Watching the Skies

The National Weather Service has officially adjusted the severe weather criteria for reporting hail… Previously, hail of 0.75 inches or larger was considered severe and would prompt a severe thunderstorm warning. Now to assist with reducing the amount of severe thunderstorm warnings and more accurately advise of severe weather, severe hail size is now increased to 1.0 inches. The change takes effect on January 5, 2010 for all regions in the USA.

To:       subscribers:  NWS partners…users and employees

Subject:  National change in minimum hail size criterion
for issuing Severe Thunderstorm Warning /svr/
and severe weather statement /svs/ products
effective January 5 2010

Effective Tuesday January 5 2010 at 0001 coordinated Universal time
/UTC/…all NWS weather forecast offices /wfos/ will operationally
change the minimum hail size criterion used to issue Severe
Thunderstorm Warning /svr/ and severe weather statement /svs/
products from 3/4 inch /penny/ diameter or larger hail to 1 inch
/quarter/ diameter or larger hail.

No change is being made to the svr and svs product wind criterion
of wind gusts equal to or in excess of 50 knots /58 mph/.

A public information statement /pns/ soliciting comments regarding
this change was issued September 23 2009 /use lowercase/:

http://www.Weather.Gov/os/notification/pns09_1_inch_hail.Txt

NWS received 63 comments in response to the pns…54 of which /86
percent/ supported this change. A web Page will be created to
address all comments since some comments indicated a need for
additional outreach. This web Page will be available by December 15
2009 and will be publicized via another pns.

NWS reviewed all comments before deciding to change minimum hail
size criterion for svr and svs products.

Central and western region wfos currently issue svr and svs
products experimentally using the 1 inch /quarter/ diameter or
larger hail size criterion /use lower case/:

http://www.NWS.NOAA.Gov/om/notification/scn09-19hail_change.Txt
and
http://www.NWS.NOAA.Gov/om/notification/scn09-36wr_hail_exp.Txt

These wfos will continue to issue 1 inch /quarter/ hail size
criterion products experimentally through January 4 2010. All NWS
wfos will adopt the new criterion operationally on January 5 2010.

For further information regarding this change please contact:

John T ferree
fire and public weather services branch
120 David l. Boren Blvd suite 2312
Norman OK 73072
John.T.Ferree@noaa.Gov

Or

mark Fox
warning and coordination meteorologist
National Weather Service Fort Worth Texas
3401 northern cross Blvd
Fort Worth Texas 76137
mark.Fox@noaa.Gov
National service change notices are online at /use lowercase/: http://weather.Gov/os/notif.Htm

Looks like severe weather potential is likely on Wednesday evening in the Tampa Bay area. Both the Storm Prediction Center and the local weather forecast office in Ruskin are anticipating this event to be notable enough to warn the public about. The SPC has the entire area under a ’slight’ risk of severe storms, or 30% likelihood of severe weather within 25 miles of any given point, with a 10% chance of significant severe. The main risks appear to be damaging winds and isolated tornadoes or waterspouts. Any severe weather that develops in these style of storms moves very fast, so if any tornado warnings or other significant weather advisories are issued for your area, don’t delay and take appropriate action immediately.

Below is a statement from the NWS regarding the upcoming weather for the Tampa Bay area.

…Potential for severe storms and coastal hazards Wednesday into
Thursday…

Developing low pressure over the western Gulf of Mexico will
continue to intensify as it moves northeast toward the northern
Gulf Coast tonight and across the southeastern states Wednesday
and Wednesday night. Ahead of the low an increasing moist
southerly wind flow will develop over the region during Wednesday.
This increasing southerly flow over the adjacent Gulf waters will
help to build seas and generate large breaking waves…dangerous
rip currents and high surf along area beaches Wednesday into
Thursday.

Tides are expected to run above normal along the entire West Coast
of Florida…ranging from around one foot above normal near Fort
Myers to 2 to 3 feet above normal around the Tampa Bay region…
to 3 to 4 feet above normal further north along the Citrus and
Levy County coasts. These above normal tides could cause some
coastal flooding at times of high tide Wednesday and Wednesday
night…especially along the Nature Coast. Therefore…a coastal
Flood Watch is in effect from Manatee County northward through
Levy County.

