[LakelandARC] 2011 Atlantic Hurricane Predictions From Dr. William Gray

Fri Apr 15 06:13:19 PDT 2011

Hi Evans,

Long time no chat with you. I went to distribute your message and I could not get the picture associated with your message to show up. I tried to find where it came from but had no luck. Could you either send me the picture or point me in the right direction so I can get the message out in a timely manner, giving you credit for the information. Tnx.

73,

Neil
W4NHL

  ----- Original Message ----- 
  From: Evans F. Mitchell; KD4EFM / WQFK-894 
  To: Polk County Fl. K4LKL ; Lakeland ARC 
  Sent: Wednesday, April 13, 2011 7:47 PM
  Subject: [LakelandARC] 2011 Atlantic Hurricane Predictions From Dr. William Gray

  Below is the latest 2011 Atlantic hurricane season forecast from Dr. William Gray of Colorado State University. Dr. Gray will update his forecast in June . 

        ATLANTIC BASIN SEASONAL HURRICANE FORECAST FOR 2011 Forecast Parameter and 1950-2000 

        Climatology (in parentheses) 
       Issue Date 

        8 December 2010 
       Issue Date 

        6 April 2011 

        Named Storms (NS) (9.6) 
       17 
       16 

        Named Storm Days (NSD) (49.1) 
       85 
       80 

        Hurricanes (H) (5.9) 
       9 
       9 

        Hurricane Days (HD) (24.5) 
       40 
       35 

        Major Hurricanes (MH) (2.3) 
       5 
       5 

        Major Hurricane Days (MHD) (5.0) 
       10 
       10 

        Accumulated Cyclone Energy (ACE) (96.1) 
       165 
       160 

        Net Tropical Cyclone Activity (NTC) (100%) 
       180 
       175 

  PROBABILITIES FOR AT LEAST ONE MAJOR (CATEGORY 3-4-5) HURRICANE LANDFALL ON EACH OF THE FOLLOWING COASTAL AREAS: 

  1) Entire U.S. coastline - 72% (average for last century is 52%) 

  2) U.S. East Coast Including Peninsula Florida - 48% (average for last century is 31%) 

  3) Gulf Coast from the Florida Panhandle westward to Brownsville - 47% (average for last century is 30%) 

  PROBABILITY FOR AT LEAST ONE MAJOR (CATEGORY 3-4-5) HURRICANE TRACKING INTO THE CARIBBEAN (10-20°N, 60-88°W) 

  1)      61% (average for last century is 42%)

  ABSTRACT 

  Information obtained through March 2011 indicates that the 2011 Atlantic hurricane season will have significantly more activity than the average 1950-2000 season. We estimate that 2011 will have about 9 hurricanes (average is 5.9), 16 named storms (average is 9.6), 80 named storm days (average is 49.1), 35 hurricane days (average is 24.5), 5 major (Category 3-4-5) hurricanes (average is 2.3) and 10 major hurricane days (average is 5.0). The probability of U.S. major hurricane landfall is estimated to be about 140 percent of the long-period average. We expect Atlantic basin Net Tropical Cyclone (NTC) activity in 2011 to be approximately 175 percent of the long-term average. We have decreased our seasonal forecast slightly from early December, due to anomalous warming in the eastern and central tropical Pacific and cooling in the tropical Atlantic. 

  This forecast is based on a new extended-range early April statistical prediction scheme that utilizes 29 years of past data. Analog predictors are also utilized. We expect current La Niña conditions to transition to near-neutral conditions during the heart of the hurricane season. Overall, conditions remain conducive for a very active hurricane season.

  Table 1: Observed versus early April cross-validated hindcast NTC for 1982-2010 using our new forecast scheme. Average errors for cross-validated hindcast NTC and climatological NTC predictions are given without respect to sign. Red bold-faced years in the "Hindcast NTC" column are years that we did not go the right way, while red bold-faced years in the "Hindcast improvement over Climatology" column are years that we did not beat climatology. The hindcast went the right way with regards to an above- or below-average season in 21 out of 29 years (72%), while hindcast improvement over climatology occurred in 19 out of 29 years (66%). The hindcast has improved upon climatology in all but four years since 1993.

