Satellite view shown below as of 845 am CDT Tuesday morning.

The wind related risk area is defined in the next image showing the extent of the tropical storm warning in blue, and the pink/blue hatched area with an additional hurricane watch given the chance it could near hurricane wind levels prior to landfall. The window for this is short with less than 6 hours now before it makes landfall.

The flash flood risk may be the greater concern. The rainfall forecast below gives an idea of the storm total rainfall for Edouard. Note the band of 4 to 6 inches in yellow along/parallel to the center track of the storm. Some of the more recent model solutions place the band a little more east, toward the Beaumont area. Some of the modelling also suggests higher amounts locally, perhaps as high as 10 inches. Will need to continue to monitor where the heavier rains set up to pinpoint where flash flooding may occur.

The graphic here from NWS Houston tries to convey this message of a locally heavier band. The Flood Watch area in green defines the main risk area. Will need to watch areas more inland tonight and Wednesday as Edouard tracks inland slowly. This will shift the heavier rain threat inland with it.

Stay tuned for updates from trusted sources including the National Weather Service and National Hurricane Center.

The latest radar loop and watch/warning map as of 215 pm CDT Monday is shown below. Notice the swirl in the radar echoes as the center tracks toward the WNW. Also shown Tropical Storm Warnings in red and a Flood Watch in green. Click on the arrow to put the loop into motion.

The map below shows point probabilities of sustained winds 39 mph or greater (tropical storm force). One can see how the higher probabilities line up with the tropical storm warned area quite well. Would expect to see gusty winds in the warned area with this as it makes landfall on Tuesday.

Rainfall forecasts from the Weather Prediction Center (below) highlight a swath of 4 to 6 inches mainly along and east of I-24 with Houston settling in with more of a 2 to 4 inch total. In truth local amounts may well be higher than this.

The rainfall map below is derived from the High Resolution Ensemble Forecast (HREF) system and can be useful when dealing with these types of systems, really anything involving thunderstorms/convection. One can clearly see the swath of higher rainfall totals along and to the right of the center track with some totals close to 10 inches in that swath of heavier rain. In reality the location of this heavier rain swath is still uncertain. A shift slightly west would put the Houston Metro right in the heart of it. In any case the rain rates and amounts support the Flood Watch that’s been issued and the flood risk is likely the greatest threat from this system.

Another way to assess the flood risk is through the Excessive Rainfall Outlooks issued by the Weather Prediction Center. Note the areas under a Level 2/Slight Risk for the 3 day period with daily outlook areas shown as well right through Wednesday. Beyond Wednesday the depression/storm will likely have moved out and dissipated with more scattered thunderstorm activity for the remainder of the week, more of a typical summertime pattern.

Finally the loop of forecast radar reflectivity from the latest (18Z) run of the HRRR model is shown below running from this afternoon through midnight Tuesday night. Note the generally progression into and through Southeast Texas as we go through the day and evening on Tuesday. This is just one model run so would not focus on the details but it does give a general timeline for the rainfall associated with this system.

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Shown here another wider satellite view of these weather systems as of Sunday morning.

Focussing on the low pressure system over the Gulf, it has gotten better organized over the past 24 hours. One can see in this animation the thunderstorms clustered in the general vicinity of the surface circulation. The white colors are the cold thunderstorm cloud tops. Also shown in this animation the satellite detected lightning flashes from the Geostationary Lightning Mapper or GLM located on the GOES-19 satellite.

Surface observations do indeed show a low pressure center with an apparent closed circulation but the winds are relatively weak, on the order of 15 to 25 mph. The barbs on this map point in the direction from where the winds are coming while the flags indicate different wind speeds.

This disturbance should take a general W then WNW track which could bring it into SE Texas as early as Tuesday morning. Whether or not it develops into a tropical depression or tropical storm it will likely enhance rainfall locally across the area. Again this is given a 30% chance of becoming a tropical depression or tropical storm before making landfall in a few days but definitely bears watching as intensity modelling can be a challenge for these systems. Given this timeline if those probabilities go up it wouldn’t be shocking to see watches issued for some areas.

You can see the impact of this system in the 7-day rainfall forecast from the Weather Prediction Center with a swath of 2 to 4+ inches forecast near and right of the center track as a first best estimate/forecast but may ultimately be higher.

