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Tropical Storm Erick Discussion Number   6
NWS National Hurricane Center Miami FL       EP062019
1100 AM HST Sun Jul 28 2019

Although Erick's upper-level outflow has continued to improve, the
overall convective pattern hasn't changed much. The earlier increase
in central convection has been waning somewhat in recent satellite
imagery, and the low-level center remains displaced just north of
the central convection. However, passive microwave imagery indicates
that the center has made a slight west-southwestward jog, possibly
due to reformation closer to the strongest convection. The initial
intensity has been increased to 40 kt based on a blend of Dvorak
satellite intensity estimates of T2.5/35 kt from TAFB and T3.0/45 kt
from SAB. An 1807Z partial ASCAT-A scatterometer pass indicated a
36-kt vector in the northeastern quadrant, and allowing for some
undersampling also supports the 40-kt initial intensity.

The initial motion estimate is 270/15 kt. It is possible that the
initial position could be too far north, and a southward shift may
be required on the next advisory. However, the general trend in the
model guidance remains a westward motion for the next 24 hours or
so, followed by a gradual turn toward the west-northwest as Erick
moves into a slight weakness in the subtropical ridge. By 72 hours
and beyond, the weakness is forecast to fill with the narrow ridge
building westward across the Hawaiian Islands. This is expected to
force Erick on a general westward to west-northwestward track
through the remainder of the forecast period. On the forecast track,
Erick is expected to cross into the Central Pacific basin Tuesday
morning. The new NHC forecast track has again been shifted south of
the previous advisory track, mainly due to the more southerly
initial position, and lies down the center of the tightly packed
guidance envelope and is close to a blend of the consensus track
models HCCA, FSSE, and TVCN.

The aforementioned ASCAT-A pass indicated that Erick has maintained
a small radius of maximum winds (RMW) of about 20 nmi. The small
RMW, low vertical wind shear, and SSTs near 28 deg C continue to
support at least steady strengthening for the next few days, and
Erick is forecast to become a hurricane in 36 hours. Although rapid
intensification (RI) remains a possibility owing to the small RMW
and low shear, the recent pronounced dry mid-level intrusion into
the inner-core region, along with mid-level shear undercutting the
other favorable outflow pattern, is expected to hinder any RI for at
least the next 24 hours. By 72 hours, strong westerly vertical wind
shear is forecast to affect the cyclone, inducing a steady weakening
trend through the 120-h period. The latest Navy COAMPS model has
backed off slightly and is now forecasting Erick to become a
high-end category-3 hurricane in about 72 hours. However, this
scenario has again been disregarded due to the abundance of dry
mid-level air expected to affect the cyclone. The official intensity
forecast is similar to the previous NHC advisory, and closely
follows the HCCA corrected consensus model.

FORECAST POSITIONS AND MAX WINDS

INIT  28/2100Z 12.0N 131.3W   40 KT  45 MPH
 12H  29/0600Z 12.3N 133.5W   45 KT  50 MPH
 24H  29/1800Z 12.8N 136.4W   55 KT  65 MPH
 36H  30/0600Z 13.5N 139.1W   65 KT  75 MPH
 48H  30/1800Z 14.1N 142.0W   75 KT  85 MPH
 72H  31/1800Z 15.3N 146.4W   85 KT 100 MPH
 96H  01/1800Z 16.2N 150.9W   60 KT  70 MPH
120H  02/1800Z 16.8N 155.9W   40 KT  45 MPH

$$
Forecaster Stewart

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