The long awaited, long advertised storm series is knocking on the door of CA, with Doppler Radar indicating heavy rains spreading onshore early Wed morning along the coast. Because of the negatively tilted trough configuration the cell motion of individual rainshowers and radar echoes is to the NNE. Rainfall will increase over CENCAL as the day progresses as the backside of the storm moves onshore later tonight offering a period of heavy rains or possible Thunderstorms overnight. Satellite Imagery shows 2 separate bands of precip, with the first moving onshore currently. The second band appears more clustered, meaning possible convective type showers and Thunderstorms. While this system is focused upon NOR/CENCAL, SOCAL is left with very little in comparison. That is not the case with the next storm which will arrive on Friday which appears more focused upon SOCAL, with CENCAL on the northern fringe zone. We need to pay close attention to the Friday storm system as the RUC model is placing some hefty Convective Parameters over Pt Conception southward to San Diego, that could produce some intense Thunderstorms, possibly SEVERE. Charts also show Convective Parameters over CENCAL, but not as strong. If the trajectory of the Friday storm system adjusts slightly further north, then Convective Parameters over CENCAL could increase dramatically, therefore due diligence is urged to monitor the evolution of the Friday storm system very closely, as we will be updating the Convective Parameters closely on Thursday for the Friday event.
Drought Water Evaporation during this dry Season; While this storm is expected to produce as much as 3-4 inches of liquid water equivalent into the Sierra during the next 96hrs and we very much appreciate that, we should also be mindful that this important storm period will not erase the Drought situation that CA has dug itself into. It will however hopefully replace what has evaporated from the lower watersheds and the SJV lowlands during approximately the past 30 Days. During the Record Setting Mon/Tue mini February Heat Wave with 80°+ temps the evaporation rates in the region ranged soared… ranging up to 0.12 inch up to 0.18 inch of water loss per day, which is similar to the spike to those levels that occurred during the same time in January. In Tulare and Kern Co the water loss thru evaporation since January 1st has reached -5.70 inches of water thru the daily loss of water thru evaporation, with an accumulation thru rainfall of about +1.2 inches, leaving a net loss of -4.5 inches of water for the area below 3,000 feet. So therefore the SJV region needs at least 4.5 inches of rainfall just to break even for this highly unusual Season…which has truly placed 2014 into a water loss season, rather than a water gain season…thus far, (And that’s not counting the water loss that occurred during December, either!) That should put the serious water situation into proper perspective. So, this storm is very much welcomed, but it is not sufficient enough to supply what is needed for our aquifers, groundwater recharge or reservoir storage…not by a long shot.
The Record-Setting warm spring-like conditions with temps reaching into the mid 80°’s on Monday/Tuesday was the end of the mini February Heat Wave produced by the influence of strong High Pressure. The long advertised, and long awaited pattern change has finally occurred which will provide the State with a much needed soaking storm period beginning today and continuing thru Sat, with another possible storm arrival next Tuesday (for at least portions of NORCAL). Although details and timings issues still show some fluctuation, the general trend from the past several model runs is indicating a very wet storm will reach into CA late today with a secondary stronger storm system on Friday. The combined storms are forecast to produce 3-4 inches of precip for the Sierra and up to 1.5 to 2 inches for the northern portions of the SJV diminishing to about 0.25 to 0.5 inch into the Kern portion of the SJV. The first disturbance is producing heavy rains into the Bay region this morning and arrives later today with rains in the lowlands and snow for the Sierra which could become heavy overnight. A brief lull in activity occurs on Thursday, with a stronger storm arriving Friday which is taking a slightly more southern trajectory, produces a plethora of active wx phenomena during Friday and Friday night, which wind down early Saturday. This storm series has the potential to produce CENCAL’s first widespread heavy rain event of the season, with prolific snow production for the Sierra of 3 feet or more. Initially high snowlevels lower late Friday as cold air aloft advects into the region, which could also produce Thunderstorms in the SJV after frontal passage. Timing of frontal passage will be of critical importance forThunderstorm development on Friday. Depending upon how fast the system departs on Saturday, convection could also fire up on Saturday, but may not be as strong as those that erupt on Friday. Hail is the primary concern for the Ag Districts. The next 96 hours has the potential to be the biggest storm of the Season for such a widespread area of CA, and especially for the Southern Sierra with up to 1-3+ feet or more of snowfall at the higher elevations above 7,000ft with gusty winds to 60mph along the Crest. The forecast for Thunderstorms on Fri are becoming increasingly probable. Strong southerly winds will accompany the storm on Friday with the South Valley winds reaching as high as 40mph with gusts up to 70mph near the base of the Grapevine with strong adiabatic warming from the downsloping winds. Overnight temps in the extreme South Valley region could remain quite warm from these expected winds.
