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KF5JRV > WX 29.08.18 13:44l 118 Lines 5105 Bytes #999 (0) @ NA
BID : 19671_KF5JRV
Read: GUEST
Subj: NWS NHC Eastern N Pacfic Forecast WX - Aug 29
Path: IW8PGT<CX2SA<SV1CMG<PI8BDG<AB0AF<KF5JRV
Sent: 180829/1120Z 19671@KF5JRV.#NWAR.AR.USA.NA BPQ6.0.16
921
WTPZ45 KNHC 290853
TCDEP5
Tropical Storm Miriam Discussion Number 13
NWS National Hurricane Center Miami FL EP152018
200 AM PDT Wed Aug 29 2018
At face value, Miriam seems to be getting a little better
organized. Its convective canopy has been expanding during the
past few hours, and continuous lightning strokes have been detected
within a well-defined mid-level circulation. However, a 0637 UTC
METOP-B microwave pass shows that Miriam remains a sheared cyclone,
with the low-level center running out ahead of the deep convection.
Still, with the expanding convection, Dvorak estimates from TAFB and
SAB have risen to T3.5, and the initial intensity is set at 55 kt.
Miriam is moving westward, or 275/11 kt, near the western end of
the subtropical ridge. A deep-layer low located northeast of the
Hawaiian Islands is expected to cause Miriam to slow down and turn
sharply northwestward and northward during the next 48 hours. The
models are in excellent agreement on this scenario. After day 3,
however, there are significant differences among the guidance, with
the GFS taking a shallow cyclone almost due westward and the ECMWF
continuing to accelerate a deeper Miriam northward on the east side
of the deep-layer low. With these models being the most acute
outliers, the NHC forecast track thinking continues to lie close to
the tight clustering of the Florida State Superensemble, HCCA, and
TVCX consensus aids.
There is also greater-than-normal uncertainty in the intensity
forecast. The SHIPS and LGEM models show northwesterly shear
persisting over Miriam and only strengthen the cyclone slightly
during the next 24-36 hours. The HWRF and HCCA models are still
showing more significant strengthening, making Miriam a hurricane
over the next day or two. I was tempted to explicitly show Miriam
becoming a hurricane in the official forecast, but I decided to hold
off since the cyclone just hasn't been able to display an improved
structure as of yet. Even if some strengthening does occur,
vertical shear is expected to increase substantially from 48 hours
onward, which will cause fast weakening and Miriam likely
degenerating into a remnant low by day 5.
FORECAST POSITIONS AND MAX WINDS
INIT 29/0900Z 14.2N 138.4W 55 KT 65 MPH
12H 29/1800Z 14.4N 139.8W 60 KT 70 MPH
24H 30/0600Z 14.9N 141.1W 60 KT 70 MPH
36H 30/1800Z 15.8N 141.9W 60 KT 70 MPH
48H 31/0600Z 17.2N 142.0W 60 KT 70 MPH
72H 01/0600Z 20.4N 142.5W 50 KT 60 MPH
96H 02/0600Z 23.0N 144.5W 35 KT 40 MPH
120H 03/0600Z 26.5N 148.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
$$
Forecaster Berg
475
WTPZ41 KNHC 290854
TCDEP1
Tropical Storm Norman Discussion Number 4
NWS National Hurricane Center Miami FL EP162018
300 AM MDT Wed Aug 29 2018
Even though there has been a dearth of microwave imagery overnight,
Norman's infrared satellite signature has the look of a cyclone
ready to strengthen significantly over the next couple of days.
Banding continues to increase, with the convective canopy expanding
in nearly all quadrants. Norman's initial intensity is set at 50
kt based on a blend of Dvorak estimates from TAFB and SAB. Ocean
waters of nearly 30 degrees Celsius and low shear for the next
couple of days are offering an ideal environment for Norman to
rapidly intensify. The various Rapid Intensification (RI) indices
continue to show high probabilities, and overall the new intensity
guidance is higher than the previous forecast during the first
36 hours. Based on these numbers, the updated NHC intensity
forecast has been bumped upward, close to the Florida State
Superensemble and intensity consensus aids, but still not nearly as
high as the HWRF or HCCA models. It wouldn't be surprising at all
for the forecast intensities to be increased further in subsequent
advisory packages, and Norman is likely to become a hurricane later
today.
Norman is moving westward, or 275/9 kt, to the south of the
subtropical ridge, which extends westward from northern Mexico.
The ridge is forecast to build westward during the next few days,
causing Norman to continue westward--or even west-southwestward--at
a fairly steady pace for the next 4-5 days. Except for the GFS,
which appears to be a bit of a northern outlier, the remainder of
the track guidance is tightly clustered, at least for the first 3
days. After that time, the overall guidance envelope has shifted
slightly northward, requiring a subtle northward adjustment of the
NHC official forecast by day 5. This new forecast generally lies
closest to the HCCA and Florida State Superensemble aids.
FORECAST POSITIONS AND MAX WINDS
INIT 29/0900Z 17.5N 114.6W 50 KT 60 MPH
12H 29/1800Z 17.8N 115.8W 65 KT 75 MPH
24H 30/0600Z 18.0N 117.3W 85 KT 100 MPH
36H 30/1800Z 18.1N 118.9W 100 KT 115 MPH
48H 31/0600Z 17.8N 120.5W 110 KT 125 MPH
72H 01/0600Z 16.7N 124.1W 110 KT 125 MPH
96H 02/0600Z 16.0N 128.0W 100 KT 115 MPH
120H 03/0600Z 17.0N 132.5W 90 KT 105 MPH
$$
Forecaster Berg
73 de Scott KF5JRV
Pmail: KF5JRV@KF5JRV.#NWAR.AR.USA.NA
email: KF5JRV@ICLOUD.COM
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