April 2020

General Weather Discussions and Analysis
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Ptarmigan
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April 2020

Post by Ptarmigan » Mon Mar 30, 2020 5:54 pm

It is almost April. COVID-19 is likely to dominate the headlines as plagues the world.

Pas_Bon
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Re: April 2020

Post by Pas_Bon » Mon Mar 30, 2020 11:13 pm

What’s COVID-19?

I kid. What a disaster this is.

We still need rain in SE Texas. Badly.

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Re: April 2020

Post by Cpv17 » Tue Mar 31, 2020 12:45 pm

There’s a chance for some severe storms on Friday. Not exactly sure yet which areas will be impacted or how significant the risk will be. I do know that hail and damaging winds will be the two most prominent impacts.

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Re: April 2020

Post by Texaspirate11 » Tue Mar 31, 2020 6:32 pm

Cpv17 wrote:
Tue Mar 31, 2020 12:45 pm
There’s a chance for some severe storms on Friday. Not exactly sure yet which areas will be impacted or how significant the risk will be. I do know that hail and damaging winds will be the two most prominent impacts.
My guess is always North northeast of me...pfft
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unome
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Re: April 2020

Post by unome » Wed Apr 01, 2020 6:09 am

maybe the parched areas will get some relief this time - hope so anyway

https://www.wpc.ncep.noaa.gov/basicwx/a ... p_ndfd.gif
https://www.wpc.ncep.noaa.gov/discussio ... isc=qpferd

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
422 AM EDT Wed Apr 01 2020
...

Day 3
Valid 12Z Fri Apr 03 2020 - 12Z Sat Apr 04 2020

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF EAST TEXAS...

A longwave trough moving across the western US will eject mid-level energy over TX that will interact with an approaching surface cold front Friday into early Saturday. With moisture and instability pooling to the south of this boundary for nearly a day, expect the atmosphere to be primed for convection. Precipitable water values will surge to over 1.5 inches, despite weak low level southerly flow. Given the moist southerly flow coming out of the Gulf of Mexico, anticipate a very unstable airmass inland with MUCAPE values surpassing 2000 J/kg. With pockets of strong divergence aloft, mid-level impulses and the aforementioned frontal zone, there will be plenty of synoptic scale ascent present across the region. Thus, widespread convection will blossom along and ahead/south of this cold front, especially Friday afternoon through the overnight.

At this update, the highest areal average precipitation forecasted will be around 1-2+ inches across central TX. A lot depends on the progression of the cold front and if/where it will become stalled. Most models illustrate a slowing/stalled frontal zone resulting in fairly decent precipitation totals. However, there are model differences with respect to where the front will reside/stall. Thus, model variability with the precipitation amounts and placement exist. Regardless, models do seem to agree on the high rain rates (>0.75 inches/hour) and the potential for convective training (as evident by the propagation vectors becoming aligned with the mean flow). With fairly high FFG, feel soils can withstand the precipitation/rain rates expected. Thus, a Marginal Risk should suffice. However, if QPF totals increase from training convection and/or hourly rain rates, an upgrade to Slight Risk may be needed.

Pagano

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Re: April 2020

Post by BlueJay » Wed Apr 01, 2020 8:49 am

Beware of April fool's day pranks and enjoy the sunny day.

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Re: April 2020

Post by unome » Wed Apr 01, 2020 6:26 pm

BlueJay wrote:
Wed Apr 01, 2020 8:49 am
Beware of April fool's day pranks and enjoy the sunny day.
they put a mixed precip rain/snow spot in the GOM :lol:

https://www.wpc.ncep.noaa.gov/NationalF ... rt/map.php
april fools - Copy.png

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Re: April 2020

Post by sau27 » Thu Apr 02, 2020 9:45 am

Boy it would be nice if the 12Z 3km Nam came to fruition. But alas, it is the NAM.

