Tuesday, September 29, 2015

A Soaking Setup for the Eastern U.S.

This has been a quiet tropical storm season so far, at least as far as systems affecting the U.S. mainland. That will likely change this week, but not quite in the way you might expect.

T.S. Joaquin became 10th named storm of the season late last night, developing from a depression that formed between the Bahamas and Bermuda on Sunday. Joaquin  sits about 405 miles northeast of the Bahamas as of Tuesday evening.

Currently, a healthy cold front is crossing through the middle of the country accompanied by a large rain shield.

Surface map and radar at 8:00 p.m. EDT September 29.
Associated with this cold front is a large trough of low pressure aloft that will likely stall along the Appalachians. A low pressure wave will move northeast along the cold front, producing rain, some of it heavy, from the mid-Atlantic through New England. That cold front should be moving off the east coast Wednesday night, but then will become stationary.  An upper level ridge extending more or less west to east from northern New England into the Atlantic will block the progression of the trough over the eastern U.S., and a closed low is forecast to form over the southeastern U.S. Thursday night.

Forecast 500 millibar map for Friday, October 2 at 8:00 a.m. EDT.
Meanwhile, T.S. Joaquin is currently forecast to reach hurricane strength and may make its closest approach to the east coast, possibly off North Carolina, Sunday morning. However, the forecast track of Joaquin is uncertain given the complexity of the upper level pattern over the eastern U.S. As of this post the models have not had a good handle on the situation and there is likely to be further adjustments to its track.

Forecast positions for Tropical Storm Joaquin issued at 5:00 p.m. EDT September 29

So, we have a stalled upper level trough over the eastern U.S., a stationary front off the east coast at the surface, and an approaching tropical storm. All of this adds up to a potential significant heavy rain event along and east of the Appalachians from North Carolina into the Canadian Maritimes.

While Joaquin is not expected to make landfall, the counterclockwise circulation around the storm will be feeding moisture from the Atlantic west across the stationary front. That, combined with the stalled trough aloft tapping moisture from the Gulf of Mexico, will likely result in prolonged and heavy rain along the eastern seaboard. Forecast models are currently indicate that in excess of six inches of rain could accumulate by early next week.

A series of low pressure waves moving along the front on Wednesday and into Friday will produce the heaviest rain in the northeast and New England. Then the focus shifts to the mid-Atlantic region as moisture associated with T.S. Joaquin interacts with the stalled frontal boundary. Joaquin is expected to be eventually absorbed by the main trough aloft and will be reflected as another low pressure wave along the front. That combination will bring rain to the Northeast and New England through this weekend before high pressure takes over on Tuesday.

Quantitative Precipitation Forecasts for the three-day period ending 8:00 p.m. EDT Friday, October 2 (left), and the two-day forecast for the period ending 8:00 p.m. EDT Sunday, October 4 (right).

Quantitative Precipitation Forecast for the 7-day period ending 8:00 p.m. EDT Tuesday, October 6.

 Flood watches are already in place from the central Appalachians through New England through Wednesday. There is still is uncertainty in the how this situation will play out, so be sure to stay abreast of the latest forecasts and advisories if you are in any of the areas to be affected by this system.

Monday, September 28, 2015

The Latest NWS Forecast at Your Fingertips

There are probably hundreds of weather apps and widgets available for your smart phone or tablet. Personally, I have two radar apps (PYKL3 and Radarscope), the Blitzortung Lightning Monitor, and a few "weather forecast" apps. The forecast apps provide a forecast for your local area and have different bells and whistles, depending on the app.

One of my "go to" programs on my smart phone is an experimental widget developed by the Southern Region of the National Weather Service. This widget can be embedded in an existing web page (for example, a web page you have created for your local weather), or can be used as a stand-alone app in a smart phone or tablet. This widget is adaptive, meaning it automatically adjusts the content to the width of the screen of device using it. What I really like about this widget is the organized and compact way it serves up the weather information users want to access on a smart phone. Most National Weather Service web pages do not have mobile versions, and navigating them on a smart phone is cumbersome. (One exception to this is the Storm Prediction Center web site). I'm not a big fan of the new NWS web page design which has, to date, only been deployed in the NWS Eastern and Central Regions. The widget addresses the mobile issue and makes accessing the forecast and other information straightforward and organized.

