Update Thu 08/11 @ 9:24 AM — Areas, especially in NJ, had some decent amounts of rain Wednesday night—
MRMS accumulated rain Wednesday night into Thursday morning. Many areas in NJ had over one inch. (Click on image for a larger view.)
Compare the above actual rain amounts above to the forecast of the experimental LAMDAX model shown here. Not perfect, but not bad!! Better placement than the NAM-NEST.
The experimental LAMDAX isn’t available every day, and when available, only web type low resolution graphics are released; no raw data is available outside of NOAA.
Rain Wednesday night into Thursday morning
Updated Wed 8/10 10:33 PM — Tonight’s models are showing considerably more rain tonight than previously forecast, in line with the experimental LAMDAX model. Many areas, but not all, may receive 0.4 to 0.8 inches. Every model shows a bullseye of localized heavy rain, but the location varies by model. Here’s the latest NAM-NEST, which is most extreme with its bullseye —
NAM-NEST. The bullseye of heavy rain is 4 inches, probably a modeling error.
Updated Wed 8/10 9:08 PM — Updated with the latest LAMDAX precip forecast which just became available below.
Updated Wed 8/10 5:54 PM —Last night, while a very few areas received a substantial rainfall, most areas last night only received a paltry amount. Even the area around Citizens Bank Park only received about 0.30″ yet it caused two rain delays.
Rainfall totals for last night (Tuesday evening/night), according to the MRMS—
MRMS total 24 hour rainfall (Tuesday evening/ night) (Click on image for a larger view.)
As for this evening (Wed), there’s lack of model agreement about where a low pressure system will develop along the stalled frontal boundary that moved through yesterday. This translates into a wide range or forecasts, most with rain south of the immediate PHL area.
NBM total rainfall forecast Wednesday night into early Thursday morning. Most of the rain falls from Philadelphia and southward. (Click on image for a larger view.)
We already know this forecast will be off….the same models forecast rain already beginning in some areas right now, but nothing to be seen on radar and I see blue skies outside my window.
Most of the rain will be gone by 8 AM, but a few areas may have some lingering showers, all gone by 10-11 AM, except in eastern NJ. Not a drought-buster.
Just for the heck of it, here’s the latest experimental LAMDAX high resolution model forecast, showing a very different location of the heaviest precipitation . (The LAMDX looks like it’s being developed and groomed for the next generation of models, likely to be ready for operational release in 2024. It’s still experimental and not finalized.) —
Today’s experimental 12z LAMDAX showing much different location of heaviest precip axis. The LAMDX has limited availability with only pre-made graphics, no raw data available. Click on image for larger view.
Updated Tue 8/09 8:37 PM — We did’t get a drop of rain. Maybe this time —
Radar at 8:39 PM
Update Tue 08/09 @ 6:03 PM — I think we have the answer: the storms fell apart as they approached. My neck of the woods didn’t get a drop. I don’t need to change the headline title of this post which I have kept since Monday evening.
Update Tue 08/09 @ 4:24 PM — Some storms have broken out to our west. The question (that will be answered soon): will they fall apart and diminish as they approach Philadelphia and New Jersey?
Courtesy of weathertap.com (Click on image for a larger view.)
Water Vapor Image at 4 PM shows considerable dry and a very warm air mass (orange coloration) Some popup storms, aided by mountain orographic lift, near the Poconos. But the overall jet level flow is anticyclonic (clockwise) as shown by the white arrows, greatly reducing the chance of showers developing here. (Click on image for a larger view.)
This afternoon’s 18zHRRR shows minimal showers moving through between 7 and 9 PM—
18z HRRR shows minimal, spotty showers moving through between 7 and 9 PM. (Click on image for a larger view.)
A Drought?
New Jersey has just issued a “drought watch”. We’re ‘watching’ here in Pennsylvania too!