The strong southerly wind flow and increasing seas will make for
hazardous boating conditions over the adjacent Gulf waters…and
mariners…fishermen…and boating enthusiasts may want to
postpone trips into the Gulf until conditions improve late in
the week.

As the low pressure area lifts northeast into the southeastern
states Wednesday a trailing cold front will approach from the
west. An increasingly moist and unstable air mass ahead of this
front will set the stage for showers and thunderstorms to develop
along and ahead of the boundary as it moves toward west central
and southwest Florida. Current timing of this front would bring
showers and thunderstorms into the Nature Coast around midday
Wednesday…with this activity spreading south into the Tampa Bay
area during the mid to late afternoon hours…and then across
southwest Florida during the evening.

At the current time sufficient low level moisture combined with
strong prefrontal convergence and increasing wind shear within
the atmosphere may support some strong to severe storms as the
front moves south through the region…especially from the Tampa
Bay area north through the Nature Coast. The main hazards from
these storms will be damaging winds and possible isolated
tornadoes and waterspouts. In addition…locally heavy rainfall
and deadly lightning strikes will accompany the storms.

All residents and visitors of west central and southwest Florida
should remain alert to rapidly changing weather conditions during
Wednesday and Wednesday night.

Stay tuned to NOAA Weather Radio or your local media outlet for
further updates on this developing weather situation.

For interests in the gulf coast states… Ida currently as a Tropical Storm, is forecast to intensify within the next 12 hours to Hurricane strength. As the storm progresses northward into the Gulf of Mexico, it will encounter areas with increased wind shear and cooler waters and will weaken again. The question mark in this forecast track is in the 60 to 72 hour period where it will interact with a mid level trough descending through the states, and transition into an Extratropical system. Eventually the storm will be absorbed by a frontal boundary and no longer be considered a tropical system around the 5 day mark. This system looks to have a very minimal impact, if any to north Texas. Interests in west central Florida should keep an eye on this storm still as it could have an impact, be it heavy rains and gusty winds or more.

Hurricane Ida formed near Nicaragua moving north very slowly today. The storm will continue north at a very slow pace, eventually making it to the Gulf of Mexico by this upcoming Tuesday. Forecasts beyond that point are very difficult to determine and we will just have to wait and see. As we all know, once a tropical system reaches the Gulf of Mexico, it basically has a 100% chance of making landfall somewhere, so this is a storm to keep an eye on for Florida residents. North Texas residents could also be indirectly impacted by this storm system, so again it is worth monitoring.

October 25, 1921 marks an anniversary of the last major hurricane to directly impact Pinellas County, FL. This storm inundated the barrier islands with storm surge creating several passes including Johns Pass between Treasure Island and Madeira beach. Below is an excerpt from Bay News 9  regarding this storm:

Link directly to Article
By Bay News 9 Chief Meteorologist Mike Clay

On October 25, 1921, Pinellas County was hit with the last hurricane to score a direct hit.

Since then, there have been other very close calls and storms that have done damage such as Hurricane Easy in 1950 and a strong hurricane in 1944 that hit Manatee County and came up through Tampa Bay.

But the 1921 Hurricane is a textbook case of the worst case scenario for Tampa Bay. The storm was a typical October threat for us, forming late in the season in the warm waters of the Western Caribbean.

It moved slowly northward, getting stronger and missed the land mass of Cuba and the Yucatan of Mexico passing through the warm waters of the Yucatan Channel. From there, stronger upper level winds that were likely blowing by late October turned the storm northeast as it became a category 3.

The hurricane was likely weakening as it hit with the center coming ashore at Tarpon Springs. The National Hurricane Center shows it a category 3 at landfall with winds of 120 mph, pressure of 951 mb and a storm surge in Tampa Bay of 10.5 feet.

The hurricane left 10 people dead and $10 million dollars in damage. Remember, not many people lived here in 1921. The population was only slightly over 100,000. A storm like this today would cause many billions of dollars worth of damage here along with a severe threat to life.

We can learn lessons from the 1921 Hurricane which caused water to go over the barrier islands and cut several passes in the sand bars which still exist today.

Major hurricanes can hit the West-Coast of Florida, and are most likely in October. Even though the peak of the season was back in mid-September, we have to remain cautious through the end of the season in November.

