Yet another monster low has formed and can bee seen spinning just south of Alaska, set to bring yet another round of powerful, potentially damaging winds onshore over South-Central Alaska. The GFS shows pressure falling all the way into the mid-950s in mb, incredible. I wonder if this depth is record challenging for September?

The centre of this monster is expected to strike the coast later today, tonight into Thursday morning with likely hurricane-force wind gusts widely, including Anchorage with 90 to 100+ gusts within canyons and over top of ridges.

Why is this system so strong?

1) WARM AIR UP AGAINST COLD

2) TWO STRONG HIGH’S EITHER SIDE OF THE STORM

3) ABNORMALLY WARM WATER OFF JAPAN AND IN ARCTIC VS ABNORMALLY COLD WATER SURROUNDING ALASKA

There is a 1028 mb high to it’s west over Siberia and a 1024 mb high to the east off British Columbia. With this wheel of air between these two highs, a lot of heat and energy is being entrained up into this system all the way from Hawaii. Not only is there an air mass temperature contrast with warm air slamming up against cold but waters are abnormally warm off Japan, abnormally cold off Alaska and abnormally warm to the north within the Arctic Ocean. All these factors provide the perfect environment for cyclogenesis and ‘bombing out’.

The Work of A Southbound Cold Front & Hurricane Miriam Supports Big 3 Day Rains From Texas to New England

With a frontal boundary working through the Central Plains and reaching into North Texas yesterday with cool to the north and hot, humid to the south, there was no surprise that we saw a cluster of severe thunderstorms break out along the front. Near record heat was being drawn north over Texas into the front and so we saw multiple severe weather reports stretching from Texas to southern Illinois including damaging wind, hail and even a tornado over southern Illinois.

Today will see less of a severe threat but the frontal boundary will continue it’s SLOW journey south. What interesting is the fact we are seeing a strong subtropical jet stream which is interacting with a weakening Hurricane Miriam out over the eastern Pacific. While Miriam won’t push towards the Baja coast making a landfall as first thought, what will happen is the low level storm of Miriam will continue moving northwestwards, likely weakening to perhaps a mere depression by Friday as it interacts with cooler waters.

The vigorous sub tropical jet which you can see in the above 200 mb chart will blow over top of Miriam dragging moisture northeastwards across the Mexican mountains and desert. This will be feed across Texas where it shall significantly cool and RAIN! Note how strong the subtropical jet gets by Thursday (above). This jet is also what is stopping a faster southbound progression of the front dropping out of the north.

Check out the below QPF chart showing rain totals over the next 3 days.

Notice how the model has a very generous corridor of 1-4 inches of rain slicing N,NE across the Lone Star State, courtesy of the moisture blown off Miriam and the work of a strong subtropical jet. You can also see significant rains centred over southern Kansas, northern Oklahoma extending into southern Missouri with 2-4 inches, perhaps locally higher amounts. This is thanks to this tropical moisture feeding right up against the front.

The corridor of widespread 1-3 inch rains runs along this near stalled frontal boundary all the way to New England.