 Image Courtesy: Pivotal Weather DISCUSSION - California is still recovering from the consistent wallop of wet winter weather that has lingered with the state since winter commenced. Some positive outlook on the situation is the D4 Exceptional Drought index has completely diminished from 2016 to 2017. Southern California still seeing the majority of drought related issues, while Central/Northern California currently contending with the Oroville Dam overflow of the spillway.
Forecasters are beginning to sound like a broken record as later this week brings precipitation back into the area. The threat for precipitation comes into the forecast area Thursday as a front will move into the Northern Bay Area on Wednesday evening. With the onslaught of this frontal passage and more rain expected to move into the area Friday, this will be a prime opportunity for Southern California to gain some headway in the drought monitor. A deep area of low pressure centered just south of Alaska will help to bring the frontal boundary into the area along with stronger winds as isobars tighten along coastal California. The front will tend to progress from Northern California and propagate East Southeast into Southern California. Central California/Bay Area can expect to see anywhere between .25-1" with as much as 1.5-2" in the hills. Today will remain dry and mild with clouds increasing in the area ahead of the front. For more updates on California's drought situation or forecast discussions visit the Global Weather and Climate Center! ~Meteorologist Jessica Olsen
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 Image Courtesy: rammb.cira.colostate.edu DISCUSSION: On opposite ends of the US our Western friends are set to experience another pounding of wet weather due to the onslaught of a strong atmospheric river making its way to the California coast. Light to moderate rain is currently falling in the Northern California region extending to the San Francisco Bay Area, as the atmospheric river from the Eastern Pacific brings moisture and a strong cold front to the region today with showers into the overnight. The immediate Bay Area is expecting flooding conditions, mud/landslides and heavy rainfall to make its way in the area, bringing similar conditions the past two months of rain that have brought to the area. In addition to the heavy rainfall expected winds are expected to increase with gusts up to 40 knots offshore. Temperatures are mid and currently in the mid to upper 60’s throughout central and northern California. Despite increased moisture in the area, southern California is still seeing the brunt of drought conditions, to which this plume of moisture will provide no relief. Thursday, February 9th, some locations can see upwards of 4 inches of rain, already adding to some dangerous conditions from previous storms. A Flash Flood Watch is in effect for: North Bay, Northern Monterey Bay, San Francisco Peninsula, Santa Cruz Mountains, Santa Lucia Mountains, and Los Padres National Forest A Wind Advisory is in effect for North Bay and East Bay Hill/Mountains. A Coastal Flood Warning for Sonoma County Coast to Monterey County Coast. For more continued coverage on drought information and forecasts be sure to check the Global Weather and Climate Center daily! ~Meteorologist Jessica Olsen Storm System Takes Aim at Western North America! (credit: NOAA Satellite and Information Service)2/3/2017 
DISCUSSION: As reflected by the discussion (attached below) which is courtesy of scientists working at the National Oceanic and Atmospheric Administration's Satellite and Information Service (NESDIS), there is a fairly potent low pressure system getting ready to officially landfall near the Washington/Oregon state border during day on Saturday (02/04). Having said that, this low pressure system is already delivering substantial impacts to many parts of the Pacific Northwest as of much earlier in the day on Friday. The majority of the impacts being felt across the states of Washington, Oregon, Idaho, and Montana include heavy mountain snow as well as rain and/or ice (depending on the given location). Many counties within the aforementioned states have already been under winter weather advisories and/or winter storm warnings for quite some time and will remain under winter weather advisories for at least the next 24 to 36 hours as this winter storm continues to impact these areas.
