A stationary front stalled out southeast of the city over the Mid-Atlantic will be the primary agent responsible for an extended period of humid, cloudy, and unstable weather over the weekend. As was the case last weekend, temperatures will be on an upward trend from the low-80s into the low-90s by the start of next week.
Rest of today – mostly cloudy with isolated showers and thunderstorms particularly closer to higher terrain north and west of the city. High temperatures in the low-80s. Overnight lows in the low-70s.
Weather Prediction Center surface forecast for 8AM Saturday
Saturday – more clouds than sun with the stationary front just south of the area. Continued onshore easterly flow behind north of this stationary front will keep things cooler and humid. High temperatures in the low-80s. Chance for showers and thunderstorms to develop again in the afternoon hours with an unstable airmass (due to the high moisture content caused by the onshore flow) as heating increases. Overnight lows in the low-70s.
Sunday – temperatures begin to warm up into the upper-80s as winds shift towards the south. The stationary front attempts to move north as a warm front but high pressure is forecast to develop west of us and block this northwards advance. Scattered showers and thunderstorms are again possible in the afternoon hours. Overnight lows in the mid-70s.
GFS model 2 meter above ground level temperature, 10 meter above ground level wind forecast for 2PM Monday
Monday – with winds shifting to towards the southwest, much warmer air will advect into the region. High temperatures expected to top out in the low-90s with overnight lows in the upper-70s. Mostly sunny skies forecast with the high pressure building.
It looks like we’re going to get lucky for Independence Day this year in NYC. While many areas of the Eastern US may see a chance for rain, the Northeast should remain under the influence of strong enough high pressure that we stay dry. That means good news for all the outdoor activities folks have planned coming up! This will be my first detailed forecast that draws on the recently released GFS FV3 forecast model upgrade, so it will be interesting to see how this upgrade performs.
My Forecast High: 88°F | Low: 74°F | Max sustained winds: 15 mph | Total precipitation: 0.00″ – verification will come from METAR data for the period between 2AM Thursday and 2AM Friday (06Z Thursday to 06Z Friday) at LGA (LaGuardia Airport), and the KLGA Daily Climate Report
Verification High: 93°F | Low: 71°F | Max sustained winds: 16 mph | Total precipitation: 0.00″ – Spot on with the wind forecast for yesterday. It was a good call to bump that forecast up with possible sea breeze enhancement in the mix. Unfortunately, these winds didn’t do enough to cool temperatures off during the day, and I was off by 5°F for the high temperature. Skies turned out to be pretty much sunny the whole day and while statistical forecast models should factor in urban heat island effects, it would have been prudent to still have forecast at least 90°F in light of this. Also, given the 850 mb relative humidity profile, I should have probably sided with a less cloudy outlook that would have favored warmer high temperatures. Of note, the new GFS model had issues initially with a cold bias that should have been corrected. In this case, it was warm on the low, but too cool on the high. This is worth noting even though these two points of data aren’t necessarily indicative of a trend.
Weather Prediction Center surface forecast for 8PM Thursday
Synoptic Set Up A stationary front currently along the northern tier of Illinois, Indiana, Ohio, Pennsylvania and western New York will attempt to push northwards tomorrow as a warm front. However, with a 500 mb ridge aloft and an area of surface high pressure over the Northeast and translating over the Gulf of Maine, this frontal boundary is forecast to become stationary, holding just southwest of the NYC metro area. Moisture above the surface looks modest, and without any impulses of low pressure at the surface or troughs aloft, there doesn’t appear to be any support for precipitation.
NAM 500 mb heights and vorticity valid for 8PM Thursday. Note the presence of a ridge over the Northeast (upside-down U pattern of the black height lines)
High Temperatures GFS, NAM, and NBM agree that July 4th a warm day. All three statistical models come in at between 88-89ºF for high temperatures. EKDMOS (ensemble MOS) 50th percentile matches is very close, at 87-88ºF. The only hitch to warm temperatures is that NAM shows the possibility for low clouds and wind directions are forecast to veer from east-northeast to southeast. Cloud cover could eat into temperatures rising too much, and winds coming from the directions indicated would bring a cooling influence of marine air with sea surface temperatures still in the low-60s at this point in the season. With these factors in mind, but also keeping in mind the effects of the urban heat island, I’ll side with a middle of the road forecast of 88ºF.