        Year 
       Observed NTC 
       Hindcast NTC 
       Observed minus 

        Hindcast 
       Observed minus Climatology 
       Hindcast improvement over Climatology 

        1982 
       38 
       101 
       -63 
       -62 
       -1 

        1983 
       31 
       20 
       11 
       -69 
       58 

        1984 
       80 
       163 
       -82 
       -20 
       -63 

        1985 
       106 
       60 
       45 
       6 
       -40 

        1986 
       37 
       32 
       5 
       -63 
       58 

        1987 
       46 
       71 
       -25 
       -54 
       29 

        1988 
       117 
       134 
       -17 
       17 
       0 

        1989 
       130 
       96 
       34 
       30 
       -4 

        1990 
       100 
       91 
       9 
       0 
       -9 

        1991 
       58 
       97 
       -39 
       -42 
       3 

        1992 
       67 
       20 
       47 
       -33 
       -14 

        1993 
       52 
       60 
       -8 
       -48 
       40 

        1994 
       35 
       71 
       -35 
       -65 
       29 

        1995 
       222 
       158 
       64 
       122 
       58 

        1996 
       192 
       189 
       3 
       92 
       89 

        1997 
       54 
       91 
       -38 
       -46 
       9 

        1998 
       169 
       166 
       3 
       69 
       66 

        1999 
       182 
       121 
       60 
       82 
       21 

        2000 
       134 
       154 
       -21 
       34 
       13 

        2001 
       135 
       113 
       22 
       35 
       13 

        2002 
       83 
       136 
       -53 
       -17 
       -36 

        2003 
       175 
       139 
       36 
       75 
       39 

        2004 
       232 
       89 
       142 
       132 
       -11 

        2005 
       279 
       185 
       94 
       179 
       85 

        2006 
       85 
       139 
       -54 
       -15 
       -39 

        2007 
       99 
       135 
       -36 
       -1 
       -35 

        2008 
       162 
       201 
       -39 
       62 
       24 

        2009 
       69 
       78 
       -9 
       -31 
       22 

        2010 
       195 
       235 
       -40 
       95 
       55 

        Average 
       116 
       116 
       39 
       55 
       +16 

  Current Atlantic Basin Conditions 

  Conditions in the Atlantic are favorable for an active season. SSTs across the tropical Atlantic remain at above-average levels (Figure 12). However, these anomalies have cooled somewhat over the past several months, likely due to a mid-winter switch from a negative phase of the North Atlantic Oscillation (NAO) to a positive phase of the NAO (Figure 13). A positive phase of the NAO is associated with anomalously strong trades across the tropical Atlantic, which promotes enhanced mixing and upwelling resulting in anomalous cooling. Figure 14 displays the cooling in SSTs observed in the tropical Atlantic from the latter part of March minus the latter part of January. The anomalous cooling has been on the wane over the past couple of weeks as the NAO has migrated back towards a neutral state. The atmospheric state across the tropical Atlantic looks quite favorable for an active season, as wind shear anomalies across the basin have been well below average over the past two months.

  8 Landfall Probabilities for 2011 

  A significant focus of our recent research involves efforts to develop forecasts of the probability of hurricane landfall along the U.S. coastline and in the Caribbean. Whereas individual hurricane landfall events cannot be accurately forecast months in advance, the total seasonal probability of landfall can be forecast with statistical skill. With the observation that landfall is a function of varying climate conditions, a probability specification has been developed through statistical analyses of all U.S. hurricane and named storm landfall events during the 20th century (1900-1999). Specific landfall probabilities can be given for all tropical cyclone intensity classes for a set of distinct U.S. coastal regions. 

  Net landfall probability is shown linked to the overall Atlantic basin Net Tropical Cyclone activity (NTC; see Table 8). NTC is a combined measure of the year-to-year mean of six indices of hurricane activity, each expressed as a percentage difference from the long-term average. Long-term statistics show that, on average, the more active the overall Atlantic basin hurricane season is, the greater the probability of U.S. hurricane landfall. 

        Table 8: NTC activity in any year consists of the seasonal total of the following six parameters expressed in terms of their long-term averages. A season with 10 NS, 50 NSD, 6 H, 25 HD, 3 MH, and 5 MHD would then be the sum of the following ratios: 10/9.6 = 104, 50/49.1 = 102, 6/5.9 = 102, 25/24.5 = 102, 3/2.3 = 130, 5/5.0 = 100, divided by six, yielding an NTC of 107. 1950-2000 Average 

        1) 
       Named Storms (NS) 
       9.6 

        2) 
       Named Storm Days (NSD) 
       49.1 

        3) 
       Hurricanes (H) 
       5.9 

        4) 
       Hurricane Days (HD) 
       24.5 

        5) 
       Major Hurricanes (MH) 
       2.3 

        6) 
       Major Hurricane Days (MHD) 
       5.0 

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