#253 Postby cycloneye » Fri Sep 04, 2015 9:36 pm
The unexpected has happened.
BULLETIN
TROPICAL STORM FRED ADVISORY NUMBER 25
NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015
1100 PM AST FRI SEP 04 2015
...FRED REGAINS TROPICAL STORM STATUS...
SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...22.8N 40.1W
ABOUT 1305 MI...2100 KM SW OF THE AZORES
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...WNW OR 290 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...1009 MB...29.80 INCHES
TROPICAL STORM FRED DISCUSSION NUMBER 25
NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015
1100 PM AST FRI SEP 04 2015
An ASCAT-A pass just before 0000 UTC showed a small area of 35-kt
winds northeast of Fred's center, and that is the basis for the
initial intensity, making Fred a tropical storm once again. The
central pressure has been adjusted upward to 1009 mb based on
observations from drifting buoy 13519, as it appears Fred is now
embedded in an environment of higher pressure. Despite rather
hostile vertical shear, Fred has managed to maintain enough
organized deep convection during the past couple of days to stave
off post-tropical status. The latest burst of convection is now
moving away from the low-level center, but this bursting pattern
seems likely to continue for the next couple of days as the cyclone
moves over gradually warmer waters in moderate to strong shear.
Since Fred has survived this long, it seems less likely that the
cyclone will become post-tropical in the short term, and that is no
longer shown in the official forecast. However, given our limited
ability to predict convective scale changes, this still remains a
possibility.
Little significant change in intensity is shown in the first 48
hours, as the guidance shows Fred between 30 and 35 kt during that
time. Subsequently, as the shear weakens all of the guidance shows
at least some strengthening. The NHC forecast shows only a modest
re-intensification later in the period, given the possibility that
the circulation of Fred could open up or be absorbed in 4 or 5 days
as shown by the GFS and ECMWF models.
The initial motion estimate is 290/09, and Fred should begin to move
around the western periphery of the subtropical ridge during the
next couple of days and then turn northeastward in the mid-latitude
westerlies. This cycle the models have trended faster with the
forward speed of Fred, and have shown a northward shift after 48
hours. The NHC forecast has been adjusted to account for these
trends, but now lies on the right side of the guidance envelope at
days 3 through 5. Given the large spread at these time ranges, and
the possibility that Fred could be absorbed or dissipate late in the
period, the extended portion of the track forecast is of lower than
normal confidence.
FORECAST POSITIONS AND MAX WINDS
INIT 05/0300Z 22.8N 40.1W 35 KT 40 MPH
12H 05/1200Z 23.2N 41.1W 35 KT 40 MPH
24H 06/0000Z 23.9N 42.2W 30 KT 35 MPH
36H 06/1200Z 25.3N 42.7W 30 KT 35 MPH
48H 07/0000Z 27.1N 41.7W 30 KT 35 MPH
72H 08/0000Z 30.5N 38.0W 35 KT 40 MPH
96H 09/0000Z 34.5N 33.5W 35 KT 40 MPH
120H 10/0000Z 36.0N 30.5W 35 KT 40 MPH
$$
Forecaster Brennan
NNNN
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