"This GOES West water vapor imagery shows an area of low pressure spinning toward the West Coast today, February 3, 2017.According to the National Weather Service, this upper-level low over the Eastern Pacific will slowly weaken and move onshore over the Pacific Northwest throughout the day, bringing a plume of moisture into Central and Northern California, and across much of the Northwest into the weekend. Coastal areas will have rain, possibly heavy at times, while areas of higher terrain will see a wintry mix of snow, rain, and ice. Snow will spread eastward into the Northern Rockies by this evening and into the adjacent Northern Plains by Saturday. Water vapor imagery, which is useful for both determining locations of moisture and atmospheric circulations, is created using wavelengths of light sensitive to the content of water vapor in the atmosphere. Bright and colored areas indicate high water vapor (moisture) content (colored and white areas indicate the presence of both high moisture content and/or ice crystals). Black and brown areas indicate little or no moisture present." To learn more about other high-impact weather events occurring across the Central and Eastern Pacific Ocean, be sure to click here! ©2017 Meteorologist Jordan Rabinowitz  DISCUSSION: Scattered showers are in the area, and have started to become a nuisance to many California residents as a low-pressure system makes its way along the coast. There will be some more scattered and isolated showers in the forecast again for the next day or so as a weak front moves through Wednesday night into Thursday morning. It is possible to see a significant change as a high-pressure system is set to build into the area bringing dry and mild weather to the Bay area. In the past hour scattered showers have allowed for the formation of hail, which hasn’t been reported in some time, since nearly the first large plume of atmospheric moisture back in December. Checkout the great footage of hailstones approximately 1/8th inch located in Carmel, California! ~Meteorologist Jessica Olsen 
DISCUSSION: Although most do not even consider to think about this type of meteorological phenomena, often times during the Winter season, hurricane-force low pressure systems can develop over large expanses of the central/eastern Pacific Ocean as well as a very large percentage of the central/northern Atlantic Ocean. During the more conventionally recognized hurricane season periods for the various Pacific and Atlantic Ocean basins, tropical cyclones which form are fueled by the presence of particularly warm sea surface temperatures which fuel the inner core (a.k.a., the internal "heat engine") of strengthening tropical cyclones. However, during the Winter-time when we observe low pressure systems with measured maximum sustained wind speeds at or sometimes well-above hurricane intensity, this unfolds as a consequence of profoundly unique circumstances.
As many people around the world have come to fundamentally understand, extra-tropical cyclones which impact large coastal (and often semi-inland) regions around the world are triggered by horizontal changes in temperature with distance over some given region. Thus, it is what is referred to as a "frontogenetic forcing" measuring or an atmospheric low pressure intensification mechanism which is driven by changes in temperature at or near the surface. This surface-based temperature gradient subsequently affects the temperature and therefore the wind field distribution in the vicinity of developing extra-tropical low pressure system at the surface as well as points higher up in the atmosphere. Thus, this deep-layer horizontal change in temperature over some horizontal difference provides the critical energy/fuel needed to sustain Winter-time low pressure system. Colloquially, when these types of Winter-time low pressure systems impact populated areas, we conventionally refer to these types of storms as "Nor'easters" since they are identified as coastal low pressure systems which typically move in a northeasterly direction with time and deliver cold northeasterly winds to the area they impact as they move through. As shown in the brief satellite footage attached above, this same process can happen over larger oceanic basins as well such as this hurricane-force low which just recently strengthened significantly over the northeastern Pacific Ocean. This just goes to show that intense Winter-time low pressure systems can form and intensify while under the influence of many different types of atmospheric environmental conditions. To learn more about other high-impact weather events occurring across the central and/or eastern Pacific Ocean, be sure to click here! ©2017 Meteorologist Jordan Rabinowitz Round 2 of Impacts for California Due Pineapple Express (Credit: Meteorologist Jessica Olsen)1/10/2017  Image Courtesy: WeatherTAP DISCUSSION: After the first battering from the Western Pacific's moisture plume, California and the Western United States are battening down the hatches as the second round of precipitation, storms and wind makes its way into