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Re: April 2020

Post by Belmer » Thu Apr 02, 2020 10:16 am

Had everything below typed up about ready to send when a glitch happened and the page refreshed and everything I typed up was lost. Auto save would have been great to have... but learned my lesson and copied everything with every few sentences I wrote so to not let that repeat again. Anyway, with some free time on my hands thought I would explain the upcoming weather this weekend:

While we are in uncertain times right now with everything going on around the world, I hope everyone and their loved ones are well. Hopefully some of you have been able to get out to a park or walk around the neighborhood on what has been a spectacular two days across our area. While we start what looks like to be a long month of April, at least we'll have some "exciting" weather to track... at least through the first half of the month with an active southern jet coupled with an amplified northern jet. That change will begin starting with our system coming in this weekend.
The Storm Prediction Center currently has most of our viewing area in a 'Marginal' risk with the far northwestern tier in a 'Slight' risk which includes College Station. With every update the risk continues to push a bit further south and east, and wouldn't be too surprised if more of our northern and western counties were included in the slight risk with the new update looking at latest model data. At the surface we have a potent spring time front moving in that will drop temperatures into the 40's in Dallas on Friday and much of Oklahoma will remain in the 30's. As the front progresses southward it will slowdown and potentially stall, which will determine our rainfall amounts come Saturday (more on that in a bit). At the same time a strong westerly flow will bring a couple mid-level disturbances allowing for thunderstorms to potentially blossom out west and across the hill country. With sufficient CAPE across the area along with steep mid-level lapse rates, large hail will be the greatest risk. Still some questioning on just how strong the impulses out of Mexico will be as that will determine the amount of widespread convection that will develop or whether it remains more isolated/scattered. Below is the latest SPC outlook for tomorrow -

SPC Day 2.gif
SPC Day 2 Risk

The bigger question out of this will be the amount of rainfall and that is determined more on where ultimately the front begins to stall. The latest high res models are more bullish and push the front off the TX coast after midnight on Saturday while the GFS stalls it between Huntsville and Fairfield down toward Columbus then washes out. The Euro is the slower of the bunch and has it stalling near the CLL region, but not until late morning on Saturday. I'm more inclined to rely on the higher res models like the NAM as it usually has a better handle on these strong shallow airmasses than the global models. If that is to be believed, heaviest axis of rain could be closer to the coast where that boundary stalls (as sau27 alluded to by the 12z 3km NAM). Though if the front hangs up more towards our northwest, that could focus the heavier rainfall across the Houston area (mainly west of I-45/69). Dew points are currently in the upper 50s to low 60s this morning but will climb to near 70F by the afternoon tomorrow. PWAT values could approach near 2 inches, especially closer to the coast (which is 2-3 standard deviations above normal for this time of year), with ample low-level moisture transport. While 1-2 inches look promising for many across our area, some may see less than an inch, especially the further east you are, though that will really hinder on where the frontal boundary ends up stalling. On the other hand, some locations could exceed over 2-3 inches and have a flood risk where storms may move slowly or move over the same areas along the boundary. Currently the Weather Prediction Center has us under a 'Marginal' risk for excessive rainfall on Saturday. While some areas have had decent rainfall across the area lately, much of us along and south of I-10 are still in moderate to severe drought with even isolated areas in an extreme drought. The latest U.S. Drought Monitor was released today (see below) and shows how beneficial this rain could be across the south. So we should be able to handle the rain as long as it doesn't come all at once. Though... this is April in Houston with high moisture and a stalling boundary... so don't let your guard down. We know better!

WPC Day 3 QPF.gif
WPC Day 3 QPF
WPC Day 3 ER.gif
WPC Day 3 Excessive Rainfall Outlook

Texas Drought Monitor.PNG
Texas Drought Monitor


While I don't want to get too far ahead, we are less than two months until the start of Hurricane Season. As we have seen over the last few years, we've had systems develop in the month of May. Gulf waters are running above normal for this time of the year with 80+ water temps over the central and eastern Gulf. Atlantic basin is also running a couple degrees above normal. With a possible La Nina in the cards as we head into the season, make sure you are prepared ahead of time. Most all seasonal outlooks are including for an above normal season.