Longer range outlooks by the GFS are somewhat uncertain, and show another possible storm system arriving into NORCAL on MonPM, Mar 3rd which could bring rains as far south on Wed as the I-80 corridor according to the GFS, and further south according to the EC model on WedPM. The GFS Fantasyland Forecast shows a low confidence, cold core upper level ‘devil’ arriving on Day 15/16, valid on Wed/Thu, Mar 12th and 13th.
PRECIP past 24hrs over NORCAL; none thru midnight Tuesday, Feb 25th.
Wed, Feb 26th As High Pressure continues to shift into the Great Basin, a negatively tilted trough approaches the West Coast, with a warm/moist flow pattern spreading into CA with an approaching alignment running from N-NW to S-SE, so it spreads over the Coast Range of NOR/CENCAL about the same time with heavy rains along the Coastal region from Crescent City to Vandenberg, with moderate rainfall rates spreading inland into the SJV and eventually the Sierra…but it’s a slow process due to the trough configuration favoring a southerly flow instead of a SW flow pattern which would bring precip into the interior much quicker, so portions of the region may not see precip until late afternoon. The heavy rainfall tonight is aided by a shortwave 500mb vortmax which pivots NE offshore, but is close enough to produce dynamic forcing with resultant heavy rains and possible overnight Thunderstorms. A secondary disturbance which is dynamically stronger organizes further west, and is nearing 140W, and is attached to a reasonably strong but narrow cold front with charts depicts the narrow but dynamically strong frontal boundary. With the approaching systems originating from the subtropics, the snow levels into the Sierra will be initially high, at or above 7-8K, then lowering.
SPC Day 1 Categorical Thunderstorm Outlook for CA, with the strongest parameters arriving LATE, overnight. The combination of increasing large scale ascent, and cooling temps aloft with the onshore flow will aid in the development of scattered Thunderstorms across the region later today, with the main dynamics arriving into the interior Great Valley overnight when diurnal heating is not present, thus instability should be weak, thus limiting the risk of SEVERE Storms. Heavy precip is likely.
Thu, Feb 27th Temporary High Pressure moves onshore over CA, in-between the departing storm and the approaching second storm. Another negatively tilted trough and cold front move onshore overnight, with heavy rains depicted by charts supplied by 1.25 inch PWAT’s initially moving into the region from SFO southward to the Santa Barbara region. The SW flow aloft at 500mb veers more southerly at 700mb which provides sufficient orographics for the Sierra, (but not the most ideal directional component). Overnight the heavy rains continue as a cold core storm center drops southward along the coast. Charts indicate the cold front with this system is impressive. While our immediate focus is upon the closest storm, also mentionable is a powerful 3rd Mid-PAC storm system which is attached to a long-fetched Atmospheric River (AR) that is supplied by a Tropical Disturbance in the Equatorial Region of the WPAC which we have been mentioning for quite some time.
Fri, Feb 28th Charts for Friday show a strong dynamically driven storm system producing heavy rains over most of CA, especially CEN/SOCAL, with the GFS suggesting the circulation opening up into a trough with a -24°C cold core moving onshore into NORCAL accompanied with a strong cold frontal passage with high prefrontal warm sector PWAT’s Vort dynamics associated with the system are in the upper medium spectrum range with much of the energy focused upon the Pt Conception region southward and then as evening approaches the energy swings into SOCAL. With FROPA an important element in the forecast, the post frontal environment appears favorable for Thunderstorms to develop over the Great Valley. Convective Charts show the bulk of activity to be focused upon the SOCAL coastal region from Santa Barbara to San Diego, with chances of strong rotating Supercells very high, which could produce SEVERE THUNDERSTORMS with large hail, waterspouts and/or tornadoes. Convective Parameters at the moment for the SJV indicate a moderate threat for Thunderstorms, with less chance of becoming SEVERE. Hail is the primary threat, with a primary target in the north Valley region of Merced Co, although chances exist throughout most of the SJV. QPF charts shows this storm could be the best of the season thus far for snow production in the Sierra with up to 2-3+ feet possible into the higher terrain and a SNOW DUMP for the Sierra Ski Resorts. The SW flow following FROPA will keep a moist onshore SW flow pattern advecting diminishing showers into CA overnight with snowlevels dropping significantly as orographics keep the Sierra wet overnight.