the area. As the Pineapple Express brings more storms to the area, Tuesday afternoon and evening is likely to be filled with gusty winds and precipitation. Models and current radar are indicating that the heaviest of precipitation will fall in Northern California and Coastal Ranges expecting rain with a great potential of more flooding in the North Bay and into the Monterey Bay region. In addition to the presence of the Atmospheric River, the synoptic pattern favors an upper level low and surface low to the Northwest while a cold front associated with this pattern moves into the immediate area tonight. Precipitation will range from .5-2 inches for most but locally heavier in the ranges. Some parts of the Sierras are expected to see 7-10 feet with gusts topping nearly 100 miles per hour. In the past several days many roads have closed due to flooding, such as Highway 1 in Big Sur due to landslides, or various roads in the Carmel Valley region as water has breached levees causing headaches for many. For current watches/warnings/advisories visit the National Weather Service! ~Meteorologist Jessica Olsen  Image Courtesy: WeatherTap DISCUSSION: The Western US is set to experience another brutal pounding of consistent precipitation, some are calling over-zealous, but most are welcome to the increase in wet weather given California’s 5 year drought. Precipitation is in the immediate forecast, in addition to the extended forecast past the 3 day mark. Current satellite indicating a large swath of moisture set to impact areas extending from southern Washington to as far west as Utah. A relatively deep upper level trough is to blame for the wet weather. The increase in water will likely pose hazard conditions for local rivers and creeks into Saturday and Sunday. Areas of the Sierra foothills, Central Coast including the Bay area as the Pineapple Express makes its way into the overnight hours. The term Pineapple Express is characterized as a intense atmospheric flow associated with increased precipitation typically seen near the Hawaiian Islands transporting moisture to mainland United States. Rainfall totals are expected to real 8-12 inches by Monday for Sonoma, Santa Cruz and Santa Lucia Ranges. Moderate precipitation is expected to begin tonight into Sunday, with some showers lingering into Monday. The Pacific coast will not go without some chance for precipitation as this moisture trend remains into the workweek. ~Meteorologist Jessica Olsen Great View of Snow-Capped Mountains in Hawaii! (credit: NASA via NWS Aviation Weather Center)1/3/2017  DISCUSSION: Here is an awesome view of snow-covered mountains on certain mountain tops within part of Hawaii. Attached below are more details courtesy of the National Aeronautic Space Administration (NASA) before being re-shared by the NWS Aviation Weather Center office.
"Snow-capped Hawaiian Mountains... The Operational Land Imager (OLI) on the Landsat 8 satellite captured these natural-color images of the snowy peaks on Christmas Day. A storm on December 18 brought not only snow, but bouts of thunder and lightning. While snow in Hawaii is not unusual (it can even fall in summer), thundersnow is less common. (Credit: NASA)" To learn more about other neat weather phenomena from across the Central and Eastern Pacific Ocean, be sure to click here! ©2017 Meteorologist Jordan Rabinowitz Expert Insight into Upcoming Atmospheric River Event! (credit: Meteorologist Sheldon Kusselson)1/3/2017  
DISCUSSION: Attached above is a great insight and expert analysis of the upcoming atmospheric river-based event expected to deliver significant impacts to a large portion of the western United States. This analysis is courtesy of retird NOAA NESDIS Satellite Analyst Sheldon Kusselson.
To learn more about other high-impact weather events from across the Central and Eastern Pacific Ocean, be sure to click here! ©2017 Meteorologist Sheldon Kusselson Atmospheric River To Impact Weather Across the Western United States! (credit: NWS Reno, Nevada)1/2/2017  DISCUSSION: As a strong atmospheric river continues on its current track towards parts of the western United States, there are a few possible scenarios which are projected to unfold (one way or the other) over the course of the next several days. These respective scenarios involve the presence of slightly warmer (or colder) air moving across much of the intermountain west. As a result of this warmer (or potentially colder) air spilling across a large portion of the western United States, there will either be a lot of rain or snow at some of the lower elevations; while there will most definitely be lots of heavy snowfall at the higher elevations (especially at those elevations above 8,500 feet). Hence, if you live across the respective parts of the western United States, be sure to keep tabs on our updates at your local National Weather Service office as well as updates from all of us here at the Global Weather and Climate Center. Be sure to check out the graphic attached above (courtesy of the National Weather Service office in Reno, Nevada) for additional information!