When you first open the widget, you will get a screen with the NOAA and NWS logos and a message the the widget is loading. It will then display the opening page for whatever location you have chosen.

The opening screen of the widget. The icon to the left of the location entry box opens a Google map where you can select a location. The icon on the right will reload the forecast information for the site you have selected.

On a smart phone, all the information available is collapsed into expandable menus on the screen. Most tablets will be able to display the expanded layout without the collapsible menu.

For example, if you select Detailed Forecast, a window with four tabs is displayed, and you can select the forecast for the time period.

The Radar menu opens to a radar loop of the local NWS radar. If you select the radar map, it takes you to the full web site radar page for that office. The Satellite menu opens to a the full U.S. infrared satellite map. Tap that map and you are taken to the very nice mobile version of the Geostationary Satellite Server from which you can view a number of other satellite images.

The More menu contains links to the full web site for that NWS office and the tabular and graphical forecasts. While these are not mobile versions, you can zoom in as you would on any web page.

To add this to your smart phone or tablet, point your web browser to innovation.srh.noaa.gov/NWSwidget/.  Enter the location you want to have a forecast page for and click Go! Once the page displays, use the "Add to Home Screen" on your browser menu to have the widget readily available on your smart phone or tablet.

Remember that this is an experimental product and could be discontinued or changed at any time. In the meantime, give it a spin.

Tuesday, September 15, 2015

Some Relief on the Way for Washington, Oregon, Northern California.

A large trough of low pressure moving in from off of the Pacific will bring some much needed rain to the Pacific Northwest and some of northern California the next couple of days.

500 millibar map forecast for 5:00 a.m. PDT Wednesday, September 16
showing upper level trough moving on to the West Coast.

The rain, along with a turn to cooler weather will be most welcome by firefighters battling the many wildfires in progress in Washington, Montana, Oregon, and northern California.

Major wildfires in the U.S.

It's not in the news much, but there are also numerous wildfires in progress across the northern half of Alberta.

Major wildfires in Canada

However, it appears northern and central Alberta may see only scattered showers and miss out on any substantial widespread rainfall with the system affecting the northwestern U.S.

Rainfall amounts of the next 72 hours are expected to be from 0.75 to more than 1.50 inches along the coast of Oregon and Washington to as well as the Cascades. Rainfall is expected to be less in the Willamette Valley and in central and eastern Washington. Rainfall in northern California is likely to be heaviest in the extreme northwest portion of the state, in the higher coastal ranges, with amounts falling off to the south and east.

Quantitative Precipitation Forecast for the 72 hour period ending 5:00 p.m. PDT September 18.

Significant rain should fall on a few northern California wildfires, but the two largest and least controlled fires, the Butte and Valley fires, will likely only see lighter rain amounts. While the rain likely won't be significant in the worst fire areas,the increasing humidity and cooler weather should be beneficial in controlling the fires. The down side could be strong winds in some areas as the low pressure center moves inland..

The cooler weather marks a big change in the weather pattern in the Pacific Northwest. Seattle (SEATAC Airport) experienced 51 days of temperatures equal to or greater than 80°F, the most on record.  Portland, OR recorded 29 days with high temperatures equal to or greater than 90°F, breaking the old record of 24 set in 2009. The average number of days 90°F or above is 12.

Some more good news is that the latest 6-10 day outlook favors cooler and wetter than normal weather for these same areas.

Much further down the coast in southern California, moisture streaming ashore the remnants of Hurricane Linda produced some impressive rainfall totals this morning.

Radar image for southern California at 8:53 am PDT this morning showing rain showers
extending from near San Diego to northwest of Los Angeles.

CoCoRaHS observers in Los Angeles County, northern Orange County, and northwestern Riverside County measured more than an inch of rain this morning with 2.08 inches at CA-LA-48, Santa Monica 1.3 NNE. Lesser but still very welcome amounts occurred through much of southern California.