There’s talk about this is the first drought here in about 10 years. Any coincidence that we’re in a similar phase (increase) in the ~11 year sunspot cycle? I don’t think so.
I have no idea about the precise mechanism causing drought conditions. BUT each solar maxima increases total solar irradiance reaching our planet by over 1 Watt/M2, which clearly must raise the temperature of the atmosphere. I’m conjecturing that an increase in upper atmosphere temperatures causes drought conditions. Superimpose that increase in temperature with climate change and the effect could be significant.
The study of sunspot cycle and Total Solar Irradiance is performed by the TSIS satellite and previously by the SORCE satellite, operated by the Laboratory for Atmospheric and Space Physics.
Here are summary plots showing the increase in irradiance for the past and current sunspot cycles—
SORCE data (Click on image for a larger view.)TSIS data (Click on image for a larger view.)
I went back through my old posts from 2012. I’ve been linking the sunspot cycle with dry conditions for 20 years.
Updated Mon 8/08 10:55 PM — Tonight’s high resolution models are showing the possibility of tomorrow’s showers being an even greater disappointment. Many areas may receive little or no rain.
Update Mon 08/08 @ 8:03 PM — Our severe heat wave will end tomorrow evening as a cold front moves slowly through. Despite high CAPE values and high precipitable water values, the models are cranking out only scattered showers and thunderstorms.
Total rainfall for most areas will be in the paltry 0.2-0.4″ range. Some areas will have less and a few up to 0.75″ in our area. I offered an explanation for the lack of rainfall earlier in this post.
NBM forecast rainfall—
NBM 1 hour accumulated rainfall at 9 PM. This 1 hour snapshot of the rainfall gives a sense of the amounts and coverage. (Click on image for a larger view.)
There’s a range for the onset of the showers: as early as 4-5 PM, but with most of the activity between 7 PM and 11 PM.
We may receive some additional rainfall Wednesday evening with a secondary cold front.
Update Mon 08/08 @ 8:36 AM — Monday’s weather will be notable for the much higher dew points (70º-75ª) than the high temperatures (92-94º).
The max heat index (maximum “apparent temperature”) according to the NBM at 3 PM —
06z NBM apparent temperature (heat index) at 3 PM Monday. (Click on image for a larger view.)
Most models keep any pop-up thunderstorms to our far northwest today. But with the increase in humidity, a pop-up thunderstorm in our area can’t be ruled out. There is a large upper air disturbance that will rotate through our area, visible on water vapor imagery —
WV image for 8:16 AM showing disturbance near Great Lakes. The greatest chance of any popup storms is just our northwest (see yellow isentropic contours). The strong anticyclonic curvature of the upper winds will work against any storm formation.
Yesterday, storms tried to develop but failed—
Cumulus with strong vertical growth on Sunday about 12:30 PM. (Click on image for a larger view.)
Originally Posted Sun 8:19 PM —
The current heat wave continues through Tuesday afternoon. Little relief from dry conditions.
A change is on the way Thursday —A significant dip in the jet stream on Thursday will result from high pressure building in to the eastern third of the country—
GEFS jet stream winds (250 mb) Thursday evening showing significant trough over the eastern third of the US. (Click on image for a larger view.)
Before we get to Thursday, we have to deal with a complex situation late Tuesday and Wednesday.
Between Tuesday evening and Thursday a cold front will struggle to move through.
Ordinarily, we’d expect heavy thunderstorms and heavy rain (much needed!) with a cold front moving into very warm humid air. And I wish I could be confident that the immediate Philadelphia area will receive that heavy rain we need.
But the GFS shows a complex frontal passage with the upper air ridge hanging tight on Tuesday night with the front stalling—
GFS forecast for Tuesday evening 11 PM. Shows showers/thundershowers but the immediate PHL area not receiving all that much as the upper air ridge (orange 576 thickness line) still hangs back over central PA. The slowing front will have several areas of low pressure develop along it. (Click on image for a larger view.)