To learn more about other high-impact weather events from across the Central and Eastern Pacific Ocean, be sure to click here! ©2017 Meteorologist Jordan Rabinowitz California Cold Snap Recap With Early Holiday Brief (Credit: Meteorologist Jessica Olsen)12/21/2016  Image Courtesy: Twister Data DISCUSSION: With everyone feeling the chill throughout the country it has been exceedingly difficult to find places that are experiencing seasonal temperatures. Recently California has experienced rainfall, snow in higher elevations, frost, and much cooler than average temperatures, which is no surprise as the rest of the country experiences colder temperatures, and an early start to winter. Californians experienced a cold snap for overnight temperatures beginning Friday, December 16, seeing lows in the mid to upper 20's in and around the San Francisco Bay Area. These cooler than average temperatures lingered into the week making headaches for those traveling for the holidays. Temperatures are expected to rebound today as the previous high pressure system located off the coast of California had pumped cold air moved into the mainland. Some places can expect to see highs in the mid to upper 60's. While locations such as Tahoe can expect snow for the holidays, Californians are crossing their fingers as rainfall is forecasted into Christmas Eve. With the presence of an upper level low churning to the southwest of Southern California, we should expect this precipitation to pull through downstream of the closed low as seen on the 500 mb map. Tonight for the Bay Area, lows will be much warmer and seasonal in the 30's and 40's. Current maps are showing the slight intrusion of a cold front located to the North, still not seen well on models but this will be the next area of concern for the Christmas Eve forecast. Coupled with the low outside of southwest California, moderate precipitation is expected with increased winds with snow possible in North Bay and Santa Lucia mountains. Between Thursday and Saturday totals between .5-1 inch with 2-4 in the mountains. ~Meteorologist Jessica Olsen  Image Courtesy: Pivotal Weather DISCUSSION: Rain will remain in the forecast for the next 24 hours as increased humidity lingers in the area coupled with a warm front, bringing warmer morning temperatures in the overnight. Previous day temperatures had readings in the mid-upper 30's with this morning temperatures starting off in the upper 40's to low 50's. Despite wind in the area, overall a mild morning with much of Central/Southern California seeing overcast skies. Coastal California may not have a white Christmas this year, though in higher elevations across the state, snow is not out of the question. However, this late fall, early meteorological winter, Californians are elated to see the consistency in unsettled weather, bringing much needed precipitation to the 5 year drought-ridden state. Forecast models indicated 1-3" of rainfall while most of the area will see 1/4-1", which will be more than welcome in many areas. Increased rainfall within the past 24-48 hours posed some difficulty for local Big Sur area of Highway 1, seeing road closures due to debris. This will likely persist as onshore flow is expected to bring increased moisture tonight and into tomorrow. ~Meteorologist Jessica Olsen  Image Courtesy: Canada-French-Hawaii Telescope DISCUSSION: Into the first day of meteorological winter there has been a Winter Storm Warning issued for Hawai'i. Not a place you'd certainly expect, however Hawai'i island is home to Mauna Kea and Mauna Loa, summits standing at 13,803 feet and 13,678 feet respectively. The National Weather Service has issued a Winter Storm Warning, valid until December 2nd, 1800 HST. While O'ahu is experiencing an influx of showers today, Hawai'i is set to experience some of this precipitation in the form of snow. This is all in part due to an upper level trough combined with increased moisture due to occur well into the Aloha Friday evening commute. The upper level low associated with this warning will bring 6-12 inches of snow through Friday, decreased visibility with gusts topping 50 mph. Road conditions are expected to be poor during this period, therefore the road to the summit of Mauna Kea was closed at the Visitor Information Station at an altitude of 9,200 feet. The warning is in place for locations above 8,000 feet, with expected precipitation at 12,000 feet on summits. Wladimir Koppen, a noteable Climatologist who devised a classification system having been used since the early 1900's. His system was based on a "subdivision of terrestrial climates into five major types," according to Britannica. Within each zone of these five climates are sub-categories, as many as 14 that can define global climate more accurately. Various climatologists define Hawaii's climates differently, but what can be said is that an average of 10 different climates are seen, some climatologists indicate as many as 13 out of 14. What makes today's forecast of particular interest is as Hawai'i summits experience winter weather, due to their Polar Tundra climate as classified by Koppen, the nearby island of Oahu experiences precipitation in the form of rain, with temperatures in the mid to upper 80's, while temperatures are expected to be 20's to 30's on the Big Island summits. O'ahu has a tropical wet and dry savanna climate as classified by the Koppen-Geiger classification system. Precipitation on both islands are all attributed to the moisture brought by the upper level instability. Video Courtesy: Canada-French-Hawaii Telescope ~Meteorologist Jessica Olsen  Image Courtesy : Climate.gov DISCUSSION: As we move well into the fall season, the winter season will undoubtedly soon be upon us. With winter arriving shortly we can also think about the weather that is expected to impact the Hawaiian Islands as one of the locations within the United States that can expect to receive mild weather. Winter typically brings the rainy season to the Islands, but it can also be one of the great locations to enjoy the large swells on the north shores of the island chain. Some of the best surf competitions are seen between November and February especially at the famed Banzai Pipeline, Waimea Bay, Peahi and Jaws.
