Tropical Storm Andrea - Bulletin #1

As we hinted at on May 28th, satellite imagery and aircraft reconnaissance  confirms the formation of Tropical Storm Andrea at this hour, allowing the Atlantic tropical season to get off to a fast start. Satellite imagery depicts a strong eastern flank of Andrea but a very quiet western side to this tropical storm. Considering the conditions in the Gulf of Mexico aren't totally primed for tropical formation, the rather unusual build of this cyclone isn't that extraordinary. Satellite imagery also indicates clouds from Andrea have already overspread Florida, and it is in Florida where I expect the primary landfall to occur.

Atmospheric steering winds for this afternoon over the Atlantic basin are shown to be trying to push Andrea due north into Alabama, and the official National Hurricane Center track predicts the tropical storm to move slightly north in coming hours. However, going into the next few days, it is anticipated that these steering winds will begin to gain a more eastward component, allowing Andrea to maintain less of a northward track and more of an eastward track, combining to make for a northeast movement.

Landfall is expected to occur Thursday afternoon.

I believe the potential landfall zone will extend from the immediate vicinity of Cross City to Sarasota, Florida. This zone is where the models are converging for a landfall. The yellow star indicates where I believe the cyclone will make landfall. This landfall spot would be right around Hudson and New Port Richey. It is expected almost everyone in this potential landfall zone could experience tropical storm force winds and potentially flooding rains. Preparation plans are advised to be activated as the first named system of 2013 becomes the first landfalling system of 2013.

Andrew

Arctic Sea Ice Forecasts Very Ominous

Long range forecasts concerning Arctic sea ice are pretty ominous, with the above image showing as little as 3 million square kilometers of sea ice present just 100 days away.

The image above, from Steven Cavallo, shows the latest ensemble forecast of sea ice over the Arctic as far as 100 days out. We see a plot of the average sea ice values over the next 100 days, and the ensemble prediction superimposed on it. The ensembles take the sea ice values at below normal levels in the next month before really dropping off after the 30 day mark. From the beginning of June onwards, it is predicted that the Arctic will have sea ice levels less than half the typical values for that time of year.

In the very long range, this could impact the winter by not being able to hold as much sea ice, and thus allowing the Arctic Circle to be warmer than normal. This could then allow the polar vortex to weaken, which in turn may move to the lower latitudes at points during the winter. Bear in mind a LOT needs to happen before we can get that sequence underway, but this is a good first step for those wanting to see the polar vortex weaken into winter.

Andrew

Long Range Winter Prospects Very Favorable

Reminder: My Preliminary 2013-2014 Winter Forecast comes out Saturday, June 15 at 12:00 PM Central Time.

Long range weather models are predicting a very favorable winter for those snow lovers and plowers who have been in a big deficit in the past two years.

Shown above are two long range forecast models, predicting 200mb heights for the month of December 2013. Areas of blue depict general lower heights and thus low pressure areas, while reds indicate high pressure systems. The contour lines are superimposed on the images to help point out areas of differing pressure. There are four regions I want to look at here, so we'll start out with North America.

Both images show a pretty favorable set-up for cold weather as far as the 200mb level goes. We have a large area of rather strong low pressure over eastern North America stretching into New England, and this is reflected by the compression of contour lines in the same region. The low pressure area over New England tells me this area would indeed be favored for at least somewhat-frequent shots of Arctic air, and the tightening of the jet stream favors this theory. The overall picture is what excites me more. If we look into the far Northern Hemisphere we see no area of low pressure- the closest persistent low pressure center is the one in North America. Now, bear with me here, the idea is pretty outland-ish. But if you were to try to place a location for the polar vortex to average out over the month of December, you would want to find the area with the lowest pressure over the general upper latitudes (including North America, northern Eurasia, and Greenland). That said, it would make sense that the polar vortex may very well have a tendency to be pushed further south towards Canada and the US.

Our second area of interest is the United States. Both models show that low pressure area trying to push into New England, but we already covered that in the above paragraph. The item I want to focus on is the West Coast into Alaska. We see a separation of the contour lines into a looser composition, as well as oranges building into those areas. This indicates the presence of high pressure, and sets up positive phase of the Pacific-North America (PNA) pattern. In the wintertime, the jet stream does exactly what is being depicted above, and this means a warm West US and cold East US. Additionally, storm systems will tend to track in a path favorable for snowfall in the Midwest, Plains and portions of the Great Lakes into the Ohio Valley. The positive PNA helps to usher in lower than normal heights across the East US, and this will deliver us into the next area of interest.

