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LU9DCE > ALERT 21.09.20 18:11z 103 Lines 5640 Bytes #999 (0) @ WW
BID : 26027_LU9DCE
Read: GUEST
Subj: STORM PREDICTION CENTER 21 09
Path: HB9ON<IW8PGT<I3XTY<IZ3LSV<DB0ERF<DB0RES<ON0AR<VK6HGR<VK2DOT<GB7YEW<
LU9DCE
Sent: 200921/1801Z 26027@LU9DCE.TOR.BA.ARG.SOAM LinBPQ6.0.20
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ESTACION DE PACKET RADIO - BUENOS AIRES (GF05OM)
BOLETINES INFORMATIVOS PROGRAMADOS (BIP)
LINUX - HELLOCODELINUX@GMAIL.COM
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SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0740
AM CDT Mon Sep 21 2020
Valid 211300Z - 221200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST
TEXAS INTO SOUTHWESTERN LOUISIANA...
...SUMMARY... Isolated severe storms are possible with Tropical
Storm Beta, mainly from southeast Texas into southwestern Louisiana.
...Synopsis... A progressive northern stream aloft, near
the Canadian border, will remain well-removed from low-level
moisture/theta-e supporting severe potential. Isolated weak
thunderstorms will be possible in a warm-advection plume from NE
to upper MI, related to a strong mid/ upper-level trough moving
from MB to northwestern ON. Isolated thunderstorms also will be
possible over portions of the Rockies and Intermountain West, as
well as over the southern half of the FL Peninsula near a residual
low-level frontal zone that extends west- northwestward across the
northern Gulf. A large anticyclone will dominate the surface pattern
north of that boundary over most of the eastern half of the CONUS.
...Northwest Gulf Coast... The center of Tropical Storm Beta
is forecast by NHC to proceed toward landfall tonight over the
middle TX Coast. The wind field is highly lopsided northward,
with generally favorable low-level wind profiles, shear values,
and hodographs for supercells apparent in VWP data and objective
analyses along the upper TX and middle/ western LA coastlines.
A westward and inland shift of favorable kinematic conditions is
expected in step with the translational motion of Beta, at least
until it weakens inland. This aspect normally would favor a broader
area of marginal and perhaps greater tornado threat with most TCs.
However, two long-observed environmental features continue to
modulate the threat:
1. Inland boundary-layer trajectories substantially through a
relatively low-theta-e, partly modified continental air left behind
the front, in tandem with: 2. The rather skeletal nature of most of
the convective field, related in part to the longstanding deleterious
effects of deep-tropospheric shear and dry-air entrainment on
this system. Some improvement has been noted in the inner-core
region the last few hours, but this trend's maintenance and radial
expansion still are uncertain. Some Beta CAMs indicate the potential
for increasing coverage, but the efficacy of midlatitude convective
models for TCs is unclear, particularly for ragged and asymmetric
systems like this.
Any growth in density/longevity of convective banding northeast/
east of center, and away from that inner-core area, would increase
potential for supercells to form in spiral convergence bands over
the Gulf and move inland before decaying. Diurnal heating through
patches of relatively thin/broken cloud cover also will destabilize
the inland air mass inland near the coast. This, combined with
onshore theta-e advection, should yield effectively surface-based
inflow parcels where they haven't yet been observed over the outlook
area, with MLCAPE potentially attaining 500-1000 J/kg values.
For now, the tornado threat is kept as marginal because of its
strongly conditional nature.
See latest NHC advisories for track/intensity guidance on Beta,
as well as tropical watches/warnings.
..Edwards/Broyles.. 09/21/2020
Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK
0352 AM CDT Mon Sep 21 2020
Valid 241200Z - 291200Z
...DISCUSSION... Depending on the progression of Tropical Cyclone
Beta, some severe threat may persist over parts of the lower MS
Valley on Day 4/Thursday as it moves northeastward and merges with
a weak mid-level trough. Considerable uncertainty exists regarding
Beta's placement, and the marginal forecast shear/instability across
the lower MS Valley suggest no severe probabilities are warranted
at this time.
Farther west, an upper trough should advance eastward from the
Pacific Northwest to the northern/central Plains on Day 5/Friday.
Low-level moisture is forecast to gradually increase ahead of this
upper trough across parts of the Plains into the Upper Midwest and
MS Valley. Warm mid-level temperatures may keep the warm sector
capped across the Upper Midwest through much of the day Friday,
although deep-layer shear is forecast to be rather strong.
An isolated/marginal severe risk may exist this upcoming weekend
ahead of a cold front across a fairly broad portion of the CONUS
extending from parts of the southern Plains to the Great Lakes.
However, details remain unclear regarding the timing/amplitude
of the eastward-moving upper trough and related surface features.
Depending on this upper trough's evolution, some severe risk may
continue across parts of the eastern CONUS into early next week.
Regardless, far too much uncertainty exists to include 15% severe
probabilities at this extended time frame.
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El estilo es el ropaje del pensamiento; y un pensamiento bien vestido,
como un hombre bien vestido, se presenta mejor.
-- Lord Chesterfield.
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