The waves in these locations are primarily a product of prevailing winds, fetch and various geographic features beneath the oceans surface. Since the Pacific Ocean provides a large fetch for waves, height can then increase before reaching the island chain. Much of this height will also be affected by whether or not waves are breaking on underwater geologic features and if prevailing winds are favorable, generally North/Northwest for the big wave locations. With the transition into a La Niña, we should expect some changes compared to the previous seasons El Niño conditions. Winter is expected to bring the wet seasons but with a weak La Niña we may see subtle impacts hit the state. With a weak La Niña, Hawaii is expected to see average precipitation this winter, whereas the Southern US is slated to experience a drought. National Weather Service forecasters are not expecting this event to sustain past March. With unprecedented wave heights reached during winter 2015/2016, notable events such as The Eddie ran after a nearly 9 year hiatus, coming back to a feverish crowd with 30+ foot surf. The La Niña is not expected to contribute to increased heights but may be another notable season to surf Hawaii's North Shores. For local surf observations in the Hawaiian Islands visit NOAA! ~Meteorologist Jessica Olsen  Hurricane Seymour in the eastern Pacific has been upgraded to a category 4 on the Saffir-Simpson Wind Scale (which measures a hurricane’s maximum sustained winds) with maximum sustained winds of 150 mph. Hurricane Seymour has a minimum central pressure of 943 mb. The storm is currently located approximately 690 miles southwest off the tip of the Baja Peninsula in southern California. The storm is expected to make a turn to the west-northwest over the next few days and gradually weaken. This is a small tropical cyclone, with hurricane winds extending outward 25 miles from the center of the storm and tropical storm force winds extending out up to 90 miles. Hurricane Seymour is not expected to be a threat to land. Above is a great view of Hurricane Seymour from the GOES-West Satellite! To learn more about other high-impact weather events from across the Central and Eastern Pacific Ocean, be sure to click here!
Discussion: Hurricane Madeline is currently located 95 miles southeast of Hilo, Hawaii and the Big Island is already being impacted by tropical storm-force winds of 43 mph. Hurricane Madeline is currently a Category 1 hurricane on the Saffir-Simpson Hurricane Wind Scale, (which measures a hurricane’s maximum sustained winds) with maximum sustained winds of 75 mph, as it moves off to the west-southwest at 12 mph. Madeline is forecast to pass south of the Hawaiian Islands tonight and tomorrow and will be weakening as it does so. In the satellite image below you can see the eye of the hurricane becoming less defined. Tropical storm warnings are in effect for the Big Island of Hawaii and specifically in Maui County. Residents of the Big Island and Maui County should be prepared for strong winds, rough surf, and heavy rainfall that can lead to flash floods and mudslides. To learn more about other high-impact weather events from across the Central/Eastern Pacific Ocean be sure to click here!
An Impressive Performance By Hurricane Georgette! (credit: NOAA Satellite and Information Service)7/25/2016
DISCUSSION: Earlier this morning, as a strengthening Tropical Storm Georgette contined moving over warmer ocean water across the Central Pacific Ocean coupled with relatively weaker atmospheric vertical wind shear, there was a great opportunity for this tropical storm to blossom. Being over a region characterized by such favorable conditions, this tropical storm grew into an intense tropical cyclone which reached a maximum intensity of 135 MPH (i.e., a Category 4 Hurricane according to the Saffir-Simpson Hurricane Wind Scale). Despite the fact that a currently weakening Hurricane Georgette (which is still maintaining itself as a Category 2 Hurricane), this tropical cyclone is not any threat to land aside from some wave action along parts of Southern Cailfornia and the western side of the Baja Peninsula.
It is interesting to note the impressive storm-relative axisymmetry (i.e., the gorgeous structure associated with the spiraling of the coldest cloud tops as indicated by the infrared satellite image included below) despite its particularly small size. This is indicative of a very intense and tightly-wrapped core circulation which fortunately will not affect any land areas directly in any way. To learn more about other high-impact weather events from across the Central/Eastern Pacific Ocean, be sure to click here! 