Low Temperatures NAM and GFS MOS both show the chance that the low temperature during this forecast period may actually fall overnight going into Friday. Either way, both are very close showing lows ranging 73-75ºF. EKDMOS 50th percentile shows 74-75ºF for the low. Increasing cloud cover should stall any serious radiational cooling, and there’s little indication of any temperature advection either way with weak winds. I’m again going with the mean here and siding with a forecast of 74ºF for the low.
Max Sustained Winds NAM, GFS, and NBM average out to 8 knots for the max sustained wind tomorrow. EKDMOS is more aggressive with winds in the 50th percentile about 13-15 knots. While forecast soundings don’t show too much evidence to support a forecast above 10 knots since the entire wind profile looks remarkably calm for tomorrow, this same tendency to weak synoptic winds could allow for a fairly robust sea breeze to develop, and this could be the what allows sustained winds to top 10 knots. I’ll go with the low-end of the EKDMOS and call for 13 knots (15 mph).
GFS forecast sounding for 8PM Thursday. Indications of high clouds are shown, but low levels remain dry. Wind profile in this forecast looks weak with no winds above 20 knots forecast anywhere in the atmospheric column.
Total Precipitation High pressure is forecast to be in control, with a 500 mb ridge in place. There aren’t any frontal boundaries moving through to create lift and even if there were, there simply isn’t enough moisture to support precipitation. Both the forecast sounding above and 850 mb forecast for relative humidity and winds below show moisture values that are insufficient to bring about any precipitation.
NAM forecast for 850 mb winds and relative humidity at 8PM Thursday
We have a beautiful, sunny start to the week for a change. This will be short-lived though, as a cold front will arrive late Tuesday and bring the first chance for rain this week. More rain arrives later this week with a storm system moving in. Looking ahead to the weekend, we should see a decent Mother’s Day weekend, but chances for rain do show up on Sunday.
Rest of today – mostly sunny, high temperatures in the upper-60s. High pressure in control today will give us a pleasant, spring day, right about average for this time of year. Overnight lows in the low-50s.
Weather Prediction Center surface forecast for 2PM today
Tuesday – most of the day should be dry with high temperatures in the low-70s. Partly cloudy but increasing clouds late as a cold front moves into the area. This frontal boundary will be the focus for any rain that develops in the evening and overnight hours. Overnight lows in the low-50s.
Weather Prediction Center surface forecast for 8PM Tuesday
Wednesday – should have another decent day after the rain moves through overnight. High temperatures in the mid-60s with partly sunny skies. Overnight lows going into Thursday in the low-50s with increasing clouds.
Thursday – mostly cloudy, chance for showers as a warm/stationary front approaches from the south. High temperatures cooler, around 60°F with overnight lows in the mid-50s.
A cool start to the week will lead into a period of extended unsettled weather, with multiple disturbances bringing chances for rain throughout the remainder of the week. During this period, temperatures will remain generally below normal under the influence of these cloudy conditions and rain, though not by much.
Rest of today – increasing clouds with high temperatures rebounding into the upper-50s from a cool start in the mid-40s. The first of several quick-hitting storm systems should move in overnight, bringing generally light precipitation leading into early tomorrow morning. Overnight lows are expected to be warmer in the upper-40s with clouds staving off radiational cooling as occurred overnight into today.
Weather Prediction Center surface forecast for 8AM Tuesday
Tuesday – brief period of dry weather Tuesday as a ridge of high pressure builds in. If more sun than clouds materializes during the afternoon, we could see temperatures nearing 70°F, though temperatures could end up in the low-60s if clouds linger all day. Rain chances increase into the overnight hours with overnight lows near 50°F.
Wednesday – mostly cloudy and cooler with a stationary front setting up near or just south of NYC. This will bring easterly onshore flow and keep temperatures in the mid-50s. As another low develops west of us and slides up along this stationary frontal boundary, rain chances will increase through Wednesday. Overnight lows in the low-50s.
