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KF5JRV > WX 09.09.18 14:45l 195 Lines 8564 Bytes #999 (0) @ NA
BID : 20962_KF5JRV
Read: GUEST
Subj: NWS NHC Atlantic WX - Sept 09
Path: IW8PGT<CX2SA<HP2BWJ<LU4ECL<XE1FH<VE3UIL<VA7RBP<KF5JRV
Sent: 180909/1215Z 20962@KF5JRV.#NWAR.AR.USA.NA BPQ6.0.16
701
WTNT41 KNHC 090844
TCDAT1
Tropical Storm Florence Discussion Number 40
NWS National Hurricane Center Miami FL AL062018
500 AM AST Sun Sep 09 2018
Florence's cloud pattern has continued to gradually become better
organized overnight, with an increase in convection near the center
and a developing central dense overcast feature. However, the
cloud tops are not particularly cold and the outer banding features
remain fragmented likely due to some nearby dry mid-level air.
Dvorak intensity estimates from TAFB and SAB range from 55 to 65
kt, so the initial intensity remains 60 kt, just shy of hurricane
strength. The NOAA Hurricane Hunters are scheduled to investigate
the storm later today, and that data should provide a better
assessment of Florence's intensity.
The upper-level outflow is becoming well established over the
cyclone, and the global model guidance indicates that Florence
will remain in a very favorable upper-level environment while the
cyclone moves over the warm waters over the southwestern
Atlantic. These conditions favor strengthening with the only
apparent negative factor being nearby dry air, which will likely
remain away from the inner core due to the low shear conditions.
The NHC intensity forecast again calls for a period of rapid
strengthening within the next 12-36 hours, and Florence is forecast
to become a major hurricane on Monday with additional strengthening
early in the week. This means that Florence is likely to be a very
powerful hurricane as it moves over the western Atlantic toward the
southeastern United States. The new NHC intensity forecast is near
the various intensity consensus aids and is very similar to the
previous official forecast.
Florence is currently located between a couple of mid-level ridges
and a slow westward motion is expected today. Another strong
high pressure ridge is forecast to build to the north of Florence
on Monday, which should cause the storm to begin moving
west-northwestward to northwestward at an increasingly faster
forward speed. The dynamical model guidance is tightly clustered
for the first 2-3 days with increasing spread thereafter. The GFS
remains along the right side of the guidance envelope with the HWRF
and ECMWF bracketing the left edge. It should be noted that both
the GFS and ECMWF ensemble means are a little to the left or west
of their operational runs. As a result, the NHC track forecast
lies to the left of the TVCA multi-model consensus, but is not as
far to the west as the FSSE and HCCA corrected consensus models at
day 5. The models are in agreement that Florence is likely to slow
down near the end of the forecast period as a blocking high
pressure ridge builds to the north of the hurricane.
Key Messages:
1. Florence is forecast to be a dangerous major hurricane near the
southeast U.S. coast by late this week, and the risk of direct
impacts continues to increase. However, given the uncertainty in
track and intensity forecasts at those time ranges, it's too soon to
determine the exact timing, location, and magnitude of those
impacts.
2. Interests along the U.S. East Coast, particularly from north
Florida through North Carolina, should closely monitor the progress
of Florence, ensure they have their hurricane plan in place, and
follow any advice given by local officials.
3. Large swells affecting Bermuda and portions of the U.S. East
Coast will continue this week. These swells will result in
life-threatening surf and rip currents.
FORECAST POSITIONS AND MAX WINDS
INIT 09/0900Z 24.5N 55.8W 60 KT 70 MPH
12H 09/1800Z 24.6N 56.7W 70 KT 80 MPH
24H 10/0600Z 24.8N 58.3W 85 KT 100 MPH
36H 10/1800Z 25.3N 60.4W 100 KT 115 MPH
48H 11/0600Z 26.1N 63.1W 110 KT 125 MPH
72H 12/0600Z 28.2N 69.1W 125 KT 145 MPH
96H 13/0600Z 31.3N 74.8W 120 KT 140 MPH
120H 14/0600Z 34.4N 77.9W 105 KT 120 MPH...INLAND
$$
Forecaster Brown
747
WTNT43 KNHC 090845
TCDAT3
Tropical Storm Helene Discussion Number 8
NWS National Hurricane Center Miami FL AL082018
500 AM AST Sun Sep 09 2018
Satellite imagery indicates that Helene continues to become better
organized with an increase in banding overnight. A couple of
recent microwave images show that the inner core continues to
organize with a low-level ring evident and indication that a
banding-type eye is forming. Dvorak satellite T-numbers have
increased and support an initial intensity of 55 kt.