Several reports of waterspouts have been submitted to the National Weather Service in Ruskin today, including one in Old Tampa Bay. The waterspout in Old Tampa Bay is the storm that prompted the tornado warning earlier, no damage has been reported at this time.

I have included some pictures of today’s waterspouts, courtesy of Bay News 9.

[Show as slideshow]

[View with PicLens]

 

A waterspout moving ashore from upper Tampa Bay prompted a tornado warning for west Hillsborough County. The tornado is near Courtney Campbell Causeway, Town N Country and Tampa Intl Airport.

BULLETIN – EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE TAMPA BAY AREA – RUSKIN FL
1123 AM EDT MON JUL 27 2009

THE NATIONAL WEATHER SERVICE IN RUSKIN HAS ISSUED A

* TORNADO WARNING FOR…
WESTERN HILLSBOROUGH COUNTY IN FLORIDA.

* UNTIL 1145 AM EDT

* AT 1121 AM EDT…A WATERSPOUT MOVING TOWARD SHORE WAS SIGHTED NEAR
TOWN ‘N’ COUNTRY…OR 8 MILES WEST OF TAMPA…MOVING EAST AT 10
MPH.

* THE WATERSPOUT WILL BE NEAR…
COURTNEY CAMPBELL CAUSEWAY.
TOWN ‘N’ COUNTRY.

PRECAUTIONARY/PREPAREDNESS ACTIONS…

REMEMBER…AS WATERSPOUTS MOVE ASHORE THEY BECOME TORNADOES AND
SHOULD BE CONSIDERED EXTREMELY DANGEROUS!

IF YOU ARE IN THE PATH OF THE TORNADO GO TO A SMALL INTERIOR ROOM IN
A STRONG AND WELL CONSTRUCTED BUILDING. CARS AND MOBILE HOMES ARE NOT
SAFE! IF NO SHELTER IS AVAILABLE…LIE FLAT IN A DITCH OR CULVERT AND
COVER YOUR HEAD WITH YOUR HANDS.

TO REPORT SEVERE WEATHER TO THE NATIONAL WEATHER SERVICE PLEASE CALL
813-645-2323.

Edit: How fitting that my 400th blog post is a tornado warning. That makes me happy.

Hey everyone, heres a brief weather update for the holiday weekend.

Friday looks to bring more of the same as there has been the last few days. Southwest wind flow will carry thunderstorms inland from the gulf creating heavy rain and localized flooding conditions. Rain chances are fairly elevated, sitting at 50%. High temps of 88 degrees are a tad lower than normal, likely due to increased cloud cover and heavy rains. As is typical with Florida afternoon storms, an isolated severe threat is possible, but not moreso than usual.

Saturday night thru Wednesday will return back to a typical Florida seabreeze pattern. The seabreeze will hug closer to the gulf coast from Tampa Bay south, and push further inland in areas north of Tampa. With this pattern it is not unusual to see an early afternoon thunderstorm over central Pinellas county anywhere from noon to 3pm, and lines of storms forming more inland anytime after that. These storms do occasionally develop outflow boundaries that push back out twards the gulf and generate more storms. This is nothing new for Florida afternoon thunderstorms though, but I am sure everyone knows about the whole ‘rapidly changing weather conditions, lightning can strike 10 miles away’ speech. Heat index values in areas that do not receive rain cooled air can reach up to 110 degrees, so keep well hydrated and keep sunscreen around.

Have a great 4th everyone!

Looks like the NWS is confirming tornado damage in Carrollwood Village from a tornado earlier this afternoon. Usually it takes the weather service a day or two to perform damage surveys so this is extremely fast. They rated this as an eF-0 tornado which toppled pine trees and telephone poles in Carrollwood Village along Golf Crest Circle. The trees that fell hit a house and broke some shingles. No other damage reports have come in at this time.

The tornado warning has ended for Hillsborough County. The storm that produced the warning weakened and rotation completely stopped. The rotation spun up over Carrollwood Village at Fletcher & Dale Mabry, continued east twards I-275 and Fowler, and occluded near Busch and 30th.

No tornado or wind damage reports have come in at this time, but if any do then I will post updates. Below is screenshot from 3:18pm of reflectivity (left) and velocity (right).