Weather Prediction Center surface forecast for 8AM Thursday
Thursday – temperatures expected to rebound into the mid-60s with the stationary front changing into a warm front and slowly pushing north. Clouds and rain yet again. Mild overnight lows in the low-50s.
We will have a warm though not too sunny start to the weekend. A solid chance for rain hits Sunday with the passage of a cold front. After that, temperatures will drop to below normal levels again. Looking ahead into next week, there should be a dry start to the week but a coastal storm may impact the area mid-week. There’s some outside chances for snow with this storm.
Rest of today – cloudy, with some chance of light rain though most rain should remain over interior. With southwesterly flow, despite clouds we should still reach into the upper-50s to 60°F. A cold front approaching from the west is forecast to stall out and acquire semi-stationary characteristics. Thanks to the continued influence of high pressure off to our east, we should stay mostly dry today. Overnight lows should be warm, near 50ºF.
Saturday – the warmth continues, with high temperatures forecast to reach well into the upper-60s though clouds will still linger around with the stationary front to our west. Overnight lows will be similar to tonight around 50ºF.
Weather Prediction Center surface forecast for 8AM Sunday
Sunday – the stalled frontal boundary finally picks up forward momentum and pushes through the area as a cold front. Ahead of it, temperatures will still be mild in the mid-50s. A line of showers is expected with this front during the day. Overnight lows behind this cold front will be considerably colder, in the low-30s.
Monday – dry, sunny weather, but with a chilly start to the day, temperatures are expected to only be in the upper-40s to near 50ºF, slightly below normal. Overnight lows are expected in the mid-30s.
In lieu of an early week forecast this week, I’m opting to share some observations about weather I experienced in Mexico last week while on vacation. I stayed in Isla Mujeres, a small island located about 13 miles off the coast of Cancun. Temperatures were of course quite warm. It was also unusually windy for this time of year down there, though nothing quite like the windy weather NYC experienced today with some peak winds recorded at over 50 mph nearing 60 mph.
METAR READINGS FROM JFK and LGA showing peak winds of 56 mph and 58 mph respectively recorded at 12:04AM and 8:31AM respectively todaY
I’m only just getting adjusted back to cold temperatures, and am not looking forward to snow possibly falling Wednesday night and another storm bringing wintry precipitation Friday. On the bright side, we are now only about 3 weeks off from the vernal equinox and the start of spring!
On the Servicio Meteorológico Nacional (SMN) – National Meterological Service of Mexico
Since I was going to be in Mexico, I started checking out the Mexican government’s weather service page. Check out the surface analysis below that’s overlaid on what looks like a GOES East image from last Thursday (02/21/2019).
Click to enlarge this surface analysis from the Mexican SMN
Unlike our own National Weather Service, the SMN numbers frontal systems that move through Mexico. Notice the stationary front in the center of the image is labeled as “Frente No. 38” (Front #38) and you can see “Frente Frio No. 40” (Cold Front #40) crossing from southern California into northern Baja California in the upper left corner of the image. They also number their winter storms. The “B” (representing a low pressure center) over Nevada is labeled as “Octava Tormenta Invernal” (Eighth Winter Storm). “Corriente en Chorro Polar” (polar jet stream), “Corriente en Chorro Subtropical” (subtropical jet stream) are familiar features to us, which we seen streaking across the northwest and central portions of Mexico respectively. A “Corriente de Bajo Nivel” (low-level jet) is seen flowing from the east towards the Yucatan. Here’s a translation of the text in the lower left panel:
Systems affecting Mexico The Eighth Winter Storm over the southwestern US combined with cold front #40 in northwestern Mexico will favor showers with some strong storms, very cold temperatures, and wind gusts over 60 km/h in the northwest and northern Republic, and also the potential for snow or sleet in mountainous areas of Baja California, Sonora, and Chihuahua, extending gradually towards Durango. Front #38 with stationary characteristics extends over the western Gulf of Mexico and will generate clouds with isolated rain in the eastern and northeastern parts of the country.
