Daweathablog

Charles E. Roop giving his own forecasts, weather discussions, photos and adventures for the Starkville, MS area, Florida, and beyond.

Monday, October 24, 2011

Hurricane Rina Forms in the Caribbean Sea

I got my slight dose of shock this afternoon as Tropical Storm Rina was upgraded to hurricane status Monday afternoon. I say slight because it just looked really nice on the GOES loops.

Sunday afternoon, a tropical disturbance over the Caribbean Sea that was given invest classification became a tropical depression. Rina was then born by the 11 p.m. ET advisory.

When I viewed the satellite imagery this morning, the tropical cyclone (TC) looked like it was getting its act together quickly. The NHC forecasts had Rina becoming a hurricane a few days out. But the satellite loops showed Rina having good outflow and looking really organized. It wasn't until early this afternoon when USAF Hurricane Hunters found a central pressure of 991 mb and winds of at least 65 knots. This storm's winds increased 30 mph in roughly three hours and dropped 10 mb within the same time frame. At that point, the visible satellite loops were showing what looked like a developing eye.

Currently, the storm is still maintaining 65-kt winds. The pressure has dropped, but only a little (currently 989 mb) and the TC is still dragging west-northwest at 3 mph. Based on infrared satellite imagery, Rina's cloudtops are starting to become taller near the center of circulation (see below).

Source: NOAA
The ridge over southern Texas and northern Mexico is keeping Rina at bay and moving it slowly west. The GFS appears to break down the ridge come Tuesday afternoon as a trough over the western US begins to dig and move eastward. Most of the guidance models track Rina to the north and northeast late in the week. The NHC however, according to their last discussion, are not confident in the future track due to inconstant paths in the previous runs (hence why the "cone of error" is so large).

It may go north over time, but if it does, it may not last very long as a TC. The upper-level environment is very unfavorable to the north of Rina. Current wind shear numbers are 30+ knots. The NHC expects southerly shear to begin impacting the storm within a few days. Dry air is parked to the northwest of the storm. Right now, Rina is doing a good job of shielding itself from this dry air. But once it finds a way in, Rina will start to deteriorate. If, for example, Rina does move towards Florida, it will likely not be a beast of a hurricane because of this. Heck, it'll likely not even be tropical in nature at that point. It depends on how strong it gets. It could be a rain maker, at least.

This storm may take off to the north and northeast over time, but I doubt it will be anything tropical by that point because of the unfavorable environment ahead of it. It's still worth watching. Stay tuned to my Twitter feed for the latest. I might post another blog entry in a day or two, if conditions (and time) warrant.

Saturday, October 22, 2011

Quick Overview: Plantation/Sunrise, Fla. Tornado

On Tuesday night (Oct. 18), an interesting weather pattern was setting up in south Florida. At the same time, I was watching the town hall session at the National Weather Association annual meeting in Birmingham, Alabama.

When me, Dan Goff, and 100+ meteorologists were listening on to what some of the general public thought about the warnings and the societal reactions to the April 27 tornado outbreak, I was checking my Twitter feed and discovered something interesting. The National Weather Service in Miami issued a tornado warning for parts of Monroe and western Miami-Dade counties. The storm was racing off to the northeast over the Everglades. It was far from the major metro areas along the east coast - I considered it an "alligator" storm.

The storms across south Florida had the potential to rotate and possibly spawn a few tornadoes. The Storm Prediction Center had issued tornado watches for the area and has issued several mesoscale discussions (such as this one and this one). 

At 8:30 p.m. ET, the rotation seems to intensify on the velocity scan (see below). Dan and I were pretty amazed on how good it looked on radar. It looked like it was still an alligator storm, if not a tornado on the ground. I started to become concerned about this storm if it continued at its current strength toward northern Miami-Dade or southern Broward counties.

Screenshot of KAMX velocity tilt 1 scan using RadarScope on iOS 5.

Over time, the storm moved in a northerly direction and began to lose its impressive velocity signature.



However, NWS-Miami issues another tornado warning for parts of Broward.





Reports of damage start to flow in from the Plantation and Sunrise area of damage from a possible tornado at roughly 10:07 p.m. ET, according to NWS-Miami's storm assessment (PDF). About 4 minutes before the tornado was thought to have initiated, a scan from the Miami radar shows some possible rotation with the velocity scan (top right), while the storm relative (bottom left) shows slight rotation. The spectrum width (SW) (bottom right), which is used to essentially measure turbulence and associated with thunderstorms and mesovoritcies. 



The storm continues to move off to the northeast for 1.11 miles doing a max of EF-2 damage with maximum winds of 120 mph. It aslo continues to lose its appearance on the Miami radar.

THE TORNADO BEGAN AT NW 135TH AVENUE AND NW 3RD STREET IN PLANTATION AND ENDED AT NW 13TH STREET AND NW 133RD AVENUE IN SUNRISE. DAMAGE THROUGHOUT MOST OF THE PATH WAS OF EF-1 INTENSITY WITH WINDS OF 95-110 MPH. MORE SIGNIFICANT DAMAGE WAS SEEN OVER A SMALL PORTION OF THE PATH, BETWEEN 8TH AND 10TH STREET JUST WEST OF 133RD AVENUE, AND WAS RATED AS EF-2 WITH A MAXIMUM WIND ESTIMATED AT 120 MPH.  
UP TO 50 HOMES WERE DAMAGED ALONG THE TORNADO'S PATH WITH DAMAGE TO ROOFS, GARAGE DOORS, AND WINDOWS. AT LEAST A DOZEN HOMES HAD  SIGNIFICANT TO SEVERE DAMAGE. ROOFS OF TWO HOMES WERE COMPLETELY REMOVED. TWO TRAILER HOMES WERE SHIFTED OFF THEIR FOUNDATIONS WITH MOST OF THE WALLS COLLAPSED. ONLY A FEW MINOR INJURIES WERE REPORTED, CONSISTING OF CUTS AND BRUISES.

The NWS in Miami gave ample warning for this storm as it had a history of showing rotation on radar, especially over the Everglades. Based on the stories told by the local media, it's great news that there were few injuries and no deaths associated with this tornado in a highly populated area.

With all the talk that Tuesday night in Birmingham of how people reacted from the April 27 outbreak, I wonder if anyone in the area received these warnings and how they prepared for it, especially since it was a tornado that arrived after dark.