May 2017: Memorial Day/End Of May Outlook

General Weather Discussions and Analysis

May 2017: Memorial Day/End Of May Outlook

Postby ticka1 » Wed Apr 26, 2017 6:26 pm

Will we see more active weather or slowdow going into 2017 Atlantic Hutricane Season!
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Re: May 2017 Weather -Active pattern contine?

Postby CarlCobb » Sat Apr 29, 2017 1:53 am

Great!
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Re: May 2017 Weather -Active pattern contine?

Postby Katdaddy » Mon May 01, 2017 5:49 am

A chilly morning across SE TX mostly in the 50s. The potential for active weather returns Late Tuesday night and again Wednesday evening and night. The SPC has a Marginal Risk area for SE TX both days.
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Re: May 2017 Weather -Active pattern contine?

Postby srainhoutx » Mon May 01, 2017 9:59 am

Monday morning briefing from Jeff:

One day of bad weather is in the forecast for the next 7 days…Wednesday.

Next storm system will rapidly approach TX late Tuesday into Wednesday with a potential for strong he severe thunderstorms and heavy rainfall. Overnight model guidance has come into better agreement on convective evolution on Wednesday yielding higher confidence on how things will evolve during the day.

Moisture return will begin later today and transport of deep moisture from the southern Gulf of Mexico will arrive into the area by Tuesday evening with PWS rising to 1.6 inches and then 1.9 inches by Wednesday morning. Air mass becomes very unstable by early Wednesday morning with CAPE values pushing 2500-3000 J/kg with steepen lapse rates. A weak short wave is forecast to arrive across the region between roughly 300am and 900am or near the same time a surface warm front is moving northward across the region. Short range models are just at the end of this period currently and show deep convection developing along the northward moving warm front in support with the NAM and GFS models. Good instability and shear suggest strong to severe thunderstorms will be possible early Wednesday morning with the main threat being large hail. Low level shear could become maximized near the surface warm front yielding a tornado threat.

Looks like a break during the late morning into the early afternoon hours and even some clearing which will only serve to greatly destabilize and already very unstable air mass. CAPE values soar toward extreme levels of around 4000 J/kg by early afternoon and a surface cold front will be approaching the region during this time along with another incoming short wave. Expect explosive deep convection to form along the frontal boundary from mid afternoon into the evening hours with severe thunderstorms possible. Main threats appear to be damaging winds and large hail with a squall line moving across the area. While weak capping may develop in the wake of the morning activity, this cap is weaker than the recent systems and appears breakable with lift or trigger temperatures in the lower 80’s.

Post Wednesday will onset several days of very nice weather with lows in the 50’s and highs in the 80’s under clear skies.
Carla/Alicia/Jerry(In The Eye)/Michelle/Charley/Ivan/Dennis/Katrina/Rita/Wilma/Ike

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Re: May 2017 Weather -Active pattern contine?

Postby tireman4 » Mon May 01, 2017 10:57 am

00
FXUS64 KHGX 011434
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
934 AM CDT Mon May 1 2017

.UPDATE...
Surface observations show that we got just a little bit chillier
than forecast overnight, but also that temperatures have rebounded
very quickly after sunrise, and so the forecast of temperatures
in the lower to middle 80s under sunny skies looks on track. Made
cosmetic tweaks to temperature and dewpoint to better match
trends this morning.

&&

.PREV DISCUSSION... /ISSUED 607 AM CDT Mon May 1 2017/

AVIATION...
VFR conditions expected. Winds will pick up later this morning and
this afternoon as the surface high moves off the coast.

40

PREV DISCUSSION... /ISSUED 317 AM CDT Mon May 1 2017/

DISCUSSION...
Weak high pressure just off the Texas coast will continue to drift
slowly east today. Light west to southwest winds this morning will
gradually increase and become SSE this evening. The high will
bring sunny skies today. The dry air in place should allow for a
large diurnal range in temps today and a 30 degree range looks
possible. A return of low level moisture should keep min temps
tonight a bit warmer. 850 temps warm on Tuesday and high temps on
Tuesday should warm into the upper 80s. Fcst soundings not showing
much in the way of cloud cover to hinder the temperature rise.

