Sea ice in the Arctic continues its record decline, thanks to unusually cloud-free conditions and above-average temperatures. For August 21, the National Snow and Ice Data Center estimated that fully one third of the Arctic ice cap was missing, compared to the average levels observed on that date from 1979-2000. Sea ice extent was 4.92 million square kilometers on August 21, and the 1979-2000 average for the date was about 7.3 million square kilometers. Arctic sea ice has fallen below the record low absolute minimum of 4.92 million square kilometers set in 2005 by about 8%, with another 3-5 weeks of the melting season still remaining. Reliable records of sea ice coverage go back to 1979.
Figure 1. Extent of the polar sea ice on August 21, compared to the average for the date from the 1979-2000 period (pink line). Image credit: National Snow and Ice Data Center.
With one third of the Arctic ice cap already gone, and another month of melting to go, we need to consider what effect this will have on weather, climate, and sea level rise. Well, we don't need to worry about sea level rise, since the polar sea ice is already in the ocean, and won't appreciably change sea level when it melts. However, the remarkable melting of the ice cap will likely lead to unusual weather patterns this fall and winter. The lack of sea ice will put much more heat and moisture into the polar atmosphere, affecting the path of the jet stream and the resultant storm tracks. Expect a much-delayed arrival of winter to the Northern Hemisphere again this year, which may lead to further accelerated melting of the ice cap in future years.
Last week, I remarked that the most recent images from the North Pole webcam show plenty of melt water and rainy conditions near the Pole. It turns out that was misleading, since the webcam is on a ship that was headed towards the pole, but had not reached it. There have been rainy conditions at the Pole this summer, and there is some open water there, but this is not uncommon in summer. Shifting ice frequently opens up leads (cracks) with open sea water at the Pole. It was one of these open leads that British swimmer Lewis Gordon Pugh swam in for 18 minutes this July to draw attention to global climate change.
Figure 2. Total rainfall from August 10-22 as estimated by NASA's TRMM satellite.
Midwest flooding
To get an idea of the magnitude of the flooding that has hit the Midwestern U.S. during the past ten days, take a look at the total amount of rain from August 10-22 (Figure 2). We can blame Tropical Storm Erin for the rain in Texas and Oklahoma (up to 11 inches), and for the nine flooding deaths that occurred in those states. However, the unbelievable rain amounts in excess of 20 inches in Minnesota and Wisconsin were primarily due to a frontal system--with the help of some copious moisture pumped northwards by the counter-clockwise circulation around Erin while it spun over Oklahoma.
Tropical update
There are no threat areas in the Atlantic to discuss. Two of our four reliable forecast models, the NOGAPS and ECMWF, are predicting that a tropical depression could form off the coast of Nicaragua on Sunday. The models forecast that this system would move inland over Nicaragua and Honduras by Monday.
I'll have an update on Saturday morning.
Jeff Masters
Bulldozer trying to clear sand and debris from Norman Manley Highway(Airport Road)
The flood is over, now the cleanup
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A weakening upper low (NE-NNE of the leeward island) is moving into the North Atlantic with little shower actvity rotating around the low.
The surface Bermuda-Azores ridge is analysed on two highs - 1021 mb near 33N/55W and 1035 mb high near 53N/18W. This ridge is producing a large area of moderate trades and fair weather over most of the Tropical Atlantic north of 10N west of 30W with only stable air stratocumulus seen embedded in the tradewind flow. A fair amount of dry air and subsidence is also adding to the stability.
Based on visible imagery, 315K PV charts and 700 mb winds and vorticity, a tropical wave is estimated to be near 55-56W south of 18N moving west at 10-15 knots. This wave continues to exhibit clear cyclonic turning in the low levels of the atmosphere but not as pronounce at the surface a indicated by QUIKSCAT and 925-1000 HPA vorticity analysis.
The little shower activity associated with this feature is confined to the ITCZ.
A possible tropical wave near 42W-44W south of 20N indicated by a clearly inverted ITCZ in satellite imagery. Light to moderate convection within 150 NM either side the possible axis, but again confine to the ITCZ.
A third wave is near 25-27W based on visible imagery which shows a broad area of cyclonic turning just south of the Cape Verde Islands. This can be backed up by looking at any vorticity charts and African Jet Analysis. ROABS from Dakar, Senegal showed the passage of the wave near the 23rd with the wind veering from northeast to southeast near 850 mb. This also showed that another wave may coming off Africa as indicated by a surge of northeasterlies on the 25th.
by W456
no convection, but definitely a circulation...... but until it moves west into some moisture, just a dry spin......
The upper flow west of 75W is advecting moisture from activity in the Bay of Campeche into the Western Caribbean and with some help from a tropical near 88-89W, scattered high clouds with embedded showers are over the area. Meanwhile, a broad area of low pressure in association with the ITCZ is producing vigorous convection over Northern South America. There is evidence of cyclonic turning with this feature but it is too early to speculate as there has always been a climatological circulation around this area. Is this what the CMC model was picking up on in the Southwest Caribbean? Only time can tell. The environment around this area is not all that conducive for development but an area to watch if the CMC is correct.
Fair weather is noted elsewhere over the Eastern Caribbean. However, a combination of tradewind moisture and some southwesterly upper moisture from South America will inducing periods of scattered passing showers over the Islands. Expect light to moderate trades over the islands, a bit gusty in showers.
by W456
We should get a detailed account of whatever he did go through when he gets back I'd say.
