Convection from northeastern Mexico moved into northwestern edge of Zapata County around 6:45 AM CDT and then moved southeastward across the entire county through the morning bringing very heavy rain, flooding and strong thunderstorm winds.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS BRO wrote it up.
Convection from northeastern Mexico moved into northwestern edge of Zapata County around 6:45 AM CDT and then moved southeastward across the entire county through the morning bringing very heavy rain, flooding and strong thunderstorm winds.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Brownsville, TX wrote its last area forecast discussion before the first event at May 21, 4:53 AM CST, 1 hour 59 minutes earlier.
Area Forecast Discussion...UPDATED National Weather Service Brownsville TX 553 AM CDT Thu May 21 2020 .DISCUSSION...The MCS NW of Laredo still has some life in it and a new cell is seen developing West of Falcon Dam. Added 20 percent for the morning hours for the Western Counties including the Upper Valley to cover if these storms move across the River and into our CWA. Mid-level shortwave energy tapping into elevated instability and subtle moisture to keep a few updraft invigorated to keep the isolated convection going. Can not rule out a strong to isolated severe storm producing gusty wind and some hail along with heavy rainfall and potential lightning strikes. && .DISCUSSION...Updated for latest aviation discussion below. && .AVIATION...MVFR ceilings this morning to lift and break up mid to late morning with general VFR ceilings the remainder of the afternoon. Stratus expected to return tonight. Slight chance of overnight convection with KMFE seeing slightly better chances. Moderate breezes with occasional higher gusts around 25 knots today. && .PREV DISCUSSION... /issued 347 AM CDT Thu May 21 2020/ SHORT TERM (Now through Friday): Weak ridge remains in place over Texas but should continue to flatten through Friday as several shortwave troughs rotate around the base of a large Western U.S. trough. Deterministic and CAM models are not in the best agreement with precipitation chances the next 36 hours making for a challenging forecast. Convection currently remains northwest of the CWA and is showing signs of weakening as well as moving northeast following on the heals of MCV tracking northeast over the Texas Hill Country. This should leave our region high and dry for the most part this morning. Atmosphere is conditionally unstable and moisture values continue to increase as moisture deepens with the upper ridge finally weakening. An isolated shower or thunderstorm is possible out west with convection firing along a potential outflow boundary form the overnight convection or new convection developing over the Sierra Madre late today and moving into our region. Probabilities remain rather low with only the GFS showing any moderate chances, mainly this morning and over the Western Ranchlands. Otherwise, a typical late spring day with temperatures slightly above normal and heat indices ranging from 102 to 108. Pressure gradient looks a bit weaker with the NE Mexico thermal low not as strong as yesterday due to the break down of the mid-level ridge. Tonight's pop forecast is somewhat uncertain with the ECMWF very aggressive with developing a MCS over West Central Texas and driving it southeast over our CWA late tonight and not exiting south of the border until Friday morning. This solution seems to be an outlier with the GFS and some CAM models showing isolated to scattered indicate convection tonight into Friday. With this said will be trending with a none ECMWF solution and keep pops in the 20-30 percent range tonight and Friday. Can not rule out a few strong storms producing gusty winds and possible hail with plenty of instability and the conditional unstable atmosphere. General mid- level flow looks relatively weak so any thunderstorms will slow moving and could produce heavy rain with amounts of 1-2 inches. Outside of the convection chances...warm and muggy conditions continue tonight and another seasonal hot day will be on tap for Friday. LONG TERM (Friday Night through Wednesday): A 500mb shortwave develops across central to east Texas this holiday weekend and keeps unsettled weather in play across Deep South Texas into next week. Surface low pressure across northern Mexico may help develop convection nightly across the border, and elevated moisture combined with warm afternoon temperatures may help seabreeze convection kick up each day. Remnant outflow boundaries from convection further north may add to the rain chances as well, with several CAMs showing squall lines developing north and heading south at various points through the weekend and early next week. The ECMWF remains the heavy handed model over the past couple of days, but at this point, confidence remains low to moderate, so will keep more blended POPs. The best rain chances at this point remain with the upper level support late Saturday into Monday, and again Tuesday into Wednesday, as spokes of the 500mb shortwave swing through. These may be the best opportunities for strong to severe thunderstorms as well, with locally heavy rainfall, as PWAT values peak each day between 1.8 and 2.1 inches. Expect near normal to slightly above normal afternoon temperatures and above normal low temperatures for persistent muggy conditions. Heat Indices may