Will of course need to keep an eye on it. Stay tuned for updates from the National Weather Service, National Hurricane Center and other trusted sources.

The cyclone should track toward the W or WNW over the next several days but will likely struggle to intensify further as it tracks into a less favorable environment. The center track cone shows the general movement over the next 3 days or so. Note no track is shown beyond 3 days as there remains some doubt the storm will hold together beyond that time.

The global models are shown below out to 6 days. Note the consensus of a WNW heading over the Caribbean Islands but again would likely be a weak storm or just remnants by that time it reaches the island chain.

The hurricane intensity models are shown below and again bear out the idea that this system should remain weak.

Much of the model ensemble guidance shows the same thing. Shown below ensembles from the Google Deep Mind AI based model showing the system maintaining tropical storm intensity until reaching the Lesser Antilles or Puerto Rico then diminishing. This is again consistent with an essentially 3-day one from NHC.

We’ll see how this all plays out but again something to watch as we head into the climatological peak of the Atlantic hurricane season.

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Is there any relief in sight as we head into September? Unfortunately no. Below we see the outlook for next week with the above normal conditions expected to persist across much of the South with some relief for the Pacific Northwest. One can see that in the 8 to 14 day outlook and the hazards maps shown below.

A look at the GFS model through 15 days for Houston reinforces the message with high temperatures in the upper 90s to near or above the century mark, coupled with high levels of humidity, as far as the eye can see. Will be keeping an eye out for the first meaningful cold front of the season for Southeast Texas. It cant come soon enough!

Update on the Tropics

The National Hurricane Center is monitoring two areas of potential development in the Atlantic as shown below. Will focus mostly on disturbance 2, a cluster of thunderstorms associated with an easterly wave that has emerged off the coast of Africa, which has a 70 percent chance of becoming a tropical depression or storm in the coming days. Note the position denoted by the X in the 2-day outlook and the 7-day development region indicated by the area outlined in red in satellite images below.

Where might it track should it develop? Most of the model guidance tracks the disturbance westward for several days with the system remaining fairly weak, disorganized. Many solutions then turn it north where it would in theory have a better environment to intensify. One can see this below in the ECMWF ensemble solutions run out for a 10-day period.

The Google Deep Mind AI model keeps the system weaker longer with more of a westerly heading, with ensemble members then makes that northerly turn later, closer to land. This cyclone location maps from this ensemble forecast system are shown out to 15-days! At this point this is all highly speculative and really no reason for concern but will of course need to monitor as we head into the climatological peak of the Atlantic hurricane season.

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The National Hurricane Center is monitoring 3 areas of potential tropical cyclone development over the next 7 days. There is a low pressure system, cyclone, approaching Portugal which is not a tropical cyclone but has a small chance of developing tropical characteristics which would be unusual for such a high latitude system. There is another disturbance over the open waters of the Atlantic near the Sargasso Sea. A third area has been added off the coast of Africa where there is some model support for development from an easterly wave coming off Africa next week. NHC is now giving that a medium chance of developing (40%) in the Days 3 to 7 time range..

The animation below shows ensemble runs from the ECMWF model showing a fairly large fraction of members do in fact develop from a wave that emerges off the coast of Africa early this week with intensification occurring as these model solutions recurve the cyclones before reaching the Continental U.S. In this figure lower central pressures and thus higher intensities are indicated indicated by the warmer line colors.

The GEFS version of this is interesting as well with many ensemble members recurving and intensifying as the ECMWF ensembles were showing while many others take more of a westward heading and dissipate before reaching the Caribbean Sea. We have seen this behaviour in the recent past as potential disturbances, candidates for development, dissipate as they encounter the high vertical wind shear and unfavorable environment found in the Caribbean Sea.

What about the longer term? The Climate Prediction Center in their outlooks highlight a pattern similar to what we have now with some development chances over the Eastern Tropical Atlantic but relatively low chances over the Caribbean. Note also the very active pattern over the Eastern Pacific. All of this is consistent with the El Nino we are experiencing.

Dover, Delaware August 20th Tornado Review

On Thursday August 20th an EF-1 tornado spun-up out of a High Precipitation Supercell type thunderstorm. The tornado occurred squarely within the highest probability area defined by the SPC Outlook earlier that day. Shown here the Day 1 Convective Outlook issued late that morning.