Servicio Meteorológico Nacional of mexico
Synotpic Conditions – the Tropical Big Picture
The consistent breezy south-southeasterly winds I felt on Isla Mujeres were tied to that low-level jet (LLJ) pictured above. This LLJ enhanced the general easterly trade winds in the area. This was a result of the influence of a high anchored over the Western Atlantic, and a low over northern Colombia pictured in the OPC surface analysis below (issued Friday 2/22 02:35Z) “funneling” the winds.
In this analysis of the Western Atlantic from NOAA’s Ocean Prediction Center, you can see that a broad high pressure center was anchored near Bermuda. Meanwhile, a low sat over northern Colombia. The clockwise flow around the high and counterclockwise flow around the low in proximity to each other act to enhance the easterly trade winds found in the tropics.
A
sounding from Philip Goldson International Airport near Belize City
(the closest sounding station I could find to Cancun) showed clear
evidence of a well-mixed layer from the surface to just about 900 mb. It
felt like in Cancun, this mixed layer extended a bit further up into
the 850 mb level where the LLJ sat because the winds were stronger.
Sounding taken above Philip Goldson International Airport near Belize City at 7PM Feb. 20, 2019, showing a well-mixed boundary layer representative of the area around the Yucatan Peninsula during these few days
By
way of brief explanation, well-mixed layers like the one shown above
provide favorable conditions for faster moving winds aloft to transfer
their momemtum downwards, in this case all the way to the surface. It
shouldn’t be a surprise that a deep well-mixed layer also existed today
over NYC – enabling the strong winds aloft to mix down, leading to some
very strong winds and gusts.
Sounding from Upton, NY for at 7AM Feb. 25, 2019, showing a deep well-mixed layer down to the surface from around 800 mb with strong winds 35-50 knots through most of this layer
Aside
from the winds, the weather followed a pretty standard tropical pattern
with clouds building in the afternoon and isolated showers. Despite how
flat the Yucatan Peninusla is, it nevertheless provides at least some
small potential for lift and convergence for air flowing off the
Caribbean Sea. This is because there’s actually a significant difference
in frictional properties of land and water, which makes sense since the
surface of the ocean is considerably “smoother” than the corresponding
forested Yucatan. One other notable trait was that the base of rain
clouds in the area took on a distinctively blue hue, which I imagine was
a reflection of the characteristically blue waters of the Caribbean
Sea.
A couple days into the forecast period for the second WxChallenge city for this fall, and I’ve experienced my worst forecast bust (for yesterday). Highlights in the post-mortem section. It has been a week of transitions for Omaha, which started off with relatively mild conditions but will end the week with possibility for patchy frost!
Synoptic Set Up
A 500 mb longwave trough will with multiple attendant vorticity maxima will pivot through the KOMA region during the first half of the forecast period before flow becomes more zonal. At the 300 mb level, multiple jet streaks could boost divergence with these 500 mb vorticity maxima. This enhanced lift, and strong wind shear profile could lead to some isolated strong-severe thunderstorms. The 850 mb shows evidence of a decently robust LLJ that would should bring a continuous supply of Gulf moisture up the Missouri Valley into the area. At the surface, a warm front looks to lift through Monday, then stall as a cold front in the vicinity of KOMA through late Wednesday due to the deep unidirectional winds parallel to the front boundary.
Notes
The potential for flash flooding, and bouts of heavy rain, is duly noted in the AFD during the first half of the weak. The synoptic ingredients for a long duration rainfall event are certainly evident. Soils in the area are already quite moist, given that flood warnings were present for stretches of the Missouri last week. GFS MOS QPF range on Sunday for 06Z Tuesday to 06Z Wednesday was 1.75-4.46”. NAM MOS QPF range for this time was 1.35-2.71”, consensus was 1.55-3.59”. Records around this time of year for QPF show that 1-2” can easily occur, despite the normal being only a mere 0.07”. SREF probabilities of >= 0.50” were above 90% for this period, and >= 1.00” was 50-70%, but over 2.00” of QPF probabilities were less than 10%. SREF mean was 2.73”, with a pretty large spread, from 0.69-5.54”. GFS mean was 3.93” with spread of 1.82-5.16”. For now, going with a superblend of the low-end of the ranges of MOS and plumes: 1.40”.
