George BM

What was the indoor temp?

Wet.

What's your current guess for RIC?

Rafael. Patty is a subtropical storm near the Azores right now.

Here we go ... Yet another one of George's weenie fantasies. 12:52PM EST Wednesday, December 25, 2024 High Wind Warning in effect from 12PM EST Wednesday, December 25, 2024 until 3AM EST Thursday, December 26, 2024. PDS Tornado Watch in effect until 6PM EST Wednesday, December 25, 2024. Discussion: We are about to experience the true limits of what nature can offer in the region. A life-threatening tornado and severe weather outbreak will impact the region this afternoon as well as dangerous synoptic hurricane force wind gusts behind the cold front from late afternoon into the evening. A very potent and compact shortwave trough is racing eastwards out of the Ohio/Tennessee Valleys and into the Mid-Atlantic region this afternoon and is taking on a negative tilt as it does so. The cold front associated with it will blast through the entire region from west to east between 2pm and 5pm local time at around 65-70kts. As the potent, compact shortwave approaches from the WSW an extraordinarily strong low-level jet ahead of the associated front is bringing in record shattering warmth and unseasonably high humidity from the south. Another thing that it is bringing with it are damaging southeasterly winds. With a tight surface pressure gradient along with the ample sunshine steepening low-level lapse-rates to above 7C/km some of the winds aloft will mix down to the surface resulting in gusts of around 55 to 65mph. With the sunshine in place, temps have already risen into the upper 70s to near 80F and will top out into the 80-82F range in most places before the cold front and associated storms arrive. Dewpoints have risen into the mid/upper 60s and will remain in the upper 60sF ahead of the front. A plume of steep mid-level lapse rates along with a shallow warm-layer aloft have advected into the region from Mexico. The steep environmental lapse rates, which will only get steeper as mid-level temps cool (down to -15C to -16C at 500mb), along with the record warm and moist low levels will allow MLCAPE to rise to 2000-3000J/kg which is just absurd for this time of year. A line of severe thunderstorms will move in along the cold front and several supercells are expected to form immediately ahead of the main line (mostly within 30-40 miles of the line). Mid-level southwesterly winds will increase to 120-140+kts as the potent and compact shortwave races over the region. The area will get under a region of strong lift as the left-exit region of a mid/upper-level jet streak moves overhead. Effective bulk shear will exceed 100kts and with the steep MLLRs and associated cool mid-level temps overhead, Lifted-Index values will drop to near -10. As a result, supercell updrafts will be strong enough to overcome the excessive shear allowing for extremely potent supercells. Tornado threat: All the above combined with excessive low-level shear (effective SRH of 500-800m2/s2) and large low-level CAPE will allow for very favorable conditions for several long-track and violent tornadoes with supercells. These tornadoes will be moving to the northeast at incredible speeds of up to and over 80 mph. Do not wait to be able to hear or see the tornado to take shelter as you will run out of time. Several QLCS tornadoes are likely with the main line as well, especially within bowing segments. With the very fast forward motion of the line, embedded circulations will have very fast winds on their southeast sides leading to EF2+ damage being likely with them, similar to what happened in the Great Plains on December 15, 2021. Wind threat: The wind threat will be widespread and destructive, particularly with bowing segments that develop in the main line of storms. With downdraft CAPE in excess of 1300J/kg and unusually moist Pwats of near 1.5” along with the strong instability in general, microbursts/macrobursts could occur allowing for swaths of extensive to extreme wind damage with gusts well over 100mph possible. Hail threat: The hail threat will also be extraordinary for the region. With the steep MLLRs allowing for large CAPE through the hail-growth zone along with the impressive mid-level shear, hail in excess of 4” in diameter could occur with supercells. The cool air aloft and dynamics will allow for severe hail (1-2” in diameter) even within the line. Rainfall: Most places will quickly receive between 0.5 and 1 inch of rain. Localized spots that get hit by both supercells and the line could get up to 1.5”+ of rain. The very fast storm motions will prevent higher totals. Now comes what happens behind this cold front. As the front moves through there will be a strong pressure surge (rise in surface air pressure). With cold air advection allowing for more efficient mixing and an 80+ kt low-level wind overhead, winds will gust up to 80mph or so worsening the damage that will have already been done by the thunderstorms. During this time temperatures will rapidly fall into the lower 40s through the early evening hours. Thereafter, winds will weaken a bit. But that’s relative as they will still be gusting upwards of 50 to 60mph through around midnight and will still be gusting up to around 40 mph by dawn Thursday. Thursday morning it will be blustery with temps bottoming out in the lower 30s giving the airports a decent chance at the first freeze since December 9th. Windchills will bottom out in the mid/upper teens. This will mark the start of a colder pattern for the foreseeable future with increasing chances of measurable snow by the weekend with a shortwave moving northeast from the deep south and additional snow chances next week and into the new year. - GBM