Helene is forecast to remain over SSTs of 27-28C during the next
couple of days. The upper-level wind pattern is also expected to
be quite favorable, and these conditions should support steady
intensification. Slightly cooler waters and increasing
southwesterly shear from an upper-level trough to the northwest of
Helene are likely to put an end to the intensification process by
day 3. After that time, Helene is forecast to move closer to the
aforementioned trough with southwesterly shear and drier mid-level
air likely to result in weakening by day 4 and 5. The NHC intensity
forecast is near the IVCN intensity consensus model, but it is a
little more conservative than the FSSE and HCCA models.
The tropical storm is moving westward or 270 degrees at 12 kt. A
deep-layer ridge to the north of the storm should steer Helene
westward to west-northwestward during the next couple of days. By
mid-week, Helene is expected to approach a weakness in the ridge
between 40-50W longitude and the cyclone is predicted to turn
northwestward, then north-northwestward by the end of the period.
The track guidance is in fairly good agreement on this scenario,
but there is some spread later in the period as to exactly what
longitude the northwesterly turn takes place. The NHC forecast is
between the various dynamical model solutions and is close to the
HFIP corrected consensus model.
FORECAST POSITIONS AND MAX WINDS
INIT 09/0900Z 13.2N 24.0W 55 KT 65 MPH
12H 09/1800Z 13.4N 26.0W 65 KT 75 MPH
24H 10/0600Z 14.0N 28.9W 75 KT 85 MPH
36H 10/1800Z 14.7N 31.9W 85 KT 100 MPH
48H 11/0600Z 15.4N 34.5W 90 KT 105 MPH
72H 12/0600Z 17.4N 38.3W 80 KT 90 MPH
96H 13/0600Z 20.5N 41.0W 65 KT 75 MPH
120H 14/0600Z 25.0N 42.5W 50 KT 60 MPH
$$
Forecaster Brown
335
WTNT44 KNHC 090840
TCDAT4
Tropical Storm Isaac Discussion Number 7
NWS National Hurricane Center Miami FL AL092018
500 AM AST Sun Sep 09 2018
The cloud pattern of Isaac has changed significantly during the past
several hours. The storm no longer has a sheared appearance, and
instead microwave images reveal a well-defined curved band that
wraps a little more than halfway around the center. Despite the
change in the storm's structure, the Dvorak classifications are
unchanged at 3.0/45 kt. Based on that data, the initial intensity
is held at 45 kt for this advisory.
Now that the shear has lessened, Isaac should steadily strengthen
during the next few days as the storm remains over warm waters and
in a low wind shear environment. Beyond a few days, however, the
SHIPS model shows a notable increase in shear, in part due to the
outflow from Florence, which should end the strengthening trend and
induce some weakening. There was no significant change in the
intensity guidance this cycle, so the official forecast is largely
an update of the previous one. This prediction lies fairly
close to the IVCN and HCCA models.
Isaac remains on the forecast track and the initial motion is the
same as before, 270/7. A strengthening subtropical ridge to the
north of the system should cause Isaac to move westward at an
increasing forward speed during the next several days. Although
there is some spread in the models, the usually more reliable GFS
and ECMWF models have been consistent in showing a due westward
motion through the forecast period. The NHC track forecast leans
toward those models, and it is fairly similar to the previous
prediction. Based on the current forecast, Isaac will be near the
Lesser Antilles in 4 to 5 days and interests there should monitor
the progress of this system.
FORECAST POSITIONS AND MAX WINDS
INIT 09/0900Z 14.5N 38.1W 45 KT 50 MPH
12H 09/1800Z 14.6N 39.6W 55 KT 65 MPH
24H 10/0600Z 14.7N 41.9W 60 KT 70 MPH
36H 10/1800Z 14.7N 44.6W 70 KT 80 MPH
48H 11/0600Z 14.7N 47.5W 80 KT 90 MPH
72H 12/0600Z 14.7N 53.1W 85 KT 100 MPH
96H 13/0600Z 14.9N 58.9W 80 KT 90 MPH
120H 14/0600Z 15.3N 64.5W 70 KT 80 MPH
$$
Forecaster Cangialosi
73 de Scott KF5JRV
Pmail: KF5JRV@KF5JRV.#NWAR.AR.USA.NA
email: KF5JRV@ICLOUD.COM
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