SPC Day 3 Categorical Thunderstorm Outlook for CA, indicating a categorical risk of Thunderstorms on Friday. A closer look on Thursday will determine the potential (if any) for SEVERE cells. Hail already appears to be a primary concern due to the close proximity to cold air advection during the diurnal max heating period.
Sat, Mar 1st With the bulk of the wet storm system to the east and south, the trough axis is slow to leave, thus clouds and possible shower continue, especially for the Sierra. With High Pressure building offshore the flow pattern changes to NW with upsloping cloudiness piling up along the South Valley and north flank of the Tehachapi Mts. Depending upon skies coverage, conditions could favorable for a chance of afternoon Thunderstorms especially near the Sierra only if there is enough clearing to allow for diurnal heating to destabilize the atmosphere. Overnight clouds and rains diminish and skies become partly cloudy. Further west, near 45N 160W another disturbance with a significant subtropical Atmospheric River (AR) approaches NORCAL which trails SW to Hawaii and then further west, connecting to a Tropical Cyclone which continues to develop.
Special Notation; We have been tracking the WPAC Tropical Disturbance for a while and it still exists on today’s forecast charts without much overall change. Global scale charts show the Tropical Cyclone developing in the WPAC late Thu, Feb 27th, near 10N 150E with sluggish directional motion. While the Tropical Cyclone spins around it manages to cast off a vast moisture field to the north which becomes fully entrained into the westerly flow pattern and into a developing MidPAC storm system as it crosses the Dateline on Feb 27th. By the 28th the PAC basin has 3 separate storm systems imbedded within the westerly flow pattern, including the developing Mid PAC storm which has crossed the Dateline and is fully attached to the Atmospheric River (AR) that is being generated by the Tropical Cyclone. On Mar 1st as the Tropical Cyclone appears to strengthen, while the AR attachment with the PAC storm system remains intact to the subtropical plume, although somewhat weaker and stretched out, which passes over Hawaii. On Sun, Mar 2nd the Tropical Cyclone continues to intensify, with the leading edge of this tropical moisture field aiming toward the West Coast and with it reach the Columbia River overnight. Meanwhile the Tropical Cyclone remains stationary and begins to reload the local SW PAC region with high PWAT’s, again. On Mon Mar 3rd the juicy Mid PAC Low Pressure storm is traveling eastward nearing 150W with the advancing Atmospheric River (AR) stretched from the PACNW and NORCAL to Hawaii. The Tropical Cyclone’s new moisture field is now flowing northward into another storm which is brewing north of Japan. High Pressure is depicted as keeping the AR nearly stationary over extreme NW CA producing heavy tropical rains on Tue, Mar 4th. Meanwhile the Tropical Cyclone’s new moisture plume stretches from the storm itself at 20N near 145E …across most of the PAC basin with a wide, impressive Atmospheric River which is now approaching 140W by Wed, Mar 5th. With High Pressure rebuilding along the West Coast this moisture is shunted NE into BC, Canada on Mar 7th. This is a very interesting long tale, which is somewhat bizarre for Feb/Mar, especially with the longevity of the Tropical Cyclone.
Sun, Mar 2nd High Pressure ridge moves over the West Coast, with fair skies. The western portion of the ridge contains a strong/moist SW flow pattern attached to an impressive AR bringing the next storm system to the mouth of the Columbia River. A very large Low Pressure storm resides in the GOA. Skies over CEN/SOCAL are fair and dry. Overnight clouds increase over the far NW region of CA.
Mon, Mar 3rd As High Pressure shifts east into the Great Basin, the long-fetched Atmospheric River (AR) that originated first from a Tropical Cyclone in the WPAC near 15N at 145E reaches into NORCAL, with increasing rains. This AR feature has been long advertised with varying timing issues but is still on the charts and has been described in more detail above within the Special Notation. Overnight the Low Pressure located near 45N 150W continues to act as a conveyor belt for the AR moisture to continue streaming across the PAC basin, which is still originating from the intense Tropical Cyclone.
Tue, Mar 4th Charts show 2 separate Atmospheric Rivers (AR) crossing the PAC basin and each one has been or is currently supplied by the Tropical Cyclone in the WAPC! Pretty unusual! A High Pressure ridge is centered inland over the West Coast with the moist onshore SW flow pattern continuing into the PACNW and NORCAL. Partly cloudy skies exist over CENCAL.
Days 8-16, Long Range into Fantasyland Outlook; Day 8 begins;
Wed, Mar 5th shows a strong zonal, westerly flow pattern continuing to race across the PAC basin with several imbedded disturbances traveling eastward toward the West Coast. The leading storm plows into the West Coast north of SFO with heavy rains supplied by the impressive AR which stretches clear back to the WPAC Tropical Cyclone. With weak High Pressure maintaining dominance over CEN/SOCAL skies are partly cloudy over CENCAL, while NORCAL gets drenched. Overnight a minor shortwave trough pushes thru NORCAL with increased rains spreading into the northern portions of CENCAL. .