Tuesday night gets a bit more interesting. A weak upper level
disturbance will approach SE TX after 06z. Moisture return really
gets going around 09z and fcst soundings show PW values climbing
to 1.90 inches by 12z. Instability also increases and SE TX will
lie in a weak 70 kt RRQ. Still expecting elevated convection to
develop in the warm air advection regime. Mid level lapse rates
are steep so would expect some of the stronger storms to produce
hail. Bumped PoPs upward for coastal regions late Tuesday night.
The storms will continue for part of the morning before ending as
the disturbance pushes east. Think there will be a break late
Wednesday morning through the early afternoon before another
upper level disturbance and a surface cold front approaches. Fcst
soundings show clouds eroding for a time in the early afternoon
with a bit of heating helping to destabilize things ahead of the
front. Fcst soundings show CAPE values 4000, PW values near 1.90
inches, LI`s around -11 and lapse rates remain steep. NAM fcst
soundings show a weak capping inversion in the 850-700 layer while
the GFS shows no capping in place. At this time, feel the front,
the second disturbance coupled with a weak splitting jet structure
and a strengthening RRQ will foster a second round of convection
that will move through SE TX late Wed afternoon or evening. This
area of convection will have the potential to produce damaging
winds. The ECMWF and GFS are on the same page with things
including the timing which has conditions clearing out after 06z
Thursday. Will hold onto PoPs for a bit longer (into Thurs AM)
because the Canadian model is slower and this model has been
rather consistent with timing.

The upper trough moves east on Thursday and SE TX will lie in a
dry northwest flow as ridging tries to amplify over Texas. Dry
conditions expected through next weekend with mild spring
temperatures through Friday and a gentle warm up next weekend. 43

MARINE...
Onshore winds will return later today and tonight as high pressure
moves overhead and east of the area. Moderate to strong onshore
winds are expected Tuesday night and Wednesday as the surface
pressure gradient tightens over the area. Conditions may approach
advisory levels late Tuesday night into Wednesday. A cold front is
expected to make its way off of the coast Wednesday night or early
Thursday morning.

A few marine impacts are possible with the mid week event:
- Long-period swells will help contribute to higher than normal tide
levels. Water levels are forecast to be highest during the time of
high tide Wednesday morning. These could approach 1 foot above
normal.
- Isolated strong to severe storms are possible Tuesday night and
Wednesday morning, and then again Wednesday night ahead of
the front.
- A small craft advisory is likely following the frontal passage
Wednesday night and Thursday.

40

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 84 58 89 66 82 / 0 0 0 50 80
Houston (IAH) 86 62 88 69 82 / 0 0 0 50 80
Galveston (GLS) 81 73 84 75 80 / 0 0 0 60 80

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

Discussion...25
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Re: May 2017 Weather -Active pattern contine?

Postby DoctorMu » Mon May 01, 2017 4:34 pm

41°F in Conroe this morning. Impressive for May!
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Re: May 2017 Weather -Active pattern contine?

Postby Ptarmigan » Mon May 01, 2017 9:51 pm

May is the wettest month on average.
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Re: May 2017 Weather -Active pattern contine?

Postby DoctorMu » Mon May 01, 2017 11:11 pm

Ptarmigan wrote:May is the wettest month on average.


June just edges out May in CLL. Most of that is in the first half of the month before the spigot is turned off for the summer.
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Re: May 2017 Weather -Active pattern contine?

Postby Katdaddy » Tue May 02, 2017 5:52 am

The potential remains for active weather early Wednesday morning and again Wednesday evening and night across SE TX. The SPC has a Slight Risk area from SE TX across Central and S LA and S MS.

Mostly sunny dry days and cooler temps to follow tomorrow night's cool front through the rest of the week with continued sunny skies and warming temps through the weekend.
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Re: May 2017 Weather -Active pattern contine?

Postby tireman4 » Tue May 02, 2017 8:24 am

000
FXUS64 KHGX 021122
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
622 AM CDT Tue May 2 2017

.AVIATION.../12Z TAF/
Latest satellite imagery shows clear skies over SE Texas and
overall expect VFR conditions for the next 12 to 18 hours. Winds
should increase from the SE today in response to low pressure
forming in west Texas.

