Sunday, August 31, 2014

Partly Sunny with Moderate Winds and Seas

The CoCoView Resort Weather Forecast
This weather forecast is intended for CoCoView Resort guests and applies only to the south side of Roatan
CoCoView is at 16.4°N Latitude x 86.4°W Longitude
in the
   NW Caribbean Sea

             CoCoView Resort, www.cocoviewresort.com , 800-510-8164

How to use this page:
The title of each of the figures below is linked to the page where the information originates.
Since I write and post early in the day and generally do not update the page until the next morning; by clicking on the link, it allows you, the viewer, to get the latest information.
This is not only convenient but allows you to track weather events such as cold fronts and hurricanes from a single web page.
In addition, in the right column is a very useful widget. It is a trip planner...yesteryear's weather at a glance.This widget lets you check historic weather for your trip dates.

2014 Hurricane Outlook and Forecasts
The hurricane season in this hemisphere starts on June 01 and ends on November 30.
During that time frame, for your convenience, you will find a section below titled, "Tropical Weather Outlook".
It will contain the daily tropical storm outlook, forecast and storm track(s).

NOAA predicts near-normal or below-normal 2014 Atlantic hurricane season.
El Niño is expected to develop and suppress the number and intensity of tropical cyclones.
This year, the Saharan Air Layer (SAL) has been decreasing in size and density since May 21, 2014. This is important because it has been postulated, that the SAL, a cool, dry, layer of air which contains particles, may inhibit the formation of tropical storms and hurricanes. In addition, as it decreases in size and density, the probability of tropical storm formation may increase.

The outlook calls for a 50 percent chance of a below-normal season, a 40 percent chance of a near-normal season, and only a 10 percent chance of an above-normal season.  For the six-month hurricane season, which begins June 1, NOAA predicts a 70 percent likelihood of 8 to 13 named storms (winds of 39 mph or higher), of which 3 to 6 could become hurricanes (winds of 74 mph or higher), including 1 to 2 major hurricanes (Category 3, 4 or 5; winds of 111 mph or higher).
These numbers are near or below the seasonal averages of 12 named storms, six hurricanes and three major hurricanes, based on the average from 1981 to 2010. The Atlantic hurricane region includes the North Atlantic Ocean, Caribbean Sea and Gulf of Mexico.

Sunday, August 31, 2017
Today, skies will be partly sunny. Winds will be light and variable in direction at 2 mph to 5 mph this morning or less; increasing to 15 mph to 25 mph from the east this afternoon and evening. Seas will be calm to choppy at 1 to 4 feet. There is a chance of scattered rain showers and isolated thunderstorms, as a tropical wave continues to pass over us today.
The air temperatures will range from the mid to high 70s (ºF) to the mid to high 80s (ºF) or 24ºC to 26ºC.
Ocean water temperatures are 82°F to 84°F or 24ºC to 25ºC. Visibility is 20 to 80 ft.


 













Fig 19 - Recent changes in the Saharan Air Layer





The Tropical Weather Outlook
1. Disorganized shower and thunderstorm activity continues in association with a tropical wave over the northwestern Caribbean Sea. Land interaction will limit significant development while the disturbance moves across the Yucatan peninsula today and tonight. However, environmental conditions are expected to be conducive for development once the system moves into the southwestern Gulf of Mexico on Monday.
* Formation chance through 48 hours...medium...30 percent.
* Formation chance through 5 days...medium...50 percent.
2. Fresh to strong SE flow and building seas will persist through Monday from the S central Caribbean to Yucatan coast following a tropical wave that moved into Yucatan yesterday. A weaker tropical wave entering eastern Caribbean will move through the central Caribbean Tuesday through early Wednesday...and the Western Caribbean Thursday and Thursday night. A third tropical wave in the tropical Atlantic will pass west of 55W tonight...approach the eastern Caribbean late Monday into Tuesday...then move through the central Caribbean through mid week.

