Hurricane Beryl Discussion Number 4
NWS National Hurricane Center Miami FL AL022018
500 AM AST Fri Jul 06 2018
Deep convection associated with the tiny tropical cyclone has
continued to become better organized overnight. An earlier AMSR2
microwave overpass showed a well-defined mid-level eye and a
pinhole eye has been apparent in the various GOES-16 satellite
channels since shortly after 0600 UTC and was most evident around
0715 UTC. Although the clarity of the eye has waxed and waned since
that time, there is enough convective organization to increase the
initial intensity to 65 kt, making Beryl the first hurricane of the
2018 Atlantic hurricane season.
The cyclone has another 18-24 hour within very low vertical wind
shear conditions and over SSTS of 26-27 degrees Celsius. These
favorable conditions suggest that the tiny hurricane is likely to
intensify further today. The NHC intensity forecast calls for
additional strengthening and is at the upper-end of the intensity
guidance, but I would not be too surprised if the compact hurricane
reaches a slightly higher peak intensity than indicated below. By
36 hours, the shear is forecast to increase to more than 15 kt, and
it is expected to be greater than 20 kt shortly after that time.
This should cause the very small tropical cyclone to quickly
weaken, however as mentioned in the Key Messages below there is
greater uncertainty than usual regarding Beryl's intensity
forecast. Although the updated NHC forecast shows Beryl
reaching the Lesser Antilles as a tropical storm it is highly
possible that the system will have degenerated into an open trough
by that time. Regardless of the system's status at 72 h, it is
likely to bring strong gusty winds and locally heavy rains to
portions of the Lesser Antilles Sunday and Monday.
The initial motion estimate remains 275/12 kt. The track guidance
is in good agreement taking Beryl west-northwestward to the
south of a deep-layer ridge over the central Atlantic. There
has been little overall change in the latest dynamical guidance and
the new NHC track forecast is similar to the previous advisory and
lies along the southern edge of the guidance envelope closest to
the latest ECMWF and HFIP correct consensus models.
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 to forecast to quickly weaken or dissipate
as a tropical cyclone on 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.
Tropical Depression Two Discussion Number 1
NWS National Hurricane Center Miami FL AL022018
1100 AM AST Thu Jul 05 2018
For the past day or so, we've been monitoring a small area of low
pressure associated with a tropical wave over the tropical Atlantic
Ocean. Despite a noticeable mid-level rotation in the convective
clouds, it had not been conclusive whether or not the system had a
closed circulation at the surface with a well-defined center.
However, the system appears more distinct and independent from the
Intertropical Convergence Zone as compared to yesterday, and
scatterometer data appears conclusive enough to support a closed,
yet tiny circulation. We are now confident enough that the system
meets the criteria of a tropical cyclone, and have initiated
advisories on Tropical Depression Two with maximum winds of 30 kt,
which is supported by Dvorak classifications from TAFB and SAB.
The depression will be located in a relatively low-shear environment
for the next 3 days or so. However, the small cyclone is surrounded
by abundant dry air, and the system will be moving over marginally
warm waters during the next few days, which could both limit
intensification. The NHC official forecast allows for some slight
strengthening and most closely follows the HFIP Corrected Consensus
guidance (HCCA), showing the depression becoming a tropical storm
within the next 24 hours. Between 72 and 96 hours, the system is
expected to begin encountering strong westerly shear and also
accelerate, both of which should cause it to degenerate into an open
wave east of the Lesser Antilles.
Even though the center has been difficult to locate, the initial
motion is estimated to be westward, or 270/14 kt. The depression is
located to the south of a sprawling subtropical ridge, although a
break in the ridge over the central Atlantic may cause the system to
slow down a bit during the next 36 hours. After that time, the
cyclone is likely to speed up again when it becomes situated to the
south of a new mid-level high. The track guidance is in generally
good agreement, and the NHC official forecast is close to the TVCX
multi-model consensus and the HCCA guidance.
Even though the cyclone is expected to dissipate east of the Lesser
Antilles early next week, the remnant tropical wave will continue
moving quickly westward, likely bringing locally heavy rains and
gusty winds to portions of the Leeward Islands on Sunday and Monday.
2. Shower activity associated with a small area of low pressure and a
tropical wave located about 1000 miles west-southwest of the
Cabo Verde Islands continues to become better organized. A tropical
depression is likely to form during the next day or two while the
system moves westward to west-northwestward at 15 to 20 mph over the
tropical Atlantic Ocean. By the weekend, however, upper-level winds
are expected to become less conducive for development when the
system approaches the Lesser Antilles.
* Formation chance through 48 hours...high...70 percent.
* Formation chance through 5 days...high...70 percent.
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