A radar 4 panel from around the time of apparent touchdown showns the classic Tornado Debris Signature with a tight inbound/outbound circulation (upper right panel) colocated with a low correlation coefficient area (lower left panel) suggestive of targets of different shapes and sizes from debris lofted by the apparent tornado. The reflectivity is also interesting showing the circulation/mesocylone embedded in a heavy rain area (upper left).

Animating the radar one can make out the rotating high precipitation supercell embedded on the line of thunderstorms with cells also developing immediately in advance of the line.

The high precipitation nature of the tornado is also shown in this video of the tornado. Notice the roof being lifted off from the tornado with the heavy rain shrounding any visible funnel cloud.

NWS Mount Holly is in the process of surveying the damage around Dover and surrounding areas. In addition to the damage near Dover the have found evidence of at least two other tornadoes. You can read their report here.

https://mesonet.agron.iastate.edu/wx/afos/p.php?pil=PNSPHI&e=202608220004

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Looking across the U.S. the heat remains the big story across the South while flooding and severe weather will be possible over portions of the Mid Atlantic and Plains. The latest watch/warning/advisory map is shown below. Note the large expanse of heat related advisories and warnings (in orange and rose color) and the flood related watches and warnings in green and dark red.

The forecast high temperatures today from the NWS show a huge expanse of near or above 100 degree values over roughly the southern half of the U.S. and much of the Western U.S. as far north as Washington State.

Forecast max temperatures for the next 7 days don’t show much change with blistering hot conditions over the south and relatively seasonable conditions across the north.

Severe Weather Threat

Today severe weather risk will be focussed on the Mid Atlantic and portions of the Northern Plains. See two areas of Level 2/Slight risk shown in yellow.

Zeroing in on the Mid Atlantic region, one can see a fairly significant damaging wind threat across the Delmarva Peninsula up into the Philadelphia area with the cities of D.C., Baltimore and Richmond also at risk.

There is a tornado threat across a similar area with greatest risk for Philadelphia, Baltimore and Dover and surrounding areas.

The loop below shows the forecast radar from the 14Z run of the HRRR model run from noon EDT Thursday to 2 am EDT Friday (times in loop labelled in Greenwich time. Subtrack 4 hours for EDT). One can see the thunderstorm activity form up into a line of thunderstorms, some possibly with supercell structure, later this afternoon and evening pushing offshore between 10 pm and 2 am north to south.

Update on the Tropics

The tropics remain relatively quiet for now, especially in the Atlantic, with thunderstorms lined up in Eastern Pacific and Tropical Atlantic roughly along the 10N longitude line, which approximates the Intertropical Convergence Zone. The only real development candidates over the next 7 days are in the Eastern Pacific in the which could become tropical cyclones in the areas within the red (high chance) and yellow (low chance) lines seen on the satellite image.

Beyond 7 days there is some model support for Atlantic development. Shown below are cyclone tracks from ECMWF ensembles in the 5 to 15 day range, getting into forecast periods that are too far out to be at all reliable. Recall a few weeks ago models showed a similar signal that ended up not coming to fruition. Certainly no cause for concern at this point. Nonetheless will be something to watch as we get into the latter part of August and early September.

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This morning Tropical Storm Lala can be seen on NWS radar swirling just southeast of the Big Island of Hawaii. The storms winds with the latest advisory are just below hurricane levels with sustained winds of 65 mph. Lala could become a hurricane today.

The latest cone and warning graphic is shown below. Notice the center is forecast to track very near the southern part of the Big Island of Hawaii with the other islands getting more of the periphery impacts on the northern flank of the system with perhaps heavy rain in the outer bands. The forecast graphic also shows the hurricane and tropical storm warnings in effect for Lala.

Whether or not the center makes landfall on the islands, the rainfall amounts will likely be significant, enough to cause flash flooding especially on the Big Island.

The situation is much different in the Atlantic. The disturbances which the National Hurricane Center identified as likely to develop into tropical cyclones just a few days ago are struggling against unfavorable environmental conditions and now are given a much lower development chance over the next 7 days, with the lead disturbance, 92L, now not expected to develop and the other invest, 94L, now given only a low chance. In the satellite view one can see a third disturbance/easterly wave behind 94L showing the active wave train that is set up now with more disturbances coming off the coast of Africa. However these disturbances will likely struggle to develop as well.

