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Rodolfo Alves

Tempo Severo EUA - 2017

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Essa semana o tempo severo deve retornar aos EUA e também atingir o Canadá.


Hoje, risco moderado pra áreas do Wyoming, Dakota do Sul e Nebraska com significativo risco de tornados intensos e granizos grandes.

A área a ser afetada é bem pouco povoada, o perímetro de risco moderado (risco grau 4) abrange 90.000 habitantes e o de risco aumentado (risco grau 3) pouco mais de 500.000



SITUAÇÃO PARTICULARMENTE PERIGOSA para a ocorrência de tornados está em vigor para o sudeste do Wyoming, Norte do Colorado e o Panhandle de Nebranka


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Pelo menos 9 tornados foram reportados ontem, 8 em Minnesota e 1 em Illinois.

Os tornados causaram danos, mas felizmente ninguém ficou ferido.

Fortes tempestades também foram registradas no TX, KS, OK e MO.










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Harvey já causou cerca de 50 tornados desde que chegou aos EUA.

Hoje pelo menos 8 foram reportados entre MS, AL e TN hoje.

O tornado mais forte ocorreu próximo de Reform, AL.







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Mais tornados são esperados hoje devido ao ciclone Harvey.

Os tornados estão previstos para ocorrer na região das Carolinas.


Alabama ontem:






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37 tornados confirmados durante o furacão Harvey.

O mais forte foi classificado com EF2.



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Risco de grau 3 (enhanced) pra Oklahoma amanhã 21/10.





Widespread thunderstorm development is expected late Saturday

afternoon into Saturday night, from portions of the upper

Mississippi Valley into the southern Plains. Some of this activity,

particularly across the Plains, will be accompanied by a risk for

potentially damaging wind gusts, some hail and perhaps a couple of




Models indicate that large-scale mid/upper troughing, currently

advancing inland of the Pacific Coast, will remain progressive

through this period, likely reaching Manitoba, northwest Ontario,

the upper Mississippi Valley and southern U.S. Plains by 12Z Sunday.

Within this regime, the corridor of strongest mid-level height

falls are forecast to spread east/northeast of the Canadian Prairies

and northern U.S. Plains Saturday/Saturday night, associated with a

couple of significant embedded short wave impulses. But another

digging impulse may contribute to mid-level height falls across the

southern Plains Red River Valley region Saturday night, while

beginning to split away from the base of larger-scale troughing to

the north.


In lower levels, a deep associated surface cyclone is forecast to

migrate from southern Manitoba into Hudson Bay, while a modest

trailing cold front advances eastward/southeastward through much of

the U.S. Plains and mid/upper Mississippi Valley region by the end

of the Period.


...Plains/Mississippi Valley...

Models generally indicate that the mid-level cold core and strongest

mid-level forcing for ascent may tend to lag to the west of the cold

front through the period. And severe weather potential, in general,

may hinge on how fast the eastward and southeastward advancing cold

front tends to undercut the pre-frontal initiating convective

development, which remains unclear at this time. However, it

appears that there will be at least a window of opportunity for

substantive pre-frontal thunderstorm activity, accompanied by a risk

for severe weather.


At least a narrow plume of seasonably moist air (characterized by

mid/upper 60s surface dew points) appears likely to precede the

front in a corridor from the southern Plains into the upper

Mississippi Valley. Models suggest that low-level moistening will

occur beneath a plume of modestly steep lapse rates associated with

elevated mixed layer air, which may contribute to CAPE up to 1000+

J/kg, and 2000 J/kg across north central Texas into Oklahoma.


Although deep layer wind fields are not expected to be exceptionally

strong, 30-50 kts in lower/mid-levels (somewhat stronger across

parts of the lower Missouri Valley into upper Mississippi Valley),

should be more than sufficient to support organized severe weather

potential, given the instability. Guidance appears suggestive that

vigorous storm development may initiate first across parts of the

east central Plains and middle Missouri Valley late Saturday

afternoon, before intensifying while increasing and spreading

northeastward toward the upper Mississippi Valley through Saturday

evening. This could include isolated discrete supercells early,

before evolving into a broken squall line, with damaging wind gusts

becoming the primary severe threat.


Farther south, stronger instability, coupled with increasing forcing

for ascent (enhanced by increasingly divergent high-level flow) may

support storm initiation across parts of western/northern Oklahoma

and adjacent portions of the Plains by early Saturday evening. This

may include discrete supercells initially, in a corridor ahead of

the cold front, and near its intersection with the dry line.