The front makes another move through Wednesday night with more showers and thunderstorms Wednesday afternoon and evening.
Zooming in on 8 PM Wednesday night, that pesky 576 thickness line hangs back after the front moves through and and the immediate PHL area appears to get short-changed in the rain department.
GFS Forecast for Wednesday 8 PM shows the immediate PHL area receives a paltry amount of rain with the front! The 576 thickness line hangs back. (Click on image for a larger view.)
Next Thursday through Sunday look great. But if you’re hoping for relief from lawn watering, I’m afraid it may not happen. Should surface low pressure develop in a slightly different position, things might change.
Update Sat 08/06 @ 10:01 PM — The models continue to forecast widely scattered light showers where none can be found. This will likely be the case again Sunday.
Tonight’s 00z NBM showing light scattered showers at 5 PM Sunday. (Click on image for a larger view.)
Sunday will be mostly sunny, with occasional clouds. While scattered showers are forecast for late afternoon and evening, most areas will remain dry.
High 93ª NBM model Blue Bell PA. Dew point temperatures in the mid to upper 60s- increasingly uncomfortable.
Update Sat 08/06 @ 10:59 AM — This morning’s models keep us dry through the day Saturday. The anticyclonically curved flow causes the air to sink inhibiting storm development.
Update Sat 08/06 @ 9:31 AM —This morning’s water vapor image shows the various potential triggers for showers and thunderstorms today—
Water Vapor shows various potential storm triggers (circled in white) today in the jet stream level flow (yellow stream contours) The sharp anticyclonic flow (yellow contours) may inhibit these triggers from storm development. (Click on image for a larger view.)
Showers and storms are possible anytime today, although most of the day will be dry in most places.
Originally Posted Fri 8:36 PM —
A diffuse summertime pattern with the moist flow of a Bermuda high in the Atlantic pushing back on a weak cold front that has been trying to move through Pennsylvania today.
Water Vapor Satellite image showing upper air disturbances (dark blue areas) around Pennsylvania embedded in a moist flow around the Bermuda high. The disturbance to our west, Lancaster/York counties, may yet produce some storms here later this evening. (Click on image for a larger view.)
No specific model has correctly identified the timing and location of the storms the past two days. That likely will be the case over the weekend.
For those hoping for rain, there is the possibility that a disturbance just to our west in Lancaster/York counties may still spark some storms later this evening.
WV showing upper air trigger near Lancaster/York with weak 500 mb flow towards us (arrow) Unfortunately, the yellow contours suggest that the disturbance may not fully make it towards us. (Click on image for a larger view.)MRMS radar with RAP 500 mb wind streamlines. (Click on image for a larger view.)
For Saturday, we remain in the hot moist airflow. Some models are forecasting scattered thunderstorms at any time during the day. The Canadian GEM is is pushing for some storms around noon to 1 PM on Saturday.
The same pattern continues for Sunday. It will be difficult (maybe impossible) to accurately predict timing and location of any showers/storms.
Saturday
A mix of clouds and sunshine. A chance of showers and thunderstorms any time, especially noon/early afternoon according to the Canadian GEM
High temperature 89.4º sd 3.3º NBM model Blue Bell, PA (higher than usual sd- standard deviation- the result of uncertainty in cloud cover and showers)
Sunday
Similar to Saturday. Showers / thunderstorms possible anytime and anywhere.
High temperature 90.6º sd 2.5º NBM model Blue Bell, PA
Updated Fri 8/05 9:52 AM —We had some showers Thursday evening, more widespread than had been forecast by the models.
For today, Friday, there’s a range of forecasts, with many models showing little in the way of rainfall to as much as an inch. The trend is for not much. Timing varies from as early as mid to late afternoon, to storms moving through late evening and even after midnight.
I’m curious whether the new, experimental limited area model clarifies the forecast. It has maintained a forecast of a moderate cluster of storms early evening.