Weather Across the CONUS

Weather across the U.S. will continue to be driven by a weather pattern featuring and upper level high pressure system parked over Texas and the South Central U.S. featuring rain-free hot and humid conditions beneath it with thunderstorm complexes developing and being steered around it. These thunderstorm complexes following one after another may continue to cause flash flooding. The rainfall forecast and Excessive Rainfall Outlook for today show this pattern as does the watch/warning map below it with flood watches and some flash flood warnings along the northern flank of the high, through IA, IN, OH and WV, and heat related warnings and advisories over much of the South.

Shown below is a satellite composite as of Noon Thursday, August 13th. Note the tropical disturbances lined up over the open waters of the Tropical Atlantic and the tropical storm located Southeast of Hawaii (all circled). This time of year waves periodically come off the coast of Africa (so-called Easterly or African Waves) then propagate from east to west across the tropical Atlantic. Some of these may develop into tropical cyclones. This is one of the main development paradigms for the Atlantic Basin.

Which one of these (if any) may develop? The Graphical Tropical Weather Outlooks from the National Hurricane Center identify possible tropical cyclogenesis candidates and show a percentage chance they will become tropical cyclones (tropical depressions, tropical storms). Note as of late this morning the lead disturbance, Invest 92-L, has an 80% chance of developing over the next 2-days while the one behind, 94-L, has a 30 % chance. There is a third wave just now coming off the coast of Africa which will bear watching.

Over the next 7 days the chances are 80 percent and 60 percent respectively. Note also the short-lived Post Tropical Storm Cristobal which ended up very briefly becoming a tropical storm over the past day or so.

Where might these systems track (should they develop)? Invest 92L looks to track toward the west through the Caribbean Sea where it will encounter strong vertical wind shear which should limit any chance of intensification beyond perhaps a weak tropical storm.

The 7-day tracking models for 94L show the system tracking toward the Lesser Antilles. From there it remains to be seen whether it recurves north or follows a similar track as 92L. A recurving storm would have a better chance to strengthen. Bottom line, neither system of any particular concern but bear watching.

The Eastern Pacific features two tropical storms, Lala and Hernan. Lala in particular has a good chance of striking the Hawaiian Islands over the next few days.

The forecast track for Lala is shown below. Notice the center is forecast to track near the big island of Hawaii sometime on Saturday with the storm likely impacting all the islands. A Hurricane Watch is in effect for the big island as shown by the pink shading on the cone map, as there is some potential Lala could become a hurricane.

Weather Across the Continental U.S.; Heat and Floods.

The latest Watch/Warning/Advisory Map from midday Thursday shows the main weather hazards across the CONUS with heat-related warnings and advisories across much of the South and Southeast and a band of flood and severe thunderstorm related watches and warnings over parts of the Midwest and Ohio River Valley.

Texas and the Southern Plains have been under the influence of high pressure aloft, a feature sometimes referred to as a “heat dome,” and this pattern will likely hold for at least another week. Hot and mainly rain-free conditions are typical under this high pressure area while thunderstorm complexes develop and track repeatedly from west to east on its northern flank. The 7-day forecast rainfall shows this very well with most of Texas and Oklahoma rain free but with a swath of several inches of rain possible from Iowa across parts of Illinois and Indiana.

The Day 1 Excessive Rainfall Outlook further highlights the flash flood risk areas for today which includes a relatively rare Moderate Risk. This general pattern will likely continue for the next several days.

The map below shows the radar composite as of 742 AM CDT Tuesday with storm reports over the past 24 hours overlaid. The squares denote thunderstorm wind damage and/or measured winds near or above severe thresholds from the past day or so. Note the current storm complexes over Eastern IA, across OH and WV. These storm complexes are riding along the northern fringe of an upper high. In this weather pattern you get periodic thunderstorm complexes during the day and night that move in the W and NW mean flow on the northern and northeast fringe of the upper high creating a so-called “ring of fire” in that zone. From the storm reports, one can see pretty widespread wind damage from a few of these systems that moved through yesterday and overnight.

Looking ahead to today one can see a Slight to Enhanced (Level 2/3) risk of more severe weather (especially damaging winds) in a similar WNW to ESE swath as more thunderstorm complexes cycle through.

The hatching in the wind specific outlook shows a zone where especially high end wind damage may occur. The intensity level 2 for wind corresponds to potential for higher-end winds typical of these bow echo/squall line/derecho type thunderstorm complexes.

