT 100 MPH
 60H  16/1200Z 14.5N  81.2W  100 KT 115 MPH
 72H  17/0000Z 14.7N  82.7W  105 KT 120 MPH
 96H  18/0000Z 14.8N  85.4W   50 KT  60 MPH...INLAND
120H  19/0000Z 14.3N  88.5W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Cangialosi
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