My thoughts below
The system coming off of SA is not at the surface...no development expected.
The Atlantic and the east PAC are quiet.
Now...go out and have a great Sunday.
That is moisture out there not Faulse Echos
APRIL 22nd 2007 for most areas and some
April 20th 2007
I know, how crazy of TWC to not forecast a category 5 hitting the gulf coast every time a thunderstorm shows up in the Atlantic. I can't believe they acctually want him to accurately forecast the tropics.
TWC must have been like..."You cant say things like that Doctor! We cant worry people! Wait till it develops before you talk like that! Tell people to take that cruise that our secret cruise line sponsors want us to get people to take!
I know, how crazy of TWC to not forecast a category 5 hitting the gulf coast every time a thunderstorm shows up in the Atlantic. I can't believe they acctually want him to accurately forecast the tropics.
lol. I just find it funny how he changed what he said about the SW caribbean in just an hour. Its almost as if he's not allowed to say anything about it.
FORECAST POSITION AT T+ 60 : 12.5N 17.1W
VERIFYING TIME POSITION STRENGTH TENDENCY
-------------- -------- -------- --------
12UTC 28.08.2007 12.5N 17.1W WEAK
00UTC 29.08.2007 12.9N 18.8W WEAK LITTLE CHANGE
12UTC 29.08.2007 15.7N 19.4W WEAK INTENSIFYING SLIGHTLY
00UTC 30.08.2007 16.4N 21.0W WEAK WEAKENING SLIGHTLY
12UTC 30.08.2007 18.2N 23.1W WEAK LITTLE CHANGE
00UTC 31.08.2007 19.4N 25.8W WEAK LITTLE CHANGE
12UTC 31.08.2007 19.7N 29.6W WEAK LITTLE CHANGE
00UTC 01.09.2007 20.1N 31.2W WEAK LITTLE CHANGE
THIS INFORMATION IS PROVIDED AS GUIDANCE FOR TROPICAL CYCLONE
RSMCS. IT REQUIRES INTERPRETATION BY TROPICAL CYCLONE SPECIALISTS
AND SHOULD NOT BE CONSIDERED AS A FINAL PRODUCT
National Weather Service Sacramento California
405 am PDT sun Aug 26 2007
Discussion...
seasonable weather over norcal for the next couple of days before temperatures
warm several degrees above normal through at least the middle of the
week over much of the interior of norcal. The temperate weather regime
today is due to a vorticity maximum vicinity of 42n/130w maintaining the upper
trough pattern over the Pacific northwest and norcal today...and the associated
onshore flow. Onshore gradients continue to be moderately strong
resulting in a strong Delta breeze with gusts 31 kts at ksuu at 09z.
Feet Ord profiler indicates marine layer has deepened slightly to
about 2800 feet...with the 00z sun koak sounding suggesting it is
around 2000 feet. With the deepening marine layer...continued
moderately strong onshore flow...and the upper trough over the Pacific northwest
coast and norcal lowering 500 mbs heights about 5 dam through 12z
Monday...we look for cooling maximum temperatures again today. The upper trough is
forecast to move through the Pacific northwest and norcal by Monday afternoon...and the
onshore gradients should decrease. This should weaken the Delta
breeze allowing for slight a slight warming trend. Models continue
to struggle with the amount of middle-high level moisture from remnants
of hrcn Dean that may advect into norcal. 06z sun runs from the
NAM/GFS have backed off on the amount of moisture that works its way
this far north. Water vapor imagery shows the vorticity maximum spinning northward from
30n/120w around the periphery of the high center over the desert SW
which is spreading the leading edge of the moisture to around kmce.
However...the bulk of the moisture will likely become shunted southward
and eastward by the northern vorticity maximum /vcnty 42n130w/ and the upper level
trough. The flow over norcal will become southwesterly and more confluent due
to the upper trough to the north and the flow around the high over the
desert SW. The will keep the moisture from spreading well northward into
our forecast area today. This is best depicted in our sky grids
where an image/ picture describes the situation better than a
worded forecast.
Looks like the 06z sun GFS backs the middle level flow to the southeast more
so than in previous runs as the vorticity maximum from 30n/120w lifts northward
towards Tahoe on Tuesday...then up The Spine of the Sierra Nevada north of Tahoe
through 18z Wednesday. This scenario would give the west side of the Sierra Nevada a
better chance of thunderstorms than the predominantly southwesterly flow
forecast by previous runs. Will hold off on mention of thunder in
our County Warning Area until we see some model continuity at this time. Maximum temperatures
are expected to trend upward through the middle of the week with
triple digits in much of the Central Valley Wednesday/Thursday as the desert SW
high expands into norcal. A cooling trend is expected by next
weekend as southwesterly flow and onshore gradients increase as a series of
troughs approach/move through the Pacific northwest. Jhm
Link? Thanks
I've been having similar thoughts.
Hoping all good things for Dr. Masters.
We lost power last night for awhile and had trouble getting the wireless back up even after the electric was on. (Router had reset itself.)
I suspect that if the issue at hand is going to last over-long, he'll find a way to call upon someone to fill in for him for a few days.
Posted By: Drakoen at 3:15 PM GMT on August 26, 2007.
Link? Thanks
Based on the UKMET model.
Link
Trough digging down across texas
Upper low now drifting back E
Activity in the BOC as others have noted.
Maybe a good chance the SE CONUS will get some rain today.
Viewing: 1301 - 1347
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