Looking at the 06Z run of the HRRR run out over the next 48 hours one can see these periodic “ring of fire” thunderstorm complexes pushing along this corridor. Note also the dearth of any thunderstorm activity under the high pressure system (so-called heat dome) itself, keeping much of TX/OK rain free.

Tropical Update

The National Hurricane Center has lowered the chance of development for one tropical disturbance east of the Lesser Antilles to be near zero percent, while raising the development chances for another farther east to high chance. The Two-Day and Seven-Day Tropical Weather Outlooks are shown below.

There is a third disturbance at higher latitudes with a low chance of briefly becoming a tropical cyclone as it heads toward the east. Most of the focus this week will be on the high chance development area shown by the red hatched area below.

If it does develop as expected, where might it track? The ECMWF ensembles over the next 10 days show some solutions recurving out to sea and intensifying (note the line colors correspond to different maximum wind speeds), while others keep it weaker and on a more westerly heading. The more southerly westward tracks will face a more hostile environment for development with strong vertical wind shear. For those that recurve to higher latitudes, the environment would be more favorable.

These ensemble maps do show other disturbances pushing off coast of Africa, which are Easterly Waves, each with some potential to develop and typical of this more active part of the hurricane season.

The National Hurricane Center is highlighting two potential development areas in the Tropical Atlantic as indicated below. There is a low chance of development in the yellow shaded area and a medium chance in the orange area over the next 7 days.

There is uncertainty there will be tropical cyclone development at all, but they do develop where might they track? Its too early to determine this with confidence but early signs indicate the lead tropical disturbance with a low chance of developing will head more west and weaken while the more easterly disturbance with a medium chance of development will likely recurve out to sea (but with a better chance of survival). The ECMWF ensembles are shown below. GEFS show a similar evolution. Note the lead disturbance dissipates in all the ensembles as it gets into the Caribbean Sea.

The lead disturbance in particular is not in an environment very conducive to development. The satellite view this morning shows a good deal of dusty, desert air in its vicinity. In the image the dust is seen by the tan colored hue near the Lesser Antilles Islands and east.

This dust plume and the disturbance are forecast to advect east with the mean east to west winds steering features. In addition to the dry, dusty air, the disturbance will be dealing with high vertical wind shear typical of the ongoing El Nino pattern.

Bottom line, it’s good to keep an eye on the tropics this time of the year but no real concern for the CONUS at this point from either of these potential tropical systems.

Continued Smoke Across the Northern Tier

Also visible in the satellite image shared above, the milky grey/white hue over the Northwest U.S. indicating smoke/haze from the wildfires there. Model forecasts of vertically integrate smoke continue to show this spreading downstream over the next few days.

If it does it would be the first storm of the season to develop within the Main Development Region, loosely defined as the stretch of ocean between 10N and 20N and 20W to 80W, which is a climatologically favored zone where many hurricanes form. Ensembles from the better operational and AI ensembles show a signal with many solutions indicating development in that time frame. Shown below are ensemble low tracks and intensities from the European and GFS model ensembles ending next Saturday around midnight. The ensembles are model solutions with slightly different initial conditions and can often can signal potential development in the days ahead.

It’s way to early to speculate where it would track should it form and, as mentioned, those chances are deemed low at this point. Conditions in general across the MDR are not conducive to formation and strengthening given the higher vertical wind shear over the area, typical of the El Nino pattern we are in. Below is a forecast of vertical wind shear between 850 mb and 200 mb in the atmosphere, verifying Wednesday evening. Note the generally higher values in that development region.

Nonetheless it will be something to keep an eye on as we get into next week as we enter the climatologically more active part of the hurricane season. From the activity map below you can see we are just now entering the climatologically more active part of the hurricane season.

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Fires and Smoke Across the Pacific Northwest

Smoke from existing fires can be seen as the milky white/grey areas on this satellite map with the bright white areas showing thunderstorms erupting this afternoon over parts of the eastern half of the U.S.

The wildfires across Oregon, Washington State and Alberta can be seen on this animation. Note the source points in this areas and the milky appearance to the smoke layers downstream.