As of Monday, SREF and GEFs means had become much better aligned, with SREF mean at 2.83” and GEFs mean 2.95”. SREF spread was 1.34-4.46”, GEFs was 1.43-4.43”. QPF forecast shows KOMA a pretty large QPF gradient, and that uncertainty seems borne out well in the ensemble forecasts. SREF probabilities of >= 2.00” increased to the 10-30% with KOMA lying right on the fringe of 30-50% probabilities of this amount. >= 1.00” probabilities increased to 70-90%. Official NWS forecast as of 10Z Monday called for 1.65” during the forecast period Tuesday. GFS MOS QPF range was 2.10-4.21”, NAM 1.01-2.06”, consensus here is 1.55-3.13”. Based on these updates, I’m increasing my forecast to 1.85” – I’m hedging down below the SREF and GEFS means because I’m still not sure where the stationary/slow-moving surface front will set up in relation to KOMA, and where the best lift will be for heavy rain/thunderstorms as a result. Also, if the 850 mb LLJ fails to materialize close to KOMA, we could be looking at lower overall totals. Low SREF probabilities of over 2.00” also help justify this call. Looking at Wednesday, rain chances diminish considerably after the front moves through, but the story then becomes strong winds possible, with MOS pointing at 17-20 knot synoptic winds.
Ensembles continue to trend upwards as of Monday afternoon with QPF, SREF mean now 2.96” and GEFS mean is 3.16”. SREF probabilities are close to placing KOMA in the 50% >= 2.00” QPF. Will take one more look at 18Z MOS guidance and some other factors before finalizing, but am leaning towards increasing the precip forecast again, this time to maybe 1.90” I’m wary of going for 3” of QPF or higher, given that the entire month’s single-day QPF record is 3.09”. Even beyond 2” still seems unlikely.
On Tuesday, looking ahead at Wednesday and Thursday, the passage of a cold front is quite evident. Temperatures are forecast to drop considerably compared with the beginning of the weak, and precipitation will end, too. The forecast for Wednesday still retains a slight chance for some measurable QPF on the tail end of the main precipitation event Tuesday. Models have backed down from up to 0.25” of precip to less than 0.10”. SREF and GEFS means show approximately 0.04” on Wednesday. SREF probabilities showed that KOMA had a greater than 90% chance of receiving precipitation >= 0.01”, but less than 10% of >= 0.10”, going to go straight up with the ensemble means here. The other story for Wednesday will be stiff winds from the northwest, with MOS synoptic winds of 17-18 knots. This suggests even stronger sustained winds, and will aid in cold advection, keeping high temperatures suppressed. These blustery conditions are forecast to gradually abate by late in the day Thursday, such that the strongest winds Thursday should occur early in the overnight hours. Cold temperatures overnight into Thursday should be somewhat tempered by decent vertical mixing and overcast skies.
Forecasts Submitted
This only reflects finalized forecasts, I’ve made small adjustments to the forecast based on checking MOS daily.
Forecast Day
Max Temp (°F)
Min Temp (°F)
Max Sustained Wind (kts)
Precipitation (inches)
10/09/2018
62
57
14
1.91
10/10/2018
48
44
20
0.02
10/11/2018
48
34
17
0.00
10/12/2018
48
35
9
0.10
Post-Mortem
Day 1: Major bust across the board. Was off by more 5 degrees or more on both the high and low. This made up about half of the error points. The rest came from being off on max precipitation by more than 1.20”. MOS was considerably off the mark with temperatures – though NAM was closer. This was all due to the fact that a stationary frontal boundary never made it close enough to KOMA to realize warmer temperatures, and heavier precip. The axis of the 850 mb LLJ stayed south and east, along with the best surface convergence. As a result, nearly all of the model guidance was horribly wrong. The closest forecast in the class was still nearly 0.50” too high. I put too much credence into the upwards trends on the models – there were some indications already that KOMA was trending to be on the drier side of this event. Still, even if I had nailed the precipitation forecast, I would have still busted hard on the temperatures. Need to be a lot more cautious going forward about situations where a frontal boundary and precipitation are around, and probably hedge down on temperatures during transitional season when a forecast site could be on the cold side of a front with rain.
