NHC issues Tropical Cyclone Discussion (TCD) at Sep 28, 5:00 AM AST046
WTNT43 KNHC 280859
TCDAT3
Hurricane Humberto Discussion Number 15
NWS National Hurricane Center Miami FL AL082025
500 AM AST Sun Sep 28 2025
Humberto continues to display a clear, circular eye about 10-15
miles in diameter. Although the eye temperatures are still fairly
warm around 15C, the area of cloud tops colder then -70C has shrunk
a bit in the southwest quadrant, and data-T numbers have
continuously been lower than 7.0 for about 8 hours now. The latest
subjective CI numbers range from 127-140 kt, and the latest
objective intensity estimates range from 125-135 kt. Based on the
above analyses and data, the initial intensity is nudged down to 135
kt.
The initial motion estimate is west-northwestward, or 300 degrees
at 11 kt. Over the next couple of days, Humberto will round the
southwestern periphery of a mid-tropospheric subtropical ridge
located northeast of the cyclone. Humberto will turn northward by
early Tuesday in between the ridge and Tropical Depression Nine,
which should be located to the west-southwest of Humberto. By
Tuesday night, Humberto is forecast to turn north-northeastward
while the aforementioned ridge weakens and shifts eastward.
Humberto should turn quickly toward the northeast to east-northeast
by mid-week in response to a large, amplifying upper-level trough
moving out of the Canadian Maritimes and into the northwestern
Atlantic waters. There remains quite a bit of along-track spread
at days 4 and 5. The new NHC forecast is slightly faster toward
the northwest through 48 h, then lies to the northwest, or left of,
the previous official forecast at 60-72 when it makes its closest
approach to Bermuda. In other words, the new forecast shows the
center passing a bit farther from Bermuda, however, Bermuda still
has roughly a 50 percent chance of getting tropical-storm-force
winds, most likely on Tuesday night and Wednesday.
There have been no recent microwave passes over Humberto in the
last 6 h, but infrared imagery suggests there could be a partial
outer ring trying to become more dominant. SHIPS predictors and
the UW-CIMSS Microwave-based Probability of Eyewall Replace Cycle
(M-PERC) guidance indicate a high likelihood of an eyewall
replacement cycle commencing within the next 12 h. Otherwise,
environmental conditions are pretty favorable for the next 12 h, so
the forecast will show Humberto maintaining its current intensity
for 12 h despite the potential for fluctuations. Thereafter, all
of the intensity guidance points toward gradual weakening as there
is potential for gradually increasing vertical wind shear during
the 36 to 60 hour time frame. By hour 72, Humberto should
encounter significantly stronger upper-level westerly flow and begin
the process of extratropical transition. Extratropical transition
should be complete around 96 h, after Humberto crosses the 26
degree C sea-surface temperature isotherm, as all global models
show a warm front extending northeastward from Humberto by that
time.
FORECAST POSITIONS AND MAX WINDS
INIT 28/0900Z 23.9N 63.3W 135 KT 155 MPH
12H 28/1800Z 24.9N 64.7W 135 KT 155 MPH
24H 29/0600Z 26.4N 66.4W 130 KT 150 MPH
36H 29/1800Z 28.3N 67.8W 120 KT 140 MPH
48H 30/0600Z 30.3N 68.7W 115 KT 130 MPH
60H 30/1800Z 32.5N 68.7W 105 KT 120 MPH
72H 01/0600Z 34.5N 67.1W 95 KT 110 MPH
96H 02/0600Z 38.2N 56.0W 85 KT 100 MPH...POST-TROP/EXTRATROP
120H 03/0600Z 46.4N 37.5W 65 KT 75 MPH...POST-TROP/EXTRATROP
$$
Forecaster Hagen
Source:
NHC issues Tropical Cyclone Discussion (TCD) at Sep 28, 5:00 AM AST---------------
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