... Another Arctic airmass expected early next week...
So what happened to the forecast of a near to slightly above normal
winter? Well as occurred last winter the Arctic oscillation (ao)
has begun to dominate the weather pattern across the U.S.
Overwhelming the effects of the El Nino southern oscillation (el
nino/la nina). The ao is a short term oscillation on the scale of
a week or two while the enso is much longer on the scale of months.
The ao has little effect on our weather during the Summer months...
but during the winter there is a high correlation between it and
the temperatures we experience. Therefore... during the winter
months the ao can radically change the temperatures across the
area causing either much above or much below normal temperatures.
As it turns out the ao went into a highly negative phase back
around November 20th and bottomed out around the 27th. It has
since recovered back to around neutral... but as is generally the
case during the late fall and winter months there is about a 10 to
14 day lag before the effects of the ao are felt here in Florida.
Therefore... when the ao GOES highly negative we tend to see below
normal temperatures within about two weeks or so and when it GOES
highly positive we see above normal temperatures. So based on this
theory we should see closer to normal temperatures return during
the middle of December... but if the forecast models are correct the
ao is expected to go highly negative again in the next week or so
which would bring more cold weather the week before and after
Christmas. More information and graphics about the ao can be found
on the climate prediction center web site listed below:
Http://www.CPC.NOAA.Gov/products/pre...index/ao.Shtml
So with this in mind its not surprising that another blast of Arctic
air is forecast to move into the region early next week... about two
weeks after the ao bottomed out. During Sunday a strong cold front
will move across the region followed by an area of cold Canadian high
pressure that will usher in the next shot of cold Arctic air for
Sunday night through about Wednesday. Temperatures during this time
period are expected to be about 15 to as much as 30 degrees below
normal... or at least as cold as what we saw earlier this week.
Ahead of the front southwest to west winds will increase to 15 to
25 mph with higher gusts Sunday morning then shift to northwest to
north behind the front. Over the coastal waters the winds will be
even stronger... especially behind the front as the cold air moves
across the relative warm Gulf waters... with gusts possibly to gale
force. The brisk conditions will continue through Monday over the
coastal waters and mariners may want to postpone or reschedule
trips during this time period. Also with the winds shifting from
southwest to northwest during Sunday some minor coastal flooding
may occur... especially along northwest facing coasts like along
portions of Pasco and northern Pinellas counties. At this time
tides on Sunday are expected to run about 1 to 2 feet above normal
from the Tampa Bay area northward and about 1 foot above normal
further south.
The cold air will become firmly entrenched during Sunday night into
Monday as the breezy northwest to north winds persist with forecast
lows dropping into the 30s and 40s combining with the winds to
cause wind chill values in the 20s and 30s. Daytime highs on
Monday will only climb into the lower 50s north to around 60 south.
And if all of this was not enough... late Sunday night into Monday
morning the combination of the cold air moving across the
relatively warm Gulf waters could cause some Gulf effect sprinkles
to develop... possibly even a few snow flurries north of the Tampa
Bay area.
The second night after the cold front moves through is typically
the coldest night which in this case is Monday night. A hard
freeze is likely across the Nature Coast Monday night into Tuesday
morning with low temperatures forecast to fall into the lower to
mid 20s... including 7 to 11 hours of temperatures below freezing.
Further south across the remainder of inland west central and
southwest Florida a freeze is likely... possibly a hard freeze in a
few spots... with temperatures forecast to drop into the mid 20s
to lower 30s... including 3 to as much as 8 hours of temperatures
below freezing. Similar to earlier this week coastal areas will
most likely escape the freezing temperatures... but still fall into
the mid 30s to lower 40s. Winds will lighten some Monday night
away from the coast... but continue between 5 and 10 mph so the
threat of frost will remain low.
During Tuesday and Tuesday night winds will diminish as the high
pressure moves toward the area with daytime temperatures remaining
rather cool and only climbing into the mid 50s north to lower 60s
south. Temperatures Tuesday night are expected to be the same or
a couple of degrees warmer than Monday night... but because the
winds are forecast to become light the threat of frost will
increase and become a good possibility.
Finally during Wednesday temperatures will begin to moderate with
highs climbing back into the 60s. However... the high will remain
across the region into Wednesday night with yet another chilly
night expected along with the possibility of some frost...
especially across the Nature Coast.
Over this weekend residents should prepare for the upcoming cold
weather. These types of severe freezes can pose a significant
threat to agriculture... exposed water pipes... such as those at
houses on stilts... some trailers... and pipes connected to swimming
pools. It can also be dangerous to people and pets that lack
adequate protection.
All residents and visitors of west central and southwest Florida
should stay tuned to NOAA Weather Radio or your local media for
further updates on this developing cold outbreak.
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During most other times of this month these forecast cold
temperatures would be close to if not new records. However...
during mid-December of 1962 the Florida Peninsula was hit by one
of the coldest outbreaks on record with widespread low temperatures
in the teens as far south as Hillsborough and Polk counties.
Thankfully we are not anticipating temperatures this cold so the
only locations that will likely see new record temperatures are
sites like Archbold Bio stn and Punta Gorda 4 ESE whose records do
not go back as far as 1962.
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