BWI: 51.8" DCA: 34.7" IAD: 54.6" RIC: 29.4" Tiebreaker (SBY): 27.9"

High of 83 today is IADs highest of the month. And, its coldest, 31, was only 3 days ago. 0.13" of rain for October.

Sunset time. Vibrant and colorful.

IAD has gotten down to 31F. I wonder if DCA manages to get down to 40F.

What did the indoor temperature get down to before the flip?

Currently IAD 55/39.

This day 70 years ago was a 10/10 spectacular weather day locally.

@Roger Smith @RodneyS

Clearly visible here. (Herndon, VA.)

All four of the Atlantic major hurricanes so far this year have peaked at at least a 120kt Category 4. Not too shabby.

Atlantic ACE to date has caught back up to average passing 100pts.

NHC has now upgraded this to Milton based on satellite data. 723 WTNT64 KNHC 051725 TCUAT4 Tropical Storm Milton Tropical Cyclone Update NWS National Hurricane Center Miami FL AL142024 1225 PM CDT Sat Oct 05 2024 ...TROPICAL DEPRESSION BECOMES TROPICAL STORM MILTON... ...FORECAST TO STRENGTHEN AND BRING THE RISK OF LIFE-THREATENING IMPACTS TO PORTIONS OF THE WEST COAST OF FLORIDA NEXT WEEK... Recent satellite wind data indicate that the depression has strengthened into Tropical Storm Milton. The maximum sustained winds are estimated to be 40 mph (65 km/h) with higher gusts. SUMMARY OF 1225 PM CDT...1725 UTC...INFORMATION --------------------------------------------------- LOCATION...22.3N 95.3W ABOUT 220 MI...355 KM NNE OF VERACRUZ MEXICO ABOUT 365 MI...590 KM WNW OF PROGRESO MEXICO MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H PRESENT MOVEMENT...NNE OR 15 DEGREES AT 3 MPH...6 KM/H MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES $$ Forecaster Brown/Kelly

The NHC forecast is fairly bullish with an intensity of 95kts for the 72 and 96 hour points.

35mph, 1007mb for the 11am adv.

Yeah multiple indices could be offline for a bit.

Winds in the upper-levels of the troposphere (~25,000-40,000ft) are very swift out of the northwest. Much faster than the modest low/mid-level NW flow where the majority of the convective clouds are located. So while the storms are moving SE with that modest NW low/mid-level flow the anvils from the storm tops are being blow to the SE of the storms. The stronger upper-level flow being orientated in about the same direction as the weaker low/mid-level is also helping with the storm-splitting action we are seeing to our NW. If, for example, the strength of the upper-level NW winds were more equal or even weaker than the deep-layer low/mid level NW winds, storms would more readily congeal into a solid SE-moving line... small line segments, however, can still form in this environment.

Dulles bottomed out at 43F.