approach 100 to 104 across the mid to upper valley this weekend into Memorial Day, with increased cloud cover and rain chances maybe knocking indices down a bit Tuesday and Wednesday. MARINE (Now through Friday): A moderate pressure gradient across the Gulf looks to be maintained through Friday. Broad high pressure extending across the Gulf to combine with weak low pressure over NE Mexico and West Texas providing a moderate onshore winds. Small Craft exercise caution conditions should suffice for the Laguna during the daytime switching offshore for the overnight and early morning hours. Buoy 42020 showing just a low to moderate wind wave and no swell and with no significant easterly or southeast winds anticpated so will maintain a steady state sea regime through the period. Friday Night through Wednesday: High pressure across the northeastern Gulf of Mexico slowly retreats northeastward through the long term, allowing breezy southeasterly winds along the lower Texas coast into Saturday to diminish into next week, eventually becoming east. Small Craft Advisories may be needed across the bay Saturday afternoon, with Small Craft Caution to possibly Small Craft Advisory conditions across Gulf of Mexico waters into Memorial Day. Favorable marine conditions return Tuesday. The best chance of thunderstorms across coastal waters remains Monday and Tuesday, however, with this pattern, mariners are urged to stay tuned to weather updates and warnings this holiday weekend into next week as unsettled weather across the state could deteriorate marine conditions rapidly. && .BRO WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && This product is also available on the web at: HTTP://WEATHER.GOV/RGV 59/65
Hazardous Weather Outlook National Weather Service Brownsville TX 431 AM CDT Thu May 21 2020 TXZ248>257-351-353-221000- Zapata-Jim Hogg-Brooks-Inland Kenedy-Starr-Southern Hidalgo- Inland Willacy-Inland Cameron-Coastal Willacy-Coastal Cameron- Coastal Kenedy-Northern Hidalgo- 431 AM CDT Thu May 21 2020 This Hazardous Weather Outlook is for portions of Deep South Texas. .DAY ONE...Today and Tonight An isolated strong thunderstorm is possible over the Western Ranchlands later tonight. Gusty winds, hail and heavy rainfall are possible. Otherwise, no significant weather is expected. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Isolated to scattered thunderstorms are possible Friday through early next week. A few storms could be strong with the potential for locally heavy downpours, gusty winds and hail. An elevated risk of rip currents is possible over the weekend, and Memorial Day. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. GMZ130-132-135-150-155-170-175-221000- Laguna Madre from the Port of Brownsville to the Arroyo Colorado- Laguna Madre from the Arroyo Colorado To 5 NM north of Port Mansfield TX- Laguna Madre from 5 nm north of Port Mansfield to Baffin Bay TX- Coastal waters from Port Mansfield to the Rio Grande out 20 nm- Coastal waters from Baffin Bay to Port Mansfield out 20 nm- Waters from Port Mansfield to the Rio Grande extending from 20 to 60 nm- Waters from Baffin Bay to Port Mansfield extending from 20 to 60 nm- 431 AM CDT Thu May 21 2020 This Hazardous Weather Outlook is for portions of The Gulf of Mexico and The Laguna Madre. .DAY ONE...Today and Tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Friday through Wednesday No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
Special Weather Statement
National Weather Service Brownsville TX
639 AM CDT Thu May 21 2020
TXZ248-211230-
Zapata TX-
639 AM CDT Thu May 21 2020
...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN ZAPATA COUNTY UNTIL
730 AM CDT...
At 637 AM CDT, Doppler radar was tracking a strong thunderstorm near
El Cenizo, or 13 miles southwest of Laredo, moving southeast at 30
mph.
Nickel size hail and winds in excess of 40 mph will be possible with
this storm. Very large hail is likely falling across the border.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.
To report severe weather, contact your nearest law enforcement
agency. They will relay your report to the National Weather Service
office in Brownsville.
&&
LAT...LON 2709 9943 2710 9944 2713 9943 2715 9944
2717 9943 2725 9944 2727 9945 2732 9937
2727 9933 2727 9927 2686 9931 2688 9933
2692 9932 2694 9939 2696 9939 2698 9938
2702 9942 2701 9943 2702 9944 2706 9945
TIME...MOT...LOC 1137Z 323DEG 26KT 2737 9958
HallmanThe Corpus Christi radar (KCRP), 206 km away, was scanning. The volume nearest the first event began at 12:49 UTC.
3 flood, 1 thunderstorm wind. Local standard time, as filed.
At least 3 power poles broken 1 mile north of San Ygnacio on US-83 and some tree damage reported in the town of San Ygnacio. Time estimated via radar.
Minor flooding and high standing water was reported 3 miles north of Zapata by Hilcorp on US 83. Time estimated by radar.
Water depth of 1.5 feet was reported across all lanes of SR-16 between Alamo and Carla Streets. Time estimated via radar.
Minor flooding was reported in the Medina addition with arroyo overflowing on Guerrero Ave. between 4th and 7th St. up with up to 2 feet of flowing water depth. Time estimated via radar.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Texas in 2020Every state in 2020This day in weather historyWarnings in Texas, May 2020
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 898031, 898026, 898027, 898029.