However, fairly rapid and considerable upscale convective growth

appears probable, with potentially damaging wind gusts becoming the

primary concern by mid to late evening, before tending to become

undercut by the southward advancing cold front.


..Kerr.. 10/20/2017

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Granizo e ventos fortes foram reportados no TX, OK e KS.

Pelo menos dois tornados reportados em OK, um em andamento neste momento.





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Fracos e breves tornados sendo reportados hoje em Oklahoma.

Um tornado atingiu Norman, OK causando alguns danos.










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Risco de tempo severo no próximo domingo em áreas do MO, IL, IN, OH, MI e KY.

O maior risco parece ser ventos fortes e granizo, com a ameaça de tornados concentrada entre Indiana e Illinois.







Day 3 Convective Outlook

NWS Storm Prediction Center Norman OK

0230 AM CDT Fri Nov 03 2017


Valid 051200Z - 061200Z












Scattered severe thunderstorms capable of producing large hail,

damaging winds, and a few tornadoes may occur across parts of the

Lower Great Lakes, Midwest, and Ohio Valley regions on Sunday.



A split mid/upper-level jet structure will likely be present over

much of the western/central CONUS on Sunday, with modest 500 mb

height falls forecast to spread across the mid/upper MS Valley and

Great Lakes region through Sunday evening. Large-scale lift

associated with the strong southern branch of the mid/upper-level

jet (100+ kt at 250 mb and 60-70+ kt at 500 mb) should promote

convective development across parts of the lower Great Lakes,

Midwest, and OH Valley by Sunday afternoon. An elevated mixed layer

with steep mid-level lapse rates (generally 7-8 C/km in the

700-500-mb layer) emanating from the central/southern Plains is

expected to overspread these regions through the period.


At the surface, a broad moist warm sector will be in place across TX

and the lower MS Valley into parts of the Southeast, TN/OH Valleys,

Midwest, and lower Great Lakes. Surface dewpoints reaching into at

least the low to mid 60s should be common across the warm sector

Sunday afternoon. A weak surface low should develop northeastward

along a warm/cold front triple point from the vicinity of eastern

KS/western MO to the lower Great Lakes by Sunday evening. A trailing

cold front should progress slowly southeastward across the mid MS

Valley and parts of the Midwest/OH Valley through early Monday



...Lower Great Lakes/Midwest into the OH Valley and Mid MS Valley...

Strong effective shear associated with the previously mentioned

southern-stream mid/upper-level jet will favor supercell structures

with any initial convective development along the warm front and

across the open warm sector. Given the steep mid-level lapse rates

and rich low-level moisture that will be present across this region,

potentially moderate buoyancy should develop by Sunday afternoon

even with only modest diurnal heating. Scattered large hail, some

possibly significant, may occur with these supercells, particularly

across parts of central/eastern IL into western IN where buoyancy

should be greatest. Damaging downdraft winds will also be a threat

with any supercell as low-level lapse rates steepen with diurnal

heating. The tornado potential should be maximized along the surface

warm front and east of the low where low-level winds will be locally

backed to a more southerly direction (versus generally southwesterly



There is at least some potential for isolated elevated convection to

be ongoing at the start of the period across IL/IN in association

with a southwesterly low-level jet. This activity, should it occur,

may delay diurnal destabilization of the warm sector, and could

result in lower severe potential than currently indicated.

Considerable uncertainty also remains concerning the northward

extent of the warm sector Sunday afternoon/evening, and severe

probabilities will likely need to be refined once model agreement

increases in the location of the warm front and best potential for

surface-based convection. Eventual upscale growth into one or more

bowing line segments may occur along the southeastward-moving cold

front by Sunday evening, probably posing a risk for strong to

damaging winds. Decreasing instability due to the loss of diurnal

heating with eastward/southward extent should result in a gradual

reduction in severe potential by Sunday night.


..Gleason.. 11/03/2017

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Risco de tempo severo hoje principalmente em Indiana, Illinois e Ohio.

Potencial tornádico de 10%, 30% para granizo e 15% de vento.



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Pelo menos 7 tornados reportados até o momento.

Danos foram reportados nos estados de Indiana e Ohio, alguns foram significativos.

Pelo menos duas pessoas ficaram feridas no estado de Ohio.










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