Thu, Mar 6th shows High Pressure rebuilding offshore west of CA with the zonal-type westerly flow continuing across the PAC basin carrying an abundance of moisture from the decaying Tropical Disturbance in the WPAC which is lifting northward. However the remnant moisture field is now entrained into the westerlies. Overnight High Pressure strengthens over CA and diverts the storm track northward into BC, Canada and the WA coast.
Fri, Mar 7th shows High Pressure dominant over the West Coast with the storm track diverted further north into BC, Canada with fair skies over CA.
Sat, Mar 8th shows High Pressure continues over the West Coast with a long-fetched SW flow carrying a developing Atmospheric River (AR) from the WPAC NE across the whole PAC basin into the BC, Canada coast. CA remains fair, mild and dry.
Sun, Mar 9th shows High Pressure broadening its width across the WCONUS and offshore to the west, as the continuous feed of moisture flows into southern BC, Canada.
Mon, Mar 10th shows High Pressure dominant over the West Coast as a very large cyclonic pattern continues into the NPAC basin with loads of moisture reaching into the BC, Canada region.
Tue, Mar 11th shows High Pressure shifting inland into the Great Basin, with the approaching westerly flow pattern moving closer toward the West Coast. With fair, sunny skies continuing over CA. Overnight a strong shortwave trough digs southward from the GOA toward the West Coast with a Low Pressure center forming west of the CA/OR border. SW flow over CA increases with clouds spreading into NORCAL.
Wed, Mar 12th shows a deep Low Pressure storm center forming west of NORCAL with a strong SW flow pattern reaching into CA. Although presently the 700mb charts show a limited amt of moisture associated with this system, if it does verify, it could produce a convective type storm pattern into CA. This should be monitored closely.
Thu, Mar 13th shows the Low Pressure upper level ‘devil’ crossing over CA, with the threat of Thunderstorms for CENCAL, and Sierra snows. This is rapidly following by High Pressure overnight.
Both Mon and Tue produced Record-Setting Heat in CA with Tuesday producing an unprecedented number of 98 Stations in the CENCAL SJV region that reached or exceeded 80° on Tuesday, and of those 10 reached or exceeded 85°. These record warm temps occurred during the mid and late afternoon, just as cloud coverage began moving inland over the region which immediately dropped temps. Tuesday was the last day of the mini February Heat Wave as the long advertised pattern change will bring a dramatic change to the region on Wednesday.
Station New Record Old Record__
Fresno 80° 78° set in 1991
Merced 77° 72° set in 2006
Madera 78° 72° set in 2006
Hanford 79° 72° set in 2006
Gilroy 80° 75° set in 1985
Modesto 77° (Ties) 77° set in 1986
South Lake Tahoe 58° 57° set in 1995
Sandberg 71° 69° set in 1963, marks the 7th Day of February at or above 70° extending the record range for the month.
Day 1 – 5 QPF:
At 12Z (9am) Tuesday thru the period Saturday night (Sunday @4am) shows;
Tue shows most of CA remaining DRY, with a few light showers of >0.1 inch along the immediate coastline from SLO northward to the mouth of the Russian River and the tip of Cape Mendocino.
Wed shows the beginning of a wet period for CA with precip spreading over most of CA on the first day of the storm series. With up to 2 inches into the higher terrain of NORCAL into the highest terrain of the Eel River basin and the Santa Cruz mts. Between 1-2 inches of precip covers most of the NW Coastal region southward to SLO and also into the wet spots of Santa Barbara Co, the Shasta River basin, the Sierra from Lassen SE into the San Joaquin River basin. With 0.5 to 1 inch covering most of NOR/CENCAL, including the SJV from the Delta southward into Kings and portions of Tulare Co, with 0.2 inch into Kern Co. The LA basin receives up to 1 inch into the San Gabriel’s and the upper Mojave desert receives >0.1 inch.
Thu shows up to 1 inch for the wet spots of the Shasta, Lassen, Feather, Santa Cruz Mts, Santa Barbara and Ventura Co, the San Gabriel’s, and higher terrain of Orange and San Diego Co, with 0.5 inch from the Trinities thru the Shasta basin southward thru the northern Sierra to near Hwy 50, and along the coast from the Russian River southward to San Diego, with 0.2 inch over most of NORCAL and in the SAC Valley, the Delta and northern SJV to Chowchilla and in the Sierra from Hwy 50 southward thru the Tehachapi Mts, with >0.1 inch of precip for the southern portion of the SJV from Madera southward into Kings and Tulare Co and the northern portion of Kern Co. Southern Kern Co receives up to 0.2 inch. Most of the Mojave Desert region receives about 0.1 inch.