Gulf moisture should return after 03-06Z allowing at least MVFR
ceilings to form, perhaps some IFR ceilings. Showers should
develop after 06Z with deep convection possible after 09Z through
15-18z Wednesday. This will likely be the first round of
convection with a short wave trough moving across the area with
higher moisture/instability. TAF will carry VCSH/VCTS for now with
future TAF updates refining timing. A second round of convection
will be possible Wednesday evening as a cold front pushes into the
region.

Overpeck


&&

.PREV DISCUSSION... /ISSUED 348 AM CDT Tue May 2 2017/

DISCUSSION...
A strong storm system expected to move across the plains will
bring thunderstorm chances back to SE TExas with the potential
for strong and possibly severe storms Wednesday and Wednesday
evening. High pressure will then build over the state and bring a
period of dry weather through the remainder of the week and into
early next week.

Another dry and warm day is expected today. Above normal high
temperatures are expected today as warm air and moist air
advection increases across the area.

The main time frame of concern will be tonight through Wednesday
evening. A warm front moving up the coast will enter into the
Matagorda Bay area by late this evening. Isolated showers ahead
of the warm front should become more widespread by daybreak. Model
forecast soundings show increasing CAPE values and helicity
values on Wednesday, indicating at least a slight chance for
isolated severe storms. Both the NAMbufr and GFSbufr soundings do
show a bit of warming aloft Wednesday afternoon around 700 to 750
mb as southwesterly winds develop. If so, this may help hinder
thunderstorm development in the afternoon. A plausible scenario
is that there will be an initial period of showers and isolated
thunderstorms moving northward ahead of the warm front in the
morning with a brief break over portions of the area in the
afternoon until the cold front arrives in the evening. The 00Z
run of the Texas Tech 3km WRF shows this scenario over the
southwestern counties of the forecast area and keeps storm chances
over the eastern counties throughout the afternoon. Like how SPC
summarizes the threat in their day 2 discussion--isolated hail and
wind threat with a possible tornado threat in the day; then a
more organized threat associated with a possible squall line ahead
of the cold front in the late afternoon and the evening. This in
line with the 00Z Texas Tech, GFS and ECMWF.

By the way, cannot rule out locally heavy rainfall with the
system. Model PWs do reach from 1.8 to 2 inches ahead of the
front. However, felt that storm motion will be fast enough to keep
amounts down. This is reflected in the accumulated model QPF which
shows only about one quarter to one half inch west of the I-45
corridor and 0.5 to 1 inch to the east. A couple of models had
0.5 to 1 inch along the coast as well.

After the frontal passage, drier conditions will persist into
Monday of next week. Do expect cooler than normal temperatures on
Thursday with a warming trend into the 80s starting on Friday
into Monday.

40

MARINE...
Low pressure is expected to form in the Texas Panhandle today
allowing for southerly winds to increase this afternoon and tonight.
Small craft exercise caution may be needed for the Upper Texas Coast
tonight. There is expected to be a surge in moisture with a weak
vorticity maximum moving over the Upper Texas Coast by Wednesday
morning. This may increase shower and thunderstorm activity
Wednesday morning. A cold front should push off the coast Wednesday
night bringing another chance of thunderstorms for the coastal
waters. Strong offshore winds should develop behind the front early
Thursday morning. Small craft advisories may be needed through the
morning hours with winds gradually decreasing through the afternoon.
Offshore winds continue for the end of the week and seas should drop
to low levels.

Tide levels may reach about 1 foot above normal in Galveston Bay
during high tide Wednesday afternoon. Gulf facing beaches may have
tides about 0.5 to 1.0 feet above normal during high tide near noon
time Wednesday. This will put most areas about 2.6 to 3.0 feet above
MLLW causing minimal impacts if any. Strong rip currents will be
possible Wednesday as well. We may need to monitor Thursday and
Friday for low water issues with offshore winds persisting. This may
cause tides to be about 1 foot below normal.

Overpeck

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 89 68 85 56 76 / 0 30 70 30 0
Houston (IAH) 88 69 84 58 78 / 0 40 70 50 0
Galveston (GLS) 82 74 81 62 75 / 0 50 70 60 10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

Discussion...40
Aviation/Marine...39
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