Heavy Rains From 99L Drench Belize and Mexico

By: Dr. Jeff Masters , 4:41 PM GMT on August 31, 2014

Tropical wave 99L is spreading heavy rains over Belize and Mexico's Yucatan Peninsula as the storm heads west-northwest at about 10 mph. Belize radar shows little rotation to 99L's echoes, and satellite loops on Sunday morning showed the heavy thunderstorm activity was poorly organized, with few low-level spiral bands. Sea Surface Temperatures (SSTs) were very warm, near 29.5°C (85°F), and wind shear was moderate, 10 - 20 knots. These conditions are favorable for development, but 99L will not be able to develop until it finishes crossing Mexico's Yucatan Peninsula and emerges into the Gulf of Mexico's Bay of Campeche on Monday. The 8 am Sunday run of the SHIPS model predicted that conditions will remain favorable for development over Bay of Campeche during the remainder of the week, with moderate wind shear, a moist atmosphere, and warm SSTs of 29.5°C (85°F.) None of our three reliable computer models for predicting tropical storm formation showed 99L developing in their Sunday morning runs, though. In their 8 am EDT Sunday Tropical Weather Outlook, NHC gave 99L 2-day and 5-day development odds of 30% and 50%, respectively. If a tropical storm does form in the Bay of Campeche, the most likely track would be to the west-northwest or northwest, with landfall occurring on the Mexican coast south of Texas on Wednesday. An Air Force hurricane hunter aircraft has been tasked to investigate 99L on Monday afternoon, if necessary.

Hurricane expert Steve Gregory has a more detailed look at the tropics in his latest blog post.


Figure 1. Latest satellite image of Invest 99L in the Western Caribbean.


INVEST 99L HEADS FOR BAY OF CAMPECHE / LARGE WAVE AFRICAN COAST

By: Steve Gregory , 4:04 PM GMT on August 31, 2014

INVEST 99L NEAR YUCATAN - NO THREAT TO U.S.

INVEST 99L with a possible center of rotation near the northern Belize coast, is moving W/NW (300°) at 13Kts, slowing from its 20Kt forward motion just 24 hrs ago. The disturbance should slow further during the next 24-48 hrs as it crosses the Yucatan and emerges in the Bay of Campeche on Monday.

While wind shear remains marginally favorable for development at around 15Kts, with more than adequately warm SST’s near 85°F – upper level winds are not currently favorable for development since no anti-cyclonic ‘outflow’ exists. An anti-cyclone (High pressure) is needed at high levels (around 200mb – 40,000 ft) directly above a tropical cyclone in order to ‘vent’ the rapidly inrushing air found at the surface of a storm. Until some outflow develops, a significant cyclone will not be able to form.

By the time the disturbance reaches the Bay of Campeche tomorrow, wind shear may fall off to as low as 5-10Kts, and upper level winds may become somewhat more favorable for the formation of a modest outflow pattern. In addition, due to the unique orientation of the topographical features found in the Bay – developing systems often have a propensity to ‘spin-up’ into tropical cyclones – though they rarely get beyond CAT 1 due to their proximity to rough terrain and the little time they usually have to intensify before going inland.

The Early cycle (12Z) model runs have a relatively wide spread in the projected tracks of the potential cyclone during the week ahead, but all show the system reaching Tropical Storm intensity. It’s worth mentioning that aside from the GFS – none of the global models, including the often overly zealous CMC – show any development of 99L - and even the GFS shows only modest development to possibly Depression strength. Regardless of development, the system is not expected to impact the US mainland.

SEVERAL TROPICAL WAVES ACROSS THE ATLANTIC
WITH A LARGE WAVE ALONG THE AFRICAN COAST

There are a couple other low latitude waves traveling across the central Atlantic, but none of them have shown any signs of development since yesterday. However, these systems are expected to reach the western CARIB by next weekend, where they may find upper level winds more conducive for development.