We can get an idea where this smoke will travel as it gets caught up in the larger scale flow and advects downstream. Shown below we have vertically integrated smoke as forecast by the 18Z run of the HRRR model projecting forward 48 hours through midday Saturday. Note the high values near the source regions over Eastern Oregon and Washington and downstream across Montana, Wyoming, South Dakota and Nebraska. Lower concentrations of smoke can be seen far removed from the source regions as far south as Texas and New Mexico, and as far east as Indiana and Ohio.

The above map gives an idea of the vertically integrated smoke which includes smoke layers aloft. To better understand near surface conditions, one can check out the latest air quality maps from airnow.gov. Note the areas of unhealthy and very unhealthy air over the Pacific Northwest near those source regions.

Tropical Update: New NOAA Seasonal Outlook

National Hurricane Center is indicating no tropical development expected over the next week or so with the Main Development Region, from the Caribbean Sea on east devoid of any thunderstorms at the moment, thanks in part to increased vertical wind shear as a result of El Nino. There is some indication in longer range models and ensembles of a more active easterly wave-train of systems coming off coast of Africa but any that do will have to fight those headwinds of less than favorable conditions. Will need to keep an eye on the tropics as we head into the more active part of the season climatologically.

Largely as a result of the intensifying El Nino and the typically unfavorable conditions that result, NOAA today came out with an update to the seasonal forecast lowering the numbers a bit more from what was issued in May. To date we have had 2 named storms, both fairly weak, sheared tropical storms Arthur and Bertha. Note even with these reduced numbers we have a long way to go.

You can read the press release with more information on the updated NOAA forecast here.

One can see the swirl in the visible satellite animation below as it continues to get better organized.

Once it develops, where does it track? The initial center point and subsequent track remain uncertain. The global and hurricane tracking models take the cyclone generally NW then W. A more northerly track would carry it over land and keep it weaker. A more westerly track would keep the center over the warm Gulf waters which which would give it more of an opportunity to intensify more.

There is a large spread with many models favoring each scenario. The ECMWF ensembles and some of the AI based models are especially bullish on the more westerly scenario which would imply a stronger storm and potentially greater impacts for Texas as early as Thursday. This is just one scenario but does have support from both the Google AI Deepmind model and the ECMWF ensembles as shown below.

Bottom line, disturbance still disorganized and its evolution uncertain, but all interests from Texas to Florida Panhandle need to monitor.

All eyes will be on the Gulf over the next few days as a mid level circulation/vortex tries to work its way down to the surface. This is one mode of tropical development or cyclogenesis. Satellite image from this morning is shown below with a cluster of thunderstorms over the northeast Gulf.

The National Hurricane Center gives this system a 30% chance of becoming a tropical cyclone (tropical depression or storm) over the next 7 days in the yellow hatched area shown below. If it were to be named it would be Bertha.

If it were to develop, it could track northwest or more due west which could bring it in anywhere along the northern or western Gulf coast. This is shown by the ensemble tracks from the ECMWF model and the Google AI models shown below. One possible would be a weaker system meandering over the NE Gulf, perhaps tracking into the coast in the area between SE Louisiana and the FL Panhandle. Another scenario would take it more westward out over water with perhaps a slightly stronger system tracking more toward Texas.

Needless to say it is something we will need to watch over the coming days. The Google AI model shown above are the ensemble tracks through Thursday evening which gives a rough idea of the timing for various scenarios.

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This Independence Day holiday weekend is all about the heat for a large part of the U.S. with Heat Advisories (shown in orange on map below) and the more severe Excessive Heat Warnings (in rose color on map) for a large part of the eastern half of the CONUS.

The NWS forecast max temps for next few days range from mid 90s up into triple digits for these areas and for much of the South. Below see the forecast max temperature for tomorrow, July 4th, with similar high temperatures on tap for today, July 3rd. The extreme heat extends into next week for much of the South.

Factoring in the humidity, the apparent temperature or heat index will be even higher. Shown below are forecasted heat index for 4 pm EDT. Note values near 110 F for much of DC and VA, and above 100 for a much larger area.

The NWS also produces Heat Risk maps with a nice interactive tool found at this link NWS HeatRisk. From the map interface you can click on a point of interest and get a look ahead and the forecast including heat risk category for the next 7 days. Heat Risk takes into account climatology and departure from average with the understanding that some parts of the country are less acclimated to the heat than others. Shown below the heat risk map for tomorrow July 4th and a legend describing what impacts are typically found with each risk category. For more information on NWS Heat Risk go to the link shared above and here.

