From National Hurricane Center

Tropical Storm Beryl Discussion Number 2
NWS National Hurricane Center Miami FL AL022018
500 PM AST Thu Jul 05 2018

Beryl has been a bit of a surprise today, which is not uncommon for
tiny tropical cyclones such as itself. A 1724 UTC SSMI microwave
pass and a 1853 UTC SSMI/S pass both revealed that the cyclone had
developed a well-defined 5 nmi-wide mid-level eye, and a dimple has
been apparent in visible satellite imagery. It’s usually difficult
to get a good handle on the intensity of these types of cyclones
given their small size, but data-T numbers from TAFB and SAB are a
consensus T3.0. The initial intensity is therefore raised to 45 kt,
but there is a lot of uncertainty in this estimate.

If the initial intensity is uncertain, the future intensity is even
more of a quandary. Despite being surrounded by abundant dry air,
Beryl has apparently been able to isolate itself and possibly
moisten the near-storm environment while located in an area of low
shear. Since the shear is expected to remain quite low for the next
36 hours or so, and small cyclones like Beryl often have a tendency
to strengthen quickly over a short period of time, continued
intensification appears likely for the next day or so. The updated
NHC intensity forecast most closely follows the statistical-
dynamical guidance, which lies at the upper end of the guidance
envelope, and brings Beryl to hurricane strength within 36 hours.
After that time, increasing westerly shear, partially due to Beryl
accelerating toward the west, is expected to cause weakening. In
addition, every global model shows the cyclone opening up into a
tropical wave in 72-96 hours, which is what the NHC forecast
continues to depict. It cannot be stressed enough, however, that
this is a low confidence forecast.

The one stable part of the forecast is Beryl’s future track. The
new guidance has not changed much from the previous forecast cycle,
and it continues to show Beryl slowing down a bit during the next 24
hours, followed by a west-northwestward acceleration in 48-72 hours
due to a strengthening ridge to the north. The updated NHC track
forecast is just a bit south of the previous one and is closest to
the HCCA and Florida State Superensemble guidance.

Even though Beryl is expected to dissipate just east of the Lesser
Antilles early next week, the remnant tropical wave will continue
moving quickly westward and will likely bring locally heavy
rains and gusty winds to portions of the Leeward Islands on Sunday
and Monday.

Key Messages:

1. Due to its very small size, there is greater-than-usual
uncertainty in the analysis of Beryl’s current intensity.
Confidence in the official intensity forecast is also much lower
than normal. Rapid changes in intensity, both up and down, that are
difficult to predict are possible during the next couple of days.

2. While Beryl is still expected to dissipate as a tropical cyclone
by Monday before reaching the Lesser Antilles, there will likely
be some rain and wind impacts on those islands early next week.
Residents there should monitor products from their local weather
office for more information.

FORECAST POSITIONS AND MAX WINDS

INIT 05/2100Z 10.3N 42.8W 45 KT 50 MPH
12H 06/0600Z 10.8N 44.5W 55 KT 65 MPH
24H 06/1800Z 11.4N 46.3W 60 KT 70 MPH
36H 07/0600Z 12.1N 48.3W 65 KT 75 MPH
48H 07/1800Z 13.0N 51.0W 60 KT 70 MPH
72H 08/1800Z 14.5N 58.4W 50 KT 60 MPH
96H 09/1800Z…DISSIPATED

Forecaster Berg

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