The third area of interest is the Bering Sea. Both models project strong high pressure in the vicinity of the Bering Sea region; the GFDL model (left) has high pressure square in the Bering Sea, while the NCAR model (right) has the high pressure more towards Asia but still influencing the Northern Hemisphere. In both situations, the Arctic Circle appears overcome with above normal height anomalies, indicative of high pressure in the region. High pressure in the Arctic would imply a weaker polar vortex (yes, the same vortex I discussed this previous winter), as well as tendency for cooler weather to make its way down to lower latitudes of the world. If we do have high pressure in the Bering Sea, it would be easier for instances of high pressure to overwhelm the Arctic, and this could (keyword is COULD) allow the polar vortex to be pushed further south and affect lower latitudes in significant ways.

The final area of concern is East Asia. All models I observed for December 2013 depicted a tightening of the contour lines and lowering of height anomalies in East Asia, sometimes even into the northern Pacific. I have described a few times on this blog the idea of the East Asia-East US storm correlation, where a stormy period in East Asia can mean a stormy period in the East US 6-10 days later. This would mean more chances for snow whenever East Asia got active, and if long range models are correct this active period could be quite often. If the tightened jet stream in the North Pacific and stormy East Asia evolves as predicted (combined with the possible +PNA pattern and weakened polar vortex), this winter may help those winter-loving souls damaged by the last couple of winters.

Don't forget, as the note at the top says, my Preliminary 2013-2014 Winter Forecast will be released Saturday, June 15th at 12:00 PM central time.

Andrew

June 1, 2013 Special Atlantic Tropical Discussion

This is a special Atlantic Tropical Discussion from The Weather Centre.

Model guidance and the synoptic flow over the next 5-10 days tells me we are likely to see development of a tropical cyclone in the Gulf of Mexico that may very well lead to a landfall in the Florida Panhandle. Model guidance then depicts this tropical cyclone to hug the Eastern Seaboard up through the Mid-Atlantic before jogging off out to sea.

The pattern across the Atlantic will be stagnant, with high pressure spread out across the waters. This will enable any potential tropical formation to stick close to the coastline and stay in the Caribbean and/or Gulf of Mexico. It looks like that set-up will enable that principle to work itself into the first 10 days of June, when we expect tropical development to occur in the Gulf of Mexico and pose a threat to land. The most common landfall area has been northern Florida, and solutions that have taken that landfall path have then taken the remnants of the tropical cyclone up the Eastern Seaboard.

Model uncertainty remains high at this point, and the tropical cyclone may not even form when it comes down to it. However, if one does form in the Gulf, these are the areas I would expect to be affected.

On another note, what would you think about me using a grid-type of graphic like the one pictured below? This is a prototype and will be changed, but what are your thoughts on it? Like or dislike?

Yellow: Threat of tropical cyclone effects
Red: Threat of tropical cyclone landfall

Andrew

Tornado Emergency - Moore, Oklahoma - May 31, 2013

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 745 PM CDT FOR CENTRAL
OKLAHOMA AND NORTHWESTERN CLEVELAND COUNTIES...

AT 705 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS AND STORM
SPOTTERS WERE TRACKING A CONFIRMED STRONG TORNADO ONE MILE SOUTH
OF THE FAIRGROUNDS. THIS TORNADO WAS MOVING EAST TO SOUTHEAST AT 20 MPH.

..THIS IS A TORNADO EMERGENCY FOR DOWNTOWN OKLAHOMA CITY...INCLUDING
THE FAIRGROUNDS...WILL ROGERS WORLD AIRPORT...THE CAPITOL...VALLEY BROOK
...NORTH MOORE...AND DEL CITY...

IN ADDITION TO A TORNADO...LARGE DESTRUCTIVE HAIL UP TO SOFTBALL SIZE
IS EXPECTED WITH THIS STORM.

LOCATIONS IMPACTED INCLUDE...
OKLAHOMA CITY...MOORE...DEL CITY...BETHANY...WARR ACRES...NICHOLS
HILLS...FOREST PARK...VALLEY BROOK AND LAKE ALUMA.