Cooler temperatures are finally upon us after a very hot and humid week. However, the cooler weather also brings a prolonged period of cloudy conditions, with chances for showers each day this weekend. Rain chances continue into the beginning of next week with a storm system approaching. Long-term, we look towards the tropics, as Tropical Storm Florence continues to have the potential for bringing some impacts to the area.
Rest of today – overcast, with much cooler high temperatures in the mid-70s. Chances for showers, especially later in the day.
Saturday – cloudy with high temperatures remain cool in the low-mid 70s with northeasterly onshore flow behind a cold front draped west-east south of us. This front (which passed through yesterday) will become stationary. Multiple impulses of energy will run along this boundary and allow for continued slight chances of showers.
Sunday – yet another cool, cloudy day with chances for rain. High temperatures around 70°F.
Monday – the stationary front stalled out south of us will return north as a warm front. As this happens, chances for rain increase, along with temperatures rising back into the mid-upper 70s.
Will Tropical Storm Florence Impact the East Coast?
Tropical Storm Florence has been active over the eastern and central North Atlantic for over a week now. Within the last few days, Florence underwent a rapid intensification that brought it up to Category 3 status, making it the first major hurricane of the 2018 Atlantic hurricane season. Subsequently, it has weakened to a tropical storm under relentless strong shear. However, it is expected to reintensify into a major hurricane once shear subsides. Worrying trends in the track forecast for Florence continue to allow for the possibility of landfall on the East Coast, or at the very least, substantial coastal impacts like dangerous surf and beach erosion. However, the National Hurricane Center continues to note that there is considerable uncertainty to the track forecast for Florence, such that it is still too early to determine what effects it will have on the East Coast. This storm will warrant careful observation over the coming days and I will have subsequent updates on it.
After a week of sweltering temperatures, the weekend brings some welcome relief from the heat. The downside is that these cooler temperatures come with mostly cloudy conditions and chances for rain. Labor Day marks the traditional end of summer, and it will feel like that this weekend, but temperatures will rise right back into the upper-80s and low-90s next week.
Rest of today – mostly cloudy with onshore easterly flow keeping temperatures suppressed in the mid-70s. This easterly onshore flow is happening on the back side of a cold front that passed through yesterday. This front will stall out and become stationary south of us over the Delmarva Peninsula. As impulses of energy move along this front, there will be chances for rain. However, it does appear the best chances for rain stay south of us.
Saturday – mostly cloudy still with slightly warmer temperatures in the upper-70s. Easterly onshore winds continue along with some chances for rain in the afternoon and more chances for showers and thunderstorms overnight.
Sunday – warming up into the mid-80s with scattered chances for showers and thunderstorms. Partly sunny skies otherwise.
Monday (Labor Day) – conditions improve just in time for the West Indian Day Parade festivities with high temperatures in the upper-80s and partly sunny skies.
The gray, gloomy, and wet weather trend that’s been semi-persistent for much of the last week continues into the weekend. Unfortunately, rain chances will exist both Saturday and Sunday. Cool temperatures to start the weekend will give way to warmer air. Things finally dry out going into the start of next week.
Rest of today – cloudy and cool with temperatures in the mid-60s. Slight chance for showers, though a strong area of high pressure well to our north in Quebec should help hold the line against rain associated with a stationary front draped west-east across Virginia and the Delmarva. Rain chances increase later into the overnight hours as this area of high pressure starts to lift to the northeast.
Saturday – the aforementioned stationary front will start to lift north as a warm front during the day Saturday. Ahead of this warm front, elevated instability could spark a few thunderstorms late in the day with an assist from vorticity maxima moving through in the mid-levels of the atmosphere. Temperatures will be cool, with clouds and rain showers throughout the day, maxing out in the low-60s. These temperatures will actually rise overnight once the warm front pushes through and allows for much warmer air to surge northward.
Sunday – warmer with high temperatures around 80°F, mostly cloudy with chances for showers and a thunderstorm particularly in the afternoon with the passage of cold front.
Monday – weather finally begins to dry up behind this cold front. High pressure will build once again and should give us a nice day with mostly sunny skies and temperatures in the mid-70s.
