[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 242037
TCDAT2

Tropical Storm Gonzalo Discussion Number  13
NWS National Hurricane Center Miami FL       AL072020
500 PM AST Fri Jul 24 2020

An Air Force Reserve Hurricane Hunter aircraft investigated Gonzalo
earlier this afternoon and found it to very poorly organized. The
aircraft even reported seeing multiple low-level swirls which is
surprising given the small size of the cyclone. The highest
flight-level winds measured by the plane were 41 kt while the
highest believable SFMR values were right around 35 kt. Based on
that data, Gonzalo's intensity has been lowered to 35 kt.

Small systems like Gonzalo are notorious for quick changes in
structure and intensity, both up and down. Therefore, despite its
current downswing, it is too soon to say for sure that Gonzalo will
not restrengthen to some degree before it reaches the southern
Windward Islands. That said, confidence in the intensity forecast is
a little higher now that we have better data to base the forecast on
and it does not seem likely that Gonzalo will overcome the dry air
that is currently inhibiting its development. Given the current
structure of the tropical storm, the NHC intensity forecast has been
lowered significantly, but still allows for some slight
restrengthening during the next 24 h. The new forecast is much
closer to the intensity consensus, below only the HWRF model which
does not appear to have a realistic initialization. Once Gonzalo
reaches the eastern Caribbean, weakening is anticipated and the
cyclone is forecast to dissipate within 3 days, if not sooner.

Gonzalo has sped westward all day with a motion near 270/16 kt. The
guidance continues to insist that Gonzalo will gain a little
latitude in the near future, and a general westward to
west-northwestward motion is still forecast for the next few days.
The NHC track forecast has again been shifted southward, but now
lies near the middle of the guidance envelope and very near the
various track consensus aids.

Key Messages

1. Gonzalo is forecast to bring tropical storm conditions across
portions of the southern Windward Islands Saturday and Saturday
night. Tropical Storm Warnings are currently in effect for some of
the islands. Interests in the southern Windward Islands should
monitor the progress of Gonzalo and follow any advice given by local
officials.

2. Gonzalo is expected to produce heavy rain over portions of the
southern Windward Islands. This could lead to life-threatening
flash flooding.


FORECAST POSITIONS AND MAX WINDS

INIT  24/2100Z 10.0N  55.6W   35 KT  40 MPH
 12H  25/0600Z 10.4N  58.0W   40 KT  45 MPH
 24H  25/1800Z 11.4N  61.1W   40 KT  45 MPH
 36H  26/0600Z 12.2N  64.2W   40 KT  45 MPH
 48H  26/1800Z 13.1N  67.9W   35 KT  40 MPH
 60H  27/0600Z 13.4N  71.1W   30 KT  35 MPH
 72H  27/1800Z...DISSIPATED

$$
Forecaster Zelinsky
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