Big Bertha

After looking rather anemic early Monday morning ...

... Bertha's "convection" erupted during the day along with the storm also getting more symmetrically and solidly organized by late afternoon:

Bermuda was buffeted by prolonged tropical storm force winds and heavy rain even though the center passed a pretty good distance to the east, because of both the extra oomph the storm had as compared to the previous night and the gigantic width of the eye. (The only 70+ mph winds measured were gusts at an elevation far above ground level, but 40+ mph sustained winds with gusts to 50-60+ were common.)

Although remnants of a small "inner" eye have been evident at times the past couple of days, and visible imagery around the time of the second IR image above showed a little swirl within the larger gyre ...

... that tiny feature was just a shallow and inconsequential one; the true eye at the time, which was surrounded by an eyewall, was dominant. This radar image, courtesy of the Bermuda Weather Service, helps pinpoint the measurement of the diameter. From the southwest edge of the eye, near the radar site, to the northeast edge, was just a hair under 150 kilometers (the rings are spaced every 50 km), or about 90 miles. I don't know if there's an official "record" for eye diameter, but I can't offhand remember ever seeing any that have been bigger than that.

Moving forward, the saga of Bertha has at least one more chapter yet to come, as a goofy upper air situation ensues downstream. This computer model forecast for Wednesday morning shows Bertha (on the left edge); an upper-level low (just to the right, or east, of Bertha); and the key to this blocked-up pattern, which is a strong ridge of high pressure aloft that will be building north of 40N latitude (in the northeast portion of the map). As a result, even though Bertha is now moving again rather than stalled, that motion will be erratic at times this week.

UPDATE 10AM EDT TUESDAY

Here's a classic "water vapor" image showing the blocked-up pattern with Bertha and the upper low to its east:

UPDATE 5PM EDT TUESDAY

From the National Hurricane Center: BERTHA IS NOW THE LONGEST-LIVED JULY TROPICAL STORM IN ATLANTIC
HISTORY [Stu's note: historical period of record is since the mid 1800s] ...WITH 12.5 DAYS AS A TROPICAL STORM OR GREATER. THIS ECLIPSES THE PREVIOUS RECORD OF 12.25 DAYS OCCURRING IN 1916 FROM STORM #2.

UPDATE 10:45PM EDT TUESDAY

A couple of folks have asked about 94L, which is the system east of the Windward Islands. It is struggling, but in the meantime an area of convection (rain/tstorms) has really flared in the eastern Gulf this evening, with a spin evident on radar centered where I've put the "x." Whether this disturbance develops into a tropical cyclone will depend in part on whether or not the low pressure system associated with it sets up over land, but at the very least it'll bring heavy rain to parts of Florida.

UPDATE 11AM WEDNESDAY

Although convection persists over and offshore of southwest Florida, enough of the system's circulation is over land to preclude tropical cyclone development for the moment. The low is weak as are its winds (other than briefly gusty in thunderstorms), but locally heavy rain will continue.

The ebb and flow with the disturbance in the tropical Atlantic continues, with its convection now being greater than, and more concentrated than, at any point in its life so far. Aircraft recon will investigate this afternoon to assess whether there's a "closed" surface circulation and how strong the winds are. Regardless of whether it's designated a t.d. or t.s., the system will bring squally weather to the Windwards.