Caribbean-On-Line's Caribbean Hurricane Blog



Hurricane Arthur

Arthur now a hurricane

Published on July 3, 2014 8:53 AM | Comments

Arthur has become a hurricane - the first of the season. It is no threat to the Caribbean.

HURRICANE ARTHUR DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL012014 500 AM EDT THU JUL 03 2014

Data from NOAA and Air Force Reserve Hurricane Hunter aircraft
indicate that Arthur has reached hurricane strength. Both aircraft
showed several SFMR winds of 60 to 63 kt southeast of the center,
and the NOAA aircraft reported a peak flight-level wind of 79 kt at
8,000 feet. Based on these data the initial intensity is set to 65
kt. Radar data show that Arthur was still having difficulty
maintaining an eyewall overnight, likely due to dry mid/upper-level
air being entrained into the storm. However, the overall radar
presentation has improved during the past couple of hours. Some
gradual intensification is forecast during the next 24 hours while
the cyclone is in an environment of low shear and moves over warm
waters. After that time, however, the shear increases dramatically
as Arthur interacts with a deep-layer baroclinic zone moving off
of the east coast of North America, and global model fields show
Arthur completing extratropical transition by 72 hours. The NHC
intensity forecast is similar to the previous one and remains close
to the multi-model consensus IVCN through 24 hours and is a little
below the consensus after that time.

Radar data and aircraft fixes indicate that the current motion is
now a little east of due north, or 010 degrees at 8 knots. Arthur
should begin to recurve today ahead of the aforementioned deep-layer
trough, and the track model guidance is in good agreement on this
scenario. The NHC track forecast is similar to the previous one and
remains near the middle of the dynamical model envelope and close
to the TVCA multi-model consensus. The official forecast shows the
center of Arthur moving very close to the North Carolina Outer Banks
late tonight and early Friday. Arthur should then accelerate
northeastward offshore of the mid-Atlantic states and the
northeastern U.S. Friday and Friday night, and move into the
Canadian Maritimes by Saturday before turning northward by the end
of the period.

The track, intensity, and wind radii forecast during the
extratropical phase of Arthur have been coordinated with the Ocean
Prediction Center.

The new experimental potential storm surge flooding map is
available at: www.nhc.noaa.gov/graphics_at1.shtml?inundation

FORECAST POSITIONS AND MAX WINDS

INIT 03/0900Z 31.3N 79.1W 65 KT 75 MPH
12H 03/1800Z 32.5N 78.3W 70 KT 80 MPH
24H 04/0600Z 34.7N 76.1W 75 KT 85 MPH
36H 04/1800Z 37.5N 72.6W 75 KT 85 MPH
48H 05/0600Z 40.9N 67.9W 70 KT 80 MPH
72H 06/0600Z 47.5N 60.0W 50 KT 60 MPH...POST-TROP/EXTRATROP
96H 07/0600Z 54.0N 52.0W 35 KT 40 MPH...POST-TROP/EXTRATROP
120H 08/0600Z 60.0N 50.0W 35 KT 40 MPH...POST-TROP/EXTRATROP



TROPICAL STORM ARTHUR DISCUSSION NUMBER 6

Published on July 2, 2014 9:57 AM | Comments

TROPICAL STORM ARTHUR DISCUSSION NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL AL012014
500 AM EDT WED JUL 02 2014

Despite a somewhat ragged appearance on satellite imagery, Arthur
has strengthened overnight. Data from two ASCAT passes between 02
and 03 UTC showed a broad area of 45-50 kt winds east and northeast
of the center. In addition, NOAA and Air Force Reserve Hurricane
Hunter aircraft have found surface winds in the 45-50 kt range to
the south and northeast of the center, while also finding the
central pressure has fallen to about 996 mb. Based on all of
these data, the initial intensity is set to 50 kt.

Arthur is still suffering the effects of dry air aloft being
entrained into the western half of the circulation, which
features only limited cold cloud tops. The primary convective band
is situated east and southeast of the center, and some semblance of
an eye has been visible in satellite and radar imagery and was
reported by the aircraft. This lopsided structure suggests that
Arthur will not strengthen quickly in the short term. However, given
an otherwise favorable environment of warm water and weak wind
shear, all of the intensity guidance shows the cyclone becoming a
hurricane in 24 to 36 hours, and so does the official forecast. By
72 hours, Arthur will be moving into a high shear environment ahead
of an advancing mid/upper-level trough, which should result in
weakening during the extratropical transition process. The NHC
intensity forecast is close to the intensity consensus aid IVCN
through the period.

Arthur has begun moving steadily northward at around 5 kt. The
overall track forecast reasoning remains unchanged, as the tropical
cyclone should continue northward for the next 12 to 24 hours
and then gradually accelerate northeastward between the
aforementioned trough and a strengthening ridge to the east. The
track guidance envelope has shifted back to the west a little for
this cycle, and the NHC forecast has been adjusted in that
direction, but now lies on the eastern edge of the guidance
envelope through 48 hours.

Given the new NHC forecast, hurricane and tropical storm watches
have been issued for portions of the coasts of South and North
Carolina. Warnings may be required for portions of these areas
later today.



Tropical Storm Arthur

Published on July 1, 2014 2:45 PM | Comments

This is predicted to be a fast moving storm - and it is the first named storm of the 2014 Atlantic season:

TROPICAL STORM ARTHUR DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL012014 1100 AM EDT TUE JUL 01 2014

Radar and satellite imagery indicate that the convective
organization of the cyclone has improved since the previous
advisory, and the cyclone is being upgraded based on a sustained
wind report of 33 kt from Settlement Point (SPGF1) on Grand Bahama
Island earlier this morning that was outside of the deep convection.

After remaining nearly stationary earlier this morning, Arthur
appears to to be drifting northwestward now with an uncertain motion
of 315/02 kt. Otherwise, there is no significant change to the
previous forecast track. The latest model guidance has continued the
trend of a pronounced mid-tropospheric trough digging southeastward
from the upper-midwest into the northeastern and mid-Atlantic region
of the United States by 72 hours. The 500 mb flow pattern is almost
identical in the GFS and ECMWF models, which increases the
confidence in this evolving pattern. As a result, a steady increase
in southwesterly steering flow over the southeastern United States
is expected to gradually turn the tropical cyclone northward over
the next 24-36 hours, and then accelerate the system faster toward
the northeast on Thursday and Friday. By Days 4 and 5, Arthur is
forecast to move over the far north Atlantic as an extratropical
cyclone. The NHC track forecast is just an update of the previous
advisory track, and lies down the middle of the tightly packed
guidance envelope close to the consensus model TVCA.

Northwesterly vertical wind shear is forecast by the models to
gradually subside over the next 48 hours, which should allow the
cyclone to develop its own upper-level outflow pattern. In fact,
latest visible and water vapor imagery indicates that cirrus
outflow has been expanding on the north side of the system during
the past few hours, suggesting that the shear conditions could
already be subsiding. The low shear conditions and warm
sea-surface temperatures should allow for at least steady
strengthening, and the cyclone is expected to become a hurricane by
72 hours. The official intensity forecast is similar to the
latest intensity model consensus IVCN through 36 hours, and then
slightly higher after that.