Meteorologist H. Michael Mogil goes on a Hawaiian vacation and then the weather heads south. Torrential thunderstorm rainfall, linked to a feeder band from Tropical Storm Darby, struck the Honolulu area last evening…To read the full story, click here - http://www.weatherworks.com/lifelong-learning-blog/?p=938  Darby’s rainfall, wind and surf affecting the Hawaiian Islands (H. Michael Mogil, CCM, CBM, DMS)7/24/2016 #TropicalStorm #Darby continues to plod along to the west coast of the #HawaiianIslands, refusing to make that anticipated turn to the northwest. However, winds are not really the big story about Darcy. Rather, #rainfall and #surf continue to offer the greatest threats…To read the full story, click here - http://www.weatherworks.com/lifelong-learning-blog/?p=938 
DISCUSSION: Previously a hurricane near Baja California that has since weakened, Tropical Storm Darby is making its way to majorly disrupt paradise in the state of Hawaii this weekend and early next week. The center of this tropical storm is currently about 390 miles away from Hilo on the Big Island with maximum sustained winds near 60 mph. With the system moving westward at about 12 mph, Darby is expected to pass near the Big Island and Maui County Saturday and Saturday night, respectively, then move northwestward come Sunday. Consequently, the National Weather Service has issued a Tropical Storm Warning (meaning tropical storm conditions are to be expected within 36 hours) for the Big Island and a Tropical Storm Watch (tropical storm conditions are possible within 48 hours) for Maui County, as shown in the graphic below (courtesy of US National Weather Service Honolulu & Central Pacific Hurricane Center).
While Darby’s center may not pass by the Big Island until Saturday, habitants of the Island and surrounding waters will face potentially damaging surf along the coastlines today, heavy rain that may result in flash floods and mud and rock slides as early as Friday evening, and tropical storm force winds (winds greater than 39 mph) Saturday. The tropical storm is not forecasted to weaken as it approaches Hawaii and throughout the weekend, so residents should prepare as soon as possible! To learn more about other high-impact weather events from across the Central and Eastern Pacific Ocean, be sure to click here! 
Darby to bring wind and rain to parts of the Hawaiian Islands (H. Michael Mogil, CCM, CBM, DMS)7/21/2016 Tropical Storm Darby, now in his 11th day, is on a westward course at 14 miles per hour toward the Aloha State. At 11:00 a.m. H.S.T. (5:00 p.m. E.D.T.) Darby, with sustained winds of 65 miles per hour, was located some 755 miles southeast of Honolulu, Oahu (and about 560 miles east of Hilo, Big Island). Forecasts keep Darby as a strong tropical storm…To read the full story, click here - http://bit.ly/29Ppluf 
DISCUSSION: Across the Central and Eastern Pacific Ocean, there is currently a triple-play of tropical systems; namely, Tropical Storm Celia, Hurricane Darby, and a Tropical Disturbance located within the Eastern Pacific Ocean! Despite this currently being the heart of the Eastern Pacific Hurricane season, it is still fairly impressive to see three tropical systems at the same time. Note how Hurricane Darby is appearing to remain fairly organized at this time as it has sustained its intensity through the course of Thursday as a strong Category 1 Hurricane with maximum sustained winds of 90 MPH and a minimum central pressure of 982 mb. In addition, Tropical Storm Celia has weakened a lot; it is maintained its current status (from as of earlier today) as a Tropical Storm with maximum sustained winds of 50 MPH with a minimum central pressure of 1000 mb. As for the third tropical disturbance, it will continue to remain within a region which is particularly favorable for tropical development over the next few days. To learn more about other high-impact weather events from across the Central and Eastern Pacific Ocean, be sure to click here!
DISCUSSION: As Hurricane Blas quickly formed on July 3rd and then fairly quickly intensified throughout the course of yesterdya and into the early morning hours of today, it has now become a Major Hurricane with maximum sustained winds of 140 MPH! Though it is not directly threatening any land to the west or east currently, there will be increased wave action across Southern California, Western Mexico, and eastern portions of Hawaii! This storm will remain a major danger for boating and shipping lanes across the Central to Eastern Pacific Ocean. For further updates on this hurricane and to learn more about other high-impact weather from across the Central and Eastern Pacific Ocean, be sure to click here!
Atmospheric Rivers Across The Central and Eastern Pacific! (credit: NWS Los Angeles, California)2/22/2016 
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