Updated Wed 9:38 PM — The forecast is unchanged for Thursday. Very hot and humid. A few scattered thunderstorms my pop up after 5 PM, but with low vertical shear, they won’t last long or cover much territory.
A cold front approaches on Friday. A large cluster of thunderstorms will develop in western suburbs and move into the city between 6 and 8 PM. Some heavy rain possible with these storms. Shear values will again be low, so we’ll have to see if the models are getting this right.
Update Tue 08/02 @ 8:20 PM — Not much happening except increasing heat. A weak front moved through about 1 PM today. A few isolated showers broke out with the frontal passage (not predicted by the models.)
The increasing temperatures for Wednesday and Thursday are well-advertised by the regular radio and TV media.
Here’s some specifics info for Thursday based on the current NBM model —
19z NBM Temperature Dew point meteogram for Blue Bell PA for Wednesday through noon Saturday. (Philadelphia tends to run a bit hotter by 2-3º) (Click on image for a larger view.)
High Temperatures Thursday—
NBM forecast high temperatures for Thursday. The “±” temp is the standard deviation of the over 20 models that comprise the NBM. Most areas are over 95-100º (Click on image for a larger view.)
Here’s the NBM forecast Heat Index (“apparent temperature”)—
NBM forecast max HEAT INDEX (apparent temperature) for Thursday about 2:55 PM. Most areas over 100º (Click on image for a larger view.)
Next chance for showers/storms: possibly Thursday night, but most likely Friday afternoon and or evening.
Update Mon 08/01 @ 1:21 PM — We finally had some large scale rain in the area last night, but amounts were overall only in the 0.4-0.6 inch range with some localized higher amounts and some areas with little—
MRMS 24 hour rain accumulation through noon Monday. (Click on image for a larger view.)
A weak front moving through Pennsylvania today (Monday) will fall apart as it moves towards the Delaware Valley with all showers associated with the front forecast forecast to die out.
For Tuesday and Wednesday: Temperatures will approach and exceed 90º but the dew points on Tuesday will drop during the afternoon and remain in the tolerable 60s on Wednesday.
The severe heat and humidity return on Thursday before a cold front slowly sinks south Thursday night with showers and thunderstorms possible. It’s possible that we’ll again see some anemic rainfall with this front.
Originally Posted Sun 5:45 PM —
The large hot air mass in Texas and the Midwest that has been making headlines for the past several weeks will be shifting northward and eastward and influencing our weather this coming week.
A warm front will move northward tonight (Sunday) and bring some showers and possibly thunderstorms after midnight and into the early morning hours of Monday—
Water Vapor with drawn warm front Sunday 5:40 PM (Click on image for a larger view.)Today’s 18z HRRR precip forecast by 5 AM Monday morning. It would be great if we get this much rain. The model forecasts regarding amounts and location can’t every be taken literally. (Click on image for a larger view.)
We’ve been in a mini-drought situation and past precipitation forecasts have fizzled. Unlike recent cold front passages, this will be a warm frontal passage that may not succumb to the issues that’s been reducing rainfall here recently.
While the HRRR shows some nice precipitation amounts, the experimental FV3-LAMDAX model (under development) shows somewhat lower amounts.
(With the recent weather pattern we’ve been in, the HRRR and the LAMDAX have been the best performing models according the NOAA’s Model Verification Web site.)
The rest of the week, we’ll be under the increasing influence of upper level high pressure—
GEFS forecast for Thursday showing jet stream winds located north in Canada with the 576 (500-1000mb) “thickness”(orange) contour showing the outline of the hot air mass extending eastward. Notice this contour encompasses most of the country! It will be extending well into Maine and into Montana and Dakotas. (Click on image for a larger view.)
At the same time as the hot air is moving towards us, a series of weak fronts associated with low pressure systems in Canada will affect our weather, especially late Thursday and Friday. More about that later in the week.
