“Cry me a(n) Atmospheric River” over Southwest California and the Baja

Meteorologists are still in amazement over the heavy rainfall event the beginning of the workweek.

From before sunrise Monday and for the next 24 hours, a very significant “atmospheric river” event brought heavy rain to the western 2/3rds of San Diego County, the Inland Empire, the Riverside County Mountains, and Coachella Valley. Heavy rain extended south of the border with flooding reported in Tijuana and as far south as Ensenada.

Rainfall in San Diego County approached 9 inches at Palomar Mountain, near 6 inches in the Mt. Laguna area, and ranged from 2 to 4 inches across much of the coast and inland valley areas. Riverside County saw totals to around 4 inches in the mountains, 2 to 3 inches Inland Empire. The Palm Springs area even saw rains around 1 inch, an uncommon event.

Down south into the Baja, rainfall amounts were likely in the 2 to 3 inch range.

See CNRFC graphic for US rainfall totals.


Rainfall totals from the Monday February 27 to Tuesday February 28 Rain event (From NOAA/NWS/CNRFC)

This is an example of an event researchers have termed an Atmospheric River. While the term is descriptive, it is overused by the media. Forecasters look for a persistent (more than 24 hours), wide, deep “ribbon” of high atmospheric moisture , especially at the lower levels of the atmosphere. This ribbon of moisture is pulled from the tropics by a approaching weather system and lifted, producing abundant widespread heavy precipitation.

This ribbon can be seen in computer weather forecasts. Shown below is the Global Ensemble Forecast System (GEFS) forecast for water vapor transport for later Monday morning into the afternoon, 2/27. The area in green outlined by red shows where large amounts of tropical moisture are being transported into southern California.


GEFS Model Output valid 1800 UTC (1000 PST) Monday, February 27

Unfortunately this event was not forecast by the computer models well in advance. While some similar events this winter in northern California were evident to forecasters 3 to 5 days (or more) in advance, this event only became evident about 12 hours before it occurred, and was more focused on far southern San Diego County and the Baja.

James Purpura CCM of WeatherExtreme Ltd. presentation at the AMS Meeting

January 26, 2017 – Meteorologist James K. Purpura, CCM, of WeatherExtreme Ltd., will be presenting at the American Meteorological Society(AMS) Conference held in Incline Village, Nevada. Along with Y. E. Kachiwanda and R. Jubach, they will be presenting “Malawi Weather Chasers: Using Social Media to Jumpstart Dissemination, Event Reporting, and Preparedness”. Jim was in South Africa at the end of 2015 with the SARFFG-SWFDP to promote weather safety in South Africa. A Flash Flood Warning System was expanded to a severe weather warning system in South Africa and 8 of its neighboring nations in the region. Their presentation will discuss that in conjunction with WhatsApp, a social media tool, they have been able to develop a weather spotter network, as well as communicate forecasts, warnings, observations and storm reports to remote villages, Disaster Risk Managers, media, and local, regional, and national government officials.

For additional presentation information, click here

For James K. Purpura’s full bio, click here

…Large summer heat wave expands across the Midwest…

Chicago graphic

Photo Credit:NOAA/NWS

A growing dome of warm air will be expanding from the Great Plains into the Midwest. Excessive Heat Watches (dark brown on the map) or Heat Warnings (purple) are in effect across a large area from Illinois, to Minnesota and North Dakota, then south to Kansas.
WWA Map 7-19-16

Photo Credit:NOAA/NWS

People in different areas of the country acclimatize to heat events in different ways. What is common to heat related deaths or heat related injuries (heat exhaustion or heat stroke) is a lack of adjustment to the heat, along with dehydration and inadequate cooling. In places where summer air conditioning is not commonly used, those in poor health and the elderly can be most at risk.

Within the City of Chicago, where 739 deaths occurred over 5 days in 1995, many of these deaths occurred in homes where seniors lived without air conditioning or other adequate cooling, and where concern over crime made them reluctant to open windows. See the warning information posted by the NWS Chicago on this upcoming event.

Chicago graphic

Photo Credit:NOAA/NWS

Long range models indicate the heat will retreat from the Midwest to the southwestern US as we begin next week, with the heat likely affecting Nevada and California.

Early Severe Weather Outbreak across the Gulf Coast and Mid- Atlantic

This week saw a major severe weather outbreak, including a number of killer tornadoes. Most tornado outbreaks in February are confined to the deep South, but even the Mid-Atlantic coast was affected.

Storm began to fire on Tuesday across the Texas Gulf Coast, then quickly became severe as they moved into Louisiana. An EF-3 tornado, a strong tornado (with winds estimated at at least 150 mph) near Convent, La killed two people in a mobile home park.

In Mississippi, a man was killed by an EF-2 (strong) tornado in the town of Purvis.

The storms moved into the southeast, then began to intensify a second day, this time over Virginia. In the town of Waverly, two men and a two year old child were killed when their mobile home was struck by an EF1 (weak) tornado. A fourth person was killed by an EF-3 (strong) tornado in Evergreen with winds as high as 165 mph.

Officials say the 4 tornado deaths in Virginia are the first ever in that state in February.

See the maps below of storm reports from the Storm Prediction Center for Tuesday, February 23rd and Wednesday, February 24.

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Photo Credits: NOAA

Jim Purpura
Certified Consulting Meteorologist
Director, Weather Forecasting
WeatherExtreme, Ltd.

The Record Blizzard of 2016

2016-blizzard-NASAThis past weekend’s snowstorm was one for the record books. Many will refer to it as The Blizzard of 2016″.

So what is a blizzard, anyway? The National Weather Service defines a blizzard as a severe snowstorm characterized by strong winds causing blowing snow that results in low visibilities. So the difference between a blizzard and a snowstorm is the strength of the wind, not the amount of snow.

To be a blizzard, a snow storm must have sustained winds or frequent gusts that are greater than or equal to 35 mph with blowing or drifting snow which reduces visibility to 1/4 mi or less. These conditions must persist for three hours or more.

Last weekend’s storm certainly met the wind and visibility criteria, but amazing amounts of snow were produced. Above normal water temperatures off the mid-Atlantic coast helped enhance moisture transport into the storm as the fuel for its “snow engine”.

This storm is also noteworthy for bringing snow totals at or nearing all-time records in multiple large metro areas. Other snowstorms have have higher totals, but none were as widespread. Highest totals include…

New York City – John F. Kennedy Airport 30.5 inches, all-time record
Central Park 26.8 inches 2nd highest of all time

Baltimore – 29.2 inches, all time record

Washington, DC – 17.8 inches 4th largest on record

The satellite image above (from NASA) shows the development of the storm over south Texas as it moved north and east over several days.

Jim Purpura, CCM
Meteorologist, WeatherExtreme Ltd.