A VERY large tropical wave is along the West African coast, with some very deep convection (primarily still over land, though). This is the same system I referenced several days ago that was over eastern Africa where a strong AEJ (African Easterly Jet) was nosing into east/central Africa, and likely forced the development of the large wave we now see along the coast. In addition, this wave does NOT appear to be affected by the ‘warm and dusty’ Saharan Air Layer (SAL) which can inhibit cyclone formation.

But what is really unusual about this tropical wave is not its areal coverage – but the appearance of a well defined upper level anti-cyclone centered right above the strongest convection! I am hard pressed to recall seeing a similar situation. The question is whether this anti-cyclone (which didn’t exist yesterday morning) is actually ‘part of’ the disturbance’s overall structure, or if it's simply an unrelated upper atmospheric feature that will not move in tandem with the lower level wave. We should have our answer by tomorrow as the tropical disturbance moves further out over the eastern Atlantic south/southwest of the Cape Verdes. All that said – without any low or mid-level rotation noted, development of this system, if any, will take some time. (None of the global models show any meaningful development of this particular system.)



Fig 1: Latest VIS image of INVEST 99L with the main wave structure over the Yucatan, with the approximate centroid of rotation approaching the Belize coast. Much of the convection remains over the waters east of the Yucatan.



Fig 2: The shear analysis shows roughly 15-18 Kts of northerly shear dominating most of the area within the disturbance, with lower, and far more favorable values for development near 5 Kts in the Bay of Campeche. Surface pressures are NOT falling at all, and what wind reports are available, do not show any hints of a surface circulation.



Fig 3: High level (above 30,000Ft) winds are generally out of the Northeast, with no indication of an anti-cyclone center nearby. However, as 99L moves out over the Bay of Campeche, where winds are quite light – if a lower level circulation can develop, along with deep convection, the system may be able to generate its own anti-cyclonic outflow system atop the developing surface system, creating a self generating, closed feedback loop of sorts.



Fig 4: The above specialized hurricane model tracks all agree the system will move slowly W/NW during the week ahead - but with a wide envelope of projected tracks – the only common denominator is the ‘Bay of Campeche’.



Fig 5: Intensity forecasts generally agree 99L will develop into a Tropical storm (probably has a 50/50 probability) – with the typically over-ambitious SHIPs model going for a full CAT 1 hurricane.



Fig 6: This mornings ‘Overview’ of the Tropical Atlantic includes a weak tropical wave along the north coast of south America (convection has weakened considerably over night) – along with 2 tropical waves in the central Atlantic which are westbound at 20-25 kts. Yesterday, this complex system had deeper convection, but I could only discern one primary wave. By this morning, however, further analysis has revealed this complex system consists of 2, separate, though inter-twined, wave structures. Or so it seems… But MOST interesting of all, is the very large tropical wave now emerging off the West African coast, and the fact that the SAL is NOT entrained in the overall structure of the disturbance – at least not yet!



Fig 7: The above color enhanced IR image over Africa reveals the deep convection associated with the very large tropical wave along the West African coast. This system is westbound at just over 20Kts.



Fig 8: The highest level winds (satellite derived) show a closed, anti-cyclone sitting atop the low/mid level disturbance – something I’ve rarely (if ever) seen. The lack of a low-mid level rotation, however, means any development of this system will be slow.

I’ll have an Interim update on 99L tomorrow, with a Full Tropical Update on Tuesday.

Steve

NOTE: I am issuing regularly Weather Updates 3-Days per week (Sundays, Tuesdays and Thursdays) – except when we have or expect active Tropical Cyclones in the Atlantic Basin – in which case Updates will be at least once daily. In addition, if a strong cyclone is expected to impact the US mainland – I will be posting my own detailed forecast charts.

 





 Fig 21a - Graphical 5 Day Tropical Weather Outlook

Fig 23 - 48 Hour Tropical Storm Probability

low tide 6:38 am LT            Moon Rise – 10:26 am LT
high tide 2:40 pm LT           Moon Set –10:19 pm LT
low tide 7:49 pm LT            Sunrise – 5:34 am LT
high tide 12:40 am LT         Sunset – 6:01 pm LT




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