Will also see thunderstorms flare up, especially in the afternoon and evening, over the next few days which may impact timing of some fireworks displays and outdoor events over parts of the country. The loop below is a recent run of the HRRR model (12Z) showing forecast radar conditions between noon EDT July 3rd and 8 am EDT Sunday July 5th. One can see a pretty strong diurnal component to the convection with thunderstorms more concentrated in the center and eastern part of the country.

The tropical Atlantic remains quiet with no tropical cyclone development expected over the next 7 days and beyond as suggested by the NHC Tropical Weather Outlooks issued this morning and a look at the global models even beyond that 7-day period.

Typhoon Bavi 09W

Although Atlantic basin is quiet, other basins remain relatively active as far as tropical cyclone development is concerned. The strongest of the storms out there now is Typhoon Bavi with latest winds as of 10 am CDT Friday estimated to be 145 mph sustained which puts it as a category 4 on the Saffir Simpson Hurricane Wind Scale. The storm may impact Guam and the Mariana Islands over the weekend, perhaps as a Category 5 storm, with the closest approach likely Sunday afternoon and evening for those areas.

The latest forecast track from the Joint Typhoon Warning Center is shown below showing more areas potentially impacted farther west as it is expected to remain a very powerful Typhoon.

Saharan dust plumes can be seen this morning on the GeoColor enhancement image from the GOES-16 satellite. I’ve highlighted two areas of dust indicated by a light brown coloration compared to the deep blue ocean surface. One can see an expansive area over the Eastern Atlantic with another pivoting up from the Western Caribbean Sea into the Western Gulf.

Looking at the CAMS model Aerosol Optical Depth forecast one can track the future movement and position of these dust plumes. The forecast shown runs from Sunday morning to Tuesday evening. One can see the dust pushing into Texas tonight and Monday. One might expect more of a hazy, milky white sky tomorrow given the nature of how the dust scatters sunlight. Some dust particles can be found near the surface too potentially impacting air quality which can irritate eye, nose and throat for sensitive individuals.

Forecast Overview/Tropics Update

The main weather story today will be flash flooding over portions of Kentucky and Tennessee. The green polygons below show Flash Flood Warnings in effect as of 915 am CDT this morning, along a band of heavy rainfall that has occurred over the past several hours. There is one Flash Flood Emergency in effect currently shown with the green/purple dashed line indicating catastrophic flooding.

A radar estimate of rainfall over the past 12 hours shows several inches of rain in this band which has led to the flash flooding.

More broadly the main weather story will be the extreme heat. The watch/warning map below shows a large portion of the Central U.S. is under Excessive Heat Watches/Warnings or Heat Advisories. Note also the Flood Watch and Flash Flood Warnings over KY/TN. Unfortunate in this case FFWs have same color as Extreme Heat Watches on this particular map.

As far as the tropics are concerned there is low chance of tropical development off the Southeast coast in the 3 to 7 day period in the yellow shaded area shown below along a cold front. Nothing to be overly concerned about at the moment but something to watch.

Zeroing in on the TX/LA storms one can see the view as of 720 am with a cluster of slow moving storms from just north of Corpus Christi to near Bay City with scattered storms moving up the coast from there all the way to near New Orleans. The storms extend some distance inland including in and around the Greater Houston area. Flash Flood Warnings as of 720 am are shown by the green polygons. Given the slow moving nature of these storms one might expect additional flood advisories and possibly flood warnings this morning.

Radar estimates of rainfall over the past 24 hours show local areas of rainfall over 6 inches (light shaded areas) north of Corpus Christi, and in a swath from Bay City to Alvin to League City as well as in a swath from near Waco to Lufkin.

Here we have more of a close up view here of the swath of rain from Bay City to Alvin through League City yesterday.

All this is added on to the rain from last week from TS Arthur and a slow moving cold front. Note widespread 6+ inch area (dark red) with some areas across LA and MS 10 to 20+ inches! The scale/legend is shown below the map.

Going Forward

Shown next forecast radar from the most recent from of the HRRR model, shown between 7 am and 7 pm today. This model suggests a fairly stormy morning, then general weakening trend by afternoon with storms/convection becoming more isolated. Should always view these models with caution as thunderstorms are not always handled well but this should give a qualitative view of trends as we go through the day.

