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Rank: F5 Superstorm
Full-time graduate student at Johns Hopkins
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28 Sep 2015
Surprised no one has posted about this yet. Something interesting to track over the upcoming days.
TROPICAL DEPRESSION ELEVEN DISCUSSION NUMBER 4
NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015
ISSUED BY THE NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
500 PM EDT MON SEP 28 2015
The low-level center has become well exposed due to continued
northwesterly shear of 20 kt or more, with the mid-level
center displaced well to the southeast of the low-level center.
Flight-level and SFMR-observed wind data from an Air Force
reconnaissance aircraft showed that the maximum winds remain near
30 kt. This is also consistent with the latest Dvorak estimates
from SAB and TAFB.
The center of the depression has been moving well to the left of
the previous track, with the initial motion estimated to be 270/05
kt. In addition to the more westward initial motion, there have
been significant changes in the model guidance, with the latest
ECMWF forecast taking the cyclone much farther south and west than
the GFS in 3-5 days. This appears to be the result of enhanced
mid-level ridging to the north of the cyclone in the ECMWF at that
time frame. This has necessitated a significant southwestward
shift of the official forecast, although for continuity the new NHC
track does not take the cyclone as far to the southwest as the
ECMWF. Given the large spread now seen in the dynamical track
guidance, confidence in the track forecast is rather low.
The strong shear over the system is likely to continue for at least
the next 12-24 hours and given the large displacement between the
low- and mid-level centers, no intensification is anticipated in
the short term. The dynamical guidance indicates some relaxation
of the shear in a day or two, so the official forecast shows the
cyclone strengthening into a tropical storm later on Tuesday. This
is close to the intensity model consensus through 48 hours, and a
little below it thereafter. Given the large uncertainty in the
track forecast, there is also uncertainty as to what kind of
environment the cyclone will encounter during the forecast period,
which also leads to low confidence in the official intensity
FORECAST POSITIONS AND MAX WINDS
INIT 28/2100Z 27.5N 70.2W 30 KT 35 MPH
12H 29/0600Z 27.7N 71.0W 30 KT 35 MPH
24H 29/1800Z 27.9N 72.0W 35 KT 40 MPH
36H 30/0600Z 28.3N 72.8W 40 KT 45 MPH
48H 30/1800Z 28.6N 73.4W 45 KT 50 MPH
72H 01/1800Z 30.0N 74.0W 45 KT 50 MPH
96H 02/1800Z 33.0N 74.0W 45 KT 50 MPH
120H 03/1800Z 38.5N 73.5W 45 KT 50 MPH
3 Mar 2012
This was posted Thursday.
NOUS41 KWBC 011848
Public Information Statement
National Weather Service Headquarters Washington DC
148 PM EST Thu Mar 1 2012
-Family of Services
-NOAA Weather Wire Service
-Emergency Managers Weather Information Network
Other NWS partners and NWS employees
From: Mark Tew
Chief, Marine and Coastal Services Branch
Subject: Minor Modification of Saffir-Simpson Hurricane Wind
Scale Thresholds Effective May 15, 2012
Effective May 15, 2012, the Saffir-Simpson Hurricane Wind Scale
(SSHWS) will be adjusted slightly to resolve issues associated
with the conversion of units used for wind speed. This change
follows a public comment period conducted in 2011.
The National Hurricane Center (NHC) and Central Pacific Hurricane
(CPHC) assign intensities of hurricanes in 5-knot (kt)
increments. For advisory products, these intensities are
converted to miles per hour (mph) and kilometers per hour (km/h),
and then rounded to the nearest 5-mph or 5-km/h increments.
Challenges occur when the current Category 4 intensity is 115 kt
(132.3 mph). Although 115 kt is within the Category 4 range, the
equivalent rounded wind speed in mph is 130 mph, which is in the
Category 3 range. To classify the hurricane as a Category 4 in
both sets of units (kt and mph), NHC and CPHC must incorrectly
convert 115 kt to 135 mph in the advisory products. A similar
issue occurs when the current Category 4 intensity of 135 kt is
converted to km/h.
Effective May 15, 2012, to resolve these rounding issues,
Category 4 on the SSHWS will be broadened by one mph at each end
of the range, yielding a new range of 130-156 mph. This will
also result in a minor modification of the Category 3 and 5 wind
speed thresholds. The SSHWS will change as follows:
Category 3: 111-130 mph (96-113 kt, 178-209 km/h)
Category 4: 131-155 mph (114-135 kt, 210-249 km/h)
Category 5: 156 mph or higher (136 kt or higher, 250 km/h or
Category 3: 111-129 mph (96-112 kt, 178-208 km/h)
Category 4: 130-156 mph (113-136 kt, 209-251 km/h)
Category 5: 157 mph or higher (137 kt or higher, 252 km/h or
There will be no change to the wind speeds currently assigned to
Categories 1 and 2.
With this change, a 115-kt Category 4 hurricane will have its
intensity properly converted to mph and rounded to the nearest 5
mph (130 mph) and remain within the Category 4 mph range.
Important note: Since intensities are assigned using 5-kt
increments, neither storms in the historical record nor any
future storms will have their SSHWS category changed as a result
of this modification to the scale.
The NWS wishes to remind media, partners, and the public the
Saffir-Simpson Hurricane Wind Scale provides information on wind
impacts only. The scale does not provide commentary or
information on other impacts or characteristics of tropical
Additional information on this change can be found at:
If you have any questions, please contact
National Weather Service
Silver Spring, Maryland 20910
301 713 1677 ext. 121
National Public Information Notices are online at:
21 Mar 2011
I haven't researched this heavily but does anyone know why ensembles are presented as means rather than medians? When I look at the ensemble members on ewall, let's say the SREF, it displays the mean in the bottom right. However, there are 21 members, thus any outliers can have a substantial impact on the mean with a sample size of 21. Medians are less affected by outliers with a small sample size. Are there any medians out there or products available to the public?
Now, I'm not questioning why it's done this way as either I am not knowledgeable enough and/or obviously, the means are shown for a reason. It's just something I've thought about because I do statistical analysis sometimes on small sample sizes, not so much for final results, but more to get a sense of what direction the data is going in. Thanks in advance.
1 Oct 2015 - 12:56
30 Sep 2015 - 11:31
28 Aug 2015 - 11:30
26 Jan 2015 - 16:45
3 Jul 2014 - 15:35
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