Fri shows a slight shift for the heaviest precip to occur into SOCAL. With up to 6 inches into the wet spots of the San Gabriel’s north of the LA Basin, which is surrounded with a larger area that receives up to 4.00-5.50 inches of precip into the San Gabriel’s with 3-4 inches into the higher terrain of Santa Barbara and Ventura Co and the remainder of the San Gabriel’s. With up to 2-3 inches occurring into the San Joaquin and Kings River basins, the Santa Lucia’s and most of the higher terrain of SOCAL. With 1-2 inches into the Sierra from Lassen southward thru the Tehachapi’s into most of the coastal region of SOCAL, and along the coast from Santa Cruz southward into Malibu. With 0.5 to 1 inch into most of the SAC Valley, (except around SAC which has 1-2 inches), most of the NORCAL coastal area and most of the SJV. With 0.2 inch into the NE quadrant and the lower Colorado River Valley.
Sat shows light shower activity over all of CA, with only Death Valley remaining DRY. Up to 1 inch falls into the SOCAL Mts, which is surrounded by 0.5 inch amts throughout the LA basin, and also into the northern Sierra, with 0.2 inch for Del Norte Co, the Shasta River basin and from Lassen southward to the Tuolumne River basin, and along the SLO Co coastal region south to San Diego, with the remainder of CA receiving up to 0.1 inch, including all of the SJV and Southern Sierra.
5DAY ACCUMULATION CHART: shows as much as 8-10 inches of precip falls into the San Gabriel Mts!
7 Day QPF Chart; showing up to 6.6 inches for the higher San Gabriel Mts, 5.2 inches for the Feather River basin and up to 5.1 inches for the Big Sur coastline. The “rainshadow” is still evident into the SJV with as much as 2 inches into the northern districts diminishing to 0.5 inch for the southern districts. The Southern Sierra are painted with -4 inches.
Close up of 5 Day QPF for CENCAL region depicting up to 4-5 inches for the Santa Barbara Coastline, with up to 3-4 inches along the higher terrain of the Central Coast and for the Sierra from YNP into the San Joaquin and Kings River basin and the highest terrain of the Kaweah, Tule and upper Kern River basins. With generally about 2-3 inches into the lower elevations of the Sierra down to near Isabella in the Kern River basin. A “Rainshadow” is consistently depicted along the southern SJV from near western Fresno Co southward into Kern Co with only 0.25 to 0.5 inch for the area surrounding Bakersfield.
16-Day QPF estimates (from the 0Z GFS model) for;
Days 1-7; shows showing up to 6.6 inches for the higher San Gabriel Mts, 5.2 inches for the Feather River basin and up to 5.1 inches for the Big Sur coastline. The “rainshadow” is still evident into the southern SJV with as much as 2 inches into the northern districts diminishing to 0.5 inch for the southern districts of Kern Co. The Southern Sierra are painted with 3-4 inches.
Days 8-16; shows 1+ inch for most of NORCAL, diminishing rapidly south with only 0.25- 0.50 inch for CENCAL and dry conditions for SOCAL.
GFS 384hr, 16Day QPF Chart, depicting a wet State of CA with up to 5-6 inches in the NW Coastal region and up to 3 inches for the Sierra and Coast Range down to Orange Co, with amts in the SJV ranging from 1.5 inches in the north, to 2.5 in the wet spots crossing the central portion of the region and then dropping to near 0.5 to 1 inch in the southern portion. Note the cross-over bridge depicted across the SJV, connecting the Big Sur region with the Sierra with a band of heavier rainfall suggest over a portion of the SJV.
Water Vapor 4KM Image of the West Coast Tuesday, February 25th, 2014, shows 2 views; 1) at noon with high level moisture approaching the CA coastline, and 2) at 4pm with high level moisture and cloudiness moving inland over CA aligned from NW to SE, with the backside of the approaching storm on the far left portion of the image.
Visible Satellite Image of the CA Tuesday, February 25th, 2014, shows 2 views; 1) at noon with clear skies over NOR/CENCAL and 2) at 4pm showing increasing clouds aligned SE to NW forming over the Great Valley…after the clearer skies earlier provided the opportunity for Record-Setting Heat to occur.
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Atmospherics Group International
Dan Gudgel Steve Johnson