28

Forecast Discussion Sunday, September 1, 2024 8:46PM EDT Current Alerts: Flash Flood Watch in effect from 1AM EDT Monday, September 2, 2024 until 7PM EDT Monday, September 2, 2024. High Wind Warning in effect from 8AM EDT Monday, September 2, 2014 until 8PM EDT Monday, September 2, 2024. For the Rivers and Bay… Hurricane Force-Wind Warning in effect from 12PM EDT Monday, September 2, 2024 until 7PM Monday, September 2, 2024. Hurricane Helene made landfall earlier this evening as the strong landfalling topical cyclone anywhere in the world in recorded history w/ a minimum SLP of 882mb and 175knot(200mph) sustained winds. Even hours after it’s landfall as it races NNE into Georgia ahead of the longwave trough it is still packing 150mph winds as of the 8pm NHC advisory. Helene will bring us locally a historic weather day tomorrow. We get into that below. Tonight through 6am: Southerly flow will continue to usher in an increasingly humid, tropical airmass into the region with dewpoints into the mid-70s or so. Scattered showers and some heavy storms that have given parts of the already saturated region another 2 to 3 inches of rain are currently moving to the northeast north of I-70 and Baltimore. But as the night wares on additional showers and thunderstorms will move in from the south with the increasing southerly flow which will back to more southeasterly near the surface as Helene’s wind field moves into the region. As a result of this, low-level shear will increase and with lift in the atmosphere also increasing this will allow for supercells which may produce a few brief tornadoes, mainly after 2am. With the tropical airmass in place, these storms will be very efficient rain producers thus, some flash flooding is possible and a Flash Flood Watch goes into effect for the region starting at 1am in the DC metro and southwestwards and at 3am for areas to the northeast. 6am through 12pm(noon): Southeasterly winds will start strengthening quickly around dawn and through the mid-morning hours from southwest to northeast and back to more out of due east as the Helene’s low pressure center enters the southwestern part of Virginia. Bands of heavy rain with embedded supercells capable of producing a couple tornadoes will continue through the morning. The greatest tornado threat locally will be between 6am and 10am before lower-level shear actually becomes too strong for supercells to sustain themselves given the fairly meager CAPE with wet adiabatic lapse rates through the entire troposphere, though it’s important to note that the tornado threat will not drop to zero as a brief tornado or two is still possible through about midday. By mid-morning easterly winds will become very strong to damaging gusting 50 to 65mph. With the soggy grounds from Gordon and the very wet pattern we had most of August in general many trees and some powerlines will come down. In terms of rainfall, rainfall come in arcing bands of tropical downpours and supercells around the metro regions. But in the I-81 vicinity as a strong shortwave trough approaches from the west and really starts phasing with Helene’s low pressure circulation, it will interact with the strong easterly winds allowing for very strong lift with very heavy SW to NE oriented rainbands stalling over that region to the immediate west of the track of Helene’s low pressure center. 12pm(noon) through 6pm: The aforementioned shortwave trough moving in from the west will cause two things to occur. 1. Helene’s circulation will receive a large amount of baroclinic energy which will quickly transition the storm into an extratropical system. 2. Cooler and drier air mixing into the back side of the storm combined with an increasing surface gradient on the backside of the system will allow for extremely strong winds to form on the southwest and southside of the low-pressure center. A sting-jet may even form which, should it become well-defined, could further increase the maximum wind gusts. Winds will calm down quite a bit for a brief period of time around midday in the local area as the storm center moves overhead with surface air pressure down into the 970-975mb range. As the storm moves northeast by the early afternoon hours the metro area will get the worst part of the storm. The very tight surface pressure gradient on the southwest side of the circulation will move overhead from southwest to northeast. By midday far southwestern parts of the forecast area such as Charlottesville, VA will start being affected by destructive westerly winds which will spread northeast into the DC metro area by 2pm or so and up into far northern MD and the Baltimore metro by 3-4pm. With the tight pressure gradient and even signs of a sting-jet with air descending and drying from the western to southern side of the circulation winds may gust over 80 mph at times. Some models even indicate that winds could be even higher than that especially if a well-defined sting-jet can form. This will lead to substantial tree and structural damage across the area as well as widespread power outages. Some light/moderate rain may accompany these winds. The strongest winds will probably last for up to two hours in any given location before winds gradually weaken below High Wind Warning criteria by around 4 hours after the onset and below Wind Advisory criteria by 6 hours after the onset after sunset. Skies will clear from southwest to northeast from late afternoon through mid-evening. Monday night: West/northwest winds may still be gusting up into Wind Advisory criteria at times (roughly 50mph or so) around sunset before decreasing by late evening though there will still be 25 to 35mph wind gusts through the night as temperatures fall into the lower 50s. Some far northwestern spots may even get into the upper 40s by dawn on Tuesday. Main Impacts (shortened): Wind: Easterly winds may gust out of the as high as 55 to 65mph during the mid and late morning hours leading to moderate to major coastal flooding in the Potomac and west shore of the Chesapeake Bay before an around midday lull in the wind. Westerly winds may gust over 80 mph during the early to mid afternoon hours before windspeeds slowly decrease from the late afternoon hours onwards. Rainfall: Rainfall totals of 1.5 to 3 inches will be commonplace in the metro regions with local amounts of 4+ inches leading to widely scattered instances of flash flooding. However, in the far western areas of the I-81 corridor could receive 4 to 8 inches with localized amounts of 10+ inches leading to major flash flooding in that region. - George BM