Looking out further ahead in time, after today Texas transitions to a dryer period with many other areas remaining wet as periodic thunderstorm complexes track more over OK and AR into MS. Shown below rainfall forecasts from the NWS Weather Prediction Center for various days this week followed by the 7-day total projection.

Below forecast for Sunday-Saturday 7-day period from the NWS Weather Prediction Center. Note the max rainfall area over portions of OK/KS/MO/AR up into IL.

The week ahead looks wet for many parts of the country but less so for Texas. It will remain hot though with heat indices generally topping out in the 100 to 110 range.

One interesting aspect of this storm, the thunderstorms and rainfall are displaced well east of the low level center due to vertical wind shear over the system. In this satellite “Sandwich” view, the colors represent the colder cloud tops associated with thunderstorms while the white colored low level clouds are still visible showing the low level swirl.

Radar composites confirm the placement of the heavier rains offshore. As a result, the flood threat has greatly diminished and most of the flood watches across Texas have been dropped.

The 1 pm update has TS Arthur tracking toward the NE along the Texas coast and into Louisiana this evening. Tropical Storm Warnings are shown in blue for winds to tropical storm strength which have already been observed today.

Going forward the focus for Texas will shift toward extreme heat. Heat Advisories are already in effect for most of the state (in orange on the map below) with darker magenta showing relatively rare Excessive Heat Warnings which have a higher heat index issuance threshold. Note the active weather pattern across the rest of the CONUS with a variety of hazards including tornado/severe potential over portions of Missouri and Illinois.

The 24-hr loop of forecast radar from the midday run of the HRRR model shows qualitatively the movement of TS Arthur and its remnants across the Southeast bringing the threat of additional flooding there, and another low pressure system and trailing cold front moving across the northern part of the CONUS bringing a variety of hazards.

PTC One Update

The center of circulation associated with Potential Tropical Cyclone (PTC) One at 7 am was estimated to be just east of Port O Connor. The latest NHC forecast brings it up to near Galveston Island early this afternoon and then northeast into Louisiana tonight, perhaps as a tropical depression or storm. It is technically not a tropical depression or storm yet, but is already producing wind gusts to near tropical storm force at some mesonet sensors near Freeport and Galveston.

This system will bring wind gusts of 35 to 45 mph near the coast as it works its way northeastward along the Texas coast, with rain, moderate to heavy at times, in advance of this surface ciculation. Will also see elevated surf and tides, with perhaps beach erosion and minor coastal flooding.

Past Rainfall/Flood Threat

The map below shows radar inferred rainfall for past 12 hours. Southern Brazoria County stands out with a bullseye. MRMS estimates show 12 hour rainfall close to 7 inches.

This brings storm total radar estimates close to 1 foot for that area. NWS has a Flash Flood Warning in effect for that area.

The radar animation from HGX Houston/Galveston radar is shown next. One can see rain pushing well inland with it falling moderate to heavy at times.

The one hour rain rates are now (as of 745 am) maximized over the east side of Harris County over into Chambers County. The image below shows the green polygons and one hour radar inferred rainfall as of 750 am today. A new Flash Flood Warning was issued for East Harris over into Chambers as shown.

The rain will shift east with the disturbance as we go though the day with heavier rains tapering off around Houston this afternoon, and around Beaumont, Pt. Arthur this evening. The forecast radar from 06Z run of RRFS is shown to illustrate qualitatively how things are likely to evolve. The loop runs from this morning until Friday midday. One can see the heavy rain and flash flood threat should end from west to east today with somewhat of a break tomorrow, then perhaps a thunderstorm complex working its way down from the north on Friday (with some wind/severe threat).

Extreme Heat

Much of the focus this week so far has been on the flash flood threat but we don’t want to lose sight of what may be ultimately more dangerous and deadly, the extreme heat and humidity we are facing here in Texas for much of this week. The maps below show maximum heat indices for the next several days. Note many areas will be above Heat Advisory Thresholds and perhaps Excessive Heat Warning levels. Heat Index Values of 110F will be common and up to 120F over South Texas! These are dangerous levels for those that work outdoors and for other vulnerable populations, not to mention all the outdoor activities and international visitors to the area for the soccer matches who might not be acclimated to the heat.

There are plenty of heat safety tips and infographics here: https://www.weather.gov/wrn/heat_infographics. Be sure to share with your friends, family, coworkers, etc.