SST Anomaly.gif
Weekly SST Anomaly


Hope everyone enjoys their weekend. Stay safe!
Blake
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Re: April 2020

Post by Cpv17 » Thu Apr 02, 2020 10:31 am

Belmer wrote:
Thu Apr 02, 2020 10:16 am
Had everything below typed up about ready to send when a glitch happened and the page refreshed and everything I typed up was lost. Auto save would have been great to have... but learned my lesson and copied everything with every few sentences I wrote so to not let that repeat again. Anyway, with some free time on my hands thought I would explain the upcoming weather this weekend:

While we are in uncertain times right now with everything going on around the world, I hope everyone and their loved ones are well. Hopefully some of you have been able to get out to a park or walk around the neighborhood on what has been a spectacular two days across our area. While we start what looks like to be a long month of April, at least we'll have some "exciting" weather to track... at least through the first half of the month with an active southern jet coupled with an amplified northern jet. That change will begin starting with our system coming in this weekend.
The Storm Prediction Center currently has most of our viewing area in a 'Marginal' risk with the far northwestern tier in a 'Slight' risk which includes College Station. With every update the risk continues to push a bit further south and east, and wouldn't be too surprised if more of our northern and western counties were included in the slight risk with the new update looking at latest model data. At the surface we have a potent spring time front moving in that will drop temperatures into the 40's in Dallas on Friday and much of Oklahoma will remain in the 30's. As the front progress southward it will slowdown and potentially stall, which will determine our rainfall amounts come Saturday (more on that in a bit). At the same time a strong westerly flow will bring a couple mid-level disturbances allowing for thunderstorms to potentially blossom out west and across the hill country. With sufficient CAPE across the area along with steep mid-level lapse rates, large hail will be the greatest risk. Still some questioning on just how strong the impulses out of Mexico will be as that will determine the amount of widespread convection that will develop or whether it remains more isolated/scattered. Below is the latest SPC outlook for tomorrow -


SPC Day 2.gif


The bigger question out of this will be the amount of rainfall and that is determined more on where ultimately the front begins to stall. The latest high res models are more bullish and push the front off the TX coast after midnight on Saturday while the GFS stalls it between Huntsville and Fairfield down toward Columbus then washes out. The Euro is the slower of the bunch and has it stalling near the CLL region, but not until late morning on Saturday. I'm more inclined to rely on the higher res models like the NAM as it usually has a better handle on these strong shallow airmasses than the global models. If that is to be believed, heaviest axis of rain could be closer to the coast where that boundary stalls (as sau27 alluded to by the 12z 3km NAM). Though if the front hangs up more towards our northwest, that could focus the heavier rainfall across the Houston area (mainly west of I-45/69). Dew points are currently in the upper 50s to low 60s this morning but will climb to near 70F by the afternoon tomorrow. PWAT values could approach near 2 inches, especially closer to the coast (which is 2-3 standard deviations above normal for this time of year), with ample low-level moisture transport. While 1-2 inches look promising for many across our area, some may see less than an inch, especially the further east you are, though that will really hinder on where the frontal boundary ends up stalling. On the other hand, some locations could exceed over 2-3 inches and have a flood risk where storms may move slowly or move over the same areas along the boundary. Currently the Weather Prediction Center has us under a 'Marginal' risk for excessive rainfall on Saturday. While some areas have had decent rainfall across the area lately, much of us along and south of I-10 are still in moderate to severe drought with even isolated areas in an extreme drought. The latest U.S. Drought Monitor was released today (see below) and shows how beneficial this rain could be across the south. So we should be able to handle the rain as long as it doesn't come all at once. Though... this is April in Houston with high moisture and a stalling boundary... so don't let your guard down. We know better!


WPC Day 3 QPF.gif


WPC Day 3 ER.gif



Texas Drought Monitor.PNG



While I don't want to get too far ahead, we are less than two months until the start of Hurricane Season. As we have seen over the last few years, we've had systems develop in the month of May. Gulf waters are running above normal for this time of the year with 80+ water temps over the central and eastern Gulf. Atlantic basin is also running a couple degrees above normal. With a possible La Nina in the cards as we head into the season, make sure you are prepared ahead of time. Most all seasonal outlooks are including for an above normal season.


SST Anomaly.gif



Hope everyone enjoys their weekend